I am going to throw some ideas out here.
Did you get this car set up like this?
You don't know what cam, what gears, what your converter stalls at and if or not your transmission is slipping. You have an efi and a race oriented distributor and ignition and are talking about putting in an OD that requires alot of work and modifications .
Sounds like you need a full accurate inventory of your car including the condition of everything.
Then break it down into its individual systems and address each system until it is in optimum tune. This will take some time but it is well worth it.
Post some videos in car driving it thru the gears (try early morning with light traffic) and outside the car while idling and revving up. It may give others more ideas about your machine based on the vids.
If your automatic is slipping, it will produce some very black and stinky transmission fluid. That is also just a symptom of fluid super old and never changed.
Do you have a tach? You can tell when a trans is slipping just by feeling the power and watching the tach.
If you suspect your transmission is messing up, research how to adjust your transmission band and kick-down linkage. Get that figured out properly. Then do a filter and fluid change. Pull the pan, dump the fluid out of the pan but leave the gunk on the bottom of the pan. Run your finger thru it once and post some well illuminated pictures of the goop on your finger and the inside of the pan itself so someone can give you an idea of the deterioration of your trans.
If the fluid is clean and red (transparent red) then you probably dont have any real trans issues and there is no sense in pulling the pan. You may just need trans band and kick-down adjustment.
On the inside of the trans pan: from my experience, fine black muck is debris from toasting clutches, lots of glitter is metal particles. Minimal muck and glitter (a light coating on the bottom of the pan) is normal wear. But 1/8" thick and piled up thicker in various places is a sign of degradation. Chunks of black fibers are clutches falling apart.
There are so many variables that could contribute to a general issue like lack of power or poor fuel economy.
Your mileage issues could be: gearing too low, sloppy high stall torque converter, big ( or improper sized) cam, efi profile or installation issues, exhaust leaks, exhaust clogged, trans failing, engine worn out, timing curves out of whack, cam timing not right. The list probably goes on a fair while.
Heck, your rear brakes could be dragging. You said you smell a clutch burning smell after driving? Or that may be just an oil leak burning on the exhaust.
I too suggest you put a clean nice TQ on there and a good clean properly set up factory distributor and ignition. Establish and understand if your machine is in good working order first before trying aftermarket and advanced modifications or major changes to the car.
Then make one modification at a time and fully get that mod working perfectly, then move on to the next.
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:burnout:
