First FI Build
First FI Build I came across a 5.3 LM7 long block for $200 (in pieces) locally, and now I've stumbled into my first turbo build.
I dropped the block and crank off at the machine shop to get checked/prepped before I move any further with forged rods and pistons. My question pertains to heads. I have a set of PRC 225 62cc as cast on my n/a build now, and a spare set of 241s completely stock laying around. At what point would a bone stock pair of 241s limit me? When would head lift become an issue with the GM casting's limited deck height? Would I be better off using the 225s with their 3/4" deck height and boosting a 10.1:1 static comp. motor? (Im planning on running e85).
Ive done a lot of searching and reading, your input is appreciated; trying not to bother the guys at TSP anymore (they've been great). Thanks in advance.
I dropped the block and crank off at the machine shop to get checked/prepped before I move any further with forged rods and pistons. My question pertains to heads. I have a set of PRC 225 62cc as cast on my n/a build now, and a spare set of 241s completely stock laying around. At what point would a bone stock pair of 241s limit me? When would head lift become an issue with the GM casting's limited deck height? Would I be better off using the 225s with their 3/4" deck height and boosting a 10.1:1 static comp. motor? (Im planning on running e85).
Ive done a lot of searching and reading, your input is appreciated; trying not to bother the guys at TSP anymore (they've been great). Thanks in advance.
TECH Enthusiast
Joined: Jan 2012
Posts: 557
Likes: 9
From: Bowling Green KY
As long as you have springs, I would expect you to be ok with a stock set of 241's until north of 1000 WHP. I'd recommend good MLS gaskets and quality head studs, I know some people using high levels of boost with stock heads, and they overtorque the head studs by about 10 ft lbs for more clamping force. I'm not recommending this, but others have had success with it. Your PRC225's I would expect to make more power at the same boost level, as they will be less restrictive, and boost is a measure of intake restriction to a degree. No doubt the PRC 225's with the thick deck are better in about every way, but lots of people are making stock heads work well with quite a little bit of boost.
As long as you have springs, I would expect you to be ok with a stock set of 241's until north of 1000 WHP. I'd recommend good MLS gaskets and quality head studs, I know some people using high levels of boost with stock heads, and they overtorque the head studs by about 10 ft lbs for more clamping force. I'm not recommending this, but others have had success with it. Your PRC225's I would expect to make more power at the same boost level, as they will be less restrictive, and boost is a measure of intake restriction to a degree. No doubt the PRC 225's with the thick deck are better in about every way, but lots of people are making stock heads work well with quite a little bit of boost.
TECH Apprentice
Joined: Aug 2015
Posts: 397
Likes: 0
What are your goals for the build ? If I could make one suggestion , as I'm fairly new to the turbo game myself , build it big the first time because it will never be enough 😂 I started out with a nitrous ls1 z28, then built a single turbo ls1 z28 that made 609/646 at the wheels uncorrected. I'm now currently building a 370 cubic inch forged lq4, twin precision 6266's and changing just about everything in the car minus the Holley efi, suspension, and a few other minor items. Shooting for 1200 rwhp . Go big and do it once cuz once the boost bug bites, it never goes away and the route I have taken has been much more expensive then shooting for the stars to begin with!
What are your goals for the build ? If I could make one suggestion , as I'm fairly new to the turbo game myself , build it big the first time because it will never be enough 😂 I started out with a nitrous ls1 z28, then built a single turbo ls1 z28 that made 609/646 at the wheels uncorrected. I'm now currently building a 370 cubic inch forged lq4, twin precision 6266's and changing just about everything in the car minus the Holley efi, suspension, and a few other minor items. Shooting for 1200 rwhp . Go big and do it once cuz once the boost bug bites, it never goes away and the route I have taken has been much more expensive then shooting for the stars to begin with!
TECH Enthusiast
Joined: Jan 2012
Posts: 557
Likes: 9
From: Bowling Green KY
You sound like a very wise man. The gaskets, the fasteners, the fuel used (you using E85 so you have got that covered) and the tune, play more of a role than what the difference in those 2 heads offer in terms of staying attached to the block. Based upon the comments above, you seem to have good sense, and are not going to try to make stupid power with it. I'm sure you'll be fine with the stock 241s.
You sound like a very wise man. The gaskets, the fasteners, the fuel used (you using E85 so you have got that covered) and the tune, play more of a role than what the difference in those 2 heads offer in terms of staying attached to the block. Based upon the comments above, you seem to have good sense, and are not going to try to make stupid power with it. I'm sure you'll be fine with the stock 241s.
