Thread: running on 4

Tweet

ok so i bent some valves 4 exhaust valves in my heads and so i had those completely redone. now i got the engine all put back together and the motor will only run on 4 cylinders, i didn't remember to mark down which cylinders had bent valves.... now she'll only run on 4 cylinders, has a slight knocking coming from the valve train on the left side of the motor and spurts some gas out of the car... i've checked the distributor, cap, rotor, points, condensor, plug wires, plugs, and still same 4 wont run... the all the cylinders are getting fuel, so i'm not sure whats goin on..... if its any help my setup is a 302, with ported and polished 1970 HO heads, 351 size valves, crower mild hydaulic cam, standard lifters, hardened push rods, erson edelbrock 1.6 roller rockers, edelbrock RPM air gap manifold, and edelbrock 600cfm carb....

Basics first, I would pull the distributor and make sure that you are not 180 degrees out.

Bill S.

If it runs at all, its not 180 degrees out. Are the four all on one side, or two each side? A bent or stuck intake will screw up one side of the intake system unless its a plenum manifold.

Another thought--what firing order are you using?Depending on the cam, it could be 15426378 or 13726548. The wrong one will run on 4.

2 on each side, dist isn't 180 out and i'm using 15426378 which is what i was running on that cam before

OK, if its two end cylinders on one side and center ones on the other, then its an induction problem, vacuum leak or half the carb not working. If they're adjacent pairs both sides, I'd guess head gaskets.

Originally posted by R Pope
Another thought--what firing order are you using?Depending on the cam, it could be 15426378 or 13726548. The wrong one will run on 4.

This is correct.

When I used to be a Ford tech in a past life, we occasionally had 5.0 Mustangs come in running on 4 cyls. Usually because someone put an aftermarket wire set on and used the 302 firing order rather than the 302HO firing order (which is the 351W order).

Sorry, missed this part earlier -

2 on each side, dist isn't 180 out and i'm using 15426378 which is what i was running on that cam before

RogueGTO

figured and fixed it!!!! .... it was the valves, a few of them were a lil tight, and since of my cam duration, i was getting overlap.... shes running on all 8 now.... took her down to the dyno shop and shes getting tested and tuned... we're shootin for 300+ HP

Doing a compression test would have saved you a lot of time. Doing that first would eliminate a lot of stuff. JMO

just because your car is faster, doesn't mean i cant outdrive you... give me a curvy mountain road and i'll beat you any day


i wouldn't say that to loud over here in moonshine country, someone might take you up on that statement.

i'd be glad to take that challenge....