Curban1

Tried it. Did not help!

car has pretty even compression across all cylinders at 175 psi

I did verify that rockers were opening and closing valves. none of the other things. As you said no equipment. No one in my area even wants to look at a car this age. Plugs are not burning lean either.

Hi everyone, Nope not fixed yet but in my defense only had 2 hours in last week to look at it. Thanks for all the help definitely food for thought. SO I did manage to pull the carb and put a camera down the intake. Cylinder 5 no issue but cylinder 7 had a thin amount of silicone squirt into the joint between intake and head. maybe affected 10% of the port. Not near enough to block it but could definitely affect the flow. I'm considering pulling my intake to clean this up however wondering why cylinder 5 is affected with no tell tale issue showing up. Could this have created a vacuum leak for both cylinders ( no I did not have time to check)

Once again thanks for all the replies. I guess I will go through my diagnosis to help everyone understand what Ive done till now. The car is idling rough and has low power. I've concluded these cylinders are not firing because when I pull a plug wire off any cylinder but these you can hear the engine miss on that cylinder. Except for 5 and 7, pulling wire here make no difference. I also see that the cylinders ARE getting spark by installing a plug in the wire that I have pulled off and grounding it. Plugs are all fine! Compression checked out fine at 175 psi on all cylinders +/- 10% including # 5 and 7 I have tried 3 different spark plug wires on these cylinders, changed the cap and rotor twice with brand new units, tried different coil, and even 2 different new distributors. At this point I dont think its spark related. I don't see any evidence of a head gasket being blown, no smoke out of pipes, no milky oil, does not run hot! Have not performed leak down but cant see that being an issue at this point ( am I wrong)? Head gaskets were new. I have looked for vacuum leaks but not around back of intake. Will try that when I have more time next week. I almost feel like those cylinders are not getting gas but I m not one for sticking rags in my intake or heads during assembly for the very reason one could be forgotten. Can I be wrong? Will check this week as well. What else have I missed? Really appreciate the help and knowledge from you guys!! Pleasure speaking to people that understand engines compared to some of our local so called mechanics lol

They are not fireing

Those are some good points, however, upon checking, my brake booster is connected to the manifold on the opposite side beside cylinder number eight. The PCV valve runs from the valve, cover into the back of the carburetor. The manifold is aluminum dual plane Edelbrock performer rpm. I’ve run this exact combination several times on other engines that I’ve had in this car over the years set up the same way only difference being this is a new 600 CFM vacuum, secondary Holley carb, which I can’t see being the culprit. One question I do have is when I put the timing gears on what if they were off by a tooth? Could being off by one tooth do something like this?

Thanks everyone for the responses, I should have said that I’m not inexperienced at diagnosing engines all though this one has me stumped. To answer some of the questions above the valves are moving I thought about the cam myself quite some time ago and eliminated that as the problem. I also thought perhaps the wires were swapped and check those they are correct. This is not something simple although I understand there’s only so many factors that would cause this and I thought I exhausted them all.

I was hoping some smart people here could help me out. I have a 69 442 convertible with a 455 in it. The motor is basically stock as it was out of a car with 50,000 miles on it. It has new timing gears, aftermarket, distributor, cap, rotor wires, aluminum intake, and Holley carb with headers. the problem is the car will not run on cylinders five and seven. The car starts fine idles with a choke on, warms up and idles on its own but it’s a very lumpy idle and those two cylinders are dead. They both have spark. They both have compression, and I’m presuming they both have fuel I don’t see how they couldn’t but they will not run. I’ve tried changing the distributor, cap, rotor, and wires. Still, they do not fire. Does anyone have an idea what could be going on here?