height of piston in cylinder

[gnbeginer]

I am mocking up my 109 build and i have installed the rotating assembly. The pistons are right at the top of the cylinder, i mean right at the top. maybe a couple thousandths from the very top. I am running a eagle stock stroke crank, eagle h-beam rods, j&e pistons. I am going to be using 9441 head gaskets with arp bolts holdin down gn1 heads. block was decked 3 thousandths to equal them out on deck height. Am I going to have a catastophic failure if i keep it like this or do i mill the pistons?

Thanks

 

[earlbrown]

depends on the rest of your combo. only way to know for sure is to clay the pistons, and CC everyhing

 

[gnbeginer]

well - im going to run a 218/212 roller, 885's, and split ratio rockers(1.5 - 1.6). I planned on clayin the pistons as well as cc'n everything.

 

[bison]

Ive been out of the hole on a couple and couldnt detect anything till i was about .010" with a .040 cometic gasket. At approx .010 i could see a faint shadow on the head rom the piston when it rocks at the top of the bore.

 

[gnbeginer]

I used my dail calipers and checked crush on old set of 9441's and it was at 60 thousandths. I guess I better get "thick" head gaskets as a added measure for keeping my sanity.

 

[earlbrown]

I think .060 is pretty thick. any idea what the CH is on those pistons?

 

[earlbrown]

Ive been out of the hole on a couple and couldnt detect anything till i was about .010" with a .040 cometic gasket. At approx .010 i could see a faint shadow on the head rom the piston when it rocks at the top of the bore.

that's ballsy setting up quench at .030". You think the turbo let you get away with that? No way I'd go that tight on a N/A setup.

 

[bison]

that's ballsy setting up quench at .030". You think the turbo let you get away with that? No way I'd go that tight on a N/A setup.

I started at about .038". I knew I was ok with that having been there before. Low rpm for the most part. Over a 2 year span i milled the block Approx. .008" more still on the same line bore and with the same rods and pistons. The engine made a crap load of power. CR was 9.3:1. Im assembling the engine right now but I'll have about .040" quench this time with different parts.

 

[gnbeginer]

Ok - I got a few measurements after work today. I have 1.5 thousandths between top of piston and deck. checked crushed 9441 head gasket again .068. Measured the distance between intake valve and deck of the head itself - .320.
Cam is a 218/212 hyd roller, dur. 269/264 lift is 511/504. Will be running 1.6 ratio rockers on intake and 1.5 ratio on exhaust. So about another .030 on lift ?? on intake side? I am in the mock up stage of this motor - put rotating assembly in to make sure everything will clear. So if I need to I can get these pistons milled if i really need to.

thanks for any/all help

 

[earlbrown]

I would run thinner head gaskets. And put the 1.6's on the exhaust.

Any idea what your static compression will be with the .068" gasket? (actually real life numbers, not published numbers.)

 

[gnbeginer]

No idea yet. I am going to call felpro tomorrow and I need to find my copy of desktop dyno and put actual numbers in and see what it tells me. I gotta cc the heads yet. I am also thinkin of runing my 212/212 instead of the 218/212, but who knows. and I will prolly go ahead and run 1.5 on both, I have two full set for a sbc in 1.6 and 1.5 ratio

 

[gnbeginer]

oh yeah Earl - what ya charge for settin up a oil pump?

 

[earlbrown]

Most likely your 212/212 would make a better cam unless you're going berzerk with the build. Only way to know for sure is to do the math. The 1.5's will give you less overlap too. No reason to blow A/F out the headers if you don't have to. It takes a bunch of compression to keep big ass cams from being dogs.

If you need a timing cover PM me. I'm pretty sure I have one that's built and ready in my attic.

 

[gnbeginer]

tryin not to go berzerk with the build - only gonna b a street car. so I will run the 212/212 with the 1.5's. Got alot of good parts going into motor, biggest difference that everyone will notice first is the M&A intake I'll have on it. Should be fun.

I'll pm ya by the weekend about the timing cover.

 

[kidglok]

...I will run the 212/212 with the 1.5's...

thats what i run, good combo

 

[earlbrown]

A lot of people don't realize that huge ass cams bleed off cylinder pressure. In a N/A setup you just have to learn to live with a dog. With our cars you have to make it up with boost. The downside of that is bad gas mileage, weak bottom end, and excessive cylinder dilution. The upside is winning a boost gauge bench race.

I know which one I choose

 

[gnbeginer]

lol - well i hope i dont have a weak bottom end - all 4 billet caps and a girdle and a forged rotating assembly. like i said - it should be a fun car.

 

[earlbrown]

I meant weak as in no balls down low.

 

[Phoneguy]

I meant weak as in no balls down low.

I run a 224 hyd roller from RPE on my stroker...plenty of balls down low.

Bryan

 

[bison]

A lot of people don't realize that huge ass cams bleed off cylinder pressure. In a N/A setup you just have to learn to live with a dog. With our cars you have to make it up with boost. The downside of that is bad gas mileage, weak bottom end, and excessive cylinder dilution. The upside is winning a boost gauge bench race.

I know which one I choose

Simple solution to that is run a cam that has a faster ramp. Keep the opening the same and chop of the overlap. Run a lashed solid and shave off even more. Then you can get more than the best of both worlds if you are not worried about spending some extra on the valvetrain. There is a crap load of potential there with the right stuff.