Classic Mustangs (Tech)Technical discussions about the Mustangs of yester-year.
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i have a 68 289 with a c4 transmission. I just swapped the old 2v stock intake and and carb and installed a Edelbrock Performer intake and a Holley 600cfm carb. When i start up the car the idle is much faster than it was originally(but still smooth not jumpy) and i have turned it down as far as the carb will allow. I sprayed carb cleaner all around the the intake seals and i did not notice any change in the engine so i dont think its a leak there. Also when i shift into reverse the car jumps a lot more than it used to(can actually hear the tires squeek) and there is also a very noticeable hiss. When i put it in drive i was doing about 25mph with my foot off the gas which is very different than how it was. Any ideas as to what happened in the swap?
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sorry for being unclear, what i meant was that i turned the idle mixture screws on the side of the carb all the way down. i just went out and checked the bolts on the intake and carb and my fittings and found that there was a small leak in the line for the brake booster hose and i fixed that. Then i started it up and it would not hold idle so i had to give the mixture screws a half turn out and that fixed the problem. With it running i used my hand to cover the carb and it took 15-20 seconds of sputtering but she eventually died so it does not seem there is a leak that is at least letting in enough air to keep it running. When i shift into reverse or when i drive i still hear a pretty loud hissing noise that i cant identify. Also to note i don't have the air cleaner on right now as i need a shorter screw to secure it, could that just be the issue? I don't see why going from park to reverse or drive would cause a louder hissing all cause the air cleaner isn't there.
When i am in park i can rev the engine and i don't hear the hiss, just when i shift into reverse or drive. Also when i shift into reverse or drive the car has a pretty big lurch (wheels squeak a little). I do have a shift kit installed so i dont know if this is the cause but it did not lurch after i installed the kit but before i swapped the intake and carb. The transmission fluid level is not low, actually i think i over filled it so i need to drain a little out. Is there a way to do that besides dropping the pan?
Like Gun jam says...I'd replace all those old vacuum lines since you've already gone to the great expense and trouble of the new intake/carb.
Get a good vacuum gauge and use it to tune the carb to the highest vacuum you can get at idle. Just follow the instructions that come with the gauge. On that 600 Holley (I assume it's a model 1850?), you should turn the idle mix adjustment screws all the way in (clockwise) EASILY (not too tight)...and then back out 1.5 turns for the initial starting point. Once you get the best vacuum level possible via the idle mix, then readjust your curb idle speed.
I think i found the issue, the carb needed the idle speed turned down and the throttle linkage was getting hung upi installed an aftermarket tach and now im idling around 1000 rpm. The car still has a decent lurch when i put it in reverse through, any thoughts?
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