AFR ?

[mike454]

I have a 1993 Chevy Truck 3500 4 door ramp truck that I just acquired, it has a 7.4 4l80e 16147060 BAMP

The previous owner said it had always, since day1, had problems with turning the exhaust manifolds cherry red while pulling.....

Well sure enough it does, just sitting here idling the manifolds are at 635* deg on my infrared temp checker....isnt normal like 300to 400?

My question is what can cause it to do that? He said its had 4 sets of manifolds on it over the years, and has pretty much done this since it was new.

My thought was originally that it was too rich and the unburned fuel was causing the overheated manifolds.

But I just got a new AEM Wideband,and it shows under wot 15.8/16.5,and cruise 15.3/15.5 to 1,which is pretty lean right?

Have been thru all the tune up stuff, and timing settings its at 8 degrees now with connector unplugged, and I tried it at 2 and 4 degrees and it still did it but was down on power a little,
'seems to run best and not ping at 8.

Exhaust is new 2 1/2 back to 2 brand new flow masters,no converters, so everything there seems to be ok, no restrictions.


Fuel pressure is a little low at 11 psi.....

I'm getting ready to work on getting that up to 15 or 16?

And to do some logs, over the weekend.

any thoughts ? or anyone else ran into this?

I know I've heard about this year motorhomes doing it