225 running rough

Hello,
Since buying my Jeepster about 6 months ago I have read alot of posts on this site but have not had a reason to post my own question until today.
My Jeepster is '67 with a '71 225 in it. I recently replaced the stock intake manifold and carburetor with 4 barrel holley carb. and offy intake manifold. The engine runs rough when it warms up, the 2-4-6 cylinders are running weak (about 40 rpm drop when spark plug wire is pulled), and foul the plugs. The odd cylinders are strong (approx. 120 rpm drop). The #2 cylinder is the weakest with a 20 rpm drop when the plug wire is disconnected. RPM drop is the same across all cylinders when the engine is cold.
Any help resolving this issue would be greatly appreciated.

 

I would do one of two things,
okay maybe both:
A) connect a vacuum gauge
B) do a compression test

If the problem started immediately after the manifold/carb change, then either a bad intake gasket or a carb problem.

 

The compression test showed all cylinders between 120-140"
The vacuume gauge read 18-20"
The vacuum gauge was very jumpy.
I have tryed tuning the carb. (adjusting curb idle screws) could one of the jets be clogged? Somone suggested removing the curb idle screws and spraying the jets with WD-40, is this a good idea, or would carb cleaner be a better solvent to use?

I also replaced the Distributor but it was tested and I was told it was working fine. (Points type dist.)

 

My 225 was doing the same about 2 years ago. I am putting off a rebuild for as long as possible. Try a couple of tanks using high test fuel. 93 octane or better. My motor cleaned up pretty well, and it even stopped knocking.

Not sure if your problems are the same, but my 2 cents anyway...

 

the readings appear good but the jumpy vac gauge needle is bothersome
needle would like to be somewhat steady
possible vac leak or timing adjustment

 

I sprayed carb cleaner all around the manifold and carburetor, and there didn't appear to be any outside vacuum leaks. Maybe an internal leak? I guess I'll take the manifold off and reinstall this weekend.

 

The Distributor is a delco that someone built into a type of hybrid points/HEI distributor. The guy that built it told me he tested it 2 different 225 engines and it performed fine. I really have no way of verifying this except to replace it with a known good dist. but I don't have access to one.
Ignition timing was what I initially suspected was the problem, maybe I have to purchase a new one and try that before I pull the intake manifold and reinstall.

 

I had a similar situation, with my 71. After spending a ton of money, and not finding a problem, I took it to a really good mechanic. He discovered a huge vacuum leak in the brake booster. He disconnected the booster and plugged the line, and it ran perfectly. Go figure. If you have power brakes, it's worth a look.

 

I had the same problem with my 225 in my cj5. It turned out it had a clogged tube in the carb. Left side was just dumping fuel.

 

I have an odd fire and it ran really rough,back fire ect.,when I bought it. What I found out was the The number one spark plug wire on the distributer was in the wrong position.Every thing in the books is for the even fire.I took the number one plug wire and went one spot counter ckock wise,then did the normal firering rotation on the cap. My two cents worth. Been running for five years now with no problem.