How to increase comprestion ratio without changing pistons

[markhpa422]

I am looking to run NA on my silvia S13..... I have a ka24de and wanted to increase the comp without going to high comp pistons..... does anybody know how to do this?..... any tips would be much appreciated!!!!!!

[96Turbo]

you can shave down the headgasket a little. I'm not sure how thick stock is, or how low you can go, but this would be one way to do it

In order to get any significant increase in comp. ratio you NEED new pistons. Some SOHC pistons are higher compression than yours. These would be cheaper to find than aftermarket. but then again they're probably used. anyone know what they cost new?

[GuardianLlama]

this is directed towards v8's but the same concept applies to all engines.

http://www.popularhotrodding.com/tech/0311_phr_compression_ratio_tech/index.html

[bo2o]

basically shave stuff is your best bet. to get high cr.

or go with sohc pistions. that will give you 10:1 i think or 11:1

and then take your head and get it ported and polish and 5 angle valve job. and get 248 exhaust cams.

[Gjohnson7]

Why are you trying to increase the compression?? What's your motive?

[okis14]

you can shave down the headgasket a little. I'm not sure how thick stock is, or how low you can go, but this would be one way to do it

:eek3: You don't shave gaskets. I believe you meant you can get different HG thicknesses or shave the head.

[KA-T_240]

Shave the head is the only thing you can do with out pulling the motor. A thinner head gasket isnt going to do that much.

Or, You could shave the head, and the block, and put high comp pistons in.....

[Silverbullet]

Why are you trying to increase the compression?? What's your motive?

cuz its better than low compression?

[Andrew Bohan]

i got brand new sohc pistons for $135 in 2004
89 and 90 are different
i forget which is higher

[haz-e]

Early production KAE were 8.6:1, in 90 they were 9:1

[TheJerk]

basically shave stuff is your best bet. to get high cr.

or go with sohc pistions. that will give you 10:1 i think or 11:1

and then take your head and get it ported and polish and 5 angle valve job. and get 248 exhaust cams.

Why go through all of that for shitty stock cams?

[airsoft]

STickers make high compression

[blownmotor]

build it or go home no point for stock

[blu808]

Just do a water injection system. That will increase CR

[deltacruisin]

you'd have to explain that one to me...

water injection increasing compression?

[blu808]

its a joke good sir.

har har.

[svensko]

you'd have to explain that one to me...

water injection increasing compression?

Water is noncompressable (okay, technically I believe it is under EXTREME pressures) and doesn't combust. Therefore, as far as combustion is concerned during compression, the water might as well be extra metal ontop of the piston as it is taking up space and therefore compressing the oxygen more. :hsdance:

[Kouki]

Here is an easy way to increase compression:
1. Remove spark plugs
2. Take several dimes, and smear super glue all over on side of them.
3. Drop them down the spark plug hole into cyl, try to make sure glue side lands down.
4. Continue to follow step 3 for all cylinders until desired volume is filled on each cyl.
5. Install spark plugs.
6. Wait for super glue to fully cure, and start engine.

There you have it, custom domed pistons, for higher compression. It will raise compression ratio as there is less volume for the air to be compressed in, but I don't know how well your engine will run.

In conclusion, If you are going to go through the trouble to remove the head and have it milled, you might as well buy some higher compression pistons, have the block decked, as close to a "0" deck height as possible, and if you're going to do that you better upgrade the valve train to be capable of revving high to make full use of a high compression NA engine. Also might as well have some port/polish done on the head, and port/polish on intake too. So basically if you want the best gain, its going to cost you money, and you have to do it all, otherwise you won't really notice much difference.