are there any sacrifices to raising compresion??

[Rollin']

planed my head.5mm

from 1000-3700, it is very flat and hardly any power, but after 4000, it kicks arse.
i have a broken throttle position sensor, it doesnt spring back for part of it. would this be my problen fixed, or is there something else.?

[Monsterbishi]

planed my head.5mm

from 1000-3700, it is very flat and hardly any power, but after 4000, it kicks arse.
i have a broken throttle position sensor, it doesnt spring back for part of it. would this be my problen fixed, or is there something else.?

Fix it and find out, no point in checking anything else until you rule out the obvious.

[Twolitre]

planed my head.5mm

from 1000-3700, it is very flat and hardly any power, but after 4000, it kicks arse.
i have a broken throttle position sensor, it doesnt spring back for part of it. would this be my problen fixed, or is there something else.?

Raising your compression would not only give you more top end power but more low end as well so I think you should look elsewhere for your problem, did you ditch your T-VIS ? is your timing spot on and is your cam timing set properly?

[Rollin']

timing should be all sorted right, still got tvis.
when i get another tps, ill rule that problem out.

just seems abit slow on the take off til 4000.

[4agepwr]

hey there
im quite interested in this modification
how much did it cost you to do it>

[Rollin']

well it was an extra, i didnt just get the head planed by its self, i had to blow my head gasket first!!

it was only an extra $22 ontop of a normal crack test and skim so $130incl gst

plus another $130 for a completer decarb of vavlves etc..

then u got $220 for a head set, $200 labour (cashy) plus 450 fluids

[Gadget]

Definately do the TPS, but I agree with Ryan here, sounds like your cam timing is a little out - maybe inlet cam 1 tooth advanced or something similar (advancing the inlet cam is what VVT does afaik).

Timing is an easy one to get slightly out on the 4AGE (apparently) 'cos even Toyota has done it wrong on a couple of engines I've seen.

Planing 0.5mm off the head should affect things too much, in old skool talk it's only about 20 thou or 0.020 of an inch. This sort of increment is normally used just to true up a head, with the (marginal) rise in compression as a by product.

The amount it will raise the compression depends on where the majority of the combustion chamber is located...(head or piston top) The other thing to think of is that afaik the 4AGE is a non-interferance engine, and what you're effectively doing is bringing the valves closer to the pistons.... Once again tho, 0.5mm isn't much I guess.

My 2c.

[badassmofo]

could also be your distributor timing, retard it a bit.

[Gadget]

dammit, forget about distributor timing these days... so long since I've actually had a distributor on my engine.....

[ChaosAD]

Planing the head will change your valve timing a bit