Hey guys! I have a 91 RS with a ZZ4 crate motor swapped in. As far as I know the motor is stock. I have a demon 650 on top of it stock mechanical fuel pump and shorty headers going into a cat and straightpipe after that. My question is what can I do to tune the power out of this thing? It has horible gas milage (10mpg) terible vaccume (9-11 pounds in gear) and the idle stumbles alot in gear. It also barely chirps the tires off the line and I have 373gears and no suspension mods. Little 4 banger cars could beat me in a race. I do think I have some bad lifters as It tics a bit. Oil pressure is good with about 45psi in gear warmed up. What could be my problem? I know it is not vaccume leaks because all has been checked and redone. I have done timing and mixture screw adjustments with no real change in performance. This motor should be giving me low 13s or high 12s in the quarter according to what a few drag guys tell me but it dont feel close my stock 350 TPI woulda smoked this. HELP!

 

Sounds like you need to tune it bad. Low vacuum points to timing and fuel. First set the timing. Not sure how your ignition is setup, but somewhere around 12-14* base would be a good starting point. Once that's close then get on to tuning the carb. Do a google search on tuning Holley carbs, should have no problem finding a good article. You'll also need to set the fuel pressure and chances are that your plugs are fouled out so it would be a good idea to replace them.

 

Timing and carb seem to make little or no difference.the timing I can run all the way up to like 26 btdc without a whole lot of improvement but it does seem happier there even though it is only supposed to be at 12-14 btdc. could the stock fuel pump be giving me too low of fuel pressure?

 

you talking base or total timing? If you can rule out timing and fuel and it's still a terd then it's time for a compression and leakdown test. What did you do with the carb? I'd at least start from scratch with the idle screws and pull the bowls and see what jets are in it. Just for ***** n grins hook up a vacuum gauge and adjust the timing until you get the highest vacuum reading and do the same with the idle screws. Then check with the timing light to see where it is.

 

that is base timing. I have reset the mixture screwws on the carb with a vac gauge several times and best idle, best vaccume, and best oil pressure helps very little. Bumping the timing up so high that the strarter barely turns helps minorly but nothin close to what it should be. I have not changed anything on the carb but the mixture screw settings. Oh yea the car has a stumble off the line, coming out of a turn, and accelerating after getting off the gas always on light acceleration and somtimes on heavy accelration. any more ideas? O-yea it previously had an edelbrock 600 on it and it had the same problems with that. I talked to the previous owner of the car and he said the only way it woke up at all was to bump the base timing up like crazy but he also went through 3 starters owning it only 9 months.

 

that screams low float level

 

float levels on front and rear seem to stay at around half. O-yea and somtimes if i turn the car on after it has been warmed up and driving and cooled down for 20 minutes or more I will start it up and go to drive and it will stumble around for 30 or more seconds when i touch the gas at all.

 

around half of what? SHould be at the bottom of the sight plug hole.

 

The demon manual specifies to run the fuel bowl sight levels on a street car at the bottom or first line and a street and strip car at the second or middle line. I have tryed both with no change in performance but decided on the second line after reading Lars tuning guide for demon carbs.

 

I wonder if your timing chain might've jumped a tooth, or your plug wires are jogged one post over at the distributor? Check those two things since it sounds like your timing is way outta whack.