Clearance / Detonation issues???

[J_Dog]

Well I just ordered a set of pm3 pistons, bearing, rings, and a hone. I'm throwing this in a d16a6 / y8 mini. Using a couple of compression calculators I found it should yield a 12.25:1 compression. The pm3's are out of a d15b7, that's what I was comparing to, to see if I would have clearance issues.

d16a6 stats:
stroke : 90mm
Deck Hieght : 212mm
piston volumn : -3.4cc
Comp Hieght : 29.5mm
Rod Length : 137mm

d15b7 stats:
stroke : 84.5mm
Deck Hieght : 207mm
piston volumn : -1.5cc
Comp Hieght : 30.7mm
Rod Length : 134mm

I don't know if these stats will help or not, I'm confussed about it.
Am I going to have clearance issues with this set up?!? In the future when I want to swap in a crower stage 2 am I going to have issues then?

I'm running between 5500 and 9000 feet in altitude. Think I'll have detanation issues with 91 octane and 12.25:1 CR??? If so I can put a OEM a6 gasket on it and drop it back down to 11.88:1. That should be okay right?

I'm trying to get this swap done in the next month so any help would be greatly appreciated. Also this is my DD, it's still going to be reliable right? with the occasional race that is ;)

[transzex]

clay will be your friend.

[leshok]

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

[shifty35]

I hear the sound of things breaking...

PM3 will stick out of the deck on a 1.6L block. Y8 head is flat on the bottom. You do the math.

[J_Dog]

I thought I calculated -1.5mm below the deck. am I wrong??? I don't really have time to clay either. It's more of a one day swap in thing for me. If I screw things up then I'm going to have to swap my a6 head back on really quick. So there's no way it's just going to swap in and fit???

[shifty35]

D16A6 -

212mm - (137mm + (90/2)mm + 29.5mm) = 0.5mm (positive, so in the hole)

D15B7 -

207mm - (134mm + (84.5/2)mm + 30.7mm) = 0.05mm (positive, so in the hole)

B7 pistons in A6 block...

212mm - (137mm + (90/2)mm + 30.7mm) = -0.7mm (negative, so out of the hole)

Yeah, those pistons will stick out of the deck, and your head is flat. Carnage w/o reallllly thick HG.

[J_Dog]

well how thick of a head gasket are we talking???? .048 ???

[d112crzy]

.048 gasket should give you just enough clearance. 1mm=.04"

[shifty35]

.048 gasket should give you just enough clearance. 1mm=.04"

Assuming your rods stretch < .3mm, sure. I'd say 1.5mm HG to be safe, but by that point, I'd be looking for different pistons.

[SupaStyl]

wrist pin height owns you on this one.

[s_18]

I don't quite understand why one would buy a set of pistons BEFORE figuring out if it is usable... Sorry, it just had to be said.

[J_Dog]

I did the research and thought I calculated everything out right but I guess I didn't. Using those Compression calculators I show a -.028 piston to deck hieght with this set up. Am I calculating wrong??? If it was -.028 then a .048 gasket would leave me with about .5 mm of clearance right?

[shifty35]

0.5mm is nothing... .02"

Your rods will easily stretch that much at 7k rpm.

[transzex]

boom boom, out goes the lights!

[sl@sh]

i think expansion thru heat and a bit of stretching
goes between .027-.033"

and if u had .020" clearance? then it means at about 6k rpm or right when u get to temp.. ur pistons will be pushing the head upwards

hehehehe

[J_Dog]

well crap that sucks. sounds like I'm out $60 bucks. Anyone interested in a set of d15b7 pm3 pistons??? Brand new, haven't even arrived at my house yet lol. Sell for $50 + shipping.

[99EJ6T]

well crap that sucks. sounds like I'm out $60 bucks. Anyone interested in a set of d15b7 pm3 pistons??? Brand new, haven't even arrived at my house yet lol. Sell for ___+ shipping.

wooh wooh, slow down there. put it in the right section of the forum, don't want to get in trouble.

[J_Dog]

Yeah I put an ad in the for sale section. Damn I wish these pistons would work. they'd give me 12.25 with a y8 gasket and 11.88 with an a6 gasket. But whatever. Back to the drawing boards.

[SupaStyl]

p29's with a y8 gasket will be perfect for a dd. trust me on that, tuning high comp. for pump gas can only go so far until you hit diminishing returns. 11.5 would be the highest i went without race gas. Hindsight is always 20/20.