84 yota ex-cab

I was wondering how much compression shaving 20 thou. off a 22re head would give you. I was looking at pistons but they are really expensive.

Flash319

Why? Do you want to run premium gas for some reason? You will get a higher compression but will do very little for power.

dcg9381

You should adjust you cam timing back into spec if you cut that much out of the head.. so factor that cost in also.

fast68

and mess up the timing chain

woops beat me to it

plus then you would have to shave the timing cover down
andthen anything bolted between the head/intake and block would need shortened

and so on and so forth

Matt16

I think you'd need premium gas or better frankly.

abecedarian

.020 off would probably not do anything to the engine if you didn't get the cam timing back into spec since the cam would be lagging. once you get the adjustable cam gear and dial it it, then you might be seeing some issues.

Sked

I'm @ 10.2:1 on my 20r and it made big difference IMO. Yes i have to run 91oct min and sometimes 94 when im playing around with timing but my truck aint slow anymore even on hills. Before keeping my truck at 100km/h on the highway was hard and impossible if there was hills, but now i can max out my speedo in 4th with no troubles.

But at the sametime i did the pistons I totally reworked the head with big valves/cam.

Matt16

Did that kill your fuel economy? What are you getting now?

Sked

i get 20-22mpg around town with 31's and 4.37's and i really like to rev my engine. If i babied it i might get up to 25 if i tried very hard, but this head revs to like 6k with a dip of the throttle.

Targetnut

I worked these numbers when I did my head, but I'm not sure where my notes are.

If I recall correctly, you cut almost 2cc's from the combustion chamber volume per .010" shaved from the head. After unshrouding my valves, and smoothing out the combustion chamber I was up to almost 60cc's. I had .053" milled to bring the volume to about 51cc's which gets about 10.2:1 or so compression ratio. at this compression ratio I run high test.

If you took off .020" with a stock volume of 56cc's that should get you real close to 10:1


I don't think .020" would have that big of an effect on cam timing, at least no more than a worn chain. But an adjustable cam gear would allow you to get that back.

I'll look for my notes and if I find anything different than what I've posted I'll get back with you.