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by **Flannelman** » Tue Jan 25, 2011 10:06 pm

Wishing to pump up the compression on a Silvertop.

Im aware of .8mm TRD gaskets and flat top pistons to give it a boost but how much can the head be plained before there comes complications in weakening the head?

by **ace_nz** » Tue Jan 25, 2011 10:18 pm

Flannelman wrote:Wishing to pump up the compression on a Silvertop.

Im aware of .8mm TRD gaskets and flat top pistons to give it a boost but how much can the head be plained before there comes complications in weakening the head?

i've taken 2mm off with no issues. Will effect cam timing a bit though.

by **cat007** » Tue Jan 25, 2011 11:31 pm

How much clearance is there normally between the piston top and valves? Or are they already an interference engine?

by **Flannelman** » Wed Jan 26, 2011 6:31 pm

Around 9mm with stock pistons and head gasket installed.

Stock silvertop is non-interference

ace_nz, cam timing can be fixed with adjustable cam gears?

by **ace_nz** » Thu Jan 27, 2011 10:49 pm

yep, you can correct the timing with gears, but the inlet being vvt makes it a bit tuff.

by **CAMB01** » Sat Jan 29, 2011 2:03 pm

Yes adjustable cam gears will be needed to adjust the slack in the timing belt.
Ive taken 1mm off my block and the top of the pistons in my EVO to raise compression slightly. Had to grind a bit off the top of the engine mount and a bit off the back timing cover tins cause when i fitted the head they were holding it off the block.

by **TRD_ZERO** » Tue Feb 01, 2011 7:32 pm

You cut up your pistons? Doesn't that mess with the integrity of the pistons?

by **Boost_4_Life** » Tue Feb 01, 2011 7:55 pm

not if you use a good hacksaw.

by **TRD_ZERO** » Tue Feb 01, 2011 8:33 pm

Oh ok, just use pro tools and it's ok.

by **Flannelman** » Fri Feb 04, 2011 6:08 pm

removing material from pistons would lower the compression ratio...

skimming the block would bump it up

by **QikStarlie** » Fri Feb 04, 2011 7:52 pm

i'd say he would have machined the pistons in the squish area, to avoid piston to head contact.

by **CAMB01** » Sat Feb 05, 2011 6:32 pm

Flannelman wrote:removing material from pistons would lower the compression ratio...

skimming the block would bump it up

Not if you take material off the top to make the dish in the piston smaller.
All machining was done by me using a lathe and milling machine.

by **AceSniper** » Tue Feb 08, 2011 7:18 pm

CAMB01 wrote:
Flannelman wrote:removing material from pistons would lower the compression ratio...

skimming the block would bump it up

Not if you take material off the top to make the dish in the piston smaller.
All machining was done by me using a lathe and milling machine.

Still going to lower it, or you run longer rods to bring the pistons up higher?

by **CAMB01** » Tue Feb 08, 2011 7:34 pm

AceSniper wrote:
CAMB01 wrote:
Flannelman wrote:removing material from pistons would lower the compression ratio...

skimming the block would bump it up

Not if you take material off the top to make the dish in the piston smaller.
All machining was done by me using a lathe and milling machine.

Still going to lower it, or you run longer rods to bring the pistons up higher?

Hence why i decked the block to suit.

by **AceSniper** » Tue Feb 08, 2011 8:49 pm

sorry my bad not reading complete story

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