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Onepieceatatime7 07-10-2019 02:33 PM

Car stumbles badly
 
This is a mut, so the problem could be a couple things. It's a SBC 350. I get it tuned, runs strong in driveway, take it to the street and romp on it and it stumbles at about 5k rpm. Stumbles as in it's out of fuel or something and then continues that when I try to get on it again. can drive it back home, idles fine, runs fine.

Is there something in the carb that could have a blockage?

Also have a MSD 6al ignition with mechanical dizzy and holley 650 mechanical carb. The rev limiter is not set up, but could that have something to do with it, or the dizzy have moved a bit?

I've changed the (electric) fuel pump, lines, filter etc. and have one of those cheap pressure regulators from autozone that you can turn the dial from like 1-6 for fuel pressure, which I have set at 5.

thanks in advance.

cerial 07-10-2019 03:00 PM

I don't have anything nice to say about a Mr. Gasket fuel pressure regulatior.

I would start by installing a gauge after that pos regulatior to see what your true reading is and how much variation you are getting.

I can almost guarantee that once warm that regulstior is allowing to much fuel through flooding the car.

BogiesAnnex1 07-10-2019 03:25 PM

Could be a lot of things but before I started spending money I'd recomment tightening up the plug gap to .030 to .035 inch. The next step would be to take the 6AL out of the circiut to see how it runs on a simple HEI.

These are tests that take a little of you time but are otherwise freebies.

Super wide plug gaps aren't necessary nor really desireable especially with high compression and overly rich mixtures.

6AL boxes introduce weird problems at times. The do demand that the heads and intake have seperate grounds, lacking these the high and abrupt energies fed to the plugs can and do mess up the electronics in their search for ground.

Bogie

Onepieceatatime7 07-10-2019 03:33 PM

Quote:

Originally Posted by cerial (Post 4683009)
I don't have anything nice to say about a Mr. Gasket fuel pressure regulatior.

I would start by installing a gauge after that pos regulatior to see what your true reading is and how much variation you are getting.

I can almost guarantee that once warm that regulstior is allowing to much fuel through flooding the car.

It's mounted right by the passenger side valve cover on the fire wall, so it probably does get heated. Could flodding cause it to stumble as in, someone turned of the switch?

Onepieceatatime7 07-10-2019 03:37 PM

Quote:

Originally Posted by BogiesAnnex1 (Post 4683013)
Could be a lot of things but before I started spending money I'd recomment tightening up the plug gap to .030 to .035 inch. The next step would be to take the 6AL out of the circiut to see how it runs on a simple HEI.

These are tests that take a little of you time but are otherwise freebies.

Super wide plug gaps aren't necessary nor really desireable especially with high compression and overly rich mixtures.

6AL boxes introduce weird problems at times. The do demand that the heads and intake have seperate grounds, lacking these the high and abrupt energies fed to the plugs can and do mess up the electronics in their search for ground.

Bogie

I don't know that I even have the alum heads and intake grounded. It's grounded from the frame to the block. It's a points distributor, and the gaps are about .40 if I recall.

36 sedan 07-10-2019 04:32 PM

What is the spark limiter set at in the 6AL?
JMHO, fuel pressure regulators work better as close to the carb as possible.

BogiesAnnex1 07-10-2019 04:43 PM

Quote:

Originally Posted by Onepieceatatime7 (Post 4683019)
I don't know that I even have the alum heads and intake grounded. It's grounded from the frame to the block. It's a points distributor, and the gaps are about .40 if I recall.

6AL is what has my attention points are just a switch in this case. Problem with grounding is these things seek ground through whatever they can find which is sometimes back through the electronis of the 6AL, using an HEI just adds another possibility. Not to say this is the issue but solving for the simple first can save a lot of money, if it isn't the problem you're just out some time not time and money.

The block ground is for the starter and mild electrical fields that are DC in nature, even the heads are pretty safe with this bonding to the block with sealant laden bolts and gaskets. The 6AL in not so kind, it is shocking the plugs with a high energy square wave pulse that is hard to absorb through these unintentional connections. Running the heads and intake together with some number 10 wire to the frame or battery negative post insures the ground side of the plugs doesn't find a sneak circuit back through the electronics. This recommendation is nothing new it usually can be found in MSD's instructions but not always it seems to come and go on reprints.

One has to realize that electrical currents move in voltage differentials not adsolute this side is hot and that side not. The left over currents from firing the plugs will take a positive 12 volt circuit to ground if a negative bonded route is not available. Smoking 6AL's, HEI's or capacitors on points is not all that uncommon.

I'm kind of leaning toward electrical rather than fuel pressure since you're not reporting a backfire with this but just a stumble. If it flames out the intake that puts both options on the table, if it doesn't that's a pretty good indicator but not absolute that the mixture is hanging in there.

My prefered electric pump layout is of course more expensive but for a carb I really like to run a lower pressure TBI rated pump for factory TBI using about 15 psi. Then a bypassing regulator with preferably a tank return but tee'ing in the feed line just ahead of the pump if it's back by the tank is OK, you first want some distance to let the pump bypass fuel to cool before being pumped again. This insures a managed oversupply of fuel in the system for a consistent supply at the carb so at high RPMs it doesn't start to lose fuel pressure as demand over runs supply. For a turbo type pump it insures there is always a fuel flow for cooling the motor, it never encounters a near deadhead situation when idleing as happens with a non-bypass regulator.

As for gauges everybody's quality is sucko, price is no indicator of quality. I have a new Stuart Warner vacuum gauge that reads 24-25 inches at a 750 rpm hot idle vacuum on a 350 with a LT4HOT cam, 1.6 rockers, with 10.3 SCR. My old quick and dirty Harbor Freight vacuum/boost gauge with multiple color LED lighting says 16-17 inches, so does my motorcycle multi-carb adjusting mercury manometer.

I also run a Mr. Gasket fuel pressure gauge at the regulator it is set for about 5.7 to 5.8 psi regulated line pressure on the left side inner fender and also a no name mini gauge in the line at the Edlebrock carb which reads about 5.5 psi.

Bogie

lmsport 07-10-2019 05:02 PM

do you know that the valves springs are correct for your setup?

Points floating out is also possible.

is the pump by the fuel tank?

36 sedan 07-10-2019 05:09 PM

Quote:

Originally Posted by 36 sedan (Post 4683025)
What is the spark limiter set at in the 6AL?

I meant to say REV limiter. 6al has rev limiter that requires setting, i believe default setting is 5k.

Onepieceatatime7 07-10-2019 06:17 PM

Ok but this is going to sound stupid. I just hooked up a new timing light that works with msd and am timing of the # 6 cylinder....yeah I know.

It ran ok before but a bit hot and had the stumble, but and it appears the timing was set after Tdc.

Net net.

Itís set at 8 degrees initial with a 21 degree total timing stop in the dizzy. Hereís the thing. Itís holding 185 temp in a 100 degree weather now and a had hot issues before. At idle. I have 15 psi vacuum and she jumps when you stomp it, but will not test tonight due to bud light.

Is 8 degrees initial and 29 total ok??......cause the motor suuuuure seems to like it.

Iíll double ground as suggested either way.

8 degrees initial??

Any more than that and she wants to buck a little on start.

Itís 350 , .40 over, zero deck
10.5 compression
Roughly .40 gap on plugs
E street alum heads
Roller rockers
Low rise single plane intake ..... I know, I know...
Shorty headers
650 carb
All mechanical carb, dizzy, manual tranny etc.

So, is 29/30 total timing sound ok?

The temp and vacuum at steady 15 or so make me want to leave it.

I just got vacuum gauge and new timing light.

I donít think the msd box rev limiter is an issue as I have no tach yet, but I did set the dials today @ 6200 to be sure

Onepieceatatime7 07-10-2019 06:19 PM

Temp holding at 185 I should say, which is much better

Onepieceatatime7 07-10-2019 06:22 PM

268h comp cam

ericnova72 07-10-2019 06:40 PM

Total timing at 29-30į may leave a little power on the table, it may prefer the total up near 32-34į for maximum power.

That means with your set-up the initial would need to be 10-12, maybe 14į initial. If it fights the starter too much check your ground connections and battery main cable sizes, Typical parts store battery cables are too small to carry the load well.
If that checks out, you may want to investigate installing an ignition interrupt toggle switch, so you can roll the motor over with the starter easer with no ignition firing, then throw the ignition power on. It helps a bunch with slow cranking cars.

36 sedan 07-10-2019 06:44 PM

Quote:

Originally Posted by Onepieceatatime7 (Post 4683041)
Ok but this is going to sound stupid. I just hooked up a new timing light that works with msd and am timing of the # 6 cylinder....yeah I know.

Why are you connecting your timing light to #6 instead of #1?

ericnova72 07-10-2019 07:02 PM

Quote:

Originally Posted by 36 sedan (Post 4683051)
Why are you connecting your timing light to #6 instead of #1?

Doesn't matter, it will time the same on #1 or #6 because they are both at TDC at the same time.
Often racers will use #6 if #1 plug or wire is in a location that is harder to get to or easier to burn wires on. It's just a convenience thing.

55 Tony 07-10-2019 07:10 PM

Quote:

Originally Posted by BogiesAnnex1 (Post 4683029)
The block ground is for the starter and mild electrical fields that are DC in nature, even the heads are pretty safe with this bonding to the block with sealant laden bolts and gaskets. The 6AL in not so kind, it is shocking the plugs with a high energy square wave pulse that is hard to absorb through these unintentional connections. Running the heads and intake together with some number 10 wire to the frame or battery negative post insures the ground side of the plugs doesn't find a sneak circuit back through the electronics. This recommendation is nothing new it usually can be found in MSD's instructions but not always it seems to come and go on reprints.


I would love to see some directions from msd that mention separate grounds and grounds from the head to the intake. And where in the world do you get the idea that "a high energy square wave pulse that is hard to absorb through these unintentional connections."? I've seen you write it many times and just wonder what your electronics background is? Have you watched the square wave signal on a scope? Have you EVER worked on equipment using a scope to check a square wave pulse? Has anyone here ever benefited from running extra grounds like you always suggest? Not that I've seen. Can you please show me one set of instructions warning you of "sneaky" electrical pulses?

36 sedan 07-11-2019 12:18 AM

I had problems with my MSD, one box failed, then the new one would miss at higher rpm, tech said to ground the heads, grounded heads miss went away and box has lasted years without a hic up.

https://forums.holley.com/showthread...Ground-diagram

msdtech1955
Guest
Default
We have discovered for decades now that the motor-plates and the ground strap to the block does not provide a sufficient ground. It was initially un-covered that the black etch marks that appear around the block holes of front and rear motor plates was made due to the poor ground paths(we even saw etches in main and rod bearings). With coated studs, aluminum heads, coated gaskets,powder coated frames and customers relaying on the ground strap from the chassis to the block was not enough.
To be frank, the spark plugs are in the head and not the block! With this in mind, it was best to have a common ground between the electronics, battery and even the coil to eliminate any floating ground issues that may occur. Majority of the time ,this elinminate "misses" ,tach issues,data logger problems..etc.

55 Tony 07-11-2019 07:06 AM

A poor ground as they say is hard to believe but I suppose possible when people are trying to get a good ground through powder coated paint. With a low ohms high frequency meter I measured from one header bolt through the head, through the block and manifold, through the other head and to the header bolt and found I have somewhere around .01 ohms or less resistance as my low ohms meter was at it's low limit. The higher the voltage the less it is affected by resistance, and we know the spark pulse is high voltage. I'll have to check the frequency of my low ohms meter, but I believe it goes higher than most engine rpms.

It's just funny that my msd 6al box instructions only say to run the ground wire directly to the battery negative cable. Nothing mentioning the heads. Think of all the phone calls alone they could avoid if that were in the instructions.

Onepieceatatime7 07-11-2019 07:53 AM

Quote:

Originally Posted by 55 Tony (Post 4683127)
A poor ground as they say is hard to believe but I suppose possible when people are trying to get a good ground through powder coated paint. With a low ohms high frequency meter I measured from one header bolt through the head, through the block and manifold, through the other head and to the header bolt and found I have somewhere around .01 ohms or less resistance as my low ohms meter was at it's low limit. The higher the voltage the less it is affected by resistance, and we know the spark pulse is high voltage. I'll have to check the frequency of my low ohms meter, but I believe it goes higher than most engine rpms.

It's just funny that my msd 6al box instructions only say to run the ground wire directly to the battery negative cable. Nothing mentioning the heads. Think of all the phone calls alone they could avoid if that were in the instructions.

True. I went by the instructions which say ground the box to the battery, now I see something different online that shows to ground from chassis to one head, then to the other head and the coil ground meeting there, from there ground to block and then the masd block ground would join this wire that is grounded to the other side of the frame and then the battery, in tendem.

definitely was not in instruction. I will wire it that way and see.

Was also thinking. if I am only at 8 degree initial timing and my plugs at .40 would not tightening the gap on the plugs help me get closer to 10-12 degrees initial?

thanks

55 Tony 07-11-2019 08:26 AM

Quote:

Originally Posted by Onepieceatatime7 (Post 4683143)
True. I went by the instructions which say ground the box to the battery, now I see something different online that shows to ground from chassis to one head, then to the other head and the coil ground meeting there, from there ground to block and then the masd block ground would join this wire that is grounded to the other side of the frame and then the battery, in tendem.

definitely was not in instruction. I will wire it that way and see.

Was also thinking. if I am only at 8 degree initial timing and my plugs at .40 would not tightening the gap on the plugs help me get closer to 10-12 degrees initial?

thanks


No on the gap/advance. Electricity/current is much too fast to ever play a role in a cars engine. If your msd box is working there is no need to close the gap on the plugs.


How exactly does the engine "stumble"? Does it get up to the rpm and just quit going faster? I've dealt with many problems with fuel turning to vapor and the pump not being able to keep up. When it stumbles, try pumping the throttle and let me know if it gives it surges of power (from the accelerator pump). That would point to a fuel problem. You say you have a points distributor, if it's very old, the distributor could be the problem.

36 sedan 07-11-2019 08:32 AM

I know it's hard to believe, but grounds make a huge difference.

Grounding the intake made my gauges settle down and read accurately, but the biggest surprise was my alternator. The 140amp alternator struggled to keep up with my cooling fans (50amps), I added a large dedicated ground and instantly no more problems. I can only image the long term damage the alternator could have caused to my motor absorbing all that current. It's eye opening, especially when you consider grounds are easy and cheap insurance.

JMHO, and I'm a little anal about ground paths, I don't like to daisy chaining grounds, I star ground everything.

BogiesAnnex1 07-11-2019 11:12 AM

Quote:

Originally Posted by 55 Tony (Post 4683067)
I would love to see some directions from msd that mention separate grounds and grounds from the head to the intake. And where in the world do you get the idea that "a high energy square wave pulse that is hard to absorb through these unintentional connections."? I've seen you write it many times and just wonder what your electronics background is? Have you watched the square wave signal on a scope? Have you EVER worked on equipment using a scope to check a square wave pulse? Has anyone here ever benefited from running extra grounds like you always suggest? Not that I've seen. Can you please show me one set of instructions warning you of "sneaky" electrical pulses?


At my age I probably have more Tektronics time than most people have lifetime, somehow high energy fields and how to dissipate them became an engineering specialty in my career. "Sneak Circuits" is a term used in electrical engineering to describe unintended current flows in places you don't want them. By the time a product is delivered to the end user these things should be worked out, but sometimes you get surprises either because you as the engineer missed some combination of possibilities or as often happens your best efforts efforts at "idiot proofing" fall short of what installers can and will do to it.



This is not something you would see on a scope unless the ground side is inadequate. From a consultant side to automotive projects and from a part to full time builder, depending on time periods in my life, I've seen several 6AL failures that appear to be ground side issues especially with the SBC Gen I. Although, I encountered a Ford small block powered kit car built by a guy in Arizona that repeatedly ate its 6AL that after adding top end grounds had no more problems. Of course since your replacing the dysfunctional box with a new one while adding grounds you don't know for sure whether you've gone through a multiple series of bad boxes and now have a good one or whether the added protection of the top end grounds are protecting the electronics from feedback.


Since I don't like comebacks no being stopped in the middle of nowhere myself; I "scrub" grounds thoroughly and add a top end ground circuit for these boxes. Compared to failure hunting, R&R time; stripping a couple three lengths of wire adding terminal ends and tucking it together is a better use of my time than responding to panic phone calls, hunting intermittent failures that don't in the shop, dealing with upset customers or being stuck myself.



Understanding what poorly bonded equipment ground side failures look like and if you read MSD's installation instructions they make a point of telling the installer to be sure the block is well grounded. Seems to me I remember some years back they recommended adding top end grounds either in their instructions at the time or it was while talking with their tech helpline people. Then adding my knowledge of electrical bonding and energy dissipation with the understanding that paint, corrosion, lubricants and sealants are poor conductors if at all it makes sense to insure that the top end is electrically tight. Given the typical engine ground strap is some distance away from the heads and generally not thought about in terms of condition or maintenance for projects that I turn out for people I started adding grounds to the heads and intake using specific bolts that typically don't end with an open passage that needs to be sealed against coolant or oil. I use an electrically conductive grease on the threads to try and stop corrosion and keep water out, but that is an uphill battle if don't live in the desert southwest.


The typical failure mode of these things is inexplicable and intermittent miss fires, inability to get power out of the engine but it idles fine sometimes even runs in the medium rev range. As time goes on this worsens till the engine just either stops running or won't start. sounds a lot like the OP's issue. Might not be, but does lead into a path I and others that have written about on this forum with some frequency. Given I'm not standing there, I can only give general advice as I have no idea of what the installation looks like in configuration or build quality. Based on my experience with automotive, boats, and aerospace many if not most installations and repairs are hacks at best and I'm not excluding myself.



Obviously if the box is failing there are no external fixes that will bring it back. If you read what I wrote carefully you will see I included contingent statements on grounds to the effect that its an "if" proposition that if good grounding is not present the failure being seen can be the box going out from unintended current flows seeking a ground path. At this point which I may not have made clear if the box is dying it's gone and will need replacement. Adding ground networks is a CYA going forward on a just in-case basis.


In the bigger picture I rather think that these multi-spark, high energy ignition boxes are far from necessary if this isn't a race car expected to earn its keep. Solid state ignitions were first designed to eliminate point contact wear which along with lead fouled spark plugs was a frequent maintenance item back in the good old days. Really except for this these issues the inductive ignitions worked fine even with the quite high compression ratios popular back in the late 50's through 60's, and they did on using 6 to 9 volts on the coil. HEI ignitions came about in the early emissions era to stabilize engine running quality over a longer time period than the typical points tune up to cover those people who didn't get a tune up till it just about stopped running. This was cause of significant pollution. The other factor was lower compression ratios to reduce NOx emissions teamed with leaner mixtures to reduce HC emissions were harder to ignite a failure here resulting in high emissions of HC's, so a harder jolt to the plugs and longer duration spark was employed to insure the burn not only started but was on time every time. Now of course this allows plugs to run wider gaps which again covers pollution from those that don't monitor such things. Today we have coil on plug which allows the individual coils more time to saturate between triggering than one coil supporting multiple cylinders. This eliminates a host of losses in the distributor and lengthy plug wiring. Some aircraft engines tried this trick in WW II using mechanical switching, but that proved too complex. Solid state switching being a much simpler solution. Multi-strike and capacitive discharge ignitions ignition came out in a similar time frame to HEI but except in rare cases the OEM's did not go that far. After 40 years of looking at and playing with these things I'm not convinced that for the average street rodder they bring anything useful to the table.



Bogie

55 Tony 07-11-2019 12:36 PM

Well Bogie, your knowledge and experience blows mine away. I have never been on the engineering side of electronics. I sincerely hope you will accept my apology for questioning your expertise in such a rude manner.

I do have a question that popped up and makes me really wonder. When you say the 6AL boxes can get worse over time, what type of components is it that is going bad?

Onepieceatatime7 07-12-2019 06:48 AM

Ok so I grounded they heads to the block then to the frame on both side. Then I cranked it up and got the timing light out again. The dizzy is moving when I increase rpms. I can literally see it going from 10 to 0 as I increase rpms. I know I know...lock it down. The dist lock sux. Itís a chrome one and the metal is soft. Iíve bent the teeth on it once as it flattened out. The lock down bolt is not bottoming out. Any suggestions on helping the dizzy lock down?

Just seems like a cheap lock down...

Will take it out this weekend after fixing this and update.

55 Tony 07-12-2019 06:50 AM

Dig out your old steel lock down and use that.

Onepieceatatime7 07-12-2019 07:25 AM

Quote:

Originally Posted by 55 Tony (Post 4683315)
Dig out your old steel lock down and use that.

don't have one. stopped by napa on the way in, and the one they have is the same i have. cheap made in china chrome crap. I know thats not hardened steel cause when I bent it the 1st time i felt real iffy, thinking is this thing gonna crack.

Ill call a couple other suppliers, but probably headed to the junk yard tomorrow.

55 Tony 07-12-2019 07:27 AM

This may sound really dumb but you don't have it on upside down do you?

Onepieceatatime7 07-12-2019 07:35 AM

Quote:

Originally Posted by 55 Tony (Post 4683321)
This may sound really dumb but you don't have it on upside down do you?

LOL, should I be insulted.....:)

55 Tony 07-12-2019 09:00 AM

It wasn't meant to be. I just think of the two I have and I've heard before that they are weak, but mine are hard as hell. Without lookiing I'd guess 1/4" steel.

ericnova72 07-12-2019 09:02 AM

Hard to beat a factory clamp, they just aren't very attractive if you are into all that fancy blingy looking stuff. Chrome sucks because it is slippery.
https://www.summitracing.com/parts/n...make/chevrolet

Check to make sure the distributor isn't bottoming out on the oil pump drive before it fully seats on the intake manifold, I usually check it without a gasket, if it seats fully without the gasket it will have enough clearance when the gasket is there. If it is held off the manifold seat, no clamp in the world will hold it because it isn't pressed down against a surface, it is pressed against a rotating pump drive.
You can end up with one that doesn't seat due to head and block machining, or incorrectly cut manifold.
Sometimes just a doubled up gasket is enough to fix a problem.

Just something to check and verify.

lmsport 07-12-2019 10:25 AM

you see the timing Mark moving or the distributor moving? the clamp doesn't have to be very tight to hold the distributor body in place.
if the timing Mark is moving then there are a whole new range of possibilities from inside the distributor to timing chain, cam gear, dist gear, etc.

BogiesAnnex1 07-12-2019 11:26 AM

Quote:

Originally Posted by Onepieceatatime7 (Post 4683313)
Ok so I grounded they heads to the block then to the frame on both side. Then I cranked it up and got the timing light out again. The dizzy is moving when I increase rpms. I can literally see it going from 10 to 0 as I increase rpms. I know I know...lock it down. The dist lock sux. It’s a chrome one and the metal is soft. I’ve bent the teeth on it once as it flattened out. The lock down bolt is not bottoming out. Any suggestions on helping the dizzy lock down?

Just seems like a cheap lock down...

Will take it out this weekend after fixing this and update.

If there is component damage already adding grounds will not fix that. If internals are not yet fried you should see an improvement but component life span may prove to be reduced.

If this unit is in warrantee MSD will repair it if it hasn't been opened up. if out of warrantee there are some shops like MSD Ignition Repair MSD Ignition Traction Control that can repair it, this is not assured repair depends on whether the condition of the circuit board(s). Or you can take a shot at home repair but unless your an electronics tech already this is a steep learning curve.

Bogie

BogiesAnnex1 07-12-2019 11:50 AM

Quote:

Originally Posted by 55 Tony (Post 4683215)

I do have a question that popped up and makes me really wonder. When you say the 6AL boxes can get worse over time, what type of components is it that is going bad?

This thing has several variations that change some of what you see inside across the years of manufacture. What you will usually find is burnt supressor diodes, resistor networks in the power transistor output section, and ancillary transistors in various supporting functions. Most all failures will evidence heat failure of some sort. I apply the old British joke about Lucas electricals and electronics. That in general says these type things operate using smoke, when the smoke leaks out, they stop working. You have to admit to the off handed logic of this. Generally if the circuit board isn't burnt these parts can be replaced, but do it yourself circuit board repair is not a place for the untrained. Usually the etched circuit has delaminated from the board and this is difficult to repair and keep it that way. If the circiut path has space to work in somtimes a wire jumper can be soldered in. But as I said unless your already an electronics technician the chances of success are pretty slim. With Radio Shack gone its a lot harder to find parts, not that theirs were all that great, but with one or more outlets in every town they were convienient.

MSD will cover this under warrantee if the unit has not been opened and in still in period. There are some shops out there that can fix these such as Tech West, I linked it an a different reply in this thread.

Bogie

BogiesAnnex1 07-12-2019 12:10 PM

Quote:

Originally Posted by Onepieceatatime7 (Post 4683313)
Ok so I grounded they heads to the block then to the frame on both side. Then I cranked it up and got the timing light out again. The dizzy is moving when I increase rpms. I can literally see it going from 10 to 0 as I increase rpms. I know I know...lock it down. The dist lock sux. Itís a chrome one and the metal is soft. Iíve bent the teeth on it once as it flattened out. The lock down bolt is not bottoming out. Any suggestions on helping the dizzy lock down?

Just seems like a cheap lock down...

Will take it out this weekend after fixing this and update.

You and we need to know if this is with vacuum advance connected or not?

Keep in mind that manifold vacuum curves differently between opening the throttle on a unloaded engine compared to when the has to get down to lifting weight. It takes very small throttle opening to get a lot of RPM when the motor isn't dragging the vehicle around. So in the case of not having to work hard, the manifold vacuum will be high for the RPM, if connected to the vacuum advance you can see the total of base , vacuum, and centrifugal all at once which would not occur on the street with the engine working to move a load.

This is not to say the distributor needs to be anchored, but also the forces on it shouldn't be so large that a chrome made in China clamp couldn't hold it, not that I cant be surprised, but I wouldn't expect this unless something else is wonky in this chain of parts.

Bogie

BogiesAnnex1 07-12-2019 12:18 PM

As far as 6 AL box reliability goes you guys will note that real serious racers install multiple boxes and use a switch to activate the back up incase of failure of the prime operating box and or a switch back to conventional ignition without these boxes being involved.

Bogie

Onepieceatatime7 07-12-2019 01:07 PM

Quote:

Originally Posted by BogiesAnnex1 (Post 4683385)
You and we need to know if this is with vacuum advance connected or not?

Keep in mind that manifold vacuum curves differently between opening the throttle on a unloaded engine compared to when the has to get down to lifting weight. It takes very small throttle opening to get a lot of RPM when the motor isn't dragging the vehicle around. So in the case of not having to work hard, the manifold vacuum will be high for the RPM, if connected to the vacuum advance you can see the total of base , vacuum, and centrifugal all at once which would not occur on the street with the engine working to move a load.

This is not to say the distributor needs to be anchored, but also the forces on it shouldn't be so large that a chrome made in China clamp couldn't hold it, not that I cant be surprised, but I wouldn't expect this unless something else is wonky in this chain of parts.

Bogie


no vacuum advance.

https://www.holley.com/products/igni...et/parts/85551

I have the blue springs in it, which are on the softer side and 21 degree stop bushing. pretty sure now that it's the distributor moving.

It would seem natural for the timing to want to retard/push back on a high compression engine with a mild cam (268H) would it not?

hypothetically, if the dizzy was left completely loose would it not eventually retard even on a mild engine.

if not, whats the use in even having a lock down. just rambling

EragonSuperH 07-12-2019 01:34 PM

Quote:

Originally Posted by 55 Tony (Post 4683067)
I would love to see some directions from msd that mention separate grounds and grounds from the head to the intake. And where in the world do you get the idea that "a high energy square wave pulse that is hard to absorb through these unintentional connections."? I've seen you write it many times and just wonder what your electronics background is? Have you watched the square wave signal on a scope? Have you EVER worked on equipment using a scope to check a square wave pulse? Has anyone here ever benefited from running extra grounds like you always suggest? Not that I've seen. Can you please show me one set of instructions warning you of "sneaky" electrical pulses?

Think of electricity like fluid pressure. When you're pumping a fluid through an orifice and the pressure gets to be too great to force it through as fast as the pump wants to, where does it go? Same way with a turbocharger when you let off the throttle and you get that fluttering sound, that's air pressure building up and forcing its way back through the "pump" in this case the turbocharger. Its the same concept for electricity, just on a sub atomic scale

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BogiesAnnex1 07-12-2019 03:25 PM

Quote:

Originally Posted by Onepieceatatime7 (Post 4683393)
no vacuum advance.

https://www.holley.com/products/igni...et/parts/85551

I have the blue springs in it, which are on the softer side and 21 degree stop bushing. pretty sure now that it's the distributor moving.

It would seem natural for the timing to want to retard/push back on a high compression engine with a mild cam (268H) would it not?

hypothetically, if the dizzy was left completely loose would it not eventually retard even on a mild engine.

if not, whats the use in even having a lock down. just rambling




The 268H and its near relative the XE268H are right at the edge separating the world of quite hot but street-able cams from the world of truly hot cams. Both of these worlds are intolerant of little set up errors, obviously getting worse the further up the scale you go. In my view the 268's are not "mild" cams. With these it takes very little effort to get into the range of 400 to 420 hp and similar amounts of torque from a 350 and that on only about 9.5:1 SCR. So what this means is all the players at the table need to bring their 'A' game.


This can is not so insane that it can't support vacuum advance. There are a lot of people who just say through this or that out vacuum advance and timed vacuum advance seeming to be leaders on that list. I'm more the experimental type that hunts for best integrations from the available tools, I don't just toss options I test and test and retest again and again.



If I remember accurately you are running a points ignition. Points ignitions put more of the shaft rotation forces into the distributor body by way of having to lift the contactor block, so yes these need to be securely restrained especially compared to a Hall Effect HEI distributor. One of the mechanical things this does is to speed wear on distributor bushings and bearings which allows the shaft to orbit with its rotation which results in unpredictable changes in gap thus dwell angle. This would affect the timing as a result of the variable shaft movement. To this end any off centered movement of the plate to which the points mount would have similar effects.


As usual the Devil is somewhere in the details.




Bogie

Onepieceatatime7 07-13-2019 08:45 AM

Quote:

Originally Posted by BogiesAnnex1 (Post 4683413)
The 268H and its near relative the XE268H are right at the edge separating the world of quite hot but street-able cams from the world of truly hot cams. Both of these worlds are intolerant of little set up errors, obviously getting worse the further up the scale you go. In my view the 268's are not "mild" cams. With these it takes very little effort to get into the range of 400 to 420 hp and similar amounts of torque from a 350 and that on only about 9.5:1 SCR. So what this means is all the players at the table need to bring their 'A' game.


This can is not so insane that it can't support vacuum advance. There are a lot of people who just say through this or that out vacuum advance and timed vacuum advance seeming to be leaders on that list. I'm more the experimental type that hunts for best integrations from the available tools, I don't just toss options I test and test and retest again and again.



If I remember accurately you are running a points ignition. Points ignitions put more of the shaft rotation forces into the distributor body by way of having to lift the contactor block, so yes these need to be securely restrained especially compared to a Hall Effect HEI distributor. One of the mechanical things this does is to speed wear on distributor bushings and bearings which allows the shaft to orbit with its rotation which results in unpredictable changes in gap thus dwell angle. This would affect the timing as a result of the variable shaft movement. To this end any off centered movement of the plate to which the points mount would have similar effects.


As usual the Devil is somewhere in the details.




Bogie


So, just curious what kind of HP you would ballpark on my setup as my goal is 400+

Balanced shortblock .40 over zero deck
Edelbrock E street heads
Roller rockers
MSD Box , coil and dizzy
Shorty headers
Weiand single plane intake
Holley 650 DP
268H cam
10.5:1 scr

I had to use the Weiand and shorty headers for clearance.....

And yeah that lock down is a POS. Broke pretty easy last night when I tried to bend the forks.

MouseFink 07-13-2019 12:43 PM

I noticed that the spark plug gap was 0.40Ē. I assume that is because you have a MSD ignition. Try closing the gap up to .035Ē or use Denso spark plugs with the platinum tips. They are preset at .035Ē.

Avoid ACDelco plugs at all cost. They are now made by various offshore producers. Those spark plugs have not been a GM product since 1992, following the GM bankruptcy.

Or get rid of the MSD ignition system. A PerTronix system is hard to beat.


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