[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.

[johnta1]

I'd check each cylinder's plug to see which one is oil covered/fouled.
Then check that cylinder valve stem oil seal. Make sure it is still seated and not riding up on the valve stem.
This part I'm not sure on, but the V8 used a rubber O-ring on the valve stem/retainer that kept the oil from running down the valve stem. (overloading the valve guide)


A compression check may help and possibly a cylinder leak-down.

[Half-Inch Stud]

Positive seals sound like a good plan. Carefully installed a best practice.

Pressurized oil path might be a leak into 1-2 CYLs. Per above check then sparkys.

[jayboyz28]

Compression is 180 across the board. Brand new engine build. New pistons, rings, etc.
No oil fouling on any of the spark plugs. Cylinder head is currently off again and at the machine shop. You can actually see the oil draining down the valve stems when I pulled the intake/exhaust manifolds off.
Just looking to see if someone who has put the positive valve seals on one of these heads has a part number for the seals.
Thanks everyone.

[steve25]

If the shop knurled the original iron valve guides to on the cheap somewhat restore the needed guide clearance, then with that amount of exh valve stem clearance the exh valves will need positive seals also.

Problem is the head will need to come off again to cut the guide tops.

This assumes that the exh valves did get the needed O-ring stem seal in the retainer.

Maybe since positive seals where used on the intakes the head was assembled without these O-rings on the exh valves, but the head gasket sets do come with the needed 12 O-rings, I know that for sure.

[steve25]

We need to know the OD of the valve guides to set you up with the right seals, but that all being said your machinist should be fully capable of determining that.

If he can’t then maybe that’s why his work is causing you problems.

["QUICK-SILVER"]

Any chance this is an automatic car with a leaky modulator valve?

Clay

[jayboyz28]

If the shop knurled the original iron valve guides to on the cheap somewhat restore the needed guide clearance, then with that amount of exh valve stem clearance the exh valves will need positive seals also.

Problem is the head will need to come off again to cut the guide tops.

This assumes that the exh valves did get the needed O-ring stem seal in the retainer.

Maybe since positive seals where used on the intakes the head was assembled without these O-rings on the exh valves, but the head gasket sets do come with the needed 12 O-rings, I know that for sure.

Valve guides were not knurled. New bronze guides. Spec for the exhaust valve to guide clearance is .0021 - .0038 and we are at .0024.
The head is off. The intake has the positive seals and orings and the exhaust has just the orings presently.

[jayboyz28]

Originally Posted by "QUICK-SILVER"

Any chance this is an automatic car with a leaky modulator valve?

Clay

Car is a 4 speed manual

[jayboyz28]

Originally Posted by steve25

We need to know the OD of the valve guides to set you up with the right seals, but that all being said your machinist should be fully capable of determining that.

If he can’t then maybe that’s why his work is causing you problems.

The OD of the exhaust guides still need to be cut for the seals. Just looking for a part number from someone who has done this before. We have picked out a few different ones, but just wondering if there is a common one everyone uses on the heads.

[johnta1]

Might try asking this question in the OHC-6 TECHsection.


Their are a lot of knowledgeable people there, that may not frequent this section as much.

[Cammer-6]

After contact from OP I suggested he post in the race section.
I have the cutter to machine the top of guides and if memory serves me well the guides are for 11/32 stems
there are a couple seals that work
the rubber with teflon insert and the all teflon one with stainless clamp.
both fit the intakes as a replacement to factory rubber ones.
I would use the steel umbrella hats on both intake and exhaust.
Is the tube in the oil galley present and has it been checked?
Since this problem is so unique I cant help but think the head or block is cracked.

Here are some pics out of the 67 service manual.
I suggest anyone dealing with the OHC-6 get a copy.
It has lots of good info in it that the other years dont.




Many years ago I ran a group buy of reprinted manuals
perhaps its time again to do this.

EDIT: every one of the pics need rotation,perhaps a mod can fix it. I dont see any way to rotate from here

[jayboyz28]

Originally Posted by Cammer-6

After contact from OP I suggested he post in the race section.
I have the cutter to machine the top of guides and if memory serves me well the guides are for 11/32 stems
there are a couple seals that work
the rubber with teflon insert and the all teflon one with stainless clamp.
both fit the intakes as a replacement to factory rubber ones.
I would use the steel umbrella hats on both intake and exhaust.
Is the tube in the oil galley present and has it been checked?
Since this problem is so unique I cant help but think the head or block is cracked.

Here are some pics out of the 67 service manual.
I suggest anyone dealing with the OHC-6 get a copy.
It has lots of good info in it that the other years dont.




Many years ago I ran a group buy of reprinted manuals
perhaps its time again to do this.

EDIT: every one of the pics need rotation,perhaps a mod can fix it. I dont see any way to rotate from here

Thank you. I am obviously new here, and not real good at navigating through all the different sections of this forum.
The tube in the oil is present and looks untouched and not damaged.
The block and head were both checked for cracks. The head was actually checked by two different shops.
I will try to navigate over to the racing section and see if there is any more insight.

Thanks again