Question: Mechnical Flat Tappet Rebuild

[Bolisk]

My "was" running geat. No smoke (except after long periods of sitting arround. . .valvue seals maybe). Lots of power. . .and reasonable fule economy.

Then after about 3 years of ownership, the car started developing a misfire . .and it just got progressivly worse.

I did a vaccume test, the vaccum was all over the place. . .indicating bad valves.

I did a compression test, cylinders 3, 5, and 6 were a bunch lower that the rest (which were the same).

Spark plugs indicated a sevear lean condition. . .which is weird. . .because the car was fine mixture wise for two years.

I did a leak down test, and cylinders 3, 5, and 6 were trumpeting through the tail pipes. . .indicating burnt exhaust valvues. Cylinder 7 was not holding as much air and was blowing through the oil fill hole.

I pulled the heads and confirmed that the valvues were not seating on 3, 5, and 6 (burnt). Everything was white, from the extream lean condition. I checked the bores and there were not scratches or groves. Cylinder 7 was ok as well. Poored some marvle mystery oil in the cylinders and let it soak into the rings.

Had the heads rebuilt with new valuves, hardened valvue seats (yes I knew the car did not have hardened valvue seats, new valvue guide sleeves (not nurled), new guid seals (not the o-ring style), and new springs.

I set the valvue lash cold using the procedure that john hinkley wrote, however it set the lash to .025 not .023.

I put it all back together and the car runs better than it ever has......HOWEVER......the car now burns oil, even after putting 25 + miles on it.....why?!?!

 

[Copdogcorvettes]

Well they is a history of on old engines; if you just fix the compression loss on the top end (heads); it is a 50/50 chance that the extra compression will blow the old ring out. The old ring just aren't strong enough to hold the compression gain. ad

Gary

 

[Bolisk]

Interesting theory. I hope that is not he case.When i bought the car, the engine only had 500 miles on it since a complete rebuild. I put 6000 miles on it before blowing the exhaust valves.Having said that, the rebuild was back in like 1985.

 

[lars]

I've had several cases of bad PC seals, causing oil smoke with new heads. If I were you, I'd simply replace all the seals with good quality PC seals - even if your seals are new.

In my 35 years of building engines, I've never seen a top end rebuild "blow out" the rings on an engine - that's a silly myth that has no technical merit. If the bottom end was tight before, it will stay tight with the new top end. If it was smoking and loose before, it will be smoking and loose now.

Lars

 

[Bolisk]

I've had several cases of bad PC seals, causing oil smoke with new heads. If I were you, I'd simply replace all the seals with good quality PC seals - even if your seals are new.

In my 35 years of building engines, I've never seen a top end rebuild "blow out" the rings on an engine - that's a silly myth that has no technical merit. If the bottom end was tight before, it will stay tight with the new top end. If it was smoking and loose before, it will be smoking and loose now.

Lars

Ok that is at least some good news. So Lars (or anyone else), here is some more detail. The engine had a full rebuild back in 1985. The car was driven maybe 500 miles. . .again back in 1985. I bought the car 3 years ago, and the engine tured freely, and started right up. . .after pre-oiling.

So I've driven the car for 3 years (just over 2,000 miles a year) before my exhaust valves got tosted. The car never appeard to "burn" oil (e.g. no smoke out the rear) when driving. The only time I would see oil smoke would be at startup after several days of sitting. . .indicating valve seals. The car had tons of power and the ONLY other smoke I ever got was black carbon on hard acceleration after a while of normal driving.

When I rebuit the heads, I had the PC seals put in, and they looked good when got the heads back. I figure that even a BAD set of these should work a ton better than a good set of o-rings. Thoughts?

Also, when I remove the heads, a bit of antifreese got in the cylinder, I tried to soak most if it up with a rag, and attemped to blow out the rest with compressed air. Then I took marvel mystery oil and coated the cylinder walls, and then added a bit more to to each cylinder (a little puddle) to keep eveything well lubricated. The car sat like this for nearly 2 weeks as the heads were out getting rebuilt.

Then before reassembly, I soaked up the oil with a rag, blew the cylinders out, and then applied a light coating (with a rag) of MMO to the walls.

Now the strange thing is the following, my friends say that it doesn't smell like buring oil. . .but like something else? Could that be the MMO in the cylinders, or trace ammounts of Anti-freeze, or the HIGH TACK i used on the intake manifold gaskets. . .or some of the high temp exhaust manifold paint that I used to clean up the stock manifolds (which got inside the exhause manifold during painting? If it were any of these things, how long would it take to "burn off" in your opinion? I would have thought that it would burn off in a few minutes. . .but maybe I'm wrong.

I've only put maybe 20 miles on the car since re-installing the heads. . .weather has not been condusive to driving the vette.

One other thing. . .it was about 5 minutes after initial starting that the left bank started blowing a little smoke. Then eventually that got less and less, and then it moved over to the right bank. Both banks pump a little bit of smoke at idle (have to really look for it) now, but when you blip the thottel, a noticeable amount comes out the back. Under normal at speed driving. . .you don't see any smoke. Only with the blip, and usually at idle.

If I need to replace the seals again, what brand to poeple trust / recommed?

Thanks,
Bolisk

 

[Crimson Thunder]

Sounds like a leaking head gasket. Try retorquing the heads first.
What kind of gaskets and sealer did you use?

 

[lars]

Any oil or antifreeze in the cylinders following a teardown will burn out within 5 minutes of operation. Head gaskets won't cause oil smoke, and modern head gaskets do not need to be re-torqued. Unless, of course, the smoke is water vapor and not oil...
Why don't you just do a cylinder leakdown test. If the cylinders are tight, you have a valve stem seal problem. The seals I have replaced have all "looked good" - in fact, they have all been new, yet they have allowed some oil smoke, exactly as you describe. Check the leakdown, then replace those seals.

 

[Crimson Thunder]

Lean condition + smoke had me thinking head gasket.

 

[Bolisk]

is there a way to replace the seals without removing the heads?

 

[joe paco]

is there a way to replace the seals without removing the heads?

sure! done it several times over 40 years. you have to pressurize the cylinder with air, of course, use a special L shaped tool that replaces the rocker to compress the springs. If the engine has domed pistons you can break the valve down against the piston, which releases the keepers. otherwise, use air.

the haynes manual has a paragraph on this same thing.

saludos, joe

 

[lars]

is there a way to replace the seals without removing the heads?

Yes, it's easy. Just buy a valve spring compressor tool from Summit like these:

Moroso 62370 - Moroso Stud Mount Valve Spring Compressors - Overview - SummitRacing.com
or
Proform Parts 66784 - Proform Valve Spring Compressors - Overview - SummitRacing.com

Along with an air hose like this:

Performance Tool W84003 - Performance Tool Air Hold Adapters - Overview - SummitRacing.com

Pull all your spark plugs out and remove all your rocker arms. Install the air hose in a cylinder, put the tranny in neutral, keep your hands clear of the fan, and pressurize the cylinder. The engine will turn over as the piston is pushed to the bottom of the bore, and the air will then hold the valve closed as you use the tool to compress the valve spring. You might have to tap on the spring retainer as you compress it to knock it loose from the keepers. Remove the keepers, decompress the spring, swing the tool out of the way, and remove the retainer and spring. You can then get the seal off and install a new one.

It goes pretty quick - I just replaced the PC seals on my new engine (I ended up with a bad set of seals - brand new) and it took me about an hour and 2 Martinis. My own engine is the 4th "new" engine I've had to replace seals on in order to fix an oil smoke problem.

Lars

 

[joe paco]

Yes, it's easy. Just buy a valve spring compressor tool from Summit like these:

Moroso 62370 - Moroso Stud Mount Valve Spring Compressors - Overview - SummitRacing.com
or
Proform Parts 66784 - Proform Valve Spring Compressors - Overview - SummitRacing.com

Along with an air hose like this:

Performance Tool W84003 - Performance Tool Air Hold Adapters - Overview - SummitRacing.com

good directions, Lars. I didn't figure he was going that far.

recently tossed the spring compressor, purchased in '66 or so. pretty handy to replace springs, generally, on several 427 and 327's I used to tune. I used to break the valve down on the piston, seldom had to use air -with those engines. with heads off, it was quicker than using the c tool. pretty ingenious design. made my air fitting from an old spark plug. what's the saying, 'poverty is the mother of creativity?'

saludos, joe

 

[Bolisk]

YePull all your spark plugs out and remove all your rocker arms. Install the air hose in a cylinder, put the tranny in neutral, keep your hands clear of the fan, and pressurize the cylinder. The engine will turn over as the piston is pushed to the bottom of the bore, and the air will then hold the valve closed as you use the tool to compress the valve spring. You might have to tap on the spring retainer as you compress it to knock it loose from the keepers. Remove the keepers, decompress the spring, swing the tool out of the way, and remove the retainer and spring. You can then get the seal off and install a new one.

Lars

I'll have to figure out a way to stop the piston from reaching BDC, as the exhaust or intake valve opens a bit before it gets all the way to the bottom. The LT-1 cam has a bit of overlap.

When doing my leak down test, I used a very large flex head ratchet on the harmonic balancer bolt, and when the engine tried to rotate backwards, the ratchet would wedge agains the passenger upper A arm .. .and prevent the cylinder from moveing all the way.

My only concern is that my compressor isn't big enought o keep the preasure up for the length of time needed.

 

[Bolisk]

good directions, Lars. I didn't figure he was going that far.

recently tossed the spring compressor, purchased in '66 or so. pretty handy to replace springs, generally, on several 427 and 327's I used to tune. I used to break the valve down on the piston, seldom had to use air -with those engines. with heads off, it was quicker than using the c tool. pretty ingenious design. made my air fitting from an old spark plug. what's the saying, 'poverty is the mother of creativity?'

saludos, joe

Yeah I do have domed pistons. . .but with my luck the valve will drop through and I will be really screwed.

 

[joe paco]

Yeah I do have domed pistons. . .but with my luck the valve will drop through and I will be really screwed.

yep, had that a number of times, but was able to pull it back up. as I recall, the rubber seals held it pretty tight for spring reassembly. plus, I could persuade it a bit with a screwdriver in the keeper groove. some risk, though, unless the pistons are domed like the 427.

saludos, joe

 

[lars]

I'll have to figure out a way to stop the piston from reaching BDC, as the exhaust or intake valve opens a bit before it gets all the way to the bottom. The LT-1 cam has a bit of overlap.

When doing my leak down test, I used a very large flex head ratchet on the harmonic balancer bolt, and when the engine tried to rotate backwards, the ratchet would wedge agains the passenger upper A arm .. .and prevent the cylinder from moveing all the way.

My only concern is that my compressor isn't big enought o keep the preasure up for the length of time needed.

You pull the rocker arms off first, as stated in my post - you can't pull the springs off with the rocker arms in place... No valves are open, so you let the engine rotate from the air pressure - there is no reason or point in preventing it from rotating to BDC.

You don't need any more compressor capacity than what is needed to keep up with ring blowby. If you have so much ring blowby that your compressor can't keep up, you have other problems to fix...

Lars

 

[lars]

Yeah I do have domed pistons. . .but with my luck the valve will drop through and I will be really screwed.

There is no way you will drop a valve with pressure in the cylinder unless you whack the valve stem with a hammer after you've pulled the spring off.

This is a very simple and routine operation - no need to make it more complicated than it is. Buy the tools and just do it.

Lars

 

[Bolisk]

Well, going to Bloomington gold tommrow. . .so if I can find the tools while there. . .I will get them.

 

[Vettehead Mikey]

There'll be plenty of tools at BG. Just ignore them.

 

[Bolisk]

Ok, update and some final questions.

So I drove the car all weekend back and forth from Bloomington Gold. Never been so embarased to be in my Corvette. Smokes like a junker at idle and when you pull away from a stop.

Now, I had friends follow me arround for a while. Here is what I know.

1) The car puffs a bit when started.
2) The longer the car idles the worse the smoke gets
3) As stoplights, the longer the car sits at the stop light, the worse it starts to smoke, and the worse the "PUFF" is when I accelerate away
4) The car dose not smoke at crusing speed, or hard acceleration from crusing speed.

So hopefully this still indicates valve seals.

The seals in my car right now: I've looked throught he valve springs and I have noticed that my heads have "BRIGHT BLUE" valve seals. They do appear to be the type with the spring wrapped arround the top portion of the seal.

Doing a little research I've read that the different valve seal materials are differnt colors. Green is Vittion and White is Teflon. . .I have no idea what blue is.

So now for my questions:
1) What material in the seal should I be using (Vitton, Rubber, Teflon)?
2) Which brands are the ones I should be looking for?
3) Do I need a special tool to install the seals?
4) Do I coat the seals in oil before install, or do I install them dry?
5) Someone said that the teflons seal too well and will burn out the valve guide. . .is that true?
6) Links to the best seal to use woudl be GREATLY APPRECIATED.

Hope people can respond soon. . .as I would like to order parts before luch today.

Regards,
JonR