Weird question but I'm wondering about the possibility of doing a valve job on a small block Chevy WITHOUT disturbing or removing the factory/original paint on the heads and engine. Could this be done on a low-mileage, survivor vehicle in order to retain as much originality as possible?
curious.....if it's so low mileage why do you think it needs a valve job? any good valve job would require cleaning, magnafluxing and resurfacing if warped. also probably new valve guides a lot of stuff to do, but i guess it could be done if the machine shop is VERY careful
If originality is that important to you, take the head off, replace just the burned valve, hand lap the others and reassemble with the old head gasket. It will be as close to original as you can get. Or you could do the job properly and repaint the engine.
The engine has in the 30-40k miles range and it sat for a number of years. It smokes a bit on startup when it sits for a few days so I presume the valve guides are the culprit. Has a miss (esp. noticeable at idle) that I can't figure out, too. Thought it might be worth pulling the engine to get to the bottom of it all. But the engine (and whole vehicle) has great original paint so I hate to disturb that if at all possible. Don't mind new gaskets and so forth but would really like to save that paint.
I've seen valve stem seals done by only removing the rocker covers and not pulling engine apart by using a spark plug adapter and compressed air to stop the valve dropping. I can't image that on an original low mileage engine the valve guides could be that worn however these things do happen? It's only factory original once.
What @mgtstumpy and @56don said. If the engine has set without running for a number of years, try Marvel Mystery Oil first. That should free up any sticking lifters and soften up the seals. You'll know pretty quickly if the miss and the startup smoke go away.
Have you done a compression test and take valve covers off and make sure all rocker arms are moving,there have been cam issues back into the 50s so do some investigation before you have to tear apart.
Using air to hold the valves closed will also indicate if a valve isn't sealing, air will bleed out through the intake or exhaust depending on which valve is leaking. Valve seals are pretty easy to change on a SBC, as mgtstumpy suggested...
It could just need a few thousand breakin miles or as others have suggested the valve seals could be shot. In those days they used a rubber umbrella seal. If they are hardened and broken up from age you will be able to see if you take off the valve cover. If you want to put on new seals, another way to hold the valves in place is to feed cotton clothesline rope into the spark plug hole till the cylinder is full and gently turn the engine until it comes up against the valves.
I would tune it up and fix the miss then do a few long drives of 100 miles or more and see if it improves before I tried anything drastic.
Thanks for all the suggestions, guys! I am no engine builder so I had more qualified hands go through all the usual suspects... plugs, wires, timing, dwell, compression, carb, etc. All seems well there. Compression was pretty even across all 8. Put in an electronic breakerless points, too. We had to put an intake manifold gasket in it so I would think they would've noticed anything amiss when the valve covers were off but guess it never hurts to check it again. I'm kinda wondering about the cam, as someone mentioned.
''I'm kinda wondering about the cam, as someone mentioned.'' Stick a pushrod in each hole & measure the lift on each as you turn the engine. Many machine shops have parts washers using chemicals that don't hurt the finish too badly. The paint on a Chevy V8 wasn't given much thought when new. After 6 months on the road, all Chevy Orange bomb can paints look like factory paint anyway ...
As mentioned, you can replace the rubber seal O rings on the valve stems without taking the heads off, and it will most likely fix the smoking problem, if indeed the engine has low miles on it. But if it's really 140k miles, you might need to do a bit more work!
LSM makes a tool to remove the valve springs not cheap. I use cotton clothes line stuffed in the spark plug hole to hold up the valves. But in the old days I used the Ford umbrellas over the guide boss and Chevy square o-rings to really help with the smoking. We found the old top oil o-ring were usually crispy critters when we removed the spring. Good luck.
I found that replacing the crispy O ring is all they usually need....but they will eventually get crispy again, if you keep the car long enough. Like 20 years. I've used my compression tester hose, with the valve core removed, connected to an air hose, to keep the valves closed. Put that piston exactly on TDC first. I have an old KD tool like this to compress the springs
I have pounded the porcelin out of a used plug, welded on a close nipple, and threaded on a Milton fitting. Cheap and effective.
The miss could be a bent pushrod. That is what i found on my 455 Buick. Check the lift on every valve and do as Squirrel suggests.
Valve seals are a cheap replacement part, and likely the culprit on this engine. I have the same tool that squirrel posted, and a homemade air charging port. (broken spark plug welded to air fitting) Takes a couple of hours in car, but usually works out.
A bit of good info and a lot of BS answers. Normally a shop hot tanks or otherwise clean a head to get it clean so it can be inspected but I have seen plenty done without it and without disturbing the original paint on the head. You just have to explain to the guy machining the head why and after he gets up off the floor from rolling around laughing at you he can do it. It will give him a good story to tell his buds later. I did it without hot tanking the heads because I was in a hurry. Ground the seats. Washed the head in the solvent tank and blew it off with the airhose and put it back together. That was off a hay weather that burned a valve in the middle of the hay field. Sent from my VS988 using The H.A.M.B. mobile app
You can’t see the valve seals without removing the valvesprings. Mine, on a ‘74 SBC 350 looked like this. I did like Squirrel suggests, with the hose from my compression tester, remove the schraeder valve, and hook up the air compressor to keep the valves from falling. A cheap and kinda crappy valve spring compressor from Hazard Fraught worked well enough. A set of new seals from NAPA are in there now. Not hard to do. Sent from my iPad using The H.A.M.B. mobile app
It’s old Pull it Fix it Paint it Then drive the crap out of it Within a few thousand miles it will look untouched
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