DZLPWR

Just wondering why my friends 1986 blazer has red exht manifolds at idle. The truck idles fine for a while but over time it just seems to just want to just shut off. Its got a edelb carb and mild cam, thats bout it. Just been freshened up with rings, bearings,gaskets and such. It wont idle when warm in gear either. Not sure whats up but i told him we needed to get the timing down to at least 10* ( hes around 16* now) before going further, but the truck wont stay at a steady idle, so timing it is a PITA! It seems to idle down slowly and eventually shuts off. Whats up with this thing?

vzdude

Sounds like the choke is stuck on, or waaayy out of adjustment. Thats where I'd start! Carb trouble..............fuel injection is the only way to fly!

Fronty Owner

timing issue is the only thing I have seen cause the exhaust manifold to get hot.

try advancing the timing a degree or so.

Hvytrkmech

Does it still have the catalytic converter on it? That was the most common problem in the mid to late 80's, they love to plug up. The symptoms you are describing is exactly what would happen. Timing can always be an issue no doubt about it, but causing the manifolds to glow red and stalling the engine is usually an exhaust restriction

DZLPWR

He had the heads ported to match a set of headers, but the manifolds are on at this point till he makes it to a muff shop. Would this have a real effect on it?

I dont think the cats are still on it.

"timing issue is the only thing I have seen cause the exhaust manifold to get hot.

try advancing the timing a degree or so."

His timing looks to be around 14* right now, should i go higher??? I thought we should try and get it down a bit.

I also asked him about spark knock and he said yes at first but last night i pointed out an exh. manifold leak and started to think that may have been what he heard thinking it was spark knocking.

chaikwa

The leaner you run a gas engine the hotter it's gonna run. Don't know if it'd get hot enough to redden the manifolds, but it's something to consider.

chaikwa.

Need95-00CTD

^^^ What he said!

It sounds exactly like what happened in my Jeep's straight 6, I had bought a carb from Holley, when I got it it didn't match the part number I ordered, but it fit, so I slapped it on and it ran. Little did I know it had a bit smaller set of jets in it...a lot smaller...and it ran so lean I ended up cracking the exhaust manifold.

The timing was off a little bit too, so that didn't help either. Good luck tracking it down, gassers can be a bit hard to tune with those sloppy carbs.

DZLPWR

Yeah, i hear ya, but the kicker is it ran fine with the same carb before the "mechanic" tore it down and rebuilt it. It did sit for about 6 mo. maybe the carb started to gum up a little? We drove it home 30min from the guys house and it ran good, but it did start cutting off at stop lights on the way. It just doesnt idle well. Last night we started it warmed it up for 15min or so and it was good and idleing, but when i went to time it, it started to drop rpms a bit and eventually would shut off unless we revved it a bit. Even then it would start to cut off 30 sec after revving it.

Hvytrkmech

In 86 Chevy was using TBI on their engines, did your friends blazer have TBI on it originally?

jmd025

No i think 87 was the first TBI for the pickups. Bought an 86 brand new and it had a carb.

Hvytrkmech

Yeah your right 86 the last year for ESP, then TBi in 87, thanks

Need95-00CTD

It might have gummed up, but was the mechanic that tore it down the one that ported it out and got the air flowing better? If you increase air flow, you need to increase fuel flow...otherwise you'll run lean.

It not quite as easy as the diesels, where you can add more air and run cooler. If you add more air you run hotter in a gasser, seems stupid, but it works that way. Thats one of the reasons you see tuners blow their motors after they slap on a turbo, they don't put in bigger injectors or compensate for all the extra air, and they burn up the motor.

j-fox

Edelbrock carbs are known to drip from the venturis if things aren't right. This will make it idle wrong and run rich.
running rich makes the manifolds glow because fuel is still burning in them.
Several things are involved.
Exhaust restiction
Wrong fuel ratio
timing. More usually reduces the problem.

rip 112

^^^^ that was what I was thinkin too...I'd also look at the vacuum advance, my old Ford had that problem idleing down to cutting off and reversing rotation for a stroke. Ended up being that with which we altered the timing to make it run good, tuned the carb to run right, and after replacing the advance everything was off, tuned it back in to what it should've been, and all was well.

j-fox

If it is running too lean, ussually the water temp goes high.
Start it and remove the air filter, carefully look down the carb and look for the veturi to drip. I can hear it drip most of the time.
Also the timing marks may have slipped. By the time you get to 16-20 degrees advanced it is hard to start.