Well i now know its not a carb problem. but when i take a corners or go up to 60 or 70 the car jolts back and forth. i thought it was a tranny prob so i had a new c4 built with 3000 stall kit manual valve body and floor shift. still the same thin. i had the carb rebuilt. still the same. could it be the engine mounts? im having a new engine put in. its almost ready. a 302/373 hp, 4 brl carb, victor jr. intake. roller rocker setup.(not that you needed to know) but could it be that my engine mounts are allowing the whole block to move around causing the back and forth and rapid deceleration?-thanx for your help guys-james
if you want to see if you have a busted motor mount, put a jack under the engine and lift a little. if the engine "tips" a little, it sure looks like a bad mount. if you have a fan shroud on the radiator, look for scuffing inside it. another shortcut to see if you have a bad mount. another surefire way (although kinda dangerous) is to have a buddy put his left foot FIRMLY on the brake. make sure you stand to one side of the car NOT IN FRONT. have him/her drop it into drive. once the car is in drive, give a little gas and watch to see if the engine hops as opposed to the normal twist. good luck!
Check Rear Spring Mounting Locations You might want to check the mounting eyes for the rear suspension. May have one cracked or completely broken. I've never had this happen, but if it's happening when you're going around curves, it may be something like this. Coultn't hurt to check.
It sounds like you might have a gas starvation problem. The engine needs a certain amount of gas at 60-70 mph. If the sock in the gas tank is collapsed, a pin hole in the rubber portion of the fuel line, or the fuel pump going out on you, you can have the problems of the car jerking back and forth and rapid deceleration. These problems will usually go away almost immediatly (but only tempararily) bacause while your engine is stumbling all over itself the fuel pump is still pumping, until you carb gets gas again, and wham!, you're back driving fine again. You may also need to check into your ignition set up. Do you have a tach in the car? If you do, does it only do this at a certain RPM?
. I'm pretty sure that the surging in the car is due to the very poor fuel system that is rigged up on it. Easy way to find out though...take the 750 off of it and put the old carb back on, and see what happens. If the surging stops, there's your problem. But even if the car is not causing the vibrations and rattling or whatever, that carb setup is not good. If you want it to run even remotely decent and be reliable at all, you need to put a smaller 2 barrel carb back on there. Or if you leave it how it is now you can expect to foul your spark plugs out every couple of days making it run even worse, the car will have terrible throttle response and idle quality (hell, it probably will even have a terrible cruising speed ride quality), terrible performance, bad reliability, etc. Expect it to die at stop lights and sputter getting on freeway onramps and all that. It's not only a bad idea, it's going to be dangerous if you keep it like that.
lol I forgot to mention that this is a different car then the one i put the carb on. i took the old carb back and got a 650 cfm. works way better. i also got a victor jr intake on it now so it all running smoothly. but my otherone is still having the problems with the stalling and the back and forth deal.
When you say the car jerks back and forth....maybe we need to be talking about your front end??? Worn out parts, springs, tie rod ends, bad shocks, etc. Any of those bad parts are amplified going 70 mph.
thanx craig i replaced the shocks and that helped some. it still does it though and now you can eel that its the engine and now the front end. but it help smooth it out so i dont look so dumb bumping back and forth. lol.
If'n it were me, I'd check the electrical circuitry (after all, you've checked everything else). Might be a bad coil, voltage regulator, or a short somewhere? Sounds like the plugs aren't getting fire *all* the time (causing the fuel to not burn, subsequently making the car act the way it is). Either that or your gears are stripped in your rear end! Just another guess.
