sccagt1racer

I'm building a ground up ls engine for my road racing project. I plan on a 6.125 rod 4 inch stroke and a4.125 bore 13 to 1 compression. The engine will be dry sumped to handle the g force. I plan on using a solid roller cam and will be turning 8000 rpm's. The engine will be carbureted 830cfm on a single plane intake. I'm looking for a head that will suit my needs. would a tfs 260 ls7 head work or do I need something custom for this application?

NAVYBLUE210

Best Heads for your application IMO MMS LS7s
Most flow & velocity from >265CCs nothing
Else even close, that means most throttle response
At all RPMs without sacrificing Peak Power.
Combine with LLSR from Cam Motion for the Win!

A.R. Shale Targa

iTrader: (2)

Might I suggest a 3.622 stroke for an 8000 rpm sustained application. Piston speed is awfully high on a 4 inch arm at 135 revolutions per second Drag racers can get by for short bursts but road racing is a whole different level of brutality

gnx7

iTrader: (28)

Shirl down in AZ has been building 4.1 stroke road race motors for well over 10 years and not serious downside; however I don't see him spinning them to 8000rpm either.
https://ls1tech.com/forums/generatio...92-engine.html

I think setting a 7000rpm redline with a 4.0" stroke crank that is buzzed to 8000rpm on occasion should be fine for longevity. That is my plan with my 441ci engine (4.190" bore/4" stroke). Spin it a little higher to avoid an upshift into a corner... but otherwise 6500-7000rpm shift points. It will have gobs of torque with the 4" stroke.

I had a 438ci stroker in my 2470lb road race RX-7 with 4.125" bore/4.1 stroke crank running a GSR dog box and 3.27 gears out back and 18x12 square setup. It performed well on track and had power everywhere. I spun it to around 7000rpm as it had a baby hydraulic cam to actually decrease power to meet a class... but it still had all the torque

AllPro makes a very nice cylinder head as well (400cfm+).... Even the Dart ProV1 LS3 head is a good choice (370cfm stock)

A.R. Shale Targa

iTrader: (2)

at 8100 rpms a 4 inch arm engine has 720 linear feet of piston/ring travel PER SECOND
just think about that for a bit........................................
an NHRA pro stock engine is at 724 when spinning 10,000 rpms with a 3.25" arm
ring friction accounts for roughly 60% of an internal combustion engine's rotating resistance

Novistar

That's a bold statement. Any results with these MMS heads?
IMO...I prefer facts vs speculation.

KCS

iTrader: (20)

Those piston speeds aren't even really that high in the world of drag racing. The IHRA Pro Stock engines are about 30% higher that that.

99 Black Bird T/A

iTrader: (4)

Customized cylinder head to get the best results and longevity for your application in my opinion.

Its my understanding the short side radius is usually done a little differently for the ideal road racing cylinder head than the short side radius is done for the typical drag race out the box cylinder head.

Your engine build plan: single plane intake and 8,000+ rpm is very similar to the type of LS2 engine Wegner did for NASCAR. Wegner can do the same for LS3 or LS7 or other build. This thread may be of interest to you.

https://ls1tech.com/forums/generation-iv-internal-engine/847060-ls2-nascar-build.

If budget allows Wegner could probably take your build to the next level. They have a lot of outstanding experience with road racing cylinder head development.

This might be an interesting read too. Apologies if your already well beyond this point in your research for the engine build.
http://Converting the GM LS Engine t...e Professional

Rise of the Phoenix

iTrader: (27)

If you got the bucks, checkout the RHS, Brodix, or Edelbrock LS -Reaper heads that Chris Frank at Frankenstein has.


https://frankensteined.net/products/...-heads/rhs-ls7

https://frankensteined.net/products/...ads/brodix-ls7

https://frankensteined.net/products/...elbrock-reaper

A.R. Shale Targa

iTrader: (2)

Good thing they only need to run for six seconds...........

BOLO

iTrader: (40)

Out of the box LS7 heads? I would definitely look into MAST.

NAVYBLUE210

Novistar
Thank you for the challenge. I also prefer Facts & Results
Vs speculation.

The MMS LS7 Heads flow 412 CFM @ .650" from a Port of only
265 CC. Flow #s by themselves are not worth very much,
but Port Efficiency as measured by Flow/CC (size) & Lift, gives
you efficiency and velocity. All other heads mentioned
with the exception of the Edelbrock/Frankenstein
(more of a drag race head requiring .800" lift and above
to take full advantage of their flow and altered valve
locations etc.) The other heads mentioned all very good
by the way range in size from 280-305 CCs and don't exceed
400 CFM until AT LEAST .700"-.800" lift. Which I would argue
is higher than optimal for a road race application with 8000 RPM
and durability/longevity. The flow #s for the MMS Heads @
.400",.500", & .600" are also exceptional.

With regards to results there are quite a few 600+ RWHP
ZO6s in the Corvette Forum ZO6 section, One in particular
"Tony Mamo heads,cam,ported msd install"
Made 642 RWHP with a medium sized cam (247/261) HR
~12.25:1 COMP W/ E85.

454" Build in progress there also with Solid Roller I Believe will crack
700 RWHP.

My own personal results with MMS LS3s (purchased before the
LS7s were available) 727 FWHP @ 7200 RPM so far with LLSR ( roughly
equivalent to 239/245 HR adjusting for lash & larger
diameter lifters) with 396" 11.7:1 Comp and attention to
"almost" all the little details LOL!

To summarize the MMS LS7 heads on a 4.125" Bore or larger
in a road race application with a LLSR of appropriate duration
and lift(~251*/259* , ~.700"/.680*, LSA and advance specced
by Tony/Kip with Carb) will out perform the previous mentioned heads.
IMO.

sccagt1racer

I talked to mast and they recommended the 305 head for my application. I am also thinking about going larger on the bore and cutting back the stroke. a local circle track engine builder suggested that approach for making the power I want in a road race application.

NAVYBLUE210

Thats what I did, 4.175" Bore X 3.60" Stroke, Long Rod, ~396"
Made 727 FWHP @ 7200 RPM, 583 LB FT @ 6000 RPM
11.7:1 Comp 243*/249* (medium/small) LLSR .670"/.640"
115*+3* with 830 CFM Carb & Vic JR.

Easily 60-80 more FWHP with MMS LS7s (+20-25 CFM .400"-.650"),
more cam (+8-10*), Different LSA & Adv (mine designed for EFI
after DYNO) more comp (+1.0-1.5:1), maybe a little more stroke (3.7-3.8").

305 CC too big especially with shorter stroke IMO.
Good Luck

8.Lug

What the hell is FWHP? I think you mean BHP unless you meant Front Wheel HP.

G Atsma

Flywheel Horsepower, before it goes thru the drivetrain.

8.Lug

Yes, that's BHP for "brake horsepower" there's no such thing as FWHP. Don't make things up.

Launch

fwhp is a term been used in the ls1 scene for ages

everything has been "made up" by someone at some time in history... we made up FWHP

G Atsma

8Lug- Don't be so rude. If you would spend some time and look thru these forums you would see the term "FWHP" all over the place.
And thank you Launch for the help here.

KCS

iTrader: (20)

They recommended less cubic inches to make more power? That doesn't make much sense.