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gasket question
milt - November 11th, 2003 at 10:24 AM

Is the gasket between the cylinder and the crankcase essential to prevent leakage?
Removing the gasket would increase the compression, since the piston moves further up the cylinder...right???

Bizarre - November 11th, 2003 at 10:31 AM

Better not be!

I used a red(?) sealant.
Cant remember the name of it.

I doubt it would effect CR much but yes in theory you are right.

milt - November 11th, 2003 at 11:24 AM

My engine had a gasket there. I'd like to use sealant but i've got a slight step in my cylinders were my rings have worn. I'm scared if i take out the gasket my rings might push against the step and cause some damage..
Hmm
What to do..

Andy - November 11th, 2003 at 11:34 AM

Um, yes, and yes to your questions, obviously the piston/rings will move up by the amount of the thickness of the gasket.
Why can't you use a bit of sealant on each side of the gasket if you want to use sealant?
I suppose your trying to do a cheap re-build? But why not hone the barrels and get new rings at least?

milt - November 11th, 2003 at 02:22 PM

Andy, i am getting new rings and honing the barrels. I was just hoping to get a wee bit more compression by removing the gaskets, but i think i'll put them back in to be safe.
:thumb

Bizarre - November 11th, 2003 at 02:40 PM

Get your heads kissed at a machine shop.
Really should be done to get a flat seat - guaranteed there will be a little lip where the steel cylinder has cut into the aluminium head

Rota_Motor - November 11th, 2003 at 03:10 PM

Quote:
Originally posted by milt
I'd like to use sealant but i've got a slight step in my cylinders were my rings have worn. I'm scared if i take out the gasket my rings might push against the step and cause some damage..



with a VW I guess it wouldnt be so important as the pisons go in from the bottom of the barrel, but with other motors, it is always cheap insurance to have the cylinders 'de-ridged' with the proper tool, which basically has blades which cut the top end of the cylinder out, until the ridges are no longer felt.

even if you keep the same stroke and line everything up the same, the rings can still touch on the ridge, causing them to fail.

vw54 - November 11th, 2003 at 03:29 PM

Quote:

but i've got a slight step in my cylinders were my rings have worn



Cheap way of fixing this is to get a Emery polishing mop on a drill and blend carefully the lip in the barrell. Ive done this on a few old motors just to get them running again.

the best method would be to fit new rings and have the barrells honned, but you proberly find that its not much more expensive to fit new barrells n pistons and have a bit more relialibility

tonyg - November 11th, 2003 at 07:27 PM

You should lap the barrels into the heads with coarse then fine valve grinding paste. Make sure everything is spotlessly clean afterwards. I wash everything in gallons of petrol and use heaps of clean rags. dirt (and particularly grinding paste) is your enemy. keep every part in its original position on the engine and store until assembly in sealed plastic bags. you can leave the gasket out. Use contact cement as sealant.. works fine and NO leaks... sets up rubbery and last 000's miles! (told to me by an old aircraft engineer and used by me on at least 12 engines over 30 yrs)no probs

70AutoStik - November 16th, 2003 at 01:23 AM

VW discontinued the use of a gasket at the cylinder to case gasket more than 30 years ago. Use a thin smear of high temp RTV in it's place.