48Super

If you do search for "lndented Head Bolts" you should be able find some pretty close looking substitute fasteners for your car. I had a 1948 Buick Super convertible for over 30 years and I managed to locate many suitable replacement hardware items.

But it looks nice in the picture......someone sure put a lot of lipstick on that pig!!!

I have changed the cap, wire and plug and verified that there is spark in the affected cylinder. The compression is 160 psi in that cylinder and the valve action appears normal, cam lobes are in good condition also. Its a mystery.

Here is the latest update, still no joy. While checking everything again, I found the #6 plug had a cracked insulator on the electrode end and I thought for sure that was part of the problem. Today I reassembled everything again with all new gaskets and a replacement spark plug. Engine still runs the same and the #8 plug still appears like it is not firing. I hate to sell the car but I don't think I want the hassle of dealing with it anymore.

Curiosity got the better of me and I took the intake manifold off again to check it for an internal leak as previously suggested. I made a pair of simple plates to block off the exhaust crossover and pressurized the manifold to 40 psi with no leaks detected. At least I now know another thing that is not the problem. I had used composition material intake gaskets thinking they might seal better than the original steel type gaskets. They might seal OK but they self-destruct when you remove the manifold and the next guy to disassemble things will hate you for using them (especially if you are the guy) as they are a real pain to scrape off. Not sure what to try next.

Sorry to say it but I'm about ready to give up on this problem. Nothing I've done so far seems to have any effect on the cylinder misfire. Now I have to decide if I want to sell the car the way it is and take the loss or spend a fortune to have the engine rebuilt. With 100,000 miles on it, if it needs to come apart for anything, I should just do it all and get it over with. I don't have the capability of pulling the engine myself anymore so I will have to find someone in my area qualified to do the work and that will probably not be easy.

Tom, The miss stays there when the engine warms up and does not go away as the RPM's increase. I know I have spark as I disconnected the ignition wire and connected it to another plug which I laid on the exhaust manifold and I could see a healthy spark when I ran the engine. Previously, I installed a new plug, wire and cap, of course the problem was still present. It seems that I have compression and spark so that leaves fuel in question. The intake manifold internal leakage problem posted by TKRIV is very interesting. I wish I had seen it before I reassembled everything. I did notice when I removed the manifold and I was cleaning it, a big chunk of carbon came out of one of the exhaust crossover ports so maybe there is a problem there. Last fall the car ran well and I experienced the current problem when I took it out for the first time this Spring (after just spending over $1000 on a brand new set of Diamondback triple whitewalls!) I may just decide to sell the car as is rather than go through the pain and expense of rebuilding the engine. I find that as I have gotten older, I am losing my enthusiasm for dealing with problems like this.

Yes, the #8 plug is clean and the others are not. I examined the intake manifold very carefully and it was in excellent condition,no cracks and the sealing surfaces were flat and smooth. This problem has really got me stumped.

Here is an update on my engine situation. I installed new intake manifold gaskets (composition type from Best Gaskets), correctly installed the carburetor mounting gaskets and put everything back together again. The engine behaves the same as before, #8 cylinder is not firing judging from the appearance of the plug compared to the others. The engine has a noticeable shake and I can feel the miss in the exhaust for that side. The cylinder compression tested good at 160 psi and I checked the cam when I had the valley cover off and it looked good and the valves seemed to move normally. I'm am out of ideas on this one. Any suggestions would be appreciated.

Sorry, you are both correct. I misunderstood what Tom said, thinking the gasket was flipped side to side. I did have it installed incorrectly. The rear carburetor did not have the steel heat shield installed but I have the correct part for it. The intake manifold gaskets were correctly installed, my picture was a little misleading as I had wiped the surfaces a little beforehand. The #8 port was definitely different in appearance however. Thanks for the input. Hopefully, once I correct these errors, the car will run properly.

This gasket, Felpro #9803, has a gap in the area shown regardless of orientation. Looking at pictures of mounting gaskets from some other manufactures, it appears that some are made more closely to the contour of the heat crossover channel in the manifold and those might work correctly. Is a stainless gasket also needed on top of the mounting gasket to cover the crossover channel on the rear carburetor?

Thanks for the advice so far. I did some more investigating which included running the engine and measuring the temperature of the exhaust manifold ports. What I found was that the #8 port was much cooler that the others on that bank. I just wanted to verify that the cylinder was not firing at all before I got deeper in the disassembly. I removed the front carburetor and saw evidence of a vacuum leak at the mounting gasket. The manifold has no heat crossover channel for the front carburetor but the the standard mounting gaskets have a cut out for the channel. You can see in the picture that the cut out extends beyond the mounting surface and definitely causes a leak but that didn't explain the problem with #8 cylinder. Also, what is the correct gasket for this location? All the ones I've seen look like what I have. Next, I removed the intake manifold and took a good look at all the mounting surfaces and the gaskets. The #8 cylinder surfaces looked more discolored than the others which might be a sign of a vacuum leak. I plan on installing new gaskets. The existing ones were Felpro, can anyone suggest something better. I did not use any type of sealer on these gaskets, should I and if so, what? While I had everything apart, I also removed the valley cover and took a look at the #8 cylinder cam lobes and they appeared normal so I think my issue was probably due to a vacuum leak at the manifold port. Any further information or suggestions will be appreciated.

For a while now, I've been unable to get a nice idle on my '65 GS but it would run fine on the road. When I recently drove it for the first time this Spring, it ran really rough and I could tell there was a very pronounced miss. The first thing I did was to remove the plugs and right away I found the #8 plug was black with carbon as if it had not been firing. I checked the ignition wire which had OK resistance, but to be sure I installed a new wire, a new plug and spare distributor cap. I ran the engine again and I could tell there was still a miss present at all RPM's. I disconnected the #8 ignition wire and hooked it up to the original plug, laid it on the exhaust manifold and ran the engine. I could see a good, strong spark so I'm sure there is spark in that cylinder. I pulled all the plugs and did a compression test and found that #8 cylinder was 165 psi, all others were around 170-185 psi. (Note: this engine has 99K miles on it) I also removed the valve cover and cranked the engine and both valves on the #8 cylinder appear to be moving normally. I've run the engine several times while trying to figure out what is going on and I noticed that when I look the plugs, they got sooty as you would expect while the engine is running with the choke on while warming up but the #8 plug is still clean like there is no fuel getting to that cylinder. I also noticed a hissing sound which I originally thought was just the normal sound of the air being sucked into the carburetor. I used a piece of hose to listen around the carburetors and manifold and found that hissing seems to coming from underneath the intake manifold. I had the manifold off a few years ago when I cleaned and detailed the engine and the core plug was secure and in excellent condition and the intake manifold gaskets are installed correctly. Before I get into pulling the carburetors and Intake manifold I'd like to know if it is possible to have vacuum leak that would affect the #8 cylinder in such a way that would cause it not to fire? Sorry for the rambling post but I thought it was important to detail what I've tried so far. Thanks for any suggestions you might have.

Sorry Tom, the were snapped up right away after I posted them.

These were on my '65 when I bought it some years back. I did not realize they were actually for a later year. My parts book lists "chrome nuts" for '65 so I assumed the original chrome nuts got shabby looking and the previous owner replaced them with these. I replaced the stainless capped nuts with a set of solid stainless ones. They are absolutely gorgeous.