[carsavvycook]

Originally Posted by Bill Adkins

I feel I'm learning from most everyone here with the different views and explanations. I can say that my background is extensive and well developed but from a different angle so to speak so don't hold back.... carp it may something I for one never thought about
Bill

Crap Bill, Your 'experience' with dyno's is invaluable.

Personally, I have been tuning engines for almost 40 years, and I have had past experience with dyno shops. They have not given me the in-depth information, or a reason to believe them, that you seem to be able to explain.

Fine Tuning is an art, not learned by reading, but only by hands on experiencing success's and failures.

Maybe we can meet some day, and talk some theory on tuning. I'm sure you could teach me something.

Stephen

[red65mustang]

eric,
how old are you????

I'm asking because your posts read like you are suffering in the teenage years brain syndrome stage we "all" go thru in life...
your posts show you are a plenty bright person but I need to change how I word my posts...
ex:
would have been better and easier to understand that chart if I had photo-edited to show crank degrees on the vertical chart axis...
I did post examples (7 turns =26* added) which you are mis-understanding/reading...

(LOL but true,,,they have tested and proven teenage brains synapse do fire based on the excess hormones causing "wrong think" mis-fires...)

NO!!!
do not wait till you can "get around to" correcting the vac adv with your timing light...
just about all the adjustable units are factory preset to the mid-turns position (to start out set to add 10-12 approx)...

use your hex wrench to count the total number of full screw turns from off to full on (usually 8 or 10)...

set the unit to be at the mid point of the total turns,,,immediately or leave the truck parked

OR,,,
(smarter!!!)
unplug the vac adv from the carb and cap the carb hose nipple immediately till you can get a light on it!!!!
(it won't perform great on mechanical timing only but won't hurt anything over just a day or two)

WHY,,,
we haven't looked at the plugs yet!!!!
you may well have a oil in the chambers problem which totally yuchs up the chambers with carbon which can lead to detonation with added timing...
the mis-fires at start up at idle are a clue/symptom of a possible oil problem...
(pcv is not the only possible source for oil fouling plugs)

[eric32]

Well guys back again. Well to start off with I am 34 years old, no I am not some dumb hilljack from the state of Ohio and Yes I graduated from high school with a good grades but heck even people who did bad in school can still be smart. Look at Einstein. I might sound dumb because of the way I might type things on here that is not my intention. I don't use a computer for a job or making extra money on the side so my computer manners might not be the best. Sorry if I offend here.

I got my timing light out to adjust my vacuum advance and I kept backing it out and it still gave me a little too much advance at idle. So I just said heck with it I will back it all the way back to give me the least amount of advance at idle and go from there. Well I unhooked my vacuum and rechecked my initial timing and its still where its supposed to be just to rule anything else out.

Well i hooked it all back up and put my timing light on and with vacuum advance hooked up I have around 32 to 34 at idle. I can't adjust it to give me any less so any suggestions. So now I have 16 at idle and 34 total timing by 3000 rpm and with 16 to 18 degrees of vacuum advanced timing added I now have a total of 50 to 52 at the most when cruising with vacuum advance fully engaged.

Hell I could buy another vacuum advance canister but it will only do the same thing. The are all made the same to adjust wise. I don't want to retard my initial timing cause then it will take away my total timing. I get about 16 to 18 degrees with my mechanical advance. As far as the missing goes it's not because of my carburetor secondary's opened up. I only have them just cracked a hair to where if you turned the screw just a little bit it would be full seated.

The stupid miss happens many different times. Some times it comes and goes and some days it happens more then others. During startup up or at idle or when cruising but mostly during idle and startup but even after its warm but the heck with it for now. I at least want to get my vacuum advance going good. Right now my engine is still running way much better then it ever has with full manifold vacuum advance. Man I will never use timed port vacuum ever again. Thanks guys for all your help and input. For now I have it where I can get the least amount of vacuum advance and it's a hair too much but close. Any way to make it give just a little less timing with out touching anything else?
have a good weekend
Eric

[cobalt327]

Use THIS to limit the vacuum advance.

[ericnova72]

You need to limit the travel of the vacuum advance unit, either with the Crane vacuum advance limiter plate #99619-1 or with a fabricated plate as shown in post #91 of thread "a different 307 sbc build, need some advice" here at hotrodders.com. The adjustable vacuum can only allows you to adjust the amount of vacuum it takes to move the diaphram, not how far the diaphram moves in degrees at the magnetic pick-up. All you are adjusting with the screw in the nipple is the start point and not the amount.

EDIT: Cobalt beat me to it.

[eric32]

Ericnova and Cobalt thank you

Ok that would definitely help me out but I know crane no longer makes there vacuum advance kits anymore so how does it work and go on? I did have the instructions downloaded but lost it on my computer restore.

I guess my Uncle from Florida is coming up and has some high dollar stuff to hook up to my ignition and can tell how much voltage I get at each plug wire and some other things but did not have much time to talk to him so that will help to trouble shoot things and find out the miss problem. Any way nothing more to discuss about the miss but that limiter plate will do the trick. Just need to know to install and use it then i will be good to go.
Have a nice weekend.
Eric

[carsavvycook]

Originally Posted by eric32

Well guys back again. I got my timing light out to adjust my vacuum advance and I kept backing it out and it still gave me a little too much advance at idle. So I just said heck with it I will back it all the way back to give me the least amount of advance at idle and go from there. Well I unhooked my vacuum and rechecked my initial timing and its still where its supposed to be. Well i hooked it all back up and put my timing light on and with vacuum advance hooked up I have around 32 to 34 at idle. I can't adjust it to give me any less so any suggestions. So now I have 16 at idle and 34 total timing by 3000 rpm and with 16 to 18 degrees of vacuum advanced timing added I now have a total of 50 to 52 at the most when cruising with vacuum advance fully engaged.

Hell I could buy another vacuum advance canister but it will only do the same thing. The are all made the same to adjust wise. I don't want to retard my initial timing cause then it will take away my total timing. I get about 16 to 18 degrees with my mechanical advance. As far as the missing goes it's not because of my carburetor secondary's opened up. I only have them just cracked a hair to where if you turned the screw just a little bit it would be full seated.

The stupid miss happens many different times. Some times it comes and goes and some days it happens more then others. During startup up or at idle or when cruising but mostly during idle and startup but even after its warm but the heck with it for now. I at least want to get my vacuum advance going good. Right now my engine is still running way much better then it ever has with full manifold vacuum advance. Man I will never use timed port vacuum ever again. Thanks guys for all your help and input. For now I have it where I can get the least amount of vacuum advance and it's a hair too much but close. Any way to make it give just a little less timing with out touching anything else?
have a good weekend
Eric

It still sounds to me of being too lean. A slightly lean running engine will run crappy on dry days, and then good on 'overcast', or 'rainy' days with higher humidity. This is referring back to my post on 'altitude', 'barometric pressure'..,.etc.

Weather can make a huge difference in 'tuning', and how well it runs.

What I am trying to explain, is the denser/cooler/heavier the outside (ambient density) air is, the richer it will run. Vise, Versa. The dryer the air, the leaner it will run.

Just trying to help, and spark some more interest from fellow members.

[a1supersport]

Hey eric,

Did you pull the dist. cap and check for any arcing? Whenever I use an HEI, I usually skip the "replacement" cap and rotors, and use a better brand. The stock coil gets pulled-out also (mostly because they seem rpm-limited). The in-cap (accel), or external coil (any aftermarket brand) should work well.

Noticed everyone is focusing on the engine side, but by-passing the "miss" you keep mentioning. I'm trying to think back because there's a lot of entries in this thread...but did you say the "miss" was around 3200rpm? My guess is it's in the dist., if not the coil itself.

[ericnova72]

Originally Posted by eric32

Ericnova and Cobalt thank you

Ok that would definitely help me out but I know crane no longer makes there vacuum advance kits anymore so how does it work and go on? I did have the instructions downloaded but lost it on my computer restore.

I guess my Uncle from Florida is coming up and has some high dollar stuff to hook up to my ignition and can tell how much voltage I get at each plug wire and some other things but did not have much time to talk to him so that will help to trouble shoot things and find out the miss problem. Any way nothing more to discuss about the miss but that limiter plate will do the trick. Just need to know to install and use it then i will be good to go.
Have a nice weekend.
Eric

The limiter plate is still available from Summit, it bolts in under the end screw that holds the vacuum advance can into the distributor, with the sawtooth edge up against the hook end of the advance rod, it becomes an adjustable return stop in 2° increments for the advance mechanism.

[eric32]

Yeah I know how weather can change the tune of a carb so I know that does not help at times. I don't have a stock cheap type cap and coil on the distributor. I have an after market 50,000 volt coil with performance plug wires from summit. Am running a after market control module as well. But anyway miss can happen at any rpm just not at 3200 rpm.

Summit won't have that plate till the 10th of May so I guess I will have to wait for a couple of weeks till they get them. But thanks Ericnova72 on the info. I have pretty much an idea on how it hooks up. I will order one once they get them. But just to be curious if I buy another brand of a vacuum advance canister will they have a different adjustable rate? I know advance autoparts sells them from Accell. I can buy another one if it will allow to have less then the one I have now. Everyone take care.

[cobalt327]

Did you also check W/Jegs, Competition Products, Northern, Rock Auto, etc.? SOMEONE has that piece in stock, I'd bet.

Instructions- http://cranecams.com/pdf/254g.pdf

[cobalt327]

Instructions for the adjustable vacuum canister = http://cranecams.com/pdf/210g2.pdf

Keep in mind that if it's not detonating under load, it is not too much vac. advance. As long as it's adjusted to not give advance too early, you'll be OK.

The vacuum advance drops the timing same amount of timing that it gives at the same point, when under load (like when accelerating or pulling up a grade, etc.). You can adjust it so that your engine will suffer zero damage as long as it's not detonating.

If it still detonates, or you feel that you want more vacuum advance earlier, just not as much (I would want to limit it to around 10º-12º), then use the limiter in conjunction w/the same vac. can you now have. There's no advantage in getting a different adjustable vac. can, IMHO.

[carsavvycook]

Reading the posts about spark advance(dist., coils,....etc) makes me think of a spark problem.

Your spark plug heat range should be in the middle, such as a #25/#26 Autolite. The plug gap(with your ignition system) should be no more than .045 of an inch. A closer to .035 plug gap may work better.

What kind of carb, and is it stock out of the box? I don't remember.

Everyone has my mind thinking! This is a good thing!

[eric32]

Thanks cobalt I will have to check with all of them. Also carsavycook my carb is a holley 600 1850s model and I am not running it stock out of the box. I went up to 70 jets in the front and 76 in the rear and running the silver spring for secondary's. The stock jetting I figured would be to lean for my build cause my Dad has the same exact carb on a 302 with the stock jetting and it was just right for his motor but from reading all the chevy magazines and my holley tuning book the more power an engine makes depending on the setup will require bigger jet sizes from say 65 on the primary.

I did try 69 but it seemed like it was a little lean so went to 70. Plugs are NGK 6630 which is the same range as an autolite 26 which I had before the NGK plugs and they look the same gapped at .045. Also I have not had any pinging going on with my vacuum advance set where it's at now. I will leave it there for now and even getting on it going up a steep hill in drive there is no pinging or else I would not have it hooked up at this point. I'm not stupid to leave me motor to detonate like that. I have seen pictures of what happens to a motor over time or what could happen in an instant. thanks guys
Eric

[red65mustang]

eric,
your posts ARE well written...
I meant no offense asking your age...
my apology if needed...
("my dad" posted by you and "I am a novice wanting to learn" sounds like a young person)

if you would please just answer some of my questions instead of asking more questions this thread can be short!!!

it's a always same step#1,step#2,step#3, etc, process of elimination to diagnose/solve the mis-fire and then go onto a always same step by step tune the motor process....
(with answers from you)

what brand and model dist is on the motor???
is the adjust vac unit original to the dist???
(you should only need the advance limiting plate if/when building a "custom" dist like swapping from a oem fixed range vac unit to a aftermarket adjustable unit)

let's take a first shot at testing to cure the random misfire because it is quick to do...
ANYTHING solid state operating with only 5VDC potential is extremely sensitive to resistance on the neg circuit supply side from the batt neg post...
(energy flow on DC neg ground is from the neg to the positive using the steel body for a supply "wire" to the device)
many dist's are lacking for adaquate/totally stable/constant/rock solid ground source 5VDC needed condition....

simply hook up a #12-14 jumper wire batt neg post direct to the ground connect on the dist and go for a test drive...

NO,,you can't just ignore a repeated misfire condition,,,when the plug doesn't fire,,,that can/will cause the coil to build to max KV possible (50-60KV) and that mega electrical juice charge (which could weld metal just for the idea) will/has to find a path to ground!!!
you are over heating/ruining the coil and likely causing arcing under the cap and eventually that will cause a crossfire which can do major damage (all V8's have 2 plugs that fire in sequence on the cap terminals)...

"hopefully" the mis-fire problem source "is" before the 500V approx supply goes to the coil described just above,,,in the spark control IC module itself which what the ground wire test is for...

post back if yes or no the ground jumper cured the mis-fire,,,,it's about a 30%+ chance it will and then just make the jumper a permanent well installed wire= cured...

for the next mis-fire test (if needed) I need to know what brand/model the dist is (ex: all dist have a minumum 5VDC IC chip "turn on" operating voltage)

PS: it's running better "sooner" because the added vac adv idle timing Hg on manifold port is cleaning the cylinders faster combined with you were able to back off the rpms idle adjust screw to be on idle only gas supply...
when driving vac advance gives the exact same added timing whether on timed or manifold...
(you proved the original 12Hg idle wasn't enough and the carb setting was off,,,not whether either port is good or bad)