Thread: 383 <gasp> stroker runs <cough> rich

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Yet another post on how to find the right carb and its settings.

1965 Chevy II Nova, 383 stroker, flat top pistons, 202/160 double hump heads w/roller rockers, Lunati hyd. 480 lift, 272 duration, Torker II single plane intake, HEI ignition (autolite 25 plugs, I think), Holley 750 double pumper through 1.75" coated headers and hooker turbo mufflers. Response through 5k is great, no hesitation, idles at 650, runs great (or did at the time).

Runs great if you can manage to see as your eyes fill up with tears because of the gas smell. It used to foul plugs frequently. I pulled the plugs this weekend and they are SPOTLESS (could the plugs have cleaned themselves through sitting?). I will run the car and check the plugs again, however, I am pretty sure I had the carb tweaked as best I could for the conditions. I have not re-jetted and can't remember what jets are in it (70 & 80?). Parts counter guy is telling me to jet for a 600 cfm. I have read a lot of posts about bigger carbs are over-hyped and most of the time not needed. Roger that, hind sight is 20/20 and I should have bought a 650, haha. I would like to make this one work before I dump 300 bucks on another carb.

The car has been sitting for a few years. I have changed the oil, filter, primed it, rolled it by hand, and am about ready to crack this thing off again. I wanted to get some feedback though, in case anyone would recommend changing jets or any other changes before I start it. Also, it is not a daily driver, but a weekend hobby, stoplight to stoplight toy. No prospects of a track anytime soon either.

Any help is greatly appreciated!!
Paul

What power valves do you have in the carb and what vacuum are you running at idle. My guess you are pretty low on vacuum at 650 RPM. I also think that comp cam you have might be on with a 110 degree lobe seperation which will lower vacuum at idle.
Check your vacuum at idle and if and your power valves in the carb and if needed change the power valves so that they aren't dumping fuel at idle. You will likely need to put an 8.5 or 10.5 power valve in it if you don't already have that in the carb presently.
On another note, are you getting that much exhaust in the cab of your car, if so you need to find out where it's coming from and fix that.
Remember too that changing your jets doesn't change your carb size, it just makes the mixture richer of leaner, so you can only go so small or large before you get into problems.

Forgive me but my memory is fading. I was attempting to remember all the specs I had while typing from work. As it turns out, it IS a 650 with jets of 67 primary and 73 secondary. So unless someone thinks I should change the jets, I think I will just try these for now while I check other things, like vacuum and a new power valve.

Power valves: the higher the number, the more vacuum you need to close it? So with a low vacuum engine, a higher number would be desirable? Or why can't I just disable it with a plug? I suppose this would have a 3 fold effect: 1) using a bigger primary jet to compensate would just add to the richness I am fighting now and 2) cut down on economy (econa-wha? hahaha, what am I saying!?!) 3) I would guess reduce response unless the secondaries are open.

Would a single plane intake affect this (assuming it is leak free)?



As for exhaust in the cab, driving was fine. It's when trying to tune in the drive way or pulling up to a stoplight and getting the plume rolling forward after stopping.

Thanks for your help!!
Paul

I think I am attaching n older pic.

OK, I thought I would add more on power valves so those of you reading don't walk away stupid after reading what I previously posted.

Power valves: open as vacuum decreases to allow fuel (in addition to main jets) to enter the mixture to increase ... hmmph ... power. So based on that, if I am showing low vacuum at idle, I want a power valve with a lower number, as in opens later, at a lower vacuum, as manifold vacuum decreases as RPM increase. Hypothetically, if I am at 7" manifold at vacuum with a 8.5 power valve, the power valve is going to dump fuel and richen things up. And ideally, if I am at 7" of vacuum with a 5 power valve, power valve is shut until I open the throttle and decrease vacuum to 5", at which time the power valve opens.

(man, I sure hope I'm right)



Paul

So I got it fired. Vacuum is at 10" at idle (in park, will tweak in drive later, MUCH later). Still rich as hell. No fuel spillin' out of the venturis, bowl levels both good, idle screws set. I don't get it. I even put a 35 power valve in the carb. So now I am starting to think it is old gas and I will just run it out and see what happens with fresh gas. So I air up the tires and decide to go for a spin. Everything is running fine, ya know, feels good to be back in the hot rod (man, I missed that stall converter), thumpin' down the road a couple miles. Naturally, I decide to jump on it a bit (bad idea). So I get through second gear and ... POP!! Not real loud, kind of a backfire. I figure, bah, must be timing. Luckily, at this point I am almost home; I make the turn onto my street and it dies. Won't restart and I coast to end of the driveway. I get it restarted and see some ... no, not some ... ALOT of white steam out the drivers side exhaust and decided it was a good time to shut it off. This can't be good. ... ... ... Anyone have a spare fuelie head for sale? I may have cracked this one. Not sure yet. Number 4 plug got in a fight with something and lost. I got tired of working on it today. I got the intake off and header off, I will get the head off tomorrow. STAY TUNED!!! I will post my findings tomorrow sometime. Hopefully its just a valve or even a head and not a cylinder wall or piston.

It was a nice day for a ride in the hot rod though.