74u

iTrader: (9)

I recently swapped H/C/I. Bottom end was untouched and same supporting parts were used..

Old combo...
LS3 block w/4.070 bore x 4" stroke
TEA TFS 225 w/nitrous exh port milled to 59cc 11.2:1
Fast 92 with bumps removed, throated to 95mm to match 95mm t-body and port matched to heads
Tick Custom 239/246 - 624/595 - 113+2
TSP 1 7/8
3" true dual over the axle

My old combo made 475/446 and ran 92mph in the 1/8 mile.

New combo...
LS3 block w/4.070 bore x 4" stroke
LS3 821's - stock runners & chambers - milled to 58cc 11.3:1 and intake flange milled to promote better port alignment
LS3 intake stock no port matching (t-body flange port matched to 95mm t-body)
CamMotion 232/240 - 621/613 - 116+4
TSP 1 7/8
3" true dual over the axle

New combo made 475/460 and went 95mph in the 1/8 mile (121.6mph 1/4 mile)

Unfortunately I don't have the graphs to post (I'll get them next time I see my tuner), but what I found interesting is the big ole rec port 260cc runner LS3 headed combo out torqued the super sonic high velocity TEA TFS 225 Cathedrals from the bottom (15ftlbs rwtq advantage at 3000rpm). In fact the only area the cathedral combo had an advantage was was in "over-rev". Both combos peaked around 5900 - 6100rpm but the cathedral combo didn't fall off as sharply. I'm sure cam timing has a lot to do with the advantages both combos have on the dyno, but the cheaper and more street friendly LS3 CamMotion combo definitely made better MPH at the track.

I pocketed about $1500 dollars after selling the TFS & Fast and buying the LS3 heads/intake...I'm going to use that money to port the LS3's in the future...will report back.

EDIT: forgot to mention, the car is a full weight 99SS M6 (3750lbs) and track times have been on all-season 60,000mile warranty tires (exactly as I drive on the street). Sixty foot times are all 1.95 - 2.0 range.

1989GTA

Not bad at all considering the tires you have on the car. That is a nice improvement.

lil john

You better take this post down, a Rectangular head made more TQ.......Ha Ha & good bye to the ole Cathedral port. So you saved money and made more HP. What more could any1 ask 4.
Also you got more room 4 improvement.....Like a stage 1's 266 cc runner up to stage 3 with over 400 cfms and dirt cheap. Try this with any aftermarket heads for a killer price. I've been saying and telling guy's that old recipe is dead and over priced.

speedtigger

iTrader: (16)

This is one of the most interesting tests I have seen in a while. Stock LS3 heads getting it done.

lil john

As always, with cash to spend. Now I'm waiting 4 for 1 of these Cathedral head lovers to post something about there AFR,TFS,Mast......etc.. small runner heads that are supposed to be TQ kings with inflated prices. LOL!!!! I find this SO FUNNY. I've told these guys over and over. With a stock intake and stock heads...BTW. This is SO FUNNY.
Better put: 2500 dollar heads that lost to a pair of 1000 dollar stock heads.
They call it MARKETING 4 a reason........To get you to spend money on stuff that the factory already has done and just needs a little work.

Ha Ha!

1989GTA

One question. You state the weight of the car is 3750lbs. I take it that is the car only and not the race weight with the driver. I am trying to compare that with my car but I am running an A6.

74u

iTrader: (9)

It weighed 3750lbs with me in it, half tank and empty nitrous bottle last year.

The other day at the track I had a full 15lb bottle and 3/4 tank of gas, and helmet. I'm probably 3775'ish as raced.

It also went 127mph the same night on a 100 shot (made 570/588 on spray) activating in second gear. One of the nitrous passes it picked up 32mph on the back half

This car is basically in showroom configuration with added subframe connectors. Battery still under the hood, sway bars untouched, everything works, 275/40/17's on all 4 corners, etc.

If I had a drag suspension, and slicks I feel like this thing would easily go 11.0's (maybe 10's) on motor and low 10's on the 100shot.

KCS

iTrader: (20)

Interesting results, I wouldn't mind taking a look at the graph when you get it. Was it the same tuner and can he overlay the two?

I guess it's pretty safe to say now it wasn't the heads or cam holding you back.

Tuskyz28

Which combo feels better as far as stop and go traffic goes ?

lil john

The ls3's......Now you all always post about time. Now we going to, how does it feel...LOL

74u

iTrader: (9)

Stop & go is where I live Definitely the LS3's drive 100x nicer although I would think the smaller cam (less overlap) is the primary reason.

Tuskyz28

Due to my lack of knowledge I THINK I have a LS3 headed combo now with a 229/244 cam in my car. I think it's a car LOL

74u

iTrader: (9)

Yes, same tuner and yes, we had them on the screen together. I was on borrowed time just getting it tuned. The tuner (Sam Miller) kind of bent over backwards to get me in, and stayed till 9pm. When we were done he was busy trying to shut down his shop. I felt guilty asking him to go print the graph for me. I will get it though.

Your last comment...please elaborate?

I feel pretty safe saying TEA heads ($2800) and the FAST intake ($850) LOST to a stock LS3's top end ($1600 including springs, milling, and head gaskets) and even more street friendly street cam.

I do think the numbers are still low, but by how much? Gaining 3mph in the 1/8 puts it all in prospective.

KCS

iTrader: (20)

He should be able to email it to you.

475whp from a 416ci LS3 is like 400whp from a 346ci LS1. Even with LS3 heads and stock manifold, I would expect at at least 500-550whp. Something is going on that is holding you back and I don't think its a coincidence that you can swap the heads and camshaft and still make the same peak horsepower.

You're new cam has 12 degrees less overlap and 2 degrees shorter IVC. If I'm reading your results correctly, all you really gained is power below peak. I wouldn't really attribute that to the heads when there such a drastic difference in the valve events.

74u

iTrader: (9)

You are correct...only notable gains were down low. I too feel the peak power is low (although I don't see stock LS3 heads going deep in the 500's too often). I stated in the OP that I think the cam change is responsible for the gains down low.

Based on what most cam only ls3's make (475 fair to say?)...how much more rwhp do you think a 4" stroke is worth? My understanding is stroke tends to improve tq and push peak power to a lower rpm...but HP gains are minimal.

The leak down numbers are in the teens while it's cold. The motor doesn't smoke, and the shortblock turns freely. I've had two different header/exhaust combo's, the driveshaft/rear turns freely. What's left?

I'm stumped.

74u

iTrader: (9)

Something else I forgot to mention.

On nitrous with the identical jetting I went from 540rwhp on the old combo, to 570rwhp with this combo. The bottle pressure was 950'ish both times, and screen fittings were verified clean prior to both dyno sessions.

I have no idea why, or what that means...just something else to confuse me

KCS

iTrader: (20)

Here's how I look at it; if you want to make a certain amount of power, the shortblock needs to be able to demand enough air from the heads to make that power. You can increase demand with more RPM and/or more cubic inches.

I think that LS3 heads can feed a 6.2L well past the RPM limit of the manifold so it never reaches the potential of the heads without going to a shorter runner. After about 6500ish, the long runner manifold is going to kill the power. By adding displacement, you're demanding more air at a lower RPM where the intake isn't going to hurt as much and the heads can still feed it.

i don't know, I'm pretty terrible at trying to diagnose something over the Internet. If it were me, and this is just a wild *** guess, but I would probably be going over the valvetrain. I'd look at lifter preload first. After that, I'd look at the reluctor signal and see if anything weird is going on there. Those are two somewhat common issues I've seen limit power by limiting peak RPM.

74u

iTrader: (9)

How far are you from DFW

I would be happy to pay for some educated help.

speedtigger

iTrader: (16)

While I am not suggesting this is a definitive reason it makes more power on the nitrous, there are few things of interest in the cam design for Cam Motion cam with the LS3 heads: The Cam Motion cam has a whopping 12.5 degrees less overlap which can reduce the amount of nitrous that is wasted out the exhaust during the overlap cycle. And, the new cam opens the exhaust valve 2 degrees sooner which can also help although 2 degrees is not much in this scenario.

One thing for sure. The reduction in overlap is certainly why the car drives smoother.

1989GTA

Does anyone have the formula for what horsepower it takes to move a 3750+ pound vehicle to 121.6mph in the quarter mile?