Lifter-head gasket-vacuum Problem?

[67 CoupeDeville]

Brand new to forum. I inherited a 67 DeVille w/429 that has been in my family since 85. It sat in storage for the last year. Had it shipped to Florida from Ohio last month. Ran great, smooth, quiet, same as always. It started running a little rough at idle. Took it to garage to have AC upgraded and had them check the idle. Picked it up and much worse.

Engine now sputters heavily at idle and at highway speeds.
Sort of either idles at high rev or so low it stalls out...? A bit noisy too.

They replaced the carb base gasket then said it needed rebuild. I rebuilt carb and found warped air horn, so took it to have good professional rebuild. This did not help.

Checked firing order.

I ran a compression test and found cylinder #2 way HIGH at 223 psi. All others were at 177 to 180 psi. Doynk sound from cylinder 2 while testing compression.

Has a tendency to Diesel a bit after shut off.

Once it bellowed a large puff of air fuel mixture from the carb at shut off.

Pulled valve cover expecting a stuck exhaust, loose rocker or bent push rod. All appears clean and valves are moving freely. Exhaust lifter seemed a bit spungier that others but could just be depleted of oil.

Has anyone seen this behavior before?
Not sure what to check next. Could it be a bad lifter doing all of this, and so fast, in about 10 miles?
Vacuum leak?
Head gasket? Even though compression shows one cylinder high?

Ideas? I am not sure what to check next. Vacuum?

Thanks,
Chris

[cadillac_al]

Points condensor and distributer cap. An old mechanic told me years ago " a lot of carburators get rebuilt because of burnt points." That high cylinder is probably a dead lifter not opening a valve. You should probably take the valve cover off to verify if #2 cylinder has a valve not moving. Don't give up on that car. My friend had one of those 67's when I was in high school. We were young and couldn't keep it running but we sure smoked a lot of weed in that car. All that time sitting in that nice black interior really made me appreciate Cadillac style and quality. We had a lot of good times in that car even though it hardly ever ran. Post a picture of it sometime. Peace.

[67 CoupeDeville]

Thanks for the reply. Here's a pic.
So...changed points, condenser, rotor and cap, and set dwell and timing. Still got the same problems. Runs rough and sputters. Also has no power when in gear, and as I said before it ran great about 10 miles ago. Any oldtimers see this before?

[67 CoupeDeville]

Sorry, pic didn't link up. Here it is again.

[jk1000]

I guess I'm an old timer.

I would put in a new set of spark plugs and ignition wires. These engines go through plugs rapidly. The original shop manual recommends replacement at 6000 miles. In my experience, a plug may look good, but will misfire under load. In other cases, the engine will fail to start or will only misfire when trying to accelerate. Again, the plug will appear normal under a visual inspection. Ignition wires can be checked with an ohm meter. But, if they are more than a few years old, just replace. We need to absolutely rule out the basics before going further.

If the problem persists, I would be thinking late timing or loose timing chain.

Dieseling is not unusual with these engines.

I'm not sure about the high compression in the #2 cylinder. It may just be carbon. In any event, this engine should have plenty of power even if one cylinder was totally dead.

Post back and let us know how it's going.

[cadillac_al]

It could very well be the coil. I junked a car once because it ran so bad I thought it bent some valves or something. Later I went to take the nice chrome coil off it and put it on another car and I found out that new chrome coil was bad. I put another coil on my junked car and it ran like a champ but it was rusty and I already registered another car. I was surprised because I always thought when a coil dies it dies and the car doesn't run but they can still run and run badly. Yours is starting to remind me of that now. Your carb has had 2 rebuilds with no change and the points condensor etc didn't change anything. It would be nice to check vacuum but if it isn't firing right the vacuum would be low anyway. I think my money is on the coil at this point. Good luck.

[67 CoupeDeville]

I tried new plugs and wires. Still not working. I haven't tested the vacuum as I don't have a gauge. I don't hear any vacuum leaks, but a few of the lines are old and have some visible cracks. I am convincing myself that the #2 exhaust lifter is making more noise than it was before this problem. My dad used to say he was always having trouble with it but I have no idea what he did to fix it. He said Marvel Mystery Oil I think. I tried this too with no luck.

I'll pull the coil and get it tested tomorrow. Any other ideas? Should I pick up a vacuum gauge while I'm at the parts store?

[67 CoupeDeville]

Oh yeah. I also have the timing at about 5 not 0. It bogs more at 0 and stalls.

[jk1000]

Try advancing the timing a little more and see what happens.
I would also check the fuel pressure, should be around 5 psi. A vacuum gauge may not be a bad idea.

Also check the PCV hoses. Sometimes they crack in hidden places, this will cause the engine to run poorly.

Does the engine run hot?

[Burntstuf]

OK,
So speaking from my own 429 fun, I rebuilt my entire motor, ground up, I upgraded to electronic points , new wire, plugs, you name it, I got the car running actually GREAT but here is where I think I can help, one of the items I upgraded was the Coil, I replaced it with a High Voltage coil which did not require a ballest resistor... a few weeks after it was done I parked it at the shop , one of the guys had to move it while I was out, he kindley left the key in the run position after turning off the engine , I got back 6 hours later and the car would not start ... He kindely fried my new coil. next day I ran and got a cheap summit coil , put it in the car and it ran GREAT, I got in the car to drive home got about 2 blocks away and it started running terrible, dying, no power, ideling rough , back fire... so strange? I went back to the shop turned off the car and it did not want to start good, and then it would start, run fine but then when I drove it get crappy fast? I looked into it deeper realized that the new coil required the balast resistor, which I put back in, thinking this would fix it, it seemed to at first but again it got bad again, turns out the coil got to hot, cracked the blastic face and allowed the oil to drain out of the coil, so the coil would work when it was cold for a very brief period but step on the gas and STRANGE things would happen. Moral of my story is get a new coil, make sure you read the directions to be sure if you DO or DO NOT need a ballest resistor but I am willing to bet this will solve your problems, as for the high compression on one of the pistons? No idea but I would not worry about it, Oh one last thought, if the car was sitting that long your gas tank may have gotten crappy and could also be causing some fuel restrictions, your best bet might be to drop the tank and have it relined, I had to have mine done after the car kept dying for unkown reasons, it turned out it was being fuel starved because of sediment in the tank... GOOD LUCK!

1 last thought, the manual recomends setting the timming at about 5 degrees, because compression on this motor is 10.5 to 1 (I guess any engine realy) DO NOT ADVANCE THE TIMING beyond 10 degrees... speaking from my first rebuild, I cracked 3 pistons, but boy did it go FAST!

[67 CoupeDeville]

Problem solved! I am posting my find here incase it helps someone else.

I bought a 67 service manual from ebay and it said that the car will not idle with out the heat shield between the manifold and carb base gasket. Seemed odd since all the holes match up with the base. Couldn't find one anywhere, but wasn't looking too hard as I was sort of sick of the problem. I ran into an old Cadillac employee that now rebuilds mainly aircraft carbs. He bought up all sorts of old heat shields when GM quit making them. Gave me one for $15, I slid it under the base gasket and incredibly the car runs fantastic.

Turns out when the service tech replaced by base gasket to fix a leak he had found he threw it away!!! You really have to watch these guys and make sure you are getting a guy that knows his stuff, or at least doesn't throw stuff away. All I wanted to do was have my old ac switched over and the idle adjusted and I got 6 months of mind boggling hell and the cost of a professional carb rebuild.

Thanks to those that made suggestions on this, and the car really runs fantastic now.

[cadillac_al]

Now that's something I have never heard of. Thanks for clearing up that mystery. The carbs must get pretty hot on those cars.

[67 CoupeDeville]

The funny thing is that it ran like crap right at start up. No heat involved. I didn't see any vacuum holes that needed covered by the shield either. I obviously didn't see something. Worked exactly like the 67 service manual said..."won't idle if missing".

[65CADILLACAMBULANCE]

Im having the same problem with my 65, but i dont understand what a heat shield is or where it goes, under the carb ??? Theres just a thick gasket?