5.0 running rough....still

[kaw550]

I am having trouble with my engine running rough at idle and just above it.

I messed with the carb but could get it to go away. I tried pulling the plug wires off one at a time and found that half of them did not change the idle speed. Cylinders 1,4, 6 and 7 did not have an impact. It appears that they are off the same runner on the intake. It seems to clear when the rpms get to around 1500 but I have not driven it far enough to know for sure.


To give a little history,
I installed a remanufactured 5.0 with 10K on it. I used the Weiand Intake and Edelbrock 1405 from my 302.

When I first installed the engine it had a skip. I found it had 0 compression in the #8 cinder. I removed the heads an d found the intake valve on the #8 cylinder was a mess. I later found that the head was crack. I had another set of heads rebuilt and installed them. I then had an issue with the intake install so I reinstalled with Fel-pro 1250 gaskets.


I did a compression test and found 1,2,3,4,5 and 8 have 145 PSI. Cylinders 6 and 7 areat 160PSI. Vacuum was steady and close to 20. It looks like the accelerator pump is pumping fuel on both sides of the carb.

What should I check next?

 

[broncnaz]

Double check your firing order. 5.0 firing order is different from the old 302 firing order.

 

[kaw550]

It is a '92 truck engine. Going by an earlier thread it should have the 1-5-4-2-6-3-7-8 firing order.

 

[TwoDalesDad]

With 20the pounds vacumm....Is that a hover.....kidding....good luck..but who did your heads?...get yourself a leakdown tester...which will show you where your compression is ruff

 

[broncnaz]

Sounds like firing order is right. Just double check remember the pattern goes CCW.
Compression numbers are good across the board I wouldnt worry about them no reason to leak down with those numbers.
I would test your plug wires make sure they are all good. might also consider replacing the distributer cap and rotor if they are not new. Might be a good idea to put in new spark plugs as well if they are old.

 

[kaw550]

I will double check tomorrow.
Would it run if the distributor is out by 180 degrees?

 

[broncnaz]

I've never had one that would run when 180 out. They usually do nothing but backfire badly. actually I was about to ask what your timing was set to?
My only other concern at this point do you know what cam they used for the rebuild? its always possible that they used a older flat tappet cam with the old firing order. Unless you have a roller cam.

 

[kaw550]

It seems to run okay for only 4 cylinders
It does have a roller cam in it.

I can see fuel enter the carb from both sides when I pump the throttle. Does an Edelbrock use anther circuit at or just off of idle that may be clogged?

 

[kaw550]

I confirmed the cylinders were right then I disassembled the carb and blew out the jets.

It;s running great.

I have slight tick but I need to go in and make sure the rockers are all tightened properly.