exhaust manifolds glowing red on sbc 406

[cheater0]

running a enduro car with a sbc 400 vortec heads 2 barrel cast intake 36 degrees of timing 2 barrel rochester with 74 jets.runs great first 5 laps of feature then the center dump of exhaust manifold starts glowing red on both sides. any ideas checked timing 3 differnt times its right on . any ideas please post!

[SRXSRULE]

Is the water temp going up also? Vortec heads like 32* timing. What are you using for fuel? Have you performed an accurate plug check by killing the ignition during hot laps and letting the car coast or get pushed back to the trailer? Check for any exhaust leaks at the heads too. Eric

[Egoracing]

Timing, To rich, or exhaust leak.

[stock car driver]

vortec on 2 barrel for me always liked 36 on dyno. I think low timing is for 4 barrel stuff. Ive had at least 5 vortec head 406s.

[Graff Spee]

Well its running rich! did you have problems adjusting the idle? It may not be even running on the idle circuit. It is most likley running on the main circuit while idling. You probably do not have enough vacuum to stop the power valve from opening . look down the carb when its idling, do you see big droplets of fuel dripping off of the boosters? If you do, thats whats happening. You can clip the spring coils on the power valve actuater rod till its weak enough to let the vacuum close the power valve. You can also drill 3/32 sized holes in the butterflies. One in each plate. that should let you get it on idle circuit.

[DANNY]

vortec on 2 barrel for me always liked 36 on dyno. I think low timing is for 4 barrel stuff. Ive had at least 5 vortec head 406s.

I agree, I ran my vortec stuff in the heat of summer 34 and when it got around 90 out I went back to 36. I do wonder is 74 enough jet cus thats what I have in my 4412 now on 358?

[sj valley dave]

Carb doesn't know what size of engine it is on...When the carb is maxed out, pulling all the air it can pull through the size of venturi's it has, you get your A/F mixture as good as you can...Doesn't matter if it is a hi rpm 358" or a 454" BBC..When the carb is the blockage and it physically can not pull additional air and you fatten it up, all you are doing is screwing up your A/F ratio...Don't forget that a 500 4412 is really only pulling about 375 cfm when tested with the same vacuum as a 4 bbl carb..

[cheater0]

its not a 4412 holley its a rochester smi 500 cfm carb

[rrcmotorsports]

Did you do a significant change in camshaft this year? Because each and every cam has a different signal to the carb. If your water temp isn't rising and your manifolds are glow then it'd be to rich and vice versa for lean.

[sj valley dave]

rrc is correct...And if it a 500 cfm Rochester 2 bbl, it flows about 375 cfm when flowed like a 4 bbl carb. They use twice the vacuum to flow a 2 bbl carb vs. 4 bbl...It is an industry standard...They rate a 2 bbl at 3" of vacuum and a 4 bbl at 1 1/2" vacuum...

[cheater0]

so what should i do timing checked good checked plug needed aliitle more jet then checked burning good now i got it to where they didnt start glowing till 3 laps left whats left to do thanks for any help

[stock car driver]

What fuel are you running, if you have too much octane it will still be burning in the exh...

[DaveBauerSS6]

Borrow another carb and try it.

[utoslow]

running a enduro car with a sbc 400 vortec heads 2 barrel cast intake 36 degrees of timing 2 barrel rochester with 74 jets.runs great first 5 laps of feature then the center dump of exhaust manifold starts glowing red on both sides. any ideas checked timing 3 differnt times its right on . any ideas please post!

Check octane if car set to long .gas can lose octane blow one up last year. It was glowing we ran 110 and it needed 114.