More compression for 1uz. Thin gaskets? Shaved heads? Pistons?

[desty]

What are the options? Whats the most cost effective? I want to go as high as I can get away with on premium.

Thanks.

[oldcorollas]

thought about the crank to cam distance?

[desty]

thought about the crank to cam distance?

Someone wrote an article on head shaving it so I assume ppl are shaving heads. The article had no useful info beyond cam timing/distance so I'm asking here.

[roadsailing]

assuming you have standard cams why do you want more compression?

[desty]

I've got some ported heads on the way which I plan to put BIG cams in. It already has itbs, bigger injectors and aftermarket ecu/ignition etc. Low compression would be the weakest link in the package afaik.

[oldcorollas]

well, you can easily calculate the effect of thinner gasket and shaving head... not much
SV+CCV/CCV=CR
SV = CCV (CR-1)
CCV= SV(CR-1)

for 1UZ, SV ~500cc
each mm of gasket/head = roughly 5.8cc

eg to go from 10:1 to 11:1 need to decrease CCV by 5.6cc, to 12:1 = 10.1cc

[desty]

Thanks! Are you saying it might be possible to get 12:1 with a combination of thin gaskets and a head shave? Do you think that would cause problems with the timing? Supposedly if you change the crank to cam distance by just the right amount you don't get issues.

A thought occurs, could that potentially cause the piston to hit the valves with big lift?

[oldcorollas]

might be difficult.

say you go from 0.8 to a 0.3mm gasket... thats 1.74cc there..
then you'd need another 8.4cc.. which, if the bore continued into the head directly, would need 1.5mm

but the head starts sloping straight away? = mayeb 2mm+ needed

this thread may be helpful.. looks like 2mm out of the head might be quite difficult?
(edit: go and read through eds various builds... could be rather worthwhie)
http://v-eight.com/tech_forum/viewtopic.php?f=4&t=977

[desty]

Well it looks like the decision may have been made for me. These arrived today and they seem to be missing a considerable amount of meat!



Would it be wise to cc the chambers before ordering cams?

EDIT: Actually, on closer examination, Are these even the same heads? I'm seeing some differences in the shape of the chamber.

[beerhead]

That looks to be shaved to the max, almost touching on the valve seats. I wonder if the heads could have been tigged then machined true to change the chamber shape? I know nothing about 1UZ's though, where's ED? I bet he can shed some light on this.

[desty]

I'm no expert but I don't believe that's the case. The chambers still have that cast finish. I'm dying to know wtf is going on here tho.

EDIT: Also,is it a no-no to grind away the valve guides? these ones are ground flush with the port surface.

[thechuckster]

the pic in oldcorollas's post is a 1UZ vvti head (std 1uz vvti piston volume is -11.5cc and std compression ratio is 10.5:1).

What are your newly minted heads off? and why did they port the bowls (and I presume ports) but leave the chamber alone?

I would expect a worked head to look something like this:

(1JZ head from here)

or this

(3SGTE head from this thread)

[desty]

Ok found a pic of a regular head. Hard to tell from this angle if mine have been machined much.



No idea why they didn't do the chambers chuck

[thechuckster]

that pic ^^ seems to match your machined head. Particularly the lower section.


Valve guides shouldn't be ground away but I have seen a few examples where the nose poking into the air-stream has been ground down to a taper so there's less bulk of metal obstructing air. If you follow the links below the pics I posted, you'll find how-TK-did-these-heads threads for porting both heads. Usual cautions about PF content (language and a no-holds-barred approach to comments) apply.

[gttv8]

Might be worth a read.

http://www.lextreme.com/Cam-Timing.html