calculations must have varied somewhere, because taking the pistons down .010 will put the dome .010 out of the hole. i already know this from when it was previously assembled with +.030 kb356 pistons.

when he says he took .010 off the crown, does he mean the entire top of the piston, or just the dome? should i have him shave .020, to give me 0 deck clearance? will shaving the dome affect CR?

 

just talked to him

hes going to discuss the .060 quench with a few people and get back to me.

he was adamant in saying that it would NOT need to be rebalanced, he was just going to check the weight of all the pistons to make sure they are equal.

he said shaving .020 from the quench pad would give me 0 deck, which is good, but it would lower compression, so i think ill just stick with shaving .010.

may be a good idea to leave the specs unaltered, as the experts had them already determined on the original build; unless i have a VERY good reason to do so.

 

High Quench on low compression motor can detonate as much as high compression motor .060 is pretty high.

I'm going for zero deck with .039 Felpros so my Quench will be aroung .039, that's on a dry motor, oil on the journals/bearings changes things a tiny bit. Nothing we need to worry about.

 

ok ill discuss the quench with him when he gets back to me with his explanation as to why quench was originally planned at .040 and changed upon completion of the build to .060.

should we shave .020 of the dome and lose compression to attain 0 deck, or shave .010 maintain CR and have the dome .010 out of the hole?

 

lets chat static compression ratio with 2 common(fel pro) heads gaskets leaving all parts as advertised or the same and keeping the dome as advertised or no milling of the dome.can only use adverized spec's to calculate,do not have the project infront of me.

head cc....60cc as advertised....need to cc chamber to be accurate...?????..eddy heads adver as 58cc but are 60cc's when filled
p head vol....+23.5....+ number adds vol which decreases compression
cyl bore dia....4.040
deck clearance....0.001
stroke....4.000

with the advertised numbers we can calculate compression with common fel pro head gaskets.

head gasket one is .039 x 4.180 bore.....gives a 10.090 static ratio

head gasket two is .054 x 4.180 bore.....gives a 9.770 static ratio

widdle down the dome will reduce the compression in either case by increasing vol..the dome is the only area that gets carved down,not the entire tops.this is were the piston compression height comes in to play and does not account for the dome.this is why i say the piston will be in the hole .001 and the dome(advertised spec .050 vs decked block height 9.589)will be .049 out of the hole and the rest of the piston will be .001 in the hole......if the dome was .010 above then he widdled them down .039 per advertised spec....want to zero(.0000) deck the dome then he would need to widdle .049 off just the dome leaving .001 of the dome.if you got the cam specs you can calculate the dynamic compression.if the pistons weight any diff it needs to be re balanced.lighter/heavier will change the bobweight/reciprocating factor which is more calculating for the weight fixtures that simulates the rod/piston assembly.

 

it looks like all kb356 weigh the same. he was absolutely clear in saying that it WOULD NOT need to be rebalanced.

heads have been cc'd

somethings not quite right... like i said before, when he shaved .010 off the dome, the piston is .010 out of the hole..... WAIT! THATS WHERE I WENT WRONG! he shaved .100! not .010! HOWEVER, after being shaved the dome WAS .010 above deck. this may be because the deck was shaved .010. however, shaving .100 would put the dome .051 in the hole, not .010 above the deck... whats the deal?

.039 gasket doesnt leave enough room for quench

when calculating CR and deck clearance, do you input dome height or the dish height or the flat part of the piston?

cam specs are a few pages back in the thread.

 

lathe turn piston crowns down .100" ... thats exactly what it says on the build sheet.

THAT MAKES NO SENSE! that would eliminate the quench pad, as it is only .050 above the rest of the piston, whats going on here?

 

Misprint?

Wonder if he "slipped" with the lathe, and cut more than he intended?

How far did the pistons stick out of the bore before being turned?

If he cuts 'em down to far..... you are going to have ping that just won't quit.

 

URGGGGH! the paper states that he turned them down .100. it then goes on to say that the dome was .010 above the deck after the lathing.

i did some calculations with a deck height of 9.59, 6.123 rods, 1.465 compression height. with those numbers deck clearance comes to -0.0019999999999989, so the piston is just barely in the hole, right?

BUT i do beleive that would be ONLY on a flat top piston, so adding .050 for quench pad elevation per KB site (summit site says .085, dont know why...) that would put the quench pad about .050 out of the hole before being shaved. so, somethings AMISS because shaving them .100 should THEORETICALLY, put the pistons .050 in the hole. .050 in the hole is BAD.

somehow, just thinking of the old pistons... it seems like the dome was higher than just .050... MUCH higher. but maybe im wrong

 

it also seems to be a toss up regarding quench pad elevation. summit says .085. KB site says .050. KB's online catalog says .085 and a multitude of other sites vary as well.... YOUR KIDDING ME, RIGHT???!!!