Hey everyone, I have a 383 sbc TPI 10.5:1 (Trickflow 23 head, Accel manifold, AS&M runners, ported plenum, Ford Red Top 30# injectors, SLP headers and a 3” cat-back exhaust).

During my 700R4 to T56 transmission swap, I changed: my plugs from Accel 416S (shorties) to NGK FR5 7373; my throttle body from stock 48mm to BBK 58mm; and I changed my cat from Catco CTO-6007 to CTO-9007.

When I run the car (idle and stationary), I smell excess fuel and after 10-15 minutes or so the cat starts to glow (and the floor pan gets really hot).

I pulled a few plugs and it appears the car is running rich. Fuel pressure is 43 PSI. #2 injector seems to be pulsing harder than the rest by feel. O2 sensor was all black and needed cleaning further confirming excess fuel.

Thoughts? Is it tuning do to tb change? Is it the wrong temp. spark plugs? Did my injectors take a dive?

Note, I suspected the engine was seized (it was not, see https://www.thirdgen.org/forums/tran...ed-now-no.html) and loaded the cylinder with WD40, but turned the engine over several times trying to drain the fluid through the spark plug holes.

Time line: ran the engine for 30 minutes to discover a glowing cat and hot floor boards; check all connections and plug wires then ran the engine again for 15 minutes to confirm glowing cat, hot floor boards and excess fuel smell; cleaned O2 sensor then ran the engine again for 15 minutes to confirm glowing cat, hot floor boards and excess fuel smell still exist.

Any and all help, comments, suggestions, and advice is greatly appreciated!

Jim

 

Humm, no thoughts?

I was thinking about switching the tb back to stock to see if that was the issue. I am first going to take a thermo gun and check the temp of each down-tube to make sure the plugs are all firing and i am not just dumping gas.

I thought i changed to a more effective cat (at least larger) and better plugs (although I never really had bad luck with the Accels).

Would switch to such a large tb cause air/fuel issues? I have heard of idling issue, but it smoothes out after a minute to a nice 600-700 rpm.

Thanks in advance.

 

The cat is hot because the excess fuel in the exhaust is being burnt off there , not because of a problem with the cat

Excess Fuel Entering Exhaust.
"The fuel that powers your vehicle is meant to burn in the combustion chamber only.
Any fuel that leaves the combustion chamber unburned will enter the exhaust system and light-off when it reaches
the catalytic converter. This can super-heat the converter far above normal operating conditions and cause a meltdown.
Possible causes are an incorrect fuel mixture, incorrect timing, corroded spark plugs, a faulty oxygen sensor,
faulty fuel injector or a malfunctioning check valve."

 

Has the tune been adjusted for the larger injectors and other engine mods?
Many run 24lb injectors on 383's
You don't mention what cam you have?

 

Nowhere in your description do i see that you have done anything with the tune? If not why not? You cannot mod these engines like you have done and then run a stock tune, especially if your running speed density,Although with all your mods a MAF system would be lost too. You will kill the rings in that engine real quick if you keep dumping all that fuel in there.

 

Thanks for the thoughts.

I had a tune for everything except the tb modification (and the trans swap). and seemed to run fine with the stock tb. The cam is Comp cams extreme energy 272 HR and it is a speed density system.

I verified with a thermo-gun that all cylinders are firing. And I bumped up the fuel pressure to where it should be.

I suppose I should check the timing to make sure it didn't change...? Is there a way to check to see if my sensors are running correctly (i.e. O2 with an ohm reading)?

Possible causes are an:
incorrect fuel mixture - would the tb change affect this or is it a sensor issue?,
incorrect timing - I will check this.,
corroded spark plugs - they are new.,
a faulty oxygen sensor - can i check this rather than just replace it and see?,
faulty fuel injector - can i check this rather than just replace it and see?,
malfunctioning check valve - what check valve?

 

Did the cam get installed properly and degreed?
Is the base timing set properly?
Valves adjusted properly?
TPS set correctly?
How about raw fuel in the fuel PSI vac tubing??

Just a quick FYI, I'm running a stock 89 350 chip in a stroked, poked, solid roller cam, mini ram, afr 235 headed 400 motor.
It runs fine but yes it will be better w a tune.

 

I put about 1500 miles on this engine prior to blowing the transimission. While swaping the trans from a 700R4 to T56, I made only 3 other changes 1) tb 2) plugs 3) cat. I was tunned originally. Engine seems to run fine and souns good. Just lots of fuel and the cat gets hot.

 

Check your TPS output voltage. Needs .54 volts+/- at idle I think.