Please help. Red hot primary on new motor

Momar
02-10-2003, 11:39 AM
Well if for any details of what I have already checked you can go here http://www.thirdgen.org/techbb2/showthread.php?s=&threadid=159455 but here is an overview:

I just got my 350 all put together and in the car along with new exhaust and headers, xe268 cam, ported 416 305 heads and maybe a couple of other minor things. Anyway, when I started it up the #7 primary got red hot. The #1 looked pretty hot but not red. The rest seemed to be decent but maybe a little hotter than they should have been. Anyway, I think it may be related to my timing somehow. I had my cousin reset the valve lash because this was the first time I had done it on my own and after he did it it still did the same thing. I used a compression tester and no mater whether it was a cylinder that got hot or not they seemed to all be right about at 150. I checked and while at top dead center according to the timing tab the rotor does appear to be pointing at the right cylinder(#6 since it was the exhaust stroke for 1). I also checked the keyway on the crank to see if it was in the right spot when the timing tab said top dead(45* from top) and it appeared to be pretty much exact for all I could tell. The reason I think it has to be timing related somehow is because when I try to set the timing it will only run decent if it is above the timing tab(advanced?). I think that if I moved it far enough away from it it may not have even got the header so hot. When I try to adjust it down to about what it is supposed to be it backfires through the carb and dies at about 8*. The only suggestion that I have heard that I dont think is ruled out for the most part is if the timing chain is a tooth off or something but I dont know if that would cause these symptoms or not. Also was trying to make sure I had that the disributer was in the right tooth. It was as far as I could tell but cant guarantee it. Would either of these cause this problem?

Thanks

Ben

Osmosis
02-10-2003, 07:02 PM
A few years back i put a big cam in my corvette, had the l98 motor. My headers were glowing after i took her around the block. I pumped up my fuel psi from 43.5 to 50 and it solved the problem, however, it could be the opposite, runing rich. I would pump the psi up to 50, take it around the block and see what happens. If you have a scan too30l, that will be even more helpful.

keepus posted!

TheGreatJ
02-10-2003, 08:01 PM
It isn't uncommon for the ring on a harmonic balancer to slip a little. Try setting your timing by ear and if the primaries cool down, then your balancer is off. Also keep in mind since it's a CC carb and distributor, the computer could be retarding your timing. I don't remember if the old q-jet cars had knock sensors, but if so then false knock could cause this to an extent. Hope it helps...

Momar
02-10-2003, 10:48 PM
Osmosis, it is carbed so it has a mechanical fuel pump and doesnt have a fuel pressure regulator.

TheGreatJ, it does have a knock sensor, but I have the computer disconected from the distributer while I am trying to set the timing. Also, I dont think it is the balancer because it is brand new. Also, I checked and the keyway on the crank was at 45 from the top when I had the timing tab lined up at 0 degrees and the rotor was pointing at #6(exhaust stroke for #1). Actually, do these things have mechanical advance? If so how much, because I was trying to set it and keep the rpms up around 2 grand to keep the cam oiled good to break in. If it has mechanical advance that could be the problem. I may need to let it idle while I set it. Let me know if this is a possibility.

Ben

Osmosis
02-10-2003, 10:51 PM
hmm, i thought it was a tpi car. You might try advancing the timming a few deg. Just a thought.

Momar
02-10-2003, 10:54 PM
Yes, I think advancing it is what it needs, but I was just trying to figure out why the timing mark was so far advanced already. Does anyone know if the computer controlled distributers had any mechanical advance?

Ben

90rocz
02-10-2003, 11:59 PM
No mechanical advance on computer contrlled distributors.
Hi, here's what I see.
You say that No.1 is hot too but not red.
Well that's telling me that 2-cylinders on the same side of the motor farthest from the carb, fed by the same side of the carb(assuming dual-plane intake) are HOT(AKA=lean).
Timing will uniformly affect all cylinders, fuel will be more extreme the farther from the carb. I would say try another carb or richen the mixture on the side "opposite" the hot cylinders, since the drivers' side of the carb feeds the passenger side cylinders and vise-versa.

Momar
02-11-2003, 08:02 AM
OK, that kind of makes sense. I dont have access to another one of these carbs though. This is the second one I have had on it because the other wouldnt run worth crap. Also, I know I have a timing problem because I cant get it under 8* without it backfiring out the carb and dying. So I may have a couple of problems but I don't know how to fix the one for sure. How do you adjust the fuel mixture on the primaries on these carbs?

Ben