V2Rocket

Hi

Anybody know of a way to pressure-test (or otherwise test) how well piston rings are sealing against the cylinder wall if there is no head on the block? Engine in question is a 1987 951 motor. Cylinder walls look good and are smooth with exception of a few spots with scratch marks that barely catch a nail. Engine was run with NOS but has under 100k miles. Mechanic who looked at the motor before thought it had a rod bearing problem. Looking at picking up the motor from a friend who is doing an LT1 swap into his 951.

Maybe if I plugged the bottom end and pressurized it with compressed air and monitored a gauge? Or is there some ancient Chinese secret?

User 41221

How hard would it be to bolt a head back onto it to test? That would probably be the easiest way. Leave the cam tower off, and you could even use the old head gasket if it wasn't blown or in terrible shape, if all you are going to do is a compression/leakdown test. This all assumes the head is in decent shape.

Otherwise, you'll have to get a deck plate made up, which would be expensive and a pita.

doabarrelroll

I'm sorry, I couldn't resist...

Darwantae951

I wouldn't try pressurizing the bottom end. You would probably blow thru a seal/gasket before you were able to see if the piston rings were sealing.

gruhsy

Wouldn't new rings and rod bearings be easier???? Their both fairly inexpensive. If you have the motor that far apart it's not much further to do them.

Just a thought.

Good luck.

V2Rocket

I don't know where the old gasket is, but maybe he has it somewhere...I just don't want to buy a new gasket for a potentially junk engine. If the engine isn't within acceptable tolerances I'm not going to buy it.

Makes sense.

It's not the rings I'm really concerned about, its the small scratches on the cylinder walls in 2 of the cylinders. I want to know how bad they really are, if they are worth worrying about and make this block basically scrap. It's a cheap engine but it's not worth $1000 to me to have the bores reconditioned.

Scott H

Is it really that much to properly hone these cylinders? I thought it was about 1/4 that much. I know it's a special process, but $1000 seems a tad excessive.

Laust Pedersen

You could buy a piece of thick Plexiglas from McMaster large enough to cover 4 head studs, drill holes for the studs and one center hole for a compressed air fitting. Make a suitable gasket (grease may even be good enough), buy/cut some tubes for stand-offs, install the thing on one at a time cylinder and do leak-down tests.
I have done something similar to that in the distant past.

Laust

V2Rocket

That seemed to be a consistent number that came up while searching. If you know a place to get it done cheaper, I'm open to suggestions. I wouldn't be opposed to taking the motor out to 100.5, but would I need new pistons for that, or just the oversize rings?

azbanks

Call these guys. It should not be $1000.

http://autosportseattle.com/index.html

Scott H

From Lindsey's site, just honing the cylinders, not boring them out, is $175. I'm pretty sure that is for all 4 bores given the way it's stated. I believe you can then use the LR Piston Ring set which can be gapped correctly for slightly larger bores (maybe think about Swaintech-ing your pistons at this time as well). I'd be surprised if you can't find a decent machine shop in California with the correct equipment to hone Alusil bores.

http://www.lindseyracing.com/LR/Parts/944MACHINE.html

m42racer

Call Performance Developments 949 646 7461. They have a tool that bolts to the block, seals to the block and can then pressurize the Cylinder. I am not sure if its something that can be bought, but from what I remember, it would not be cheap.

Paulyy

1+ i was going to say the same thing