Did a compression test on my stroked Olds 215, not good. #4 cylinder at 50 lbs.

[BlownMGB-V8]

If your gasket is .005 then you want your gear to stick out about .004-.0045". If it sticks out .006" then you need a gasket that is .0065 to .007" thick. Important to distinguish between clearance and interference.

Jim

[Gswest236]

I got the surface sanded down to a .006 clearance using a straight edge on the gears and measuring the gap between the gasket surface and the straight edge. The thin gasket is .005 which would give .001 clearance theoretically. The plasti gauge showed a .002 crush. I think I'm good, what say you guys?

[mgb260]

Scott, much better. The gasket will crush a little too.

[BlownMGB-V8]

Sounds backwards to me. If your gears stick out .006" and you put a .005" gasket on the flange, doesn't your gear still stick out .001"? That's an interference fit. Were you putting your plastigage on the flange, or the gear?

Jim

[mgb260]

Scott, Jim B is correct unless you are describing it wrong. You have a thicker gasket?

[Gswest236]

You're right, once again I'm ass backwards. A .007 gasket would theoretically get me to .001 clearance if I actually had .006 gap.  The measurement with the straightedge is probably off. But I ground the mating surface down enough to get the .002 crush on the plasti-gauge with a .005 gasket, where I got no crush with the same gasket before I did the sanding. So, it's better, but is it good enough though. Are there .004 gaskets out there? The shim kit didn't have anything smaller than .005.

[mgb260]

Are you using the Plastigauge between the gears and the booster plate. .004 is the wrong way, you want a thicker gasket. About .007. What's the next one after the .005?

[Gswest236]

Yes, between the gear surface and the booster plate is .002 on the plasti-gauge.  That's what I thought I needed.

[BlownMGB-V8]

I'd go tighter than that. As long as the gears will turn using a big screwdriver and only drag a smidge you have enough clearance. That very slight drag (turns easily but you can feel it) will wear in quickly and the housing grows more than the gears as it warms up which gives more clearance. Any more than .001" is a leakage path and reduces oil pressure.

Jim

[Gswest236]

I'll remove some more of the surface.

[BlownMGB-V8]

Or just use a thinner gasket. Didn't you buy the TA shim pack?

Jim

[mgb260]

Scott somethings not adding up. The clearance with the straight edge and feeler gauge with a gasket .001 thicker than that should be perfect. Why would the Plastigauge show .002 when the interference was .001?

[BlownMGB-V8]

Measurement and parallax error, not surprising. This is why the screwdriver test works so well.

Jim

[Gswest236]

I'll redo the straightedge measurement before I remove more material. I have the TA shim kit; it has 3 diff size gaskets .005 being the thinest. It has a bunch of shims; I assumed they wont work as gaskets being made of Mylar. I understand that if I actually had .006 interfearance, I should be able to use .007 gasket and get .001 clearance. So, something is off. The plasti gauge isn't exact. But let me redo the measurement.

[BlownMGB-V8]

The shims do work as gaskets and are more accurate than the paper ones. Dry fit and use the screwdriver test until you get the best clearance. No need for plastigage, it isn't really much use here because of the parallax error. Once you have the best fit, carefully fill with vasoline being extra careful not to get it on the flange. Apply a thin tacky sealant to all surfaces and torque the cover down. Test the rotation. Use sealant on the bolt threads and copper seal washers under the bolt heads. That might sound like overkill but this is one of the bad places for oil leaks and extra insurance is good. You can get the seal washers from McMasterCarr and get them next day. May be a bother right now but you'll thank me for it later.

Jim

[Gswest236]

OK, I'll redo the straightedge measurement and go from there. If the mylar shims can be used I should be able to dial it in. The sealant must add something to the clearance; is there a rule of thumb on what to expect when we're dealing with thousanths of an inch.

[BlownMGB-V8]

The sealant will squeeze out so don't use too much of it. Just a very light coating is enough. A thin flexible sealant is best. If your gears are making very light contact with the cover torqued in place, after you apply the sealant, pack the gears and re-torque you will probably not be able to feel the difference.

Jim

[Gswest236]

Today I removed some more material from the pump surface and started with a .003 shim and torqued it down,(out of curiosity I did a plastigauge test before I tried the screwdriver on it and that showed a .001 clearance) So I thought I was golden. But no, screwdriver would not turn the shaft. Added a .001 shim to that and still got no turn with the screw driver. Went to the next shim size, .005, and got movement but seemed to be too tight. I added a .001 shim to that and got it to turn but maybe not enough resistance. That's with it snugged but not torqued. So, tomorrow I'll torque it to spec and see if I get that resistance that Jim B. is suggesting.
Thanks

[BlownMGB-V8]

You are in the ballpark, and now you see why I said the depth and plasigage tests weren't much use. The gears are almost never perfectly square with the cover.

You are probably there. If you torque it and feel any contact at all but can easily turn it, that's ideal. If you feel no contact but .001 less gives definite drag add the .001 back in.

Jim

[Gswest236]

OK, Thanks Jim! I torqued it down with the .005 and .001 shims and found that torqued to spec it was too tight. I used a .0015 shim instead of the .001 and when torqued to spec it rotates but has a tight spot due to the slight imperfect pump vanes or imperfect pump bore (as you mentioned). But it's good to go after I take it apart and add the petroleum jelly. That's next and the water pump is ready to go on and then maybe the heads. I appreciate the help here believe me!

[mgb260]

Scott, Set the heads and intake on and trial fit the front cover before you do the water pump. You have to correct the interference with the front intake gasket clamp.

[Gswest236]

OK, I dont have the right RTV for the gaskets so I'm waiting to finish the pump until tomorrow. so, I'll put the heads and intake on next. I've got to clean up the intake first. Is this the interference point?

[mgb260]

That's it. You have to cut it off about a 1/2" off below the middle block surface for the intake gasket clamp to clear.

[Gswest236]

OK, got it! Thanks!

[mgb260]

Scott, with the heads, put the lifters and pushrods in before you put in the long headbolts and rockers.