Zfan

So I am thinking about making some changes to my build and was looking to get some input on wether it's worth it or not.

My motor is an LSX 436 with a 242/257 .629/.609 on a 113 ls, hyd. roller cam with Chris Frank stage 2 LS3 GM heads and a Tony Mamo ported Fast 102 intake. I was entertaining going to some LS7 heads and 102 Fast intake manifold.

Would the power gains be worth the expense, my current combo thru a 4L80E made 477 RWHP and 650 RWHP on a Nitrous Outlet wet 102 plate system (200 shot). I know the 15 degree heads vs the 12 degree heads make a difference just not sure and how much of a gain vs money spent if it's worth it. Has anyone been down the same road?

I would love to get my ride (Datsun 240Z) into the 5's, currently runs 6.00's at 115.

Thanks,
Mike

blk00ss

iTrader: (66)

Ls3 heads should never be on a bore larger than 4.125 IMO. So yes you will see a huge gain. Had a buddy with a 454 and TFS 245's that made 550 through a 4l80.

Tuskyz28

Interesting thread that needs more attention..

Tuskyz28

Interesting thread that needs more attention..

redtan

iTrader: (5)

IMO, going from some properly ported LS3s to stock LS7s is not going to be that huge of a deal and certainly not worth the expense and labor to do them.

Now going to some aftermarket or ported LS7s, I would say it's going to be a decent gain in power.

Although it really depends on how that engine is built and the bore size. If it's an undersquare engine with relatively small bore but long stroke then you might not see as much of a gain as in an oversquare engine with big bore and relatively short stroke.

Tuskyz28

I've asked some well respected names in the business this question. They ALL told me the LS7 head is a totally different animal from a LS3 head. I'm not go call no names here but one said the intake valve on the LS3 head is to close to the chamber wall so this is why this head seems to have people scratching they heads at the track from their e.t times.
Another cam guy said the LS3 is the BEST budget head ever for a 4 inch or larger note motor but it'll never catch it match the power output of a LS7 head. The conclusion is that these cam guys is all saying the LS7 head is the way to go.

KCS

iTrader: (20)

I agree 100%. For the money, the LS3 is a great budget head to feed a 400ci engine, but it wakes up everyday wishing it was an LS7 head.

dr_whigham

iTrader: (49)

I'd ditch the FAST intake as well and grab an LS7 MSD from Mamo... Even HE will tell you it blows his own ported FAST out of the water.

DoodadZ06

If it were me, I'd absolutely ask Tony Mamo for his opinion. He's getting impressive results from a 265 runner and even more from larger heads.

Tuskyz28

So OP you want to be FASTER and dip down into the 5s ..... I would go with a 245 TFS with a Nitrous exhaust port and I say this due to what I've seen on dyno results...
-look at katech 427ci LS7 headed motor they put inside the white 4th gen they built years ago.... motor dynoed 640 horsepower and 555 ft lbs of torque.
- look at some of Tony Mamo/Brian Tooley and Richard Holderner articles on SMALLER 402-416 ci motors... you'll notice a serious cathedral head will be over 30-50ft lbs more torque than a LS7 casting head on the bigger cube motor. I've seen a OUT THE BOX AFR head on a 408ci produced 630 hp and 580 ish on torque. Yikes

KW Baraka

iTrader: (7)

Which AFRs is that.....the 245's?

KW

Tuskyz28

-Yea the 245s on a 11.0 compression 408ci motor with a 240/246 cam.

-The katech 427ci LS7 (LS7 headed) motor I mentioned also had more compression than the 408ci.

KW Baraka

iTrader: (7)

Nice!

KW

movealong

I do not know the exact answer, but as food for thought, I noticed that Lingenfelter does a LS3 head based 427 with I think 11-1 compression. Not sure what cam.... They advertised that motor at 570 HP

Then, they do two different LS7 based 427's, also with I think 11-1 compression.... the one with the smaller cam they advertise at 630 HP. I think that is a 227/239 cam..... (The other motor has a big cam I think advertised at around 660 HP)

Not sure what other differences between the LS3 based 427 and the small cam LS7 based 427 aside from the cylinder heads, but 60 HP different advertised is pretty darn big difference. Some of that might be from the difference in the cam utilized for each, but I doubt if all of it. I gotta believe half of that is just in the cylinder head and maybe even more.

Food for thought.

Tuskyz28

Well the bore and stroke plays a role. -A LS3 base 427 have a 4.100 crank I'm thinking with a 4.065 bore.
-A LS7 base 427ci have a 4.000 crank and a 4.125 bore.
Well that's a different there.
Ls3 heads have smaller valves and valve angle....
Ls7 heads are 12 degrees I'm thinking with huge 2.20 intake valves.

pantera_efi

iTrader: (1)

I believe all will agree that the LS-7 has a "shrouded" exhaust.
The FIX is to use a much greater exhaust duration camshaft, one that you may have fitted at this time.
Another concern is Piston Valve Pocket angle change, the valve will have less clearance, a problem not sure.
Another MAJOR concern is Valve Weight, will you fit a titanium valve ?
When a heavy steel valve is fitted to LS-7, you will lose HP.
If asked my opinion for your "5s" request, I would specify a "dry" Nitrous system.
The second choice would be a "custom" LS-3 style head.

Lance

dr_whigham

iTrader: (49)

For an LS7 exhaust valve, I'd be running a Ferrea F2042P hollow stem if I were going with a stainless valve if weight is a concern. I'd never run a solid stem. Ever.

sbf

the copo 5.3 (327) 4.065 bore run the ls7 heads and its not a valve clearence issue

DavidBoren

Is it worth the expense to make the switch to stock LS7 heads? No. Or at least, probably not.

Are there gains to be had in getting new heads? Yes.

I am a huge fan of cathedral port heads, and would seriously be looking at Tony's CNC+ MMS250's with his N.F.I. exhaust port. But you didn't ask about cathedral port heads.

If you can afford to step up to some aftermarket LS7 castings, then yeah, I would imagine you could see some gains that would warrant the expense. If you are only going to "upgrade" to stock-ish LS7 heads, then I don't think it will be worth the price of the switch.

Almesri_GTO

u should get better heads for that large stroker