[jayboyz28]

I am a mechanic in Windsor, Ontario, Canada. I have a customer with a 1967 Firebird with the OHC Sprint motor in it.
About a year ago, he was driving the car home from a show and it began to huff blue smoke out the tailpipes when leaving a stop. Doesn't seem to blow smoke while driving, but it might be. He brought to me and ask me to do valve seals. After pulling the cam carrier off and removing a few valve springs, it was determined the head needed to come off as the valve to guide clearance was too big. Sent the head to the machine shop and after lots of waiting, finally found new valves for it and got the head back and installed.
Customer took it and brought it back, still smoking.
Ended up pulling the engine and doing a full rebuild on it. New pistons, rings, bearings, etc.

Believe it or not, still huffs blue smoke when leaving stops, but only after it is fully warmed up. Will not smoke when cold.
The intake valve to stem clearnace is 0.0016 and exhaust is 0.0024. We have positive valve seals on the intake valves, but just the oring seals for the exhaust. When I pulled the exhaust manifold off, the exhaust ports are full of oil. We are lost. PCV systems seems to working properly. So we are at a point to put positive seals on the exhaust valves too. Seems most people I have talked to have done this. Do you use positive seals on intake and exhaust? If so, do you have part numbers for the seals you use?
Any help would be greatly appreciated.

[north]

What about piston rings, oil burn on load is often ring related. Also was the head tested for trueness? A leak between oil passages and combustion chamber could cause oil loss and could be temperature sensitive.

[north]

My second point was about leakage at the head gasket. These OHC engines had a reputation for overheating in the day, which can obviously lead to distortion of the head.

[Cammer-6]

I never experienced or heard of overheating issues.
Perhaps having an AC car is Florida isnt a true test.

[jayboyz28]

Originally Posted by north

What about piston rings, oil burn on load is often ring related. Also was the head tested for trueness? A leak between oil passages and combustion chamber could cause oil loss and could be temperature sensitive.

Brand new rebuild. New pistons, rings, bearings, etc.
Block was decked and cylinder head resurfaced.
Both surfaces are perfect.
Only huffs smoke after a stop and when taking off. The exhaust valve stems are leaking oil. I'm going to have the cylinder head guy redo the guides again and install positive seals on the exhaust valves also.

[george kujanski]

The OHC situation is a bit different than a pushrod setup from the perspective of oil getting on the valve tops, obviously. It very well may require sealing the exhaust valves also, in my opinion. Do the intake valves show any sign of stem leakage?

George

[694.1]

Intriguing, I will be watching. The only things that come to mind are the rings, valve guides, PVC system. Head gasket?
Hmmm.

[north]

Rings that didn’t set?

Most period magazine reviews in the day complained about temperature issues at higher speeds and consumer reports put it on the not recommended list due to premature cam and valve gear wear, overheating and head gasket failures.

[Jeff Hamlin]

VITON Seals with Bronze Guides are all I use and would highly recommend.






I too have never had or heard of Overheating issues with these Cammers.
Oil pressure issues were one of the biggest problems early on.

[Cammer-6]

Jeff perhaps if you have 66-7 Craftsman News to see of any mention.
I ll look too.

As for the seals on exhausts I was using the all teflon with stainless band on all but was cautioned to use a less effective seal on the exhausts
Because they need the lubrication.
Also wondering if the bronze guides installed were as long as the as cast iron ones.
There are pros and cons to the liners,others say to punch the old guides out and press in new iron ones.


heres the all teflon ones.

https://www.speedwaymotors.com/COMP-...RoCE8cQAvD_BwE
They may seal too good for your application,more for race motors.
But with tight guides they will stop the leakage.
Has any one of the hands thats touched this project even once tested the stem seals with a vacuum source?

[johnta1]

The only service bulletins I saw (for 67) were to make sure to use the valve tip covers to keep from tearing the seals on installation. Most said to check the seals before blaming rings.


I could post them if needed possibly.

[jayboyz28]

Originally Posted by george kujanski

The OHC situation is a bit different than a pushrod setup from the perspective of oil getting on the valve tops, obviously. It very well may require sealing the exhaust valves also, in my opinion. Do the intake valves show any sign of stem leakage?

George

Intake valves are good.

[Formulas]

What transmission is beind this? anything with a vacuum modulator? sucking oil through it?

[Cammer-6]

Originally Posted by Formulas

What transmission is beind this? anything with a vacuum modulator? sucking oil through it?

he said its a 4 speed manual

[Cammer-6]

Again I ll ask
Has anyone done a valve guide seal test using vacuum?
Mityvac has an adapter and procedure for this.
Valve stem should be oiled just like splash oil would do

[Formulas]

Originally Posted by Cammer-6

he said its a 4 speed manual

I don't see a trans mentioned in this thread

[Cammer-6]

Originally Posted by Formulas

I don't see a trans mentioned in this thread

he has 2 threads going
look in the race section

[jayboyz28]

Originally Posted by Jeff Hamlin

VITON Seals with Bronze Guides are all I use and would highly recommend.

Do you know what the valve stem to guide clearance is set to for the intake and exhaust on your head? We are having a hard time finding the spec for that.

[Cammer-6]

Again this is info from the factory service manual.
Have the owner buy it so you can use for this build.
Wasting 30 minutes of shop time chasing your tail would pay for it.

[Cammer-6]

any updates?