Lifting C/R of TVIS Redtop

[ee904age]

Whats the safest most reliable way to raise the comp ratio on a Tvis Redtop? I'm looking for around 10.5:1, I've heard that milling 1mm off the block will do it but a) I have a feeling this is BS and b) how reliable will this be?
Any info greatly apreciated.

[kingcorolla]

Yep you could also skim 1mm off the head face also, then "supposebly" have roughly 10.5:1. But this is internet information im basing it on.

IMO Safe way is to go trd h/g. Come in .8mm, and .5mm i believe. i think its all composite material (metal) gasket so reliabitly is expected, AND theyr re-usable. Cant go wrong.
Stock h/g is 1.2mm, so its a decent bump in squash

Or you could do the rebuild mission and replace with redtop pistons. IIRC The red/black top had lower c/r, but recieved the 42mm bigend (20mm gudgeon) so 10.5 redtop pistons straight swap. I think they both curcliped gudgens aswell.

[ChaosAD]

Your going to have to strip down the engine to mill the block so you would be better off just dropping in some redtop pistons as kingrolla said.

Or if you decide to just replace the headgasket then you might aswell take a little bit off the head aswell to get about 10.5:1.

From memory my red/blacktop piston dishes cc'd at 5cc and the head cc'd at 39cc stock and 35cc after taking a decent amount off.

You just need to find what your piston height is then run the figures through this program http://www.rbracing-rsr.com/compstaticcalc.html to find out what size combustion chamber and headgasket you will need.

[ee904age]

So in theory if I enter a negative number into the head gasket thickness that sould be how much I need to take off? If so I worked out that taking 1mm off the head and using a 0.5mm gasket would give me around 10.57:1. Cool.

Looking at my engine, the pistons sit flush with the top of the block so this means I cant skim block, does it not? Just take 1mm of the head?

How did you get yours so high chaos?? If you dont mind me asking

[ChaosAD]

I got mine up to 11:1 with aftermarket pistons.

The combustion chamber has less area than the headgasket because of the squish bands so your theory wont work. If you find the area of the combustion chamber you could probably estimate how much you need to take off, cc it. Then choose a suitable headgasket to fine tune the CR.