Smell at idle

Belgian1979vette

Belgian1979vette

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I have run my engine again today. Made some adjustments with regards to ignition timing curves and reconnected the pcv to the carb. Was able to close the throttles some more, but the stink remains. If I stay in it's neighborhood when it's running long enough I have to take a shower :skeptic:

Ok, this is a long duration, big overlap cam with only 7 inches of vacuum, but still...anything that can be done about that or is it going to improve once it warms up fully ?
 
Raise your idle rpm to 900 or 1000 rpm and lean out your idle mixture to about 14:1 AFR, and run more timing - about 30 degrees including vacuum advance total.

As a starter, I'd run 15 to 18 degrees initial and have a vacuum contribution of 15 or 12 degrees - just make sure that the vacuum canister is fully advanced with your vacuum at idle - there's one for the mid-60s Special High Perf SBCs that had full vacuum advance at only 8" Hg.

Depending on how much centrifugal advance you have, you may need to limit its contribution to keep the initial + centrifugal to 36 degrees.
 
larrywalk said:
Raise your idle rpm to 900 or 1000 rpm and lean out your idle mixture to about 14:1 AFR, and run more timing - about 30 degrees including vacuum advance total.

As a starter, I'd run 15 to 18 degrees initial and have a vacuum contribution of 15 or 12 degrees - just make sure that the vacuum canister is fully advanced with your vacuum at idle - there's one for the mid-60s Special High Perf SBCs that had full vacuum advance at only 8" Hg.

Depending on how much centrifugal advance you have, you may need to limit its contribution to keep the initial + centrifugal to 36 degrees.
Click to expand...

With vacuum, I'm at 26 right now. I had to limit the vacuum advance to somewhat around 10° full open. That limited the initial at 8°. Might have to get the msd limiter that doesn't change spring pressure in order to get more advance at idle.

the smell of a hot rod :bounce:
 
Timing is only part of the fix - make sure that the mixture is right and that there are no misfires, too!
 
Went at it again today. Couldn't get it to warm up. Had a infrared meter at my disposal. Temp was around 55-60° C not more.

Took the car out on the driveway which was no fun, because of snow. It stalled when trying to get it going in first. Difficult to start also.

On some advice that was given, I took my dizzy out to change to a 10° advance bushing, but decided to give locked out timing a chance. First set at 32°. AFR was way to lean (17 range). Corrected that and set timing to 36°. Vacuum connected to ported.

AFR's are much more stable. Idle screws on the Holley are so far out they do not seem to have much effect anymore. AFR at idle is around 13.7-14.3. Every now and then a spike to 20, but a lot less spikes than before.

Didn't get it out on the driveway though.

I'm not much for locked out timing, but that seems to be where I'm heading for the moment.
 
36 deg full mech or total? hook the advance to manif and see if it likes it. If 36 is full mech, how much is the vac pulling additionally?

Spikes = misfires
 
36 mechanical locked. The vacuum to manifold setup was no good. When I put it in first and wanted to get it going, apparently manifold vacuum went down, causing the vacuum to pull out ignition timing. So I was left with initial only (18°) which was not enough apparently since it stalled on me.

Only other alternative would be to set idle rpm higher (like 1100-1200) and put in light springs with a 10° bushing.

Might need to go immediatly to my electronically controlled distributor and MS ecu to get it done right.

It's pulling 2-3" additional with it.

I have been wondering about the misfires and what could be causing that. The cam ?
 
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Do you have a crank retard? If not you will break the mounting ear on your block, guaranteed! All it takes is 1 good kick bank and you're toast (or if you're lucky the starter will break)

What plug gap? What is your ignition combo? What coil?

Xanders corvette has idle misfires also, the sidepipes are partially to blame. He's running stupid advance too but the motor seems to like that better and it's running fine & detonation free. The only difference is... he doesn't mind the smell. A good drive and you smell like eau de hydrocarbons
 
gap is .045 I believe. MSD Pro Billet HEI at the moment. Will convert to an electronical dizzy when going to the final EFI setup after break in.

I was weary about running the locked out timing. However it does seem to like it in the sense that it seemed to stabilize the AFR's a lot. I have a 14 and 10° bushing for the MSD. So with that I could go to either 22° or 26° initial.

No spark retard at the moment. Cold starts are not a problem. It's hot starts i'm worried about.

What amount is usually enough to get problems with the starter ?

I see 3 other options :
- going to a 10° bushing unless 26° initial will create the same starter issue.
- running higher idle rpm (like 1100), with loose springs so that it will pull in some centrifugal advance combined with either an 18° or 14° bushing.
- going to the efi dizzy and hopefully there is some programmable start retard.
 
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