General Engine Question

[Bill Pritchard]

I'm planning to replace the umbrella type valve seals on my Camaro's 350 small block engine with the engine in the car, because it's oil fouling the plugs on cylinders 6 and 8. I have a plan in my head and I just want to make sure I'm thinking correctly.

I intend to bring the number 1 cylinder up to TDC. At that point, I believe the piston in number 6 cylinder would also be at the top of its stroke, albeit between the exhaust and intake strokes.

I have the tool that screws into the spark plug hole and attaches to compressed air, in order to hold the valves in the closed position. I'm thinking I should be able to replace the seals on both the number 1 and number 6 cylinders at this point. Once that's completed, I plan to rotate the crank 180 degrees and then I should be able to replace seals on cylinders 8 and 5. Another 180 degree rotation to do cylinders 4 and 7, and finally cylinders 3 and 2.

Does that sound logical? I don't want to screw this up and have to pull the heads off. Thanks in advance.

[LetsFNgo]

Yes. You’ll be able to do companion cylinders by the pair. When one is on TDC the other will be in valve overlap(both intake and exhaust valves will be open slightly and those rockers will have no lash.

[Too Many Projects]

You'll want to have a breaker bar on the crank socket and braced against something. Once you pressurize the cylinder, the piston may want to go down unless you have the rod perfectly straight top dead.

[markjohnson]

Originally Posted by LetsFNgo

Yes. You’ll be able to do companion cylinders by the pair. When one is on TDC the other will be in valve overlap(both intake and exhaust valves will be open slightly and those rockers will have no lash.

I absolutely do not understand why you’d want to jump over to #6 next since that cylinder has the valves in active overlap. I’d much prefer them static and I’d do #1 at TDC of the compression stroke followed by #8, etc. all methodically in 90* increments. BTW, if it’s a solid or solid roller, take a cold lash measurement before removal so you can put it back extremely close to what it was.

[Bill Pritchard]

Thank you for the input, gents.

Mitch,

The car is a manual trans and I plan on having it in gear and the parking brake engaged, so don't think crank movement is going to be an issue.

Mark,

It's a hydraulic cam. If I had a timing tape on the balancer, it would be easier to go in 90 degree increments, but I don't have that, so it would be a bit more difficult. I might just consider that, though...thanks for the suggestion. I intend to measure from the top of each rocker arm stud to the top of the corresponding adjustment nut using a dial vernier caliper prior to removing the rocker arm so I can run the adjusting nut back to exactly the same place when it goes back together. Should be no valve lash issues that way.

[LetsFNgo]

If you’re putting the cylinders at TDC(or valve overlap) don’t waste your time with compressed air. As long as you can tighten the valve spring up enough to compensate for the valve falling slightly just let it rest on the top of the piston.

[big gear head]

DO NOT put compressed air in the cylinder with the piston at TDC. If it's slightly off it's going to go to BDC VERY QUICKLY. Always have the piston at BDC when using compressed air in the cylinder. Do not put the car in gear and do not have a breaker bar or anything on the crankshaft bolt. You will damage stuff or hurt yourself.

[daveg]

When replacing springs after so many laps we just take all rockers off, and all plugs out.
Start wherever and put air chuck in cyinder.
let it find bottom and change spring.
Seals are right there if you want to change them.
Nothing to it.

How much use have the springs had?
Cheap insurance.

[Hawkeye]

Originally Posted by LetsFNgo

If you’re putting the cylinders at TDC(or valve overlap) don’t waste your time with compressed air. As long as you can tighten the valve spring up enough to compensate for the valve falling slightly just let it rest on the top of the piston.

Just to confirm you don't need air to complete this task? As long as the spring compresses enough to compensate for the valve dropping slightly until hitting the top of the piston?

What other tips should be considered while doing valve seal replacements?

Is it recommended or necessary to replace the springs while each one is off?

Do the umbrella seals slide off and then replace by just sliding back on? Any special tools needed for installation?

This is an interesting topic. Thanks in advance for the replies.

Bill, please keep us posted on how your removal and replacement is going.

Thanks,
Marty

[Kurt S]

How much psi?