427435

I'm in the process of having my '67 made reliable and streetable. The engine (recently rebuilt) smokes some on start-up (blue gray smoke). This car has also always burned a quart of oil every 600 miles or so.

I want to put some viton valve guide seals on the intake and viton umbrellas on the exhaust valves------------------unless there is a better route to go.

Suggestions as to seal source would be appreciated.

64365coupe

You will have to have the valve guides machined to accept the positive type seals. The heads will have to be pulled. Thank GOD that the old vettes are easy to pull the heads. Machine shop should charge maybe 150.00 or so to pull the heads down and machine the valve guides down to .530 diameter to accept the new seals and reassemble them. The old umbrella seals are a thing of the past but always worked pretty good. Comp cams sells the .530 / .373 seals for like 25 bucks.
hope this helps. Steve www.big-machine.com

4 Speed Dave

If you burn a qt of oil every 600 miles you have other issues and the valve seals are the least of your problems. Burning that much points to a oil ring seal problem.

427435

Well, it did that from new. I did get Chevy to replace the rings on warranty. It got worse------------the dealer put in wrong rings.

They were then replaced again. No real difference. I also had the engine rebuilt at about 100,000 miles (cam gear wore out) and no real change---------although, by then, it didn't get driven enough to get an accurate mpq.

It does smoke a little on start-up so I'm thinking oil is coming down the guides. Remember that this is the L71 with a higher pressure oil pump (more oil on top of the head).

6T7L71CPE

Do you use the positive seals such as Sealed Power ST-2014 on the exhaust too?

domenic tallarita

I think you are right about the oil pump filling the valve covers with oil faster than it can drain.
I was a line mechanic at a Chevrolet dealer back when the positive valve seals came out. It was normal to burn 1quart of oil every 1,000 miles. The oil change was 2,000 miles and adding a quart before your oil change was normal.
Then complaints came in about new cars blowing smoke. Part was the oil that seeped down the guides, but the rings they used were chrome and would not seat unless you ran the engine hard for a while. Some customers were not able to run the engine hard and we had to do it for them or change the rings. The factory stopped the use of the chrome ring and also began using the positive valve seals. The problem with the positive valve seals is that the valve guides wear because of lack of oil. I did many valve jobs back then and the heads with positive seals usually needed exhaust guides and a few intake guides. The heads with the o-ring seals out lasted the ones with positive seals but would get a oil build up on the top of the intake valve that made it heavy. When we borrowed the family car and raced it the valves would float because the valve springs had a hard time closing the heavy valve at high RPM's.
GM had a cure for that in a can that could be bought at the parts counter. You poured it in the carb with the engine just above idle until it stalled the engine. Then let the engine sit for about 30 minutes, then run the engine hard, it was meant to remove carbon build up. Some mechanics had another way to clean the valves and carbon. They ran the hot engine about 2,000 RPMs and kept it running while they poured water down the carb to steam clean the carbon out of the combustion
chamber and off the pistons.
I had a work order that said "engine knock". When I started to take the engine apart and got the first head off I saw the knock. There was so much built up carbon between the top of the piston and head that it touched and knocked. I pulled the other head and cleaned the carbon and that was that.
Just thought I would fill in some blanks as to what can happen if we don't run our engines hard once in a while.

Dom

cardo0

Quart every 600 miles is to much. I really think u need to diagnose for the real problem here. Maybe rings, maybe vlv guides, bad intake gasket or even a bad PCV.

An easy test on the PVC is to splice in a glass or clear jar between PVC and intake manifold connection. connect the hose to the top of the jar/container and put an extension on the PVC side hose inside the jar so it forces any oil to the bottom and the intake side hose pulls on the top forcing the oil to drop to bottom of container/jar. Short drive should show some oil in jar if thats where its using oil.

For the intake gasket u can pull the and look at the plugs first (i expect to be good and block) then pull the intake and look at the back of intake vlvs and their runners. Or use one of the those flex shaft digital cameras and snake down the after removing the carb. If oil on back of intk vlvs then pull intake and inspect gaskets for signs of leaks.

Finally check the rings with a compression test. If compression low then use a squirt of oil in the plug hole and check again to see if compression increases - heck do this if compression looks normal anyways. If compression increases then u have bad ring seal and blowby to. Next u could test the cyl leakdown which give a condition of each cyl wear/blowby.
FYI stock o-ring vlv seals under the spring retainer slash guards work well enough though sometimes/occasionally leave a puff blue on start up. But not a quart of oil every 600mi.

Hope this can help.

427435

Thanks for the replies-------especially Domenic Tallarita's.


Like I said previously, the oil consumption has been steady over several sets of rings and 100,000 miles. Especially when it was new, it got "excersised" hard and often. I worked about 20 miles south of Milwaukee and it got run through the first 3 gears on a frequent basis on the highway to my work.

The one thing that really hasn't changed are the umbrella seals (although they were supposedly changed when I had the engine overhauled a few thousand miles and 12 years ago). I figure there is a reason for the positive seals being developed for use in place of the umbrella seals.

So, what I'm looking for are recommendations on the best source for those positive seals. Also whether putting them on the exhaust valves is a good idea or not.

By the way, the engine runs fine and strong.

427435

Bump.

Surely someone has put seals of this kind on a BB.

domenic tallarita

I have seen the o-ring seals put on the wrong way many times and they do not seal the umbrella to the valve stem.
Some put the O-ring on first which will damage it or move it out of it's groove.
It is supposed to be put on while the spring is compressed a bit further than it normally fits. Then the O-ring is put in the bottom groove and the 2 keepers. Then the spring is slowly let up to seat in the retainer and now the O-ring seals the valve stem to the retainer.
A lot of younger shops were not aware of this along with some older mechanics.
A O-ring installed improperly will cause oil to drain down the center of the umbrella and down the guide.
The intake stem has intake suction to pull the oil down the stem when the valve opens, but the exhaust stem has pressure trying to push exhaust up the stem when the valve opens. That is one reason the exhaust guides & stem wear faster than the intake.

Dom

427435

So are you saying that a properly installed umbrella seal may be all I need??

64365coupe

This is a 427 we are talking about? big blocks have no "o" ring and only have one groove in the valve. Kind of hard to install the o ring when big blocks never came with them.

domenic tallarita

If that were the case, yes it would.

Dom

domenic tallarita

Well,
Disreguard, I thought we were talking about a small Block!
I'm not much good on the L's ore some acronyms used.

Sorry,

DOM

427435

So replacing the the umbrella seals on the BB without an O-ring with a valve guide mounted seal would be a good idea???

427Hotrod

The umbrella seals aren't the best for oil control. Pretty much just keep the guide from getting splashed with tons of oil....but the small block O Ring didn't do a lot better.

A "positive" seal can do a lot of good by actually having contact with the valve and sealing off the oil from running down the guide. The true nylon style hard seals can do a great job IF the valve guides are in great shape. I've got a set of Brodix heads that I've had for 15 years with lots of street and race miles on them....using nylon seals on both intake and exhaust....and the guides are still perfect. I freshened the valve job a while back and didn't have to touch the guides. The head must be machined for these...but again..the guides and valves have to be in great shape to start with.



Here's some good reading...

http://www.enginebuildermag.com/1998...s-and-designs/


If you really want a "dry" big block with low oil usage you need to look at piston/ring design. L-71's had old style forged pistons which work very well...but were set up with looser clearances by design. Newer design pistons can run a lot tighter by using 4032 material and can also use better ring packs and still be incredibly strong.


JIM

nilsthemis

Many years ago I had a passenger 454 rebuilt, the heads were fitted with 1.88/2.19 valves and new guides (all TRW). The springs were GM LS-6, and they had nylon umbrellas on the retainers as I remember.
The new guides had clearance pretty close to max.
The engine ran fine but consumed oil.
Machining and fitting the intake guides only with Crane white Teflon seals of the period solved the problem.

bb62

Are your main rear seals leaking? That may also play a contributing part in the quart lost each 600 miles. My L71 leaks a bit at the rear main seal - less after I start using it during driving season. I've been told that if I replace it, I'd just get the same leak in a year or two as the seal dries out during the winter from sitting.

427435

No the front and rear seals are good. The only place that leaks a little oil is a rear corner of the intake manifold------------but that wasn't the case when it was new.