VERY rough idle, hard start, getting worse need help

[Myles]

Hi guys,

81 Malibu 355sbc 11.89 @112

At the track, car started running rough, would backfire/ shoot gas out of carb when stalling.

Now the car is barley startable, will only start if I advance the timing all the way, runs like garbage, stalls, etc..

This misfire has evolved into almost not starting.

Iv tried:

-my new 750hp dp
-rebuilt 650hp dp
-2 hei stock distributors
-replaced intake manifold gaskets
-adjusted all my valve lash

Car keeps doing the same thing.
When we used to be able to keep it running the vacuum was around 10

Have you guys ever felt with this?
Did I get bad fuel? Slowly diluting my good fuel between warm up and then stalled after 1st burnout? Head gasket issue? Cheap jegs harmonic balacer, dont think its that cus can barley make it run at low rpm any. Its mark and hasnt slipped.

Starting to loose my mind!
Thank you

81 Malibu drag only
355ci stock dish piston
Cam is right lash solid
510 530 lift,
242 250@50
106lobe

64cc dart iron eagles
215cc runners (on a 355 lol)
Offenhouser intake
1" carb spacer
Holley 750hp mechanical
Stock hei
Electric water and fan

Th350
5000stall
4.56
28"slick

Bat and fuel cell in trunk

Please let me know what your think. Plugs are dark now due to trying to get it running 1000000 times

 

[fleming442]

Flat cam.

 

[pontiacgp]

you have started a few threads about this problem, stick to one so we don't get confused

 

[olds307 and 403]

Flat cam.

Never seen that on a sbc😏

 

[MrSony]

Never seen that on a sbc😏

Or a Buick with no oil pressure

(srsly i broke in my old engine with no oil pressure)

 

[1bad79]

have You done a compression test if so what are the results

 

[Clone TIE Pilot]

Check for vacuum leaks.

 

[pontiacgp]

Check for vacuum leaks.

maybe he'll read your suggestion this time around....

HELp! heavy missfire- runs horrible

Hi guys, 81 Malibu 355sbc started running like crap at the track. After tuning to eliminate hesitation, bigger nozzles amd 50cc pump, etc, it was fine. Then noticed my timing was somehow move to 55deg at idle! Maybe was moved when guys installed new stall.. Backed it off to normal ...

gbodyforum.com

 

[Clone TIE Pilot]

maybe he'll read your suggestion this time around....

HELp! heavy missfire- runs horrible

Hi guys, 81 Malibu 355sbc started running like crap at the track. After tuning to eliminate hesitation, bigger nozzles amd 50cc pump, etc, it was fine. Then noticed my timing was somehow move to 55deg at idle! Maybe was moved when guys installed new stall.. Backed it off to normal ...

gbodyforum.com

He probably won't.