Mark Maras

Check the float levels. you may find that elusive 5%.

I don't recall any talk of adjusting the float levels (the primary mixture adjustment). The easy way to check them is remove the domes and pistons, raise the mixture screws to the top, then lower them 9 1/2 - 10 turns down from the uppermost position. The fuel level should be close to the jet height at 9 1/2 - 10 turns down. Then raise the jets back up to 2 1/2 - 3 turns down from the top. How many turns down are your mixture screws now?

I've set them cold and hot. Both methods worked for me.

That brings back the memories of my first car, a 64 Catalina land yacht.

Early to bed and early to rise, your girl goes out with other guys.

#4 looks to be a radio bracket.

Sputtering at 3500 rpms while climbing a hill sounds like fuel starvation to me. Especially if it will rev to high rpms in neutral (no load). Fuel filters, float levels, carb balance, fuel pressure, and fuel volume, are where I'd start looking.

@jalexquijano take a look at the video above.

Welcome. We'd love to see some pics.

It's possible that Columbia Rubber Mills in Clackamas, Or (just south of Portland) could refurbish the bushings. I've not inquired about that type of bushing but over the years I've used them on other projects with great success.

Both are excellent suggestions. As I recall he has a reasonably new set of NGK wires and we tried swapping two wires. He eventually bought a Bosch cap and rotor and verified a hot spark. I hadn't thought of a helicoil.

My first one required a pipe wrench and a jack. Much like Cliff, I recall a bit of vehicle lift before it loosened.

We narrowed an ignition problem down to cap, rotor, wire and their connections because it affected one cylinder. I thought we had ruled those out in the beginning. Thoughts?

I expected that answer from C.D. No crystal ball needed. C.D. is a likely person to point a finger at but the question is ,where do we go from here? He's not going to offer any help. If it were mine (I wish), I'd either pay someone with a good borescope to take a look in all the cylinders or buy a good borescope and take a look myself. The cost of either option may be similar, IMO. Looking down the road, I'd also be keeping my eyes open for a used engine.

I shudder at what I'm about to theorize and I hope I'm wrong. I'd like to hear everyone's opinion on this theory and if there's a method of confirming it or hopefully blowing it out of the water (borescope?). So far, we've crossed off ignition problems, valve seal has been renewed, several compression tests have always been within specs or explainable if they weren't (throttle closed), carbs are tuned, valves have been set, I'm now down to asking myself what could foul #4 plug and I'm left with a broken oil ring in #4, If the top ring compression ring is good, that could explain no compression loss. What do y'all think?

@jalexquijano Give us the details of the compression test. Throttle open or closed? Oil or no oil in the cylinders? I'm pleased and bewildered that the compression is that even. I too expected something closer to 160 psi and #4 lower than the rest. If the throttle was closed during the test, I'd like to see the #s again with the throttle wide open.

I can't be the only one here who has never used a torque wrench on lug nuts.

@jalexquijano Do you have access to a borescope? It would be interesting to look at the cylinder walls of #4 as well as a wet, dry compression test before you consider pulling the head.

Measure the diameter and spline width. Google "9 splined shaft couplers". It also looks like Mcmaster Carr has a good selction.You may get lucky.

I wouldn't worry too much about the rise in heat after that much idling. The carbs don't need to be connected to the cooling system. The early four screw carbs had no cooling connection. I'd determine if the dampener has slipped first before buying one. You'll need to determine the exact position of TDC on #1 cyl. There are a number of ways of doing this. A M14-1.25 bolt screwed into the #1 spark plug hole (when the piston is down) will act as a piston stop. SLOWLY bring the piston up until it bumps the bolt. Mark the dampener at the timing tab TDC mark. Turn the engine the opposite direction (piston will go down and come back up) until the piston LIGHTLY bumps the bolt again. Mark the dampener at the TDC timing tab again. Actual TDC is halfway between your two marks which should be the same as the factory TDC mark on the dampener. That's a brief explanation. I'm sure there are plenty of videos on Youtube that explain it much better. I don't see how the #4 fouled plug can be balance tube related or carb related. That's why I'd do yet another dry, wet compression test. Don't ask why, it's an ugly subject and I sooo want to be wrong.

I'd weld a nut on it.

A couple of questions? Did you use a straw over the valve stems to prevent damaging the new seals? Are those plugs a new set? Don't pull the head yet. You need a good reason to do that. If you're absolutely positive you didn't damage the new seals, I'd do another compression test, dry and wet.

After a few tries at adjusting choke cables and not being satisfied, I settled on what I think is the opposite of @Captain Obvious's method. I would pull the choke knob about a 1/4" to the on position, then connect the choke cables. My logic was the choke cables having a bit extra slack would ensure the nozzles were being pushed all the way to the top by the choke cables. I lost a bit of choke because the cables wouldn't pull the nozzles all the way down but I never had starting problems in cold weather.

The flat bar (ish) choke linkage that attaches to the nozzle can cause the nozzle to bind and not return to the top. The ends of the linkage must be parallel to their mating surfaces. A slight twist to the linkage piece, with pliers, is usually all that's required to align it. Unfortunately, the carbs have to come off to check the alignment accurately.

I don't know if it's recommended but many years ago a friend and I matched piston weights by add TIG weld to the inside of some of the pistons. It was a weird project. 510 pistons in a 128 FIAT engine to bring it up to 1300 CCs. (The wrist pins were the same size) It worked for us.