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Won't idle under 60 degrees timing

21K views 42 replies 13 participants last post by  cobalt327 
#1 ·
I've been viewing this forum for about two years now, and have found the solutions for many of my cars issues by reading old posts. Well, I've searched and searched but can't find a good thread for this issue. Any help would be greatly appreciated!

Background.

I have a sbc 383 with 500 miles on it
hydraulic flat tappet, w/ 1.6rr
Aluminum heads 210 runners, 68cc chambers
MSD 6a, Msd wires, Blaster 3 coil, msd tach adapter, pro billet distributor
Professional Parts Typhoon intake
Holley S/A 770
Optima red top in the trunk

Problem
I can't get the car to idle under 40 degrees advanced. It actually pulls better vacuum and idles better at 60 degrees. It doesn't sound good at all and it shakes quite a bit. I've let it idle like this for about a total of 30 minutes. I pulled the plugs to run another compression check and the plugs were very carbon fouled.

I have checked the distributor position no less than 20 times. I cranked the balancer to TDC, took the valve covers off and verified both rockers on #1 were closed on the compression stroke. With the dizzy locked down at 60 degrees advance the rotor is now pointing to the next cylinder in the firing order when the balancer is on TDC #1.

I've built this car from the frame up and I'm about to give up and tow it to shop just to save my sanity. Help!!
 
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#2 ·
Has it been like this from day one? If the pointer is at TDC and the rotor is pointed at #8, and you're sure the piston is actually at TDC, sounds like you need to move the wires one tower clockwise or reposition the distributor.

If that doesn't fix it, maybe you have the wrong balancer or timing cover/pointer, do you have a timing tape on it or just the factory markings?
 
#3 ·
Thanks for the reply!
No, in its first incarnation it ran at 13 degrees initial. Since then I've installed new heads, the 770 carb and put the battery in the trunk. Next time I'll change ONE thing, check it and move on to next thing.

I added a timing tape the other day so I could use a cheapo timing light instead of my digital. Same reading with both lights.

If I stabbed the dizzy incorrectly, couldn't I just rotate the cap until I found normal timing on the balancer?
 
#4 · (Edited)
AllRi5e said:
Thanks for the reply!
No, in its first incarnation it ran at 13 degrees initial. Since then I've installed new heads, the 770 carb and put the battery in the trunk. Next time I'll change ONE thing, check it and move on to next thing.

I added a timing tape the other day so I could use a cheapo timing light instead of my digital. Same reading with both lights.

If I stabbed the dizzy incorrectly, couldn't I just rotate the cap until I found normal timing on the balancer?
I think the heads are too big & the carb is too big. JMO That's what was changed.
What intake ?
 
#5 ·
AllRi5e said:
Thanks for the reply!
No, in its first incarnation it ran at 13 degrees initial. Since then I've installed new heads, the 770 carb and put the battery in the trunk. Next time I'll change ONE thing, check it and move on to next thing.

I added a timing tape the other day so I could use a cheapo timing light instead of my digital. Same reading with both lights.

If I stabbed the dizzy incorrectly, couldn't I just rotate the cap until I found normal timing on the balancer?
Well, the cap won't rotate without the distributor, moving the timing. Just moving the wires one tower should would do it.
 
#9 ·
AllRi5e said:
Too big, eh? I thought the carb might be too big but I didn't think the heads would be an issue. Any suggestions?
210 might be a little large, and slightly effect intake velocity, not a show stopper IMO. You can jet the 770 down if you're running rich.
 
#10 ·
That carb seems ok to me assuming its the vac secondary it'll size itself accordingly

Your sure that timing light is any good with the MSD? Used it before on any msd systems? Some lights cant read multispark correctly

At 20' (for example) timing what exactly happens? Does it just stall out, sputter, or rpm drops?

The rough idle and fouled plugs you describe sounds like a carb or spark issues. At 60' timing what are your rpms at idle? It sounds a little like your using the timing to compensate for bad fuel mixture or even a dead spark on a cylinder.
 
#12 ·
bubbahotep said:
That carb seems ok to me assuming its the vac secondary it'll size itself accordingly

Your sure that timing light is any good with the MSD? Used it before on any msd systems? Some lights cant read multispark correctly

At 20' (for example) timing what exactly happens? Does it just stall out, sputter, or rpm drops?

The rough idle and fouled plugs you describe sounds like a carb or spark issues. At 60' timing what are your rpms at idle? It sounds a little like your using the timing to compensate for bad fuel mixture or even a dead spark on a cylinder.
At 60* it idles roughly at 1300

I used my digital light with this MSD before and it worked fine. I thought the gun could be wrong after I relocated the battery so I bought the cheap one and got the same reading.

Is it possible to compensate bad mix with advanced timing?

20* is a no go. Once I get below 40 the rpm starts dropping, it starts shuddering and dies.

I was thinking weak spark but I didn't think the MSD could "do" weak spark.
 
#13 ·
Custom10 said:
Have you double checked your valve/rocker adjustments? what is the engine pulling for vacuum? maybe a leaking intake gasket. Is the dist power and ground OK?
Carb has vac secondaries. Suppose to be plug a play for cars under 450hp. I think someone messed with it and returned it.

Would tight valves cause this? I did install the rockers myself and it was my first shot at it.

Vacuum 17-19", the gauge shakes back and forth.

I spray the carb base plate and intake with carb spray and listened for any change in idle. No change.
 
#14 ·
First I would do is verify TDC. Its pretty common for balancer rings to slip on the rubber ring, so the timing mark isn't always a good indicator. Don't worry about being a tooth off... that is only a problem with points ignition. With more modern ignitions, it doesn't matter what tooth its on you just turn the dizzy until its lined up right.

Second I would verify the carb tune. Look down the throats while its idling. Is there liquid fuel dripping from the boosters? If there is, chances are its a blown power valve or a needle/float issue.

This is assuming that you have the firing order right. I know, its a stupid thing for me to say, but I have chased all kinds of issues only to find out that I skipped the basics.

Help us out.... cam specs and compression?
 
#15 ·
bubbahotep said:
That carb seems ok to me assuming its the vac secondary it'll size itself accordingly

Your sure that timing light is any good with the MSD? Used it before on any msd systems? Some lights cant read multispark correctly

At 20' (for example) timing what exactly happens? Does it just stall out, sputter, or rpm drops?

The rough idle and fouled plugs you describe sounds like a carb or spark issues. At 60' timing what are your rpms at idle? It sounds a little like your using the timing to compensate for bad fuel mixture or even a dead spark on a cylinder.
I recall some lights aren't compatible, and require use of an Equus type digital light. Yours might be that, but like he says here...check to be sure.
 
#16 ·
AllRi5e said:
Carb has vac secondaries. Suppose to be plug a play for cars under 450hp. I think someone messed with it and returned it.

Would tight valves cause this? I did install the rockers myself and it was my first shot at it.

Vacuum 17-19", the gauge shakes back and forth.

I spray the carb base plate and intake with carb spray and listened for any change in idle. No change.
Yes, tight valves could cause it. Shaking gauge indicates a valve that isn't closing (or cracked rings, or a few other issues that aren't likely with a new engine assembly)
 
#17 ·
AllRi5e said:
At 60* it idles roughly at 1300

I used my digital light with this MSD before and it worked fine. I thought the gun could be wrong after I relocated the battery so I bought the cheap one and got the same reading.

Is it possible to compensate bad mix with advanced timing?

20* is a no go. Once I get below 40 the rpm starts dropping, it starts shuddering and dies.

I was thinking weak spark but I didn't think the MSD could "do" weak spark.
MSD can do weak spark and since your #1 cylinder has a good spark you'll read everything fine with your light. You could have 1 or more dead cylinders or maybe a wire crossed? You might be able to use the timing light to test for a spark by just timing off each of the other cylinders (just looks for the light to flash but disregard the timing readings). The MSD is probably working fine but the sparks not getting to where it should. Just a guess, could be as others suggest.

60' is insanely high and if thats accurate its going to cause damage eventually. At least get down to below 40 if you can and work on it at idle from there.

How well adjusted is the carb idle mixtures and idle speed screw? If you drop below 30' timing can you increase the idle speed (with the screw on the card) to keep it running or does it still die?
 
#18 ·
curtis73 said:
First I would do is verify TDC. Its pretty common for balancer rings to slip on the rubber ring, so the timing mark isn't always a good indicator. Don't worry about being a tooth off... that is only a problem with points ignition. With more modern ignitions, it doesn't matter what tooth its on you just turn the dizzy until its lined up right.

Second I would verify the carb tune. Look down the throats while its idling. Is there liquid fuel dripping from the boosters? If there is, chances are its a blown power valve or a needle/float issue.

This is assuming that you have the firing order right. I know, its a stupid thing for me to say, but I have chased all kinds of issues only to find out that I skipped the basics.

Help us out.... cam specs and compression?
I turned the idle screws all the way in and the engine died. So, the valve is power valve is working. At least, that was how Holley siad to test it.

Don't sweat the firing order thing, it would be cool if that was it. I once couldn't get a car started, only to realize I didn't ground the engine.

I checked the firing order and wire placement several times.

Compression test reults were 160-170 across the board.

Cam is Comp Thumpr
lift .479 intake .465 exh
duration .319/ .310
 
#19 ·
bubbahotep said:
MSD can do weak spark and since your #1 cylinder has a good spark you'll read everything fine with your light. You could have 1 or more dead cylinders or maybe a wire crossed? You might be able to use the timing light to test for a spark by just timing off each of the other cylinders (just looks for the light to flash but disregard the timing readings). The MSD is probably working fine but the sparks not getting to where it should. Just a guess, could be as others suggest.

60' is insanely high and if thats accurate its going to cause damage eventually. At least get down to below 40 if you can and work on it at idle from there.

How well adjusted is the carb idle mixtures and idle speed screw? If you drop below 30' timing can you increase the idle speed (with the screw on the card) to keep it running or does it still die?
It'll fire at 30* but won't start, I tried increasing the curb idle to compensate but it just dies.

Its a new engine with a ton of new parts, I hate to damage it. Dialing it back to 30 and trying to start it from there seems safer than waiting for it to detonate itself to death. My starter doesn't like cranking it at 60 anyway.

Could a faulty pick up module or coil cause weak spark? I read that these parts either work or don't.
 
#22 ·
Comp Thumpr. How many times are we going to read posts from guys that could not get their engine tuned with one of these turds installed in their engine? Too much overlap means not enough vacuum signal at idle for the carb to function.

OP, do you mean to tell us that your initial timing is set at 40 degrees tdc with an HEI that adds 20 degrees more mechanical advance? How would you even get the engine to turn over? Check your timing light or your balancer. One of them it totally out of whack.
 
#23 ·
1932bantam said:
did you have the 1.6 rockers on the other heads? if not ,pushrod length- was the cam degreed ? almost sounds like a flat lobe but you said had good compression on all 8 .just throwing out an idea or two
No, I had stock rockers on the old heads. The head builder sold me longer pushrods for this setup. I did not degree the the cam. I don't know if its "good" compression, but its even across all cylinders.
 
#24 ·
cool rockin daddy said:
Comp Thumpr. How many times are we going to read posts from guys that could not get their engine tuned with one of these turds installed in their engine? Too much overlap means not enough vacuum signal at idle for the carb to function.

OP, do you mean to tell us that your initial timing is set at 40 degrees tdc with an HEI that adds 20 degrees more mechanical advance? How would you even get the engine to turn over? Check your timing light or your balancer. One of them it totally out of whack.
Initial timing is 60 degrees. I know its crazy. I've used two timing lights and I'm checked TDC from the mark on the balancer to the rockers no less than 10 times. I have a high torque Hitachi starter. I don't think a stock starter would crank the engine like this.

I now know the cam isn't great. I would have gone full roller if I knew how the cam was before I bought the engine. If I have to remove the intake I will swap it out.
 
#25 ·
I'm just trying to gather as many ideas as possible before I take my last stab at this thing.

Valves being too tight could cause this. Whats the best way to attack that? Back all the rockers off a turn?

How about a spark issue? Bad coil or pick up? Is it possible? My MSD isn't grounded at the battery like MSD likes, its grounded at the block.

I've seen similar post to mine but no one posts the solution. I'll try everyone's ideas and report back. If I have to take it to shop, I'll report those results as well.
 
#26 ·
It is surprising that a cam with that duration would pull 17-19"wg vacuum, must be an inaccurate gage.

The compression test may rule out valves being held open from poor valve adjustment.

Yeah the thumper cam blues is becoming a familar tune but the engine ran OK before the head swap?

I am thinking intake gasket seal failure or misallignment (not the carb gasket)

Also you should use a piston stop and verify TDC not the rocker arm position. I doubt it is actually 60 inital, check for true TDC:

http://www.crankshaftcoalition.com/wiki/Determining_top_dead_center
 
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