Riser Plate for Block

[Tony Betts]

Check the thickness of the gasket, in case someone has made them to thin.

Gaskets are usually cut in 17 thou and 27 thou.

The base gasket should be supplied in 27 thou.

I dont know about the cylicone gaskets, or what they compress to.

Tony.

[Jamie]

Thank you, Chris and Tony.

The pistons stand 20 thou or 0.5mm above the top of the block. I have not measured the head gasket, but shall do so out of interest. The base gasket is already in place, so I shall not be ablea

I had wondered about skimming the pistons instead, but would rather avoid this if I can get hold of a shim for the block.

Regards,

Jamie.

[Nick Lettington]

Jamie. Its not something I have done, but  was considering a block skim to restore the height of valve seats... when you refer to the paper gasket not being an option, where are you expecting to put the shim plate? I suspect you will need to disturb the paper gasket!

To make that a little clearer... the shim goes underneath the block... you will need to remove the block to fit it.

[Chris KC]

I was wondering about that too Nick, the sentence petered out half way so I'm not sure.
Definitely fitted beneath the block.

If valves are deeply recessed, it may be the only way - but personally I avoid skimming unless there is no choice.

[Jamie]

I am not sure what happened to my last post. It was meant to say that measuring the base gasket is not an option because it is already fitted. I do realise that I need to dismantle it all, put the shim at the base of the block and put new gaskets in.

Regards,

Jamie

[Nick Lettington]

Aha...sorry Jamie. Ambiguity is the source of much humour and confusion!

[Terrytuned]

John Barlow shims are .5mm or .75mm = 20 or30 thou he is not very quick at answering emails phone 01159220680. When fitting shims do not use a gasket coat both sides of shim with sealant, I use ThreeBond 1215. Terry.
You can use 2 shims if the top of block has been machined.

[Nick Lettington]

I was wondering about that too Nick, the sentence petered out half way so I'm not sure.
Definitely fitted beneath the block.

If valves are deeply recessed, it may be the only way - but personally I avoid skimming unless there is no choice.

I was lapping in new exhaust valves and they were sticking shut... In the end I just went with a fraction of a cut with a 30° cutter to remove a small vertical face at the top of the seat... the idea to skim came from Lotus the Early Years...

[Stuart Giles]

Jamie. Its not something I have done, but  was considering a block skim to restore the height of valve seats... 

This is something I have done quite a few times, seems pointless wasting  some of the valve lift with exhaust valves pocketed into the block. I've not always found it necessary to skim the piston crowns on A7 motors after doing this. When the pistons do need skimming I use this home made jig.





This  jig locates in the piston  ring lands and could be used on a lathe faceplate if a milling machine isn't available. The one here has done all sorts from small Jap bike pistons right up to American "big block" items. Do not be tempted to just put pistons in a lathe chuck as the skirt is likely to be squeezed out of shape at best, and may fly out of the chuck, bounce all round the workshop, and be transformed into a piece of mangled scrap metal as one of my brothers proved right in front of me whilst  "decking" a Ford 10 piston when I was a kid.

[JonE]

so just digesting posts, paper gaskets are 27 thou but compress to 17-ish in use.
Does Threebond's double layer on a non-compressible shim equate to any measureable thickness?