Weak Cylinder Diagnosis Help Please

[Longhorn 70]

My 70 feels like one cylinder is a little weaker than the others. It runs well but just not the smoothest. It idles smoothish and steady. It will spin off the line and bark 2nd and sometimes 3rd but just doesn't feel smooth under load.

I don't have a compression tester that will get behind the headers. Could reading the plugs or other methods be quick and cheap. I have a feeling I am overlooking something.

It has a USED 350 with an HEI in it but other than that I have no real specs on. It has an Edelbrock on it with new plugs and wires. The center insulator of the plugs I have checked are white and clean.

Thanks in advance for hints and duh's.

[marvgarr68]

With out testing compression you wont find out. The best method is to do a leak down test and see what is leaking compression. Might just need a valve job

[Longhorn 70]

Thanks Marv. Off come the headers I guess.... I'll do a compression and leak down.

Like life, I guess the right way is better than an easy way.

[geezer#99]

THe right way is to make less work for yourself and save money. Get a compression tester that fits!
If one like this won't work how do you even get plugs in it.
http://robrobinette.com/S2000Compression.htm

[Longhorn 70]

I do have to tighten one plug with a box end wrench. I am going to try the AutoZone loan a tool one. I'll see if that one fits. If not, it was free to use.

Thanks for the tip.

[Longhorn 70]

UPDATE: I found the weak cylinder(s). I made a mistake by not checking all things well when I put a used engine in. I should have checked EVERYTHING out. The previous engine owner hadn't tightened the rotor screws under the distributor cap well and one was missing when I pulled the cap. I looked around in there and figured he just put one in. I did pull the cap and install a new cap, module and capacitor. I DIDN'T find the missisng screw. Well guess what, it was still in the distributor. Today I had new mufflers put on the truck and driving home it felt like I lost 3 cylinders. When I got home, I pulled the cap and laying across the reluctor was the missing screw. Pulled it out, tightened everything back up and it runs smooth as glass.

Lesson learned! Don't overlook details.

[marvgarr68]

Very nice.