Critique my 340 build .......

[orangecrush]

Wait, a zero deck piston with 5 cc valve reliefs in a 72 cc head and a .039 gasket eqaul 9.8-1 so sez the KB site and with thought to the KB107 piston in my 360.

Is it that much different in a 340?

Holy crap, I just went to that thread, I guess it is what it is! My bad, but error on the side of caution. I'm thinking piston to head contact ..........BAMMMMMMM!

Don't worry, we'll be checking first. Hoping for the best - these pistons have 7.5cc valve relief - x-head chambers are pretty deep, may make it okay - we'll see.

 

[ramcharger]

Modeling clay is our friend, lol!

 

[daves66valiant]

Sounds like a cool build. I was eyeballing that cam as well.

 

[rumblefish360]

Don't worry, we'll be checking first. Hoping for the best - these pistons have 7.5cc valve relief - x-head chambers are pretty deep, may make it okay - we'll see.

Good great. I was just not sure of it and wondered (Very) outloud about it. I'd hate to see bad things happen.

 

[doktor_x]

Running that tight, I'd go on the side of paranoia and check every cylinder with clay. A theoretical .008 doesn't leave much room for variances in machining, con rod stretch or the possibility of the big end of the rod being briefly (albeit hypothetically as a function of inertia) non-concentric with the rod journal during high-speed operation.

Paranoid ramblings aside, good luck with the build. It should stress the seat rails a bit.

 

[ramcharger]

Running that tight, I'd go on the side of paranoia and check every cylinder with clay. A theoretical .008 doesn't leave much room for variances in machining, con rod stretch or the possibility of the big end of the rod being briefly (albeit hypothetically as a function of inertia) non-concentric with the rod journal during high-speed operation.

Paranoid ramblings aside, good luck with the build. It should stress the seat rails a bit.

Hey Doc!

.035 is the absolute minimum with steel rods. Just a FYI. I've heard of people running less, but they are running under 5k rpm.

 

[doktor_x]

Hey Doc!

.035 is the absolute minimum with steel rods. Just a FYI. I've heard of people running less, but they are running under 5k rpm.

I was thinking that it was somewhere around there. It seems like I ran around .030 in my Pontiac 455 and it weirded me out for the first year or so of vicious abuse. Amazingly, it wasn't prone to detonation despite the relative eternity those pistons spent at the top of the bore. Still, it wasn't intended to see action above 5100 rpm.

Thanks for the info. Knowledge is good stuff.

 

[ramcharger]

I was thinking that it was somewhere around there. It seems like I ran around .030 in my Pontiac 455 and it weirded me out for the first year or so of vicious abuse. Amazingly, it wasn't prone to detonation despite the relative eternity those pistons spent at the top of the bore. Still, it wasn't intended to see action above 5100 rpm.

Thanks for the info. Knowledge is good stuff.

Quench (the distance between the piston and head or some head surface) is a very good thing and actually quells detonation! You were on the right track and didn't even know it at the time. 'Aint it cool to be a mad scientist? lol! Yeah, .030 is close, but with a BB Poncho, you really didn't need to go beyond the 5100 rpm you previously stated and had no detonation problems.

Anyway, here's a good read on quench and how it is our friend, lol!

http://kb-silvolite.com/article.php?action=read&A_id=39

There's a buttload more info on this site and I'm sure you'll find it without my links.

 

[ramcharger]

Doc,

This book is on my bedstand, and what's funny is that the first time I found it I was about 14. The best reading for someone serious about HP. I hope you dig math, lol! :http://www.bentleypublishers.com/product.htm?code=g140

This book is becoming exceedingly rare.