yotafreakshow

well, i'm in the middle of my 22r rebuild, got the bottom end assembled, everything plasigauged ok, but my quench height is between .030 and .034 on all 4 pistons, guy at the shop thought maybe only .004 or so had been decked off...rods were re-honed, block bored .020, new ITM pistons, rings, pins, crank ground .010, new bearings, so the excessive quench could be a combo of these things, or they really decked alot more off than they said. I guess I need a thicker headgasket now...does anyone know the compressed thickness of a stock toy headgasket. I have a new one, it measures .056 or so out of the box. I thought I read somewhere that it is like .020 compressed, which would leave pistons with .014 to go, then holes in the head...I've seen these http://www.summitracing.com/parts/CGT-C4269-040 advertised...assuming the stock head gasket compressed was .020 and assuming(I really wish I'd measured) the stock quench at .006 (which seems to be the consensous), that leaves .014 between piston and head at TDC...theoretically, so that .040 thick gasket would leave me with .006 clearance on my highest piston...I doubt that's enough? If so, will the compression be too high? I've seen the .020 copper headgasket spacers too, I don't think it will be thick enough that way either. I was well aware that this might be an issue before I started, guess I should have been more clear with my machinist about minimal decking, or maybe the pistons are a bit taller? Got to figure it out and move forward at any rate.

xxxtreme22r

are you saying you had the rods cut and crank turned and your pistons are still above the deck height? or was the block shaved as well.

yotafreakshow

block was shaved...they said .004

yotafreakshow

my bet is more like .040...

xxxtreme22r

there is an article somewhere posted on here talking about quench and stuff that i used as a guide when I did mine. it was a forum article post by Ted at ENGNBLDR, i will see if I can find it. It mentions on how far you can go with positive quench.

xxxtreme22r

that seems way too much, I believe max Tod at ENGNBLDR told me was 20 or 30 thous. without it drastically affecting cam timing. I had mine done at 20 thous. with brand new crank, brand new rods and 30 over pistons from EB i was still slightly at a neg quench but not by much. maybe .005 -.008. I can't remember off hand.

yotafreakshow

thanks, got a call in to my machinist to get the scoop too.

xxxtreme22r

found the link to the article. http://www.4x4wire.com/forums/showfl...fpart=all&vc=1

xxxtreme22r

I stand corrected on my 20 thous block deck it was 10 not 20.

xxxtreme22r

from that article it looks like this is what you should be shooting for. Quench set to zero/+.006"

yotafreakshow

they said they decked .006 off the block, and their chart shows a .032 max protrusion spec for all 22r's...way more than anything i've seen posted. machinist also claims that a headgasket is only compressing about .003 leaving about .053 or so of gasket thickness, thus a head/piston clearance of about .019...wonder where all these specs come from. Ted @engnbldr has alot of experience that results in his preferred quench spec of 0-.006 which is what I am/was going by. My shop says I will be fine with stock gasket, I am curious how I will be upon first startup.

xxxtreme22r

i would be willing to bet that .032 spec they give is the actual piston to valve clearance and not a quench clearance. and to my knowledge 0 quenching has nothing to do with the headgasket thickness. it solely relies on the piston tops to the block deck, now adding a spacer shim height would be included but not the headgasket.

xxxtreme22r

if you search for quench on here you will come up with a thread of mine that i started when i was doing the rebuild on mine. some people has some good info in it.

xxxtreme22r

from that article : "So "dummy" up the short block, and measure how close the piston is to the top of the block. A straight edge and a feeler guage makes this easy. We want it to be zero deck, or as close to that as we can get. Stock, the piston does protrude by about .006" or so, if yours does, this is fine. "

yotafreakshow

I understand this, if you have a +.006 quench and you set the head down on the block, the head will make contact with the pistons, so the headgasket's compressed thickness plays a vital role in how close the piston comes to the bottom of the head. I am just wondering how much variance/tolerance there is there. I guess what I'm looking for is the magic number of how close can the piston come to the head without a). hitting it at high rpm, b). screwing up the compression.

It just seems really crazy that the little bit of machining that was done added up to a .030 of variance there, unless the block has been decked alot before, though no one thought it had, is there a measurement from the deck to the mains or something? The new pistons measured .025 shorter from the top of the wrist pin to the top of the piston than the stock ones too...I'm kind of stumped here.

greatskiiiier

i have never built a 22r so i wont discuss any specs on it, but quench is distance from top of piston to bottom of the head

depth in the hole+gasket thickness
i know small block chevy's optimal quench is .040 but many people leave more room for 2 reasons, 1. machining cost 2. safety room
i can go in more detail about anything engine building wise but i can only relate to small block chevys as that is the only engine ive personally blue printed, but the art of engine building doesn't change from chevy to toyota, only the specs do

greatskiiiier

the term you are looking for is deck height, not quench

Trainwreckinseattle

IF you are getting those measurements your block would have to have been decked before.

Most Aftermarket pistons are de-stroked to allow for decking. Most are cut at about 10-15 Thousanths. Assuming you found some factory height pistons that wern't de-stroked, and your machine shop only cut .006. you would only have +.012 not the crazy number you're coming up with.

Also from my experience when cutting decks. Most of them truely clean up at about 8-10 thousandths. I cut all my factory dech blocks at 10 thousanths. This works well with the ROCK pistons ONLY WHILE USING A DECKED HEAD. I switch to a Totally different piston if I am going to use a NEW HEAD. This is because Rock pistons are destroked .032 which is a large amount. Proper compression is only achieved with a decked head. A new head which has a lower compression chamber because it's never been decked yields too low of overall compression with the destroked Rock pistons. Other pistons have to be figured out based off their own measurements.

Quench, piston de-stroking, decking of block or head. These things all have HUGE effects on compression, power, spark knock, etc. Also too high of compression can also destroy a headgasket. This stuff has to be right.

There is a LOT to getting any engine Right.

xxxtreme22r

come to think of it, we are both slightly wrong.

deck height is the distance from the center of the main bore to the top of the block.

The quench is the distance from the head to the piston when the piston is square in the bore.

The piston to deck height is what you are measuring.
This is commonly referred to as deck height but this isn't really correct.

with that said I guess it depends on what type of combustion chamber your head has.

Quench, or squish area is typically the flat area on the top of the piston that's almost level with the top of the block deck. It must have a corresponding flat area on the deck surface of the head to qualify as quench.

Perfect example of this would be the differences between the pre and post 85 22r heads which is why one had dished pistons (post 85) and one has domed pistons (pre 85)

xxxtreme22r

Trainwreckinseattle to my knowledge my rebuild kit was from ENGNBLDR which uses rock pistons, when asking him about the pistons and whether or not they were destroked he told me no the rock pistons are not destroked. However your comment about them being destroked 10 thousandths might be correct which explains why when I decked my block 10 thous (using a new head) I almost came to a 0 piston to deck height.