Dynamometer Results & Comparisons - LSX Block 427ci, PRC 265cc Ls7 Heads

Plans for the Spring LSX Block 427ci, 11.2:1 CR, 150 Fogger
PRC 265cc Ls7 Heads, Linked Bar Lifters
‎247/255 .670 .670 112 LSA+4 Hydro Roller
Fast 102/102 Combo

Drive Line:
Built Th400, Yank 4k Stall, Moser 9in Wave Trac 3.89 Clogs

Leaven off the T-Brake n 2 Step Trying for High 9s w No Spray

Est WHP off the Juice 580ish

What ya think?... Trying to see if any else had thrown together a combo like this n gotten around what Im looking for Track times and Power

Sounds interesting. Subscribed

520 to 530

I'd want at least 550rwhp out of this.

535rwhp SAE on a Dyno Jet with a properly set up weather station. Depending on the wheel/tire setup.

I'd want at least 550rwhp out of this.

Not gona happen with prc heads and only 11.5 to 1 comp

Not gona happen with prc heads and only 11.5 to 1 comp

Can you elaborate some?

I guess 580 WHP isn't crazy and out of the question, but you gotta get more out of that. ... but my 402 is 530 with a 102/102 combo and a custom ground cam similar to the MS4. Im also running AFR 230V2 heads.

I would guess 520. Prc heads are a good head but the 400 and 9inch are going to kill your rwhp.

I guess 580 WHP isn't crazy and out of the question, but you gotta get more out of that. ... but my 402 is 530 with a 102/102 combo and a custom ground cam similar to the MS4. Im also running AFR 230V2 heads.

you have no concept of how much power a th-400 and converter eat up for power. I bet your 2400 stall converter was locked for thoes numbers

Can you elaborate some?

To reach 580rwhp(with a th-400) is gona take 14 to 1 ,More cam , and a good ls7 head like a mast

I know this short block made 520whp threw a th350 trans and a 12bolt w PRC 237cc Cathedral Port heads and a Fast 102/102 combo and a little smaller cam.....Car went 10.30s Guy was local we watched it run at the track

I bought the Long Block off him sold the heads and Cam and Going w the PRC 265cc Heads and the Cam in the OP

My Car last yr w a Stock Longblock MS4 Cam, Fast 102/92 combo w th400 and the 9in made 402whp 3320lbs w stock front K n A arms went 11.26@121mph Leaven at 2k ft braking

And Sommer86 now has my Fast 102 on his car lol

you have no concept of how much power a th-400 and converter eat up for power. I bet your 2400 stall converter was locked for thoes numbers

LOL they don't get it man it's alright!:jest:

Also from what I've seen that cam is all wrong for LS7's.

you have no concept of how much power a th-400 and converter eat up for power. I bet your 2400 stall converter was locked for thoes numbers

True, did not think of that, TH400 does eat more power AND unless you have a switch for the converter, it will be open.

To reach 580rwhp(with a th-400) is gona take 14 to 1 ,More cam , and a good ls7 head like a mast

I just noticed that he has the 265 PRC not the 285 PRC which (when I bought them) have the option of Carrie's casting (ETP) now Mast Motors.

My Car last yr w a Stock Longblock MS4 Cam, Fast 102/92 combo w th400 and the 9in made 402whp

You wont gain 180rwhp over that setup going to the 427 w/ PRC heads. Maybe 100 if everything's right.

Comparing dyno numbers from car to car and dyno to dyno is essentially useless.

LOL they don't get it man it's alright!:jest:

Also from what I've seen that cam is all wrong for LS7's.

Dont think Pat G knows his stuff?

Goin From a 237cc Cathedral Port to a 265cc Ls7 Head n Intake has no HP Gains than?....

you have no concept of how much power a th-400 and converter eat up for power. I bet your 2400 stall converter was locked for thoes numbers

I got 402 Whp on a dynojet out of stock longblock no Fly Cutting n Stock CR w Cam n Intake and UNLOCKED converter threw a th400 and my 9in.....

So say my car was 6spd whats it supposed to make 470whp the baddest stock LB Ls1 on this site?! Dont think so.... Prb 420ish area

you have no concept of how much power a th-400 and converter eat up for power. I bet your 2400 stall converter was locked for thoes numbers

Just an FYI, my 347ci motor made 449rwhp through an 80E locked and only 402rwhp unlocked. Same exact drivetrain behind my 418 with AFR 225 heads made 521rwhp locked and 469rwhp unlocked. I saw right about a 10% loss with my 4,500 converter unlocked (BTW that converter instantly became a 5,800ish converter behind the 418)



I know this short block made 520whp threw a th350 trans and a 12bolt w PRC 237cc Cathedral Port heads and a Fast 102/102 combo and a little smaller cam.....Car went 10.30s Guy was local we watched it run at the track

I bought the Long Block off him sold the heads and Cam and Going w the PRC 265cc Heads and the Cam in the OP

My Car last yr w a Stock Longblock MS4 Cam, Fast 102/92 combo w th400 and the 9in made 402whp 3320lbs w stock front K n A arms went 11.26@121mph Leaven at 2k ft braking

And Sommer86 now has my Fast 102 on his car lol


BTW, thanks for the heads/cam. Going to check the combustion cc's tonight since I had them decked (just to make sure they were square). Order my gaskets on Monday and put it together next week.

Still on the fence with running my current cam or the new one I got from you. Performance Trends engine analyzer has shown to be very accurate when I have modeled motors (with in 2% through out the full curve, and hitting peak rpms +/- 100rpm). Says I will loose low end TQ/peak TQ and make the same peak HP at the same RPM. I might try them both one weekend at the track.


You wont gain 180rwhp over that setup going to the 427 w/ PRC heads. Maybe 100 if everything's right.

Comparing dyno numbers from car to car and dyno to dyno is essentially useless.


I agree it will be hard to make an extra 180rwhp with out a LOT of changes. Also consider the 520rwhp that was once made with the 237's/427ci combo was through a TH350, not a TH400.

Take the above example of my old 347 with stock ported heads against my 418 with AFR 225 heads. Same compression (11.1-1), intake(Super Victor), Dominator TB, 1 3/4 stepped to 1 7/8 headers, and drivetrain (80E, 4,500 verter, 12 bolt, 4.56's, and 315/60/15 DR's). Unlocked I picked up 67rwhp, locked 72rwhp.

I am hoping to make 520rwhp with my new heads, higher compression, better headers and Power Glide. But more importantly is going 10.5x..

Once you go with a th400 your dyno #'s can vary huge. Our real street rhs 461, trickflow 265, solid roller .800 lift, beck intake, 15:1 comp made 861 on the engine dyno and dynoed 590whp. It did run 141 mph on motor though. Once you go with a glide, th350, th400 toss the chassis #'s in the can.

Just an FYI, my 347ci motor made 449rwhp through an 80E locked and only 402rwhp unlocked. Same exact drivetrain behind my 418 with AFR 225 heads made 521rwhp locked and 469rwhp unlocked. I saw right about a 10% loss with my 4,500 converter unlocked (BTW that converter instantly became a 5,800ish converter behind the 418)






BTW, thanks for the heads/cam. Going to check the combustion cc's tonight since I had them decked (just to make sure they were square). Order my gaskets on Monday and put it together next week.

Still on the fence with running my current cam or the new one I got from you. Performance Trends engine analyzer has shown to be very accurate when I have modeled motors (with in 2% through out the full curve, and hitting peak rpms +/- 100rpm). Says I will loose low end TQ/peak TQ and make the same peak HP at the same RPM. I might try them both one weekend at the track.





I agree it will be hard to make an extra 180rwhp with out a LOT of changes. Also consider the 520rwhp that was once made with the 237's/427ci combo was through a TH350, not a TH400.

Take the above example of my old 347 with stock ported heads against my 418 with AFR 225 heads. Same compression (11.1-1), intake(Super Victor), Dominator TB, 1 3/4 stepped to 1 7/8 headers, and drivetrain (80E, 4,500 verter, 12 bolt, 4.56's, and 315/60/15 DR's). Unlocked I picked up 67rwhp, locked 72rwhp.

I am hoping to make 520rwhp with my new heads, higher compression, better headers and Power Glide. But more importantly is going 10.5x..


I just dont see why it wouldn't pick up some power on the dyno switching to the Ls7 stuff over what I sold U. Above everything It should shine at the track pretty good

I was just kinda surprised when we dynoed my Stock LB build w the TH400 vs my buddys same build but w a 6spd n 10bolt his car made 25whp more than mine n we dynoed on the same dyno back to back

Once you go with a th400 your dyno #'s can vary huge. Our real street rhs 461, trickflow 265, solid roller .800 lift, beck intake, 15:1 comp made 861 on the engine dyno and dynoed 590whp. It did run 141 mph on motor though. Once you go with a glide, th350, th400 toss the chassis #'s in the can.

Right so typically The higher the HP the more loss ur going to see, and alots got to do w the converter slip % and whats its set up for correct?

Your dyno #ers certainly wont do that motor justice through that drivetrain. I would guess 660 minimum at the flywheel NA. Thats a pretty good size cam for LS7 heads with that intake. The intake will be your restriction for peak horsepower.

Post it here http://ls1tech.com/forums/dyno-guesses-bench-racing-forum-150/

Moved...

Also from what I've seen that cam is all wrong for LS7's.[/QUOTE]

Really?? Interesting.......:cool:

Also if you have a loose converter that flashes to a pretty substantial rpm off the hit, most dyno's have a hard time being able to keep up with the torque curve/output and the numbers will be skewed.

Pat G does know his stuff, I just think your heads would do better with more exhaust split on a wider lsa.

Also from what I've seen that cam is all wrong for LS7's.

Really?? Interesting.......:cool:[/QUOTE]

Whats your imput on this? Sounds like u may have ran a LS7 heads n cam before

Really?? Interesting.......:cool:

Whats your imput on this? Sounds like u may have ran a LS7 heads n cam before[/QUOTE]

Me? Naw, only thing i can say is that cam looks pretty darn good to me;)

Ya Iv herd of big cam spec in LS7 and LS3 headed build and ppl saying how it ran like crap down low so they swapped out cam for a smaller one and it rans just as good but pulled harded down low.....but this may have only been a issue w the newer style PCM and not our 4th gen style

Ya Iv herd of big cam spec in LS7 and LS3 headed build and ppl saying how it ran like crap down low so they swapped out cam for a smaller one and it rans just as good but pulled harded down low.....but this may have only been a issue w the newer style PCM and not our 4th gen style

I worked with 7 different cams on the engine dyno and in my car so trust me, more then one of those was bigger then that and idled like a kitten at 900 rpm's. How does 646 lbs of torque at 5250 rpms sound to you!? It's all in the combo...

I worked with 7 different cams on the engine dyno and in my car so trust me, more then one of those was bigger then that and idled like a kitten at 900 rpm's. How does 646 lbs of torque at 5250 rpms sound to you!? It's all in the combo...

lol feel free to pm me those cam specs

lol feel free to pm me those cam specs

Hahahahahahaha!!!:eyes:

My 402ci is 545hp and near 132mph in a 3,700lbs car. A 427ci proper built could see 570-580hp set up right.

My 402ci is 545hp and near 132mph in a 3,700lbs car. A 427ci proper built could see 570-580hp set up right.


I thought your car was M6 ?

Here's a little help...
GMPP LSX block 427ci
Callies 4 inch stroke crank
Howards 1000hp billet rods
Wiesco -2.8 cc pistons
deck height -.003
.036 comedic gasket
Heads are PI/MAST 6bolt angle milled by WCCH to 58cc's (and now 11 degree angle) = 13.6 to 1 compression
Crower Shaft rockers
Cam is a 243/255 113+4 660/670 lift (found out quick that bigger cams don't work that well with a FAST manifold on these combos).
FAST ported and raised to fit the heads by LS2 PORTWORKS
Nick Williams 102mm t-body
ARH 1 7/8 headers, Dual/Dual cat back, 4inch race ready cut out after the cats...
Strange 12 bolt 3.73 gear ratio.
4L80E
Circle D 4C converter... Flash rpm 5400 on the dyno

It made SAE 584, STD 601 (locked). Unlocked SAE 530, 547 STD. I will have to wait to see what the extension is on the track to find if I need to restall. With a little break in time, NO cats and a 4L60E, I might have seen 560 unlocked. So you can see how hard it is to make 580 unlocked with a Fast manifolded combo "with a loose converter"(...54hp is getting up there). I do have video on you tube but I can't get on it for the link from work. If you want to see a few pulls search "Nohorsepower" on youtube...