9:1 compression too much for 15psi?

Well I have posted recently about my engine buildup. i bought aggiez28's rotating assy and block. Here are the components again:

Cola 3.75 crank
Eagle H beam 5.7: rods
JE/SRP -31cc pistons
Oliver Billet Splayed 4 bolt mains
214/224 .565/.605 114LSA (I am buying that seperate)

My heads are currently running 55cc chambers according to my head porter. That puts me at around 9.0-9.1 to 1 compression. Is this bottom end gonna hold up to 15psi at that compression, and is it safe to run 15psi @ 9:1 anyway? I dont really want to take the dremel to the heads to pick up a few more cc's. Thanks in advance.

Originally posted by RealQuick
Well I have posted recently about my engine buildup. i bought aggiez28's rotating assy and block. Here are the components again:

Cola 3.75 crank
Eagle H beam 5.7: rods
JE/SRP -31cc pistons
Oliver Billet Splayed 4 bolt mains
214/224 .565/.605 114LSA (I am buying that seperate)

My heads are currently running 55cc chambers according to my head porter. That puts me at around 9.0-9.1 to 1 compression. Is this bottom end gonna hold up to 15psi at that compression, and is it safe to run 15psi @ 9:1 anyway? I dont really want to take the dremel to the heads to pick up a few more cc's. Thanks in advance.

What kind of head unit will you be running to produce 15lbs of boost? I think you will not have a problem running 15lbs of boost with your setup. Just make sure the car is tuned properly and you may want to run a little race gas to be on the safe side when you go to the track. :)

Originally posted by IDOXLR8
What kind of head unit will you be running to produce 15lbs of boost? I think you will not have a problem running 15lbs of boost with your setup. Just make sure the car is tuned properly and you may want to run a little race gas to be on the safe side when you go to the track. :)

Ah yes, you are my new friend :) I seem to be getting alot of answers form you lately :) It is an S Trim, so it may be only good for 12-14psi, I dunno. I will use the pullies to produce the 15psi, but it will actaully do is anyones guess. I do have an alky kit installed. I will be using 91% Isopropyl?? (rubbing alcohol). I'll have it come on at about 5psi.

I ran 17# of intercooled boost w/9.1:1 compression on pump gas. up to 27# on race gas, never hurt anything.

new motor is 9.33:1 ;)

Originally posted by Brady_96Z
I ran 17# of intercooled boost w/9.1:1 compression on pump gas. up to 27# on race gas, never hurt anything.

new motor is 9.33:1 ;)

:eek: What king of components did you use on the bottom end?

Originally posted by RealQuick
It is an S Trim, so it may be only good for 12-14psi, I dunno. I will use the pullies to produce the 15psi, but it will actaully do is anyones guess. Based on our experience and many posts from other S trim owners, I would be surprised if your S trim made 12 lbs. boost. I'm thinking more like 8-9 lbs.

Originally posted by stealth2
Based on our experience and many posts from other S trim owners, I would be surprised if your S trim made 12 lbs. boost. I'm thinking more like 8-9 lbs.

:confused: I thought Rich made close to 15psi with his 383? Anyone else have any experience out there?

Originally posted by RealQuick
:eek: What king of components did you use on the bottom end?

TRW forged pistons, eagle h-beam rods, GM forged crank (355 c.i.)

It's all in the tune. ran a 6.17 @ 117 in the 1/8th. on around 19# boost.

Originally posted by stealth2
Based on our experience and many posts from other S trim owners, I would be surprised if your S trim made 12 lbs. boost. I'm thinking more like 8-9 lbs.

He should be able to get a little more since he is not going to be running an intercooler. :) I am thinking 12-13 lbs.

ZBass28 has a similar setup to that, it's s 355ci with an S Trim pulleyed for 15psi.

I think that you can see 15psi but that is the max. The S Trim is rated for 625fwhp but it's been shown that they can in fact make up to 650rwhp but that might be a blower on kill that is being significantly overspun.

I think it will come down to your intercooling.

I would go 8.5:1 if have to order pistons anyway.

My Griffin FMIC has allowed me to make 746rwhp thru an unlocked T400 on what is basically 110leaded. That is thru a 9", 4.11's and 28" slicls. So that is the dyno queen equivalent of 825rwhp. That was with 17psi. I think I could make a dyno queen number of 700rwhp on pump gas but it might be on the edge, 675rwhp for sure.

Originally posted by Pro Stock John
ZBass28 has a similar setup to that, it's s 355ci with an S Trim pulleyed for 15psi.

A 383 SHOULD EAT UP A LITTLE OF THAT BOOST THOUGH SHOULDNT IT?

Originally posted by RealQuick
:confused: I thought Rich made close to 15psi with his 383? Anyone else have any experience out there?

With a rigid intake I saw 14-15psi on my 383 with the S-trim. This was with mediocre heads and a small cam though (same cam - my "design"). With better heads it would likely make a bit less boost.

Rich Krause

Originally posted by rskrause
With a rigid intake I saw 14-15psi on my 383 with the S-trim. This was with mediocre heads and a small cam though (same cam - my "design"). With better heads it would likely make a bit less boost.

Rich Krause

On the intake side...like a Brad Brand tube? Are there cheaper alternatives to Brad brand? My heads flow 271/187 @ .550 lift (I dont have mid lifts on me), so they arent ground breakers either. They probably flow similar to your unported AFR heads.

Yes, I used Brad Brand's tube. I don't know of any cheaper alternatives unless you can fab up something yourself.

Flow numbers sound fairly similar, so if you have low intake restriction you should see decent boost with an S-trim An intercooler/aftercooler will eat up boost if you are using one (but should make more hp).

Rich

Originally posted by rskrause
Yes, I used Brad Brand's tube. I don't know of any cheaper alternatives unless you can fab up something yourself.

Flow numbers sound fairly similar, so if you have low intake restriction you should see decent boost with an S-trim An intercooler/aftercooler will eat up boost if you are using one (but should make more hp).

Rich

alky for me...

Not trying to rob your thread but I have been contemplating selling my shortblock or longblock and building a lowcompression 355" LT1 setup to run 15+psi. I would run a T-trim or lower the compression and run the D3 Procharger I have but don't know if I could make it fit. ;) My question is how would a heads/cam low compression with say 12psi stack up to my 150-175hpN2o setup I am currently running? My car ran on a 150 shot- 1.60-1.63 60's 10.80's@126mph 3550lbs raceweight, 3.42's and 3500converter and +3000' DA this past weekend. I would think I could run 10.50's@128-130mph with the blower and then a little gas on top of that could get down in the lower 10teens or so?

Brady what was the part# on those TRW's and what size dish were they? Would I be better off with a 454 BBC on gas than a supercharged and N20 355" LT1? I have the K-member in my car to run BBC or SBC so it wouldn't be too tough to swap and I already have a 454 LS6 shortblock. LMK Later Clint

i am currently at 17-18psi with 9.2:1 compression and 92 octane. i have had no problems with detonation. i have the vortech aftercooler without the large water tank and am running 28-29* timing across the board at WOT

Originally posted by chevyguy3
i am currently at 17-18psi with 9.2:1 compression and 92 octane. i have had no problems with detonation. i have the vortech aftercooler without the large water tank and am running 28-29* timing across the board at WOT

wow....thats alot of timing and boost for pump gas. I had no idea you could run a setup like that on 92. Must be some good 92:)

The water to air setup is helping ALOT. Typical IAT's with a good Air to Air still see north of 140-150, vs a good water to air will see 85-90 degs. Heck Mike Barreras mustang dynoed 1200hp and saw IAT's of 85 degs

Jose

i havent given them a good look yet at 17-18psi, but on 12psi my IATs were ~95 at part throttle, ~120-125 in the boost WOT. there are 2 water coolers on my setup, but i might be taking one off since its taking too much air from the radiator and i have nowhere else to put it

Originally posted by chevyguy3
i am currently at 17-18psi with 9.2:1 compression and 92 octane. i have had no problems with detonation. i have the vortech aftercooler without the large water tank and am running 28-29* timing across the board at WOT

What was your hp/tq if you dont mind me asking...

havent gotten it on a dyno yet. trying to get the tune a little closer on the street/track before i go blowing $ wasting extra time on the dyno that i wont need to once i get it dialed in a little better here first. also am about to change some parts on the engine so im waiting till i do that to pay $ for the dyno time to get it tuned in since the tune will just be off after i make those changes. hopefully ill be turning the rollers in 2-3 weeks

Hey Chevy Guy 3, which supercharger are you running? That's a gang of boost with intercooling! I'm using SPEED PRO pistons, part# L2441F with a 21cc dish. Which pistons do you use?