Ok, I bought the 1986 Mustang GT 5spd Convertible in January from South Carolina. I had it checked out by a local shop (that I chose) before making the deal, then drove there and paid for it the next week.

The engine had been rebuilt it's a 306, stock heads, stock intake, no cats, Prochamber, stock headers, dual Flowmasters, but he put in an E303 cam.

It ran terrible, I almost didn't buy it, but figured it could be tuned up, etc. Under 2000 RPM it would Buck, it didn't have any power. Some other groups said the E303 cam doesn't work with Speed Density, so I converted to Mass Air. (C&L 76mm, new MASS sensor, ECU from Advance Auto)

It had a lot more power with Mass air, but still not what I remember my 1st 1986 GT 5spd Vert having that I sold 12 years ago. It still Bucked under 2000 RPM as well.

Next I set the timing, turns out the guy had it set to 30 or 40 base timing. I moved it back to 14. (Yes with the SPOUT connector out) That stopped the bucking and it seemed to be better. At this point I only had a problem with idle, when COLD it would not idle at all. Once warm it sometimes hunts a little, but not badly.

Next I took it to a repair shop for a driveline vibration and AC repair. He said he found some vacum leaks and adjusted the TPS as well for free while he was working on the other things.

While he had the Mustang for a week or more, I had to drive my Porsche. When I got the Mustang back it seemed to have less power than before and would hesitate some. I tried playing with the timing no change. It actually seems to backfire at some points now. It sounds like the backfire is in the mufflers sometimes and the Prochamber others. It typically seems to backfire when the engine is still cold and I am at partial throttle just trying to normally accelerate.

Everyone says with that big E303 cam I need new Heads, Headers, Intakes and throttle body. I plan on saving up for this stuff and putting it all on at once. It looks like it is going to take longer than I hoped to acheive this, so is there a good Tuning shop for Fuel Injected Mass Air Mustangs in the Huntsville area that could get this thing running the best it can the way it is now?

Thanks,
Sam

 

Interesting psychology project here. I suggest you drive a diesel powered VW Rabbit for a week, and try it again.

 

Uh, yep. The HCI is a package. I have no idea why people want to throw a cam in on a stock engine. You say stock heads, but if you are talking E6 instead of E7, that is even worse. Heck, you could throw GT40 heads on there and still not need anything more than the stock 87-93 cam (yes, I know there were minor changes with the grind throughout those years). Anything else is a mistake.

That is going to be a hard tune due to the mismatched parts. Yet, the best advice that I can offer is to drop by Dairy Queen this Wednesday night and ask around for a few folks to talk with there.

 

I am no expert at all but I have had a few different cams in my Mustangs over the years.. With an E cam on a stock engine you are going to have those problems no matter what.. Just my opinion. Your combo is working against itself until you upgrade everthing else.