Had the cam in my 71 350 replaced last summer by a guy that doesn't normally work on Buick engines. Mostly Chevy and Mopar. Went from stock to a TA 284, along with new timing set and lifters. Stock cam had several worn out lobes. Engine ran poorly before the replacement, but was not burning oil. After replacement, brand new plugs, the engine fires up and runs great for a couple of minutes, then starts running rough. Pulled the plugs and they appear to be covered in oil. Took the car for a drive for a couple of miles and I get a lot of blue smoke when getting on it. All 8 plugs appear to have the same amount of fouling. Cold compression test yields 140-150 psi on all cylinders. Anything obvious I should check first that could be causing this? Getting ready to get her pulled back out of the garage, hopefully this weekend. Just looking for some ideas/insight from the experts on where to start on this. I've included a picture of one of the plugs. All 8 of them look like this.
With a new cam, could it be you are getting more intake vacuum and cylinder pressure? If the rings and valve seals weren't replaced, they may be seeing more pressure than the old cam was able to produce in the engine.
I'm sure that's a possibility. It is a 52 year old engine at this point that's never been rebuilt. I've never dug that deep into an engine before, hence why I had someone else install the cam, so hoping to maybe try a few simpler things before I go that route. I was thinking it's possible the guy that put my cam in maybe did something wrong in the process that I can try correcting. Maybe overtightened rocker arms, or maybe wrong tightening sequence and torque on the intake? I have no idea if either of those could cause this, but was thinking those would be the 2 most likely things to go wrong in the process. Especially the rockers, if he tried to adjust lash/preload like a chevy instead of just torqueing them to the correct spec. I don't know. Just trying to avoid tearing the whole thing apart if possible.
Which intake gasket was used? Not properly sealed intake can allow oil going into the chambers and vacuum leaks. Just throwing it out there. Hope that you find a solution.
You likely need valve seals. I'm sure there was a crusty oil ridge built up on the old valve lift height. The new cam pushes the valve further open and the rock hard brittle original valve seals probably all shattered. Pull a valve cover and have a look.
This^ sounds like the most logical answer to the problem. You could do a leakdown test they are easy to do just need a gauge set and compressor. Intake leak could be but unlikely that is problem most oil comes from seal on valves or the rings . Make sure carb is ok and not flooding as this can blacken up plugs also but I think this is a seal or ring related problem
I had a blueprint chevy engine do that ; it ran great and strong. After about 200 miles it was hard to start then would start at all. I checked the plugs and they were fouled really bad. I put a hotter plug in and advanced the timing a few degrees and haven’t had any issues with founded plugs.
The cam was replaced last summer? You just started running the car now? How old is the gasoline in the tank? When the E10 in my car went bad over the winter one year, the car smoked a bit and the plugs were black when I pulled them.
Messed with a couple different carbs and timing after the replacement and couldn't figure it out at the time, fuel was fresh. I'm a truck driver and work a lot of hours so don't have a lot of free time to mess with it, unfortunately. Have not yet ran it this year. Getting ready to, hopefully this weekend. I'll make sure to run fresh gas. I don't know with 100% certainty what gasket was used, but it's most likely the one the local parts places carry. Which would be the Fel-Pro MS96006. I did try looking for vacuum leaks around the carb and intake with some carb cleaner. Didn't find any. I know it could be leaking internally, though. I haven't tried hotter plugs, but these ones foul out extremely fast. I'd be surprised if the car would make it 10 miles before it won't start anymore. I did mess with timing a bit. I have my distributor springs and limiters set to be all in at I believe 2200rpm with a 20 degrees mechanical advance limit. Tried between 10-16 degrees initial and 30-36 total, verified with a dial-back timing light. Cleaned the plugs between adjustments. Didn't seem to make any difference with the fouling. Plugs I'm using are NGK 6630s. Stock heat range. Edit: Springs are set to all in at 2000rpm, 20 degree limiters. Running the Pertronix D151700 aluminum distributor paired with their flamethrower coil. Replaced resistor wire with thicker regular wire. This definitely sounds like it could be the issue. I'll pull the covers hopefully this weekend and have a look. Thanks everyone for the tips and info. I really appreciate it.
I once revived an oldsmobile that had sat for decades. It came back to life and ran excellent. Unfortunately it used a ton of oil- like a quart every hundred miles! I pulled the valve covers to replace the leaky gaskets and to have a look. Every valve seal was broken or missing. They were rock hard and would shatter if I tried to squeeze them. It only smoked on heavy acceleration or if it idled for awhile and then stepped on the gas. The world would disappear.
Valve guides may be worn....old cam low lift new one pushing valves where they have not gone before. May have had a ridge or at least carbon buildup on them.
Are you still using the stock valve springs? The stock 350 cam is under .400 lift, IIRC ITS LIKE .381/.398 or something similar. You MIGHT be smashing the valve seals with the retainer, or worse, coil bind.
Stock springs, yes. TAPerformance said stock was fine. I'm assuming it's fine since the seals I've pulled so far are still intact, just small cracks. Didn't have a lot of time today to work on it but I've got the seals pulled from the valves on cylinders 1 and 3. 3 of the 4 are cracked, and they're all hardened. What seals do you guys recommend I order for replacement? I see TA offers 4 different kinds. Which ones are the best option? Or should I order from somewhere else?
I'll probably go with those, then. Cheaper than TA's Viton seals and free shipping. Thanks for the recommendation. Do they come with the little installation sleeve that slides over the stem before you slide the seal on to prevent the seal from tearing where the keepers sit? Or is that not necessary? And I'm assuming a socket and hammer will work to seat them.
