Higher compression?

[thegreatdane]

How much can you grind of the cylinder head without thrashing the valves? Or how much should you grind it, to gain the most power? It's a carburetted engine...

[shepherd79]

yeah i would like to know that too.

[thegreatdane]

Anybody?.. :stick:

[thegreatdane]

No? :( :fight:

[smufguy]

i would say that its much more cheaper and easier and right to get high compression pistons and not shave ur head.

[thegreatdane]

Wouldnt that be freggin expencive? A grinding is done for about fifty dollars or so. What would four high comp. pistons cost?

[dXsquared]

4 pistons are around 500 bucks... plus it costs 1000 bucks for a shop to replace them, or like 2 weeks down time on your own, with the chance of fucking somthing up

Travis

[thegreatdane]

Yea, I thought so... I'll stick to the original question.

[Jareds 89 LX-i]

Alright since nobody else has answered the question...here ya go

The most you can shave off your cylinder head is 0.05mm, or 0.002 inch (not very much!). I had mine shaved though and haven't had any problems. Slightly higher compression too.

[thegreatdane]

Thats not much! What is your compression ratio now then, do you know?

[Jareds 89 LX-i]

I'm not sure what the actual compression ratio is (although there is probably a calculation to figure it out...I'm not sure though), but when I did a compression test not long ago my cranking compression ranged from 199-210 psi accross all 4 (not bad for 314k and original piston rings, eh? hehe). Normal for a new engine is 178 psi, so I'm about 20-30 psi higher

:)

[88accordlxcarb]

I had my to shace my head when it blew the head gasket. It warped the head a TINY bit... SO it is now shaved.

Higher compression. I like it, its been two yars and no problems so far. I am not sure what the compression is.

[shepherd79]

i think you can shave more than just 0.002".
Jered, you bumped your compression ratio from 9.3:1 to about 10.1:1
http://www.geocities.com/terminalvelocitycoaster/adr/
it is not a bad gain, but as i said there is a little more room to shave. may be another 0.001" or 0.002" making total of 0.003" or 0.004" to shave.
Jered, how much did you pay to shave 0.002"?

[Jareds 89 LX-i]

I paid $347 for everything. That included shaving the head, valve job, 1 new valve guide, pressure test, magnaflux (if necessary), and a full head gasket set ($120 something by itself)

[thegreatdane]

Originally posted by Jareds 89 LX-i
I did a compression test not long ago my cranking compression ranged from 199-210 psi accross all 4 (not bad for 314k and original piston rings, eh? hehe). Normal for a new engine is 178 psi, so I'm about 20-30 psi higher

:)

Pretty good. I now a Honda workshop, that says an Accord is just warn fit at 250.000 miles... (screwy sentence i think... don't know the right words)

shepherd79--> I dont think you can calculate an excact compression ratio, just from the compression. I've never heard of such, anyway.

[AccordEpicenter]

when you shave the head it also sets your ignition and cam timing off by a few degrees, enough to cause performance issues.

[1987HondaAccord]

how can that be true? The cylinders still reach maximum pressure at the same degree and BDC is still the same so there will be the same amout of time for the air to get in.

[thegreatdane]

Originally posted by AccordEpicenter
when you shave the head it also sets your ignition and cam timing off by a few degrees, enough to cause performance issues.

Are you sure about that? As i see it, the only thing that happens is that the timing belt looses micro little tension, wich can be fixed by tightening the belt, although it probably wouldn't be necessary. Correct me if wrong?

[shepherd79]

there shouldn't be any problem with the belt. you are shaving .002". it is not like you will shave .5"

thegreatdane, i didn't say it was exactly, but it is possible to tell what is your compression.

[AccordEpicenter]

nope still tweaks the timing of both because you are bringing the cog closer to the crank cog and the tensioner is after that it just takes up the slack.

[Vanilla Sky]

why not have a shop make an adjustable cam gear? wouldn't that fix it? i'm not exactly of "sound mind" at the moment, but wouldn't an adjustable cam gear fix that?

[79EK1]

An adjustable cam gear will fix the cam timing problem. That's one reason people use them (the other is to fine tune the cam timing). The more you shave the head, the more the timing is off. Even with a deep shave, the timing will only be off a by few degrees.

The only way to know your compression ratio for sure is to measure the volumes in the head with a buret. Any performance machine shop can do this for you, or you can buy the tools and do it yourself (not cheap $$). You'll also need to know the bore and stroke, deck height, piston dish/dome volume, and compressed head gasket thickness. The Hot Rod or Car Craft websites used to have a how-to tech article, but I don't know if it's still there.

[Vanilla Sky]

what about shaving and high compression pistons... would that be too much on the block? if it wouldn't blow up, that would be a decent bit of extra power

[79EK1]

Shaving the head and using high compression pistons will definitely raise the compression ratio fast. You'll have to measure everything and do the math to stay out of trouble.

[thegreatdane]

Originally posted by shepherd79
thegreatdane, i didn't say it was exactly, but it is possible to tell what is your compression.

Okay. I wasn't trying to bother you or anything, just making sure people wouldn't think you can get excact results from this.