Ok, Almost a year later and I was recommended to a shop with a great reputation. (What a mistake) He said he saw an intake manifold leak with his smoke test and changed the intake gasket. No change at all and he did not conduct the tests that were recommended on this thread to see if the cam was off. So here I am again with a great looking car that runs like ****. I was thinking of pulling the engine and having it rebuilt. Is it better to have the top end rebuilt wile it is still in the car or have it removed?
Be sure your car does not have laminated exhaust pipes. The inner walls can collapse when the hot pipes get splattered in cold rain water. One old Buick would only start and die. The other buick had stumble and no power. New exhaust pipes behind the manifolds sent them both flying down the road. Another mistry was a result of the original resistor wire breaking down. A new fat red wire and 56 buick resistor on the firewall fixed that problem. HEI needs no resistor, but needs a clean new big fat red wire for sure.
Easy way to test for a plugged exhaust. Hook up a vacuum gauge. Rev the motor to 2000 RPM in Park, and hold that RPM. Vacuum should be at least 20" and hold steady. If it increases and then drops at steady RPM, there is an exhaust obstruction.
Ok, let me get this correct. So, I should hold the RPM to 2000rpm and the vacuum gauge should go up to 20lbs. (which it currently goes up with throttle advance now when I stab the throttle) And if I hold it at 2000 rpm and drops there is an exhaust blockage?
I dont think any exhaust pipes are double wall these days. That was back in the early 70s when they were made like that
Yes, not necessarily 20", but something higher than idle. If you hold the RPM steady, the vacuum should be steady. If you see it start to slowly drop, that is an indication of an exhaust restriction.
He says the problem is idling. An exhaust restriction would show up under heavy load or WOT. Tom, what was the second carburetor that you tried? Can you richen it up by manually closing the choke plate some? Do you have the points distributor back in? With the initial timing over-advanced so it will idle somewhat, can you post a video of the engine running when you pull the PCV valve?
A young fella told me he bought a beautiful 430 electra that would not run at all. Just hit and die. I told the boy to drop the exhaust pipes. Next day he ran up to me and said "it sounded like a drag car soon as I hit the key! Thank you Mr B"
Latest news: I had a shop pull the manifold and thought they saw a leak. Sorry to say it runs the same as before. The motor runs exactly the same with the same issues. It idles great until you put it in gear or turn on the lights or the air conditioning. Any load on the motor makes it want to stall. Still extremely low vacuums 11 to 13 lbs tops. Runs smooth when traveling down the road under throttle, but falls apart when at a stop sign in gear or turn on the lights and load the alternator. I know something is not right, but can not figure it out. Myself (not a bad tinker guy) and 3 shops that boast old school tuning can not figure this out. The last shop took the advice of one of you and lined up cylinder #6 top dead center and found the timing marks at where they belong. (so they say) They also took off the intake manifold and stated all the cam lobes are not showing any wear at all. I think the engine is tiered and needs a rebuild because when starting cold it makes noise that goes away with oil pressure. My gut says its tiered. However I can not get my mind around the low vacuum and the dead spot in the throttle when I added HEI ignition. It seams as if the low vacuum is a bad manifold or a warped manifold issue. The old Carb will eliminate the dead spot and the brand new one brings it back regardless to the dead spot the idle falls apart as soon as you put any load on the engine. (brand new alternator). I bypassed the voltage regulator when In went to HEI, but I did bot replace the small wire going to the coil. I am going to try and add a thicker wire tomorrow and see if it helps. However I have not much hope. My next move is to pull the motor and have it rebuilt. If any one has suggestions to do this professionally and improve oil distribution as well as make it run as stock with better heads and power please let me know who is the best at this for Buick.
Starting loud and quieting sounds from warm up my be from forged pistons. I'm not the person to really know though. Why do I think it's modded with a upper rpm power cam also? You said it ran really good after 3000 rpm's. I think you need a higher stall converter and steeper gears like many posted. AT 140 to 155 psi I don't think it's that tired, just mismatched parts maby. The #6 cylinder test that the shop did should of showed you the test, it takes all but 5 or 10 minutes tops to a knowledged mechanic. You can easily do the check also.. JW is the man with Buicks and actually everyone else who posted.. "I" personally kinda got butt hurt LOL when you listened to your mechanic over JW about only being on solid lifters. I understand you have been flustered for a couple years though.. Could very well be a leaky intake or wire issue though as you put alot of time in it.
Yeh, pretty frustrated. I did ask for the test JW suggested, butt no one would listen but the last mechanic. He said he did the test and the timing marks lined up. I had a feeling he was humoring me though. If anyone knows a good Buick guy in the North East it would be helpful. I would drive pretty far for the right gut to bring it to.
Northeast? If John Csordas can’t figure it out, I’d be surprised. If you can get it to him? https://autocentercc.com/
Unless I missed it have you taken the intake manifold off yourself to check for straightness? A precision steel machinist ruler will give you a decent look. You can also check the heads. Could also be a gasket issue with the way Buick makes them. Did the mechanic buy new ones when he supposedly took off the intake to check everything he claimed?
I have not looked myself for straightness with Manifold off. I am going to start looking at things for myself and give up on NH backyard mechanics that claim they know how to diagnose a troubled motor. I have a precision machine shop for CNC machine tool spindles dealing in microns that I am now going to leverage now. I did not want to bring a simple problem of a collector car to this level, but it's time I take over and look for myself at what is going on. I have had 10 collector cars and have always been able to tune and figure out common issues. This one has got me stumped. I am going to personally rebuild the original carb without the dead spot and also pull the intake manifold and check for flatness, cracks and fit. I may elect to buy a new aluminum intake to eliminate the manifold leaking all together. (of course I will check flatness of the mounting surface of the engine as well) Is there an aluminum intake that will fit the stage 1 air filter hight? I thank everyone who has reached out to help me figure this out. This is a super long thread so let me recap. After seeing low vacuum and rough idle I ordered a new rebuilt carb from a reputable rebuilder. Mounted carb and saw no change. Purchased Protronix HEI ignition system and installed and no change in idle performance but now picked up a dead spot from cruise speed when trying to accelerate. Put old carb on and dead spot goes away. Jerk Mechanic I had has the bright idea to steal parts from old carb and put in new carb and now I have the dead spot and no older carb to install to remove dead spot and sputtering while accelerating from cruise speed. (So thanks for taking away the only step forward) So now I ordered a rebuild kit for the older carb to see if I can get my step forward back so I can at least drive the car with crappy idle issue. Any advice for checks would be welcomed.
If you’re going to be switching to an aluminum intake manifold go with the Edelbrock performer the air breather will line up with the hood correctly.
Wonder if part of the top of this motor was taken apart when it was still hot and not cooled down from running a while before for some reason..
Ok on a hunch I thought maybe someone mixed and matched parts in this engine causing me the issues I am chasing. So I thought let me track down the #s. I am hoping the Buick experts can help. This car was an original skylark Custom SOC (special order car) with a 455. The seller told me the motor came from a 72 Buick riviera possibly. They restored the car to clone a GS 455 stage 1. All details are very well appointed right down to the air cleaner and everything else I check. So the block # is 1238861. The intake is B-1231718-E The heads are 1231786 and the carb that it came with is a Qudrajet 7041540. Should this all function together? Could someone mixed and matched parts from a few motors and got things wrong? My low vacuum, choppy idle when any load is applied to the motor (including lights) and now a huge dead spot off of cruise, tells me things are way off. The car drives ok when you get it rolling, but falls apart if any load is put on the engine. Lights, air conditioning, in gear etc. If I try and time it to normal standards it will not idle at all. I have to get it advanced to speak plug knock to idle properly. I also noticed when I start from cold it takes 15 to 20 seconds to see oil pressure and then the oil pressure noticeably loads the engine as well for a moment or 2. I am not a complete rookie at owning classic muscle cars, but by far no expert. This one is killing me.
15-20 seconds to get pressure is way too long. Cold oil will load the motor a bit, and the motor dies under any load you put on it, so that isn't that unusual to me, but the delay to get oil pressure is. That may be a separate problem though. Your parts should work together. It's either a valley vacuum leak, or the cam is in wrong. How far are you from Chappaqua, NY?
