My son has a 400 CID small block, carb., on gas and automatic trans. He bought the car used a couple of years ago doesn't know when it was built. Started as an intermittent problem now more frequently. When shifted into high gear car falls on its nose, looses a bunch of rpms never regains. I am thinking fuel. He has went to bigger inlet needles. set the floats, changed fuel filters, went from mechanical to Holly electric fuel pump no change. He called me from track for suggestions. asked if he had ever blown the fuel lines out? He replied no. I then asked him what type fuel line he had on car. He replied rubber hose? I asked how long has it been on car? He replied I don't know on car when I bought it. Me change to steel or aluminum. Do you guys think of something other than fuel problem? Is changing to metal line bad advice?

Changing old fuel lines is never a bad idea. I'd put a fuel gauge that was visible going down the track, even if you don't watch it you can put a go-pro or any kind of camera on it. It's the best cheap data recorder there is, I've known people that taped their cell phone in place to watch the gauges.

First off check to make sure it is actually flowing good fuel supply to carb. Remove the line near carb and do a flow test. If there is a Deadhead Regulator take it and throw it far away.
If you have mechanical advance in the distributor check it.
Blow out all the air bleeds on the carb and verify they are all clean and open.

check the trans converter-had a sprag go out and it acted very similar. just a thought.

Definitely do a flow test on the system, put end of fuel line in a bucket, turn on pump, it should pump about a quart in 10 seconds or less. (NOTE: Do this OUTDOORS, have a fire extinguisher handy, and a helper to turn pump on / off at your signal).
Is the fuel cell / tank in the rear of the car?
If this is a moderate performance SBC car, use minimum -6 or 3/8" fuel line. (Preferably -8 to allow for future upgrades). Nothing wrong with using metal fuel line from rear to front on a mild footbrake car.

quote:

Originally posted by Curly1:
First off check to make sure it is actually flowing good fuel supply to carb. Remove the line near carb and do a flow test. If there is a Deadhead Regulator take it and throw it far away.
If you have mechanical advance in the distributor check it.
Blow out all the air bleeds on the carb and verify they are all clean and open.

All great advice. To clarify Curlys comment on dead head regulator he is suggesting using a return style regulator and I second that recommendation.

It sounds like a fuel supply problem and that is the direction I would look first.

When you do your fuel flow check also check every line and the inlet on your fuel tank. Test it AFTER your regulator and as close to the carb as possible. People have got plastic bags or other stuff in the tank that move around and end up getting stuck in the inlet. When you test it listen for the pump sucking air or lugging. Then remove regulator from the system and try it again. Check all the fuel filters. If your test does not seem right temporary remove filters to try to narrow it down. I have seen a steel braided rubber hose that was damaged in assembly. Looked good from outside and did not leak but it had a flap inside by the fitting that was restricting flow some.

Some fuel pumps have a small screen on the inlet of the pump it does not take much to clog it. Works great driving to the lanes but not enough fuel wide open.

If you are sure it is not a fuel supply problem to the carb then look at carb itself. If floats are bad or needle and seat is bad then you adjust it to compensate and it will not drop down much to allow it to fill properly. Easy way is to just change out carb with a known good one and see what it does.

It is not missing, banging and popping so I do not think it is ignition related. I doubt it is the converter sprag when I lost mine it was a dog from the hit the stall was 6400 before then it was 4200 and a dog. It could be but from what you are saying I would look first at fuel.

I do not like metal lines with gas as they draw heat and can cause vapor lock. Make sure all your fuel lines are away from any heat such as exhaust pipes or basic engine heat. Alcohol is more forgiving here and return style regulator eliminates that potential problem. This is also one major reason I will not run a Deadhead regulator.

quote:

Originally posted by Curly1:
If you are sure it is not a fuel supply problem to the carb then look at carb itself. If floats are bad or needle and seat is bad then you adjust it to compensate and it will not drop down much to allow it to fill properly. Easy way is to just change out carb with a known good one and see what it does.

If the carb has recently been freshened, pop the bowls off, and check to make sure the pump diaphragms don't have the thin rubber stem sticking up into the bowls under the floats. Those need to be clipped off when the diaphragms are replaced. You'd be surprised how often people forget to trim them. They will keep the floats from dropping down enough to fully open the inlet needle/seat valve. Won't notice any issue except at full throttle going down track.

quote:

Originally posted by vetman:
check the trans converter-had a sprag go out and it acted very similar. just a thought.

It could be a fuel issue, but totally agree it could be a bad sprag in the converter.

quote:

Originally posted by N2Ofrog:

quote:

Originally posted by vetman:
check the trans converter-had a sprag go out and it acted very similar. just a thought.

It could be a fuel issue, but totally agree it could be a bad sprag in the converter.

A converter issue seems pretty low on scale to me but still easy way to find out is to try a known good carb. If it does same with different carb then check fuel supply and then start looking at other things. Much easier than changing converters.

Actually I have had problems with Deadhead regulators and that is the very first thing I would do is throw it away or better yet give it to some you really do not like. Lol. Kidding, I would not do that to anyone.

quote:

Originally posted by vetman:
check the trans converter-had a sprag go out and it acted very similar. just a thought.

I’ll second this. Had one do this and changed everything fuel system and ignition wise on the car, it was a new converter, so I didnt even consider it. Finally changed it and it was fixed.

Check the vent…………
How fast is this car?

Another vote that it could be a bad sprag in the converter. My wife’s Nova had the same symptoms, leave fine and as soon as it went to high gear would fall on its face. Changed everything fuel and ignition related and no change. Even spoke with trans builder and converter company and both said no if it was the sprag it would be slow in the 60ft. After chasing the issue for a while I pulled the converter out of my car and put it in hers and problem solved.

charlie t. any results?