Chevrolet Mustang?

I cant seem to get my car to run… OK heres some info… The car is a 1995 Ford Mustang. The engine is an early model 350 chevrolet. I just put new cam bearings, new rod and main bearings. new 284 comp cam 480 lift. it has holley 750 carb. The car will start if you hold it to the floor while youre cranking it. It will idle good for about 30 seconds then it will slowly die. If you put the car in reverse it will die also. this car is as simple as they come… NO computers or any of that fancy stuff, and what has me puzzled is that I bought the car like it is and it ran fine untill I pulled the motor and went through it. I was told that the carb was junk but this is the third carb i have had on it and it does the same thing with every one of them. What could be wrong???

Stopped up exhaust system?

No, seriously, don’t overlook that possibility. Mud wasps, neighborhood brats stuffing potatos up the pipe. It produces symptoms almost exactly as you describe. The engine starts but dies after the back pressure builds up. Because the problem is not common, it often stumps even experienced mechanics.

Have you monitored the fuel pressure when it’s running? Slowly dying makes me think that it’s losing fuel flow for some reason, perhaps from a weak fuel pump.

Just out of curiousity, was this an issue of the 'stang having a bad engine and the 350 was lying around, or is this just the dream car of someone with eccentric tastes?

As for the running issue, have you tried hooking this thing up to an vacuum gauge? If the valve timing or clearance isn’t right, your engine could be generating very low vacuum, which is very bad for the operation of a carburetor.

Ditto that, I’m thinking maybe you didn’t get the cam installed correctly, or you didn’t get the distributor in correctly.

I agree about connecting a vacuum gauge. If you don’t own one then you should buy one. They’re cheap and can be one of the handiest tools in the box.
Your symptoms point to a major vacuum leak, incorrect cam or distributor timing, too much carburetor, or possibly the camshaft profile is too radical for the application.

If I looked at the right specs on this camshaft it is stated that this cam is for elevated RPMS, likes a high stall torque converter, headers and gears along with a rough idle.

It could be with the camshaft profile and possibly being over-carbureted that the engine is doing what is called “loading up” at an idle. This simply means too rich at idle but the carburetor may not be responsible for all of it.
My opinion is vacuum gauge and go from there.

I think you did too much at the same time.

I would have just replaced the bearings then get the car running…Once I get it running THEN I’d replace the carb. Now you’ve done several things all at once and any ONE of them could be the problem. It’s very very difficult to diagnose.

Who in the world would put an old small block chevy 350 in a '95 Mustang? No computers? Did you strip everything out? “I bought the car like this and it ran fine until I pulled the motor and went through it” Why did you pull the motor? What did you go through? New bearings and cam . . . OK . . . why? If you’re serious and not a prankster . . . let’s get back to basic stuff . . . how early a 350? Timing? Where’s the carb from? Compression? Spark? Fuel pressure? Sounds a little fishy to me . . . post back with more details. Rocketman

I’m amused that someone still refers to computers or fuel injection as “fancy stuff” considering we’ve had them for going on three DECADES. I haven’t worked on a car with a carb in 12 years.

The reason for the Chevrolet conversion is price. Chevy motors on average can be found more easily and cheaper than a comparable Ford engine.
When it comes to rebuild and performance parts the Chevy parts are often about 1/2 or 2/3 the cost of comparable items for the Ford. Never understood that at all since CNC machine tools are not able to differentiate between a Ford or Chevy piston when whittling them out of aluminum stock.
It’s also why every single guy running at the local dirt track uses Chevy small blocks since engine damage is a common occurrence. Even winning the feature race does not earn enough to pay for the cheaper Chevy parts but it helps a little.

The engine ran fine before on what was probably the stock camshaft. The engine now has a race cam in it and that can open up a can of worms.

I’ll assume the fuel pump has been converted and is not an issue because an FI pump is going to sink a caburetor float pretty quickly.

I will just say that some race camshafts aren’t meant to idle. I know that it could idle and a lot of them do but not always. They’re not really good with automatic transmissions either. There probably isn’t enough vacuum to idle an engine, what with the overlap of the valves opening. Or you have a really warped intake manifold because it’s acting like a bad vacuum leak.

WOW, thanks guys for all the replys. I will try to answer some of these questions. I used the same manual fuel pump that was on the motor when I got the car. The car will rev very good and will continue to run if you tap the gas pedal when it starts to die.I havent checked the vaccum, but will do that today and post results.If there were any wasp nests or dobber nests shouldn’t they blow out after a few high revs? When I got the car I knew the cam was bad in it, and when I pulled the cam, I noticed that the cam bearings were pretty bad, so I replaced them and while I was in it that far I just went through the bottom end. I wouldnt call this a race camshaft, It is just a couple steps up from stock ok well a few, but ive had bigger in cars with no stall convertor… Since posting I have gotten the car to idle a little better, but it still stalls out when you put it in reverse or drive. What kind of vaccum readings should I look for?

You’re using the manually operated fuel pump but have you disabled the in-tank electric pump?

The vacuum reading is going to vary based on altitude, ignition timing, barometrick pressure, any potential vacuum leaks, and the camshaft profile.

In a “normal” stock engine at ab average altitude you will usually see about 17-18" of vacuum. The gauge needle should be rock steady at an idle. With a performance cam those numbers may be a bit lower; say 15-16". It depends. It could be even lower depending on the camshaft specs and of course the lower it goes the rougher the idle and the more difficulty you may have with things like power brakes, vacuum operated widgets on the car, etc.

I installed a performance cam into a guy’s near stock, fuel injected Ford 5.0 a few years back and it opened up a can of worms. The engine ran great off-idle but it ran a bit rich and had a choppy idle.
It was discovered a bit later this guy fibbed to me a bit (a lot) about the camshaft profile and the speed density fuel injection system was not able to handle that camshaft. This required a complete changeover to a MAF fuel injection setup.

It could be that the engine with that particular camshaft is being loaded down with too much carburetor. Normally a 350 cubic inch motor will only require about a 400-450 CFM carburetor unless it’s an all-out race motor.