checking clearances

[dehall88]

I was thinging about shaving my head for higher compression. I know I need to check the piston to valve clearances but I'm not quite sure how to go about doing that.
I was wondering if anyone knew a good diy site or could explain it to me?
Also Im pretty sure I can figure out how to recalculate the compression ratio but if someone could go over that it would be helpful

[BigTuna]

Go buy some play-doh and some gasket tacky spray. Spray the piston and spread a about a 1/8 layer of play doh on one piston, and smear some oil on the head and all the valve faces so nothing will stick. Then assemble the entire motor timing belt ect check timing. Check you valve lash if you removed them or had and work done. Put the spark plug in tight, i like to gob a some play doh around the eletrode so it wont catch and pull the play doh off the piston.Turn the motor over by hand slow for at least 4 full rotations. Pull everything apart and look at the play dough, if the valve come within 40K of inch then its a good idea to run a smaller cam or thicker hg.

What head? What cam? What Pistons? What Head Gasket? How much do you want to mill?

[dehall88]

d15b2 stock head and cam, prob some kind of aftermarket pistons (I want to bore it out slightly) I'm thinking stock hg. this is really just a rebuild to make it run with a slight preference for performance

[signorelli21]

heres a write up on how to properly clay an engine

http://www.c-speedracing.com/howto/claymotor/clay.php

[dehall88]

hey thanks alot guys
now I just wish I could find some oversized pistons that are similar to stock profile. all i can find are stock and aftermarket ones with a dish or dome. Does anyone know where I can find some, or if I can somehow get away with stock pistons and oversized rings??

[BigTuna]

If you are going to stay NA then get a piston with some dome, it wont disapoint you.

[dehall88]

If i get a piston with dome that would raise compression, meaning I would mil the head less, or not at all. but I haven't been able to find pics of the domed pistons, so I don't know what they look like.
I'v been looking at some thing that lead me to belive that a domed piston would induce detonation at a lower cr at each octane rating of gas.
depending on the shape of the dome of course, but then i haven't been able to find pic's

http://www.theoldone.com/archive/quench-area.htm
http://www.theoldone.com/articles/The%5FSoft%5FHead%5F1999/

It probable wouldn't make much, if any difference at the cr's I'm looking at, but it might be the difference between being able to run super unleaded(89) instead of premium(93) which would save money :)

[BigTuna]

Here some pic of a P-29 domed pistons, if you can get pistons with dome for your motor than that is always a good route to go. Dont bother with anything from endyn, Im not a big fan of there work. Figure out what you want your goals to be and there is plenty of good setups out there to mimic. Dont overthink it and follow the KISS method of thinking, Keep It Simple Stupid.

http://i18.photobucket.com/albums/b114/quick85supra/Picture45.jpg

[dehall88]

Well I don't know about their work, but the theory put forth in the soft head article makes a lot of sense to me.

The idea is that high compression(good) leads to detonation(bad), something about gas laws pv/t=pv/t. but that is all relative given any specific combustion chamber. detonation comes from the fuel/air mixture absorbing enough heat to burn from a source other that the spark plug(before the fuel is burned under control). heat is absorbed through the surface of the mixture then distributed though the volume. therefore the surface area to volume ratio has something to do with the rate of heat absorption relative to temperature change. If heat absorption is at a minimum (removal of "hot spots", cooler range spark plugs, etc) then some amount of temperature change is unavoidable. what is important is to keep the absolute temp of the fa mix below the ignition point.

one way to do that is to start with a lower temp (intercoolers, cold air, etc). another is to slow the rate of temp change by changing the sa/v ratio. the lower the sa/v the less heat energy is absorbed per given volume the lower the temp change.

now on a honda engine a domed piston makes kind of a upside down 3d u shaped fa mix, high sa/v ; a flat piston makes a hemisphere like fa mix, ok sa/v ; and a dished piston makes the closest to spherical(ideal) fa mix.
also if the mix is flat and thin the edges of the mix are a greater distance form the point of ignition (assumed at relative center) thus a longer burn.
longer burn=more time for detonation to occur and less power. both bad.
thus a slightly dished piston would seem to be the way to go.

But I am looking to increase compression and a dished piston would mean the even more of the head would have to be milled, which I'm not sure would be safe, or long lasting. thus my search for flat top pistons. A good compromise between compression, detonation resistance, an integrity of the head.


Anyhow thats my take on what i'v read. if there's holes in my logic anywhere PLEASE let me know.
granted all that random stuff could be completely wrong or it could be right but make so little difference it's unimportant, but i'd kinda like to give it a try.
as for simple, i think to much for anything to be simple :)

[BigTuna]

Im not gonna argue with you just do what you want...

DOME=POWER The only difference between a dome and flat piston is you have to start the flame front a lil later due to the piston now being closer distance wise to the spark plug. A motor is simple suck squish bang blow, if you can squish what you have already sucked into a smaller area you gonna have a bigger BANG.

[transzex]

ask Larry this......if domed pistons are bad, why they still running them in Pro Stock?

Going semi-hemi or hemi chamber does help, but unless you have a small chamber to start with, you not gonna make much gains.

Look into his Boss 429 info, it used a semi-hemi design.

K.I.S.S.

Just look at the fastest NA SOHC.....running a ACCORD motor on old Webers.

Two myths put to rest with Bisi's car.....
DOHC VTEC is faster
Fuel injection is better

K.I.S.S........

[dehall88]

No doubt i would be happy with domed piston. They work very well.

But like I said I think to much to leave well enough alone and I spend way to much time online looking at all sorts of crazy peoples ideas when I really should be going to class.

anyhow does anyone know where I could find flat pistons or if I could somehow get away with stock piston and some kind of oversized rings for a slight overbore