Misfire on acceleration 85 cutlass 305 4brl HEI

[stevo88]

i havent had my car for very long, i picked it up for cheap, its an 85 cutlass salon with a 305, QJ 4brl and an HEI ignition system. The car runs so i have been driving it every day but the guy i bought it from has put alot of mods into the car and it appears he has been a little reckless with some of the factory parts. Its got hooker headers, a twin coldair intake from spectre and dual 3" exhaust from the headers to the axel with an x-pipe and 2 thrush mufflers. The exhaust ends at the axel it looks and sounds very nice.

At first i thought it was running too rich (which it was) because the motor would really bog down on hard accel in the low rpm range (it sounds almost like misfire i could be wrong but it doesnt have any power and its similar to gas flooding). I have adjusted the mixture it seemed to have slightly fixed the problem (gets better mileage too) but i cant get rid of the nasty hesitation. So then i turned my focus to the electrical/ignition system. I havent tested it yet but i am wondering if maybe i am not getting enough power to the spark plugs therefore not producing enough spark to burn the gas it demands at low rpm, i have also checked every sparkplug and they are all in great condition. I also thought about exhaust back-pressure aswell since it can reduce low-end power. Can anyone shed some light on what may cause an issue like this? I am a do-it-yourselfer and i am very electrically enclined aswell so any help would be greatly appreciated.

I would also like to point out that since ive had the car the tachometer has not been behaving correctly, it always seems to read high and bounces around. I have read about HEI systems and power filters causing that issue. It looks like the HEI distributor/coil came stock on this car so i would understand if it was added to replace a points distributor why i would be having this issue but that does not appear to be the case. Just figured having that peice of information could help isolate my acceleration problem.

85 cutlass salon
chevy 305 - stock cam/valvetrain
4 barrel quadrajet (750 i believe)
lots of airflow in and out of motor
have tried higher octane fuel up to 94octane

 

[Pontiac455]

Change the acc. pump in the carb. first make sure the choke blade is open and staying open when engine is at opperating temp.

 

[gk666]

yeah basically boils down to the carb and the distributor so i would work on the carb first.... better than efi IMO but carbs are very finicky systems

 

[pontiacgp]

check the spark plug wires and make sure they are separated so your not getting cross fire induction, also look in the cap for for any indication of the spark jumping around in there. For the tach take the cluster out and then remove the tach and make sure the jumper in the back is secure. I sent a tach that was doing the same thing as yours to bonnewagon thinking it was no good and he told me that all that was wrong with it was that loose jumper. I had already replace the OEM tach with a VDO but I had driven around with that tach bouncing around for way too long..

 

[madmaxstyle]

One time I had this fairly new dizzy and it had a loose prong on the top where the wire snaps to. Not real loose but it was enough to cause a horribly random miss.
Could be fuel related too......

 

[tc1959]

Make sure the coil has the ground strap installed the on under the coil cover,without that it will have fits,and it will make a tach go nuts.

 

[stevo88]

ive checked the wires they are pretty organized, i have clips installed that came with the new wires i put on so that they stay away from the headers so they are certainly not touching one-another.

at operating temp the choke blade goes wide open and doesnt seem loose at all so that seems to be operating fine.

when i rev the motor in park/neutral the carb doesnt gurgle or make any spitting noises so it sounds like its giving a good mist of gas/air.

havent had time to take the cap off the distributer yet, but if all looks good there should i check to see if my voltage regulator is working properly? could also be timing i suppose.

also would like to mention there is absolutely no hesitation of any kind when the motor is not under load, so in park it revs great, its only when its in gear and moving where torque is applied that it does this

 

[stevo88]

btw it has no AC, the pump has been removed entirely, no AC at all
all it has is alternator and power steering on the belt

 

[pontiacgp]

it sounds like it just may be the timing that's off..

 

[stevo88]

it sounds like it just may be the timing that's off..

thats good news! ill get to it and let you know how it goes, thanks!