87silverbullet

iTrader: (11)

I think those heads would be a step backwards for a 410 cu in motor. I would go with the PRC small bore LS7 head if you have the bore for it (4.065) Those heads and a well matched cam will make some wicked power.

fastvet

iTrader: (2)

Well my bore is a 4.04". Hence why I'm having trouble picking the right head

topbrent

iTrader: (1)

Guess it kinda depends on overall goals and budget. The aftermarket cathedral stuff produces great results when paired with a FAST intake and other supporting mods which can cause the costs to add up quickly.

Though possibly/probably down in power from the afore mentioned $$$ packages, LS3 head based engines can yield some pretty impressive results with factory based castings and factory based intakes which lowers overall costs significantly.

As one example of many that run quite well, look at the performance of Stanger383 and his stock LS2 shortblock with SDPC LS3 CNC heads.
He has run as fast as 10.15 and 131mph with that combo (in - DA).
His times improved from 10.50's to 10.30's just by basically bolting on the CNC SDPC heads vs stock LS3 heads.
http://forums.corvetteforum.com/c6-t...heads-now.html
http://forums.corvetteforum.com/c6-t...-in-300ds.html
https://ls1tech.com/forums/automatic...-10-15-et.html
http://forums.corvetteforum.com/c6-t...post1582361022

- Stock LS2 shortblock,
- SDPC CNC LS3 heads,
- Ported L76 intake
- 231/240 .617/.613, 114+2.
- LG headers, PTB, CAI,
- 3.42 gears,
- Yank SS4000 converter

All you cathedral head faithful will insist that the LS3 head just won't run very well on a 4" bore, but cars like Stanger383's just go ahead and prove that it is possible to produce great results even with all that atrocious valve shrouding and port volume.

87silverbullet

iTrader: (11)

^^^^^That is sick!

87silverbullet

iTrader: (11)

In that case, I would just go with a good ported proven LS3 head and a cam to match. PatG or Geoff@ EPS can spec you something for an LS3 head and you won't be disappointed.

Tainted

iTrader: (9)

Its not that the ls3 heads domt perform well, as theres plenty of people making great power with them. But for a street car with the smaller bore i think the cathedrals are the better choice.

Zfan

Geoff at EPS set mine up!

87silverbullet

iTrader: (11)

Yet, the L76 4.000 bore is in a G8, a 4000lb street car. Alot of power has been made with them no matter street car or more race oriented on a 4.000 bore.

Tainted

iTrader: (9)

like I said, they are good, but not exactly ideal all the time. Theres a reason why pat G took his square port heads off in favor of the cathedral heads.

valve shrouding, limited ptv clearance, and with that you cant mill for compression. just things to consider.

87silverbullet

iTrader: (11)

He also never tried to use them to their full potential either like WKMCD did either.

I think there was more to be had in playing with the rect port more instead of just jumping ship to a cathedral.

Tainted

iTrader: (9)

and I agree there with you. I think the small bore LS3 heads are the real deal for the square port heads, unless of course you already have the ls3+ bore.

hymey

square port heads all the way! cross section is king! Look at some of the small bore ones and stick with them.. valve shrouding is an issue but tends only to hurt low lift flow, so stick more lift in it and faster ramps

redtan

iTrader: (5)

A lot of power has been made on those G8s yes, but still nothing to the amounts seen on LS3s in Camaros and Corvettes with the 4.065 bores.

Yes the LS3s have 16 more cubes, but you often see cam only engines making high 400s easily. A cam only L76 G8 is usually low-mid 400s. It takes a pretty big cam and headwork to make a 364 with 4.000 bore hit close to 500 with stock L92 heads.

Tainted

iTrader: (9)

thats only going to add insult to injury for small bores.


Yall can do what you want, bbut I promise these past 3 months since I got this 408 I have read thousands of threads from all different sites, talked to many sponsors on the phone and local people. ls3 heads on small bores is NOT the way to go. If you are looking for 450-475rwhp on a budget, then by all means yes! they are a GREAT budget head! HOWEVER if you want a very well rounded combo with power everywhere without sacrificing PTV clearance amoung other things then you should stay cathedral.

Now if you start talking small bore style ls3 heads thats a whole other ball game.

Grr

iTrader: (2)

I just with the chambers werent so damn big on square stuff, I would have switched but theres no way to get a chamber below 50cc like a cathedral head!

WKMCD

iTrader: (2)

Well rounded - power everywhere???

GM L92 castings. West Coast Cylinder Heads (ProHeads.com) Stage 2 on the 403 and Stage 3 on the 427.

The bottom line is the 403 with a ported L76 intake. I couldn't find the final chart for the 403 but it ended up at 530RW on 2 different DJ's.

The top line is the 427 with a FAST 102. Both builds well optimized and extremely mild. The 403 was with a 230-240 cam and the 427 runs a 234-242. I don't think you'll see those number without going much bigger with on the cam and then you'll loose on the bottom. CR on both is 11.3 to 11.4. Both builds so mild your mother could drive them with a 6 speed and 3.90's.

Had the car out today in Washington, DC rush hour and it's no more difficult to drive in that crap than a stocker.

The large runner/valve LS3 heads kill low end, yada, yada, yada theory should go the way of "the earth is flat" thinking.

JakeFusion

iTrader: (7)

Yeah, but you actually cam correctly for those heads. The huge splits just drive overlap way up, killing drivability and power due to reversion with those heads. They don't need a ton of cam because they move a ton of air. Nor do they need a ton of overlap to carry power or make torque - just good valve events (early IVO and later IVC) paired with good compression.

This isn't rocket science. It's the same way you cam any high flow head.

Folks here are all so used to camming in a way that acts like a crutch for stock LS1 heads. The LS1 has pitiful compression and weak I/E ratio. Things like the T-Rex are born to create power within those confines with huge overlap and very tight LSA/ICL to get dynamic compression up within a very narrow RPM window. Well, that thinking needs to go the way of the dinosaur for LS3 and any high flow cathedral port offering.

Tainted

iTrader: (9)

And it had very nice results, and theres plenty of people making good power with them. But these are also bigger ci motors that can take advatage of the flow and have the low end advantage on stock cubes and a smaller bore. They are good heads and theres def some that perform fantastic, but I think in most cases a well thought out cathedral like tfs or afr with a fast 102 can make the same and better numbers. Now im making that statement with factory heads, the small bore ls3 style im sure are much different.