bortous

What do you guys think of the flow data of our own version of the GM LS3 heads?
The Small bore LS7 head looks like a monster for flow also.

GrannySShifting

iTrader: (10)

How does the straighter LS7 port not pull away from the LS3 heads at .600 lift and above? was ahead of curve at .500 then made a sharp downturn

What CC are these ports

bortous

Unfortunately I do not know the cc sizes.
I found it a little strange that the small bore LS7 head has less peak flow numbers however the lower lift values are higher so I would assume there would be more torque low down with the small bore LS7 heads.
Then again the LS7 heads were originally designed on a bigger bore.

big hammer

Aren’t the mast ls3’s as good or better than their ls7’s too?

Darth_V8r

iTrader: (4)

Honestly at 600 lift, not too impressed

Smokey B

Port is rather small. This is what happens when you don't no the csa. Older port Darin did they have options not listed contact Darin. Btw they flow what old etp 240 -255cc ls7 heads now MAST. CFM is not everything CSA matched to rpm and CID ....the cfm will be there. It's there being the cfm ...what size engine and rpm does it match?

Bazman

Impressive low lift cfm, the larger port LS7 is even better. The top end cfm is far less important. Anything near 300cfm by 400 lift is outstanding. An engine that can supply that will have great velocity and a fat TQ curve. For street use I'm more unimpressed with the bigger 400cfm+ heads of other brands that are weak till 500 lift - they're dogs by comparison unless you deliberately need to take bottom end/mid-range TQ out, in which case they'll sure do that. Higgins heads have a reputation foe excellent velocity - read - crisp fat power curve.

Smokey B

Granny thought you had gotten this on YB.... About ls3 vs a ls7 head.
I can go into detail.

Mines flow 300 @ .400
379 @ .700
2.9csa: ls7 head .060 bore tested same porter

268 cc ls3 head runner is larger in height x width than a 275cc 2.9csa ls7 head with a raised runner.
Ls3: 37 mm bottom of the runner to head face
Ls7: 46 mm raised almost 10 mm

Smokey B

Yeah that ls7 head is a 250 to 258 cc head.

bortous

So going by those flow figures, would you guys choose the CNC LS3 head for a 4.060 bore or the small bore LS7 head?

Smokey B

What is the rpm range? Match csa to rpm and CID. Me i would get a Ls7 head but a brodix casting and have a cnc program added for my intended cid and rpm. Bottom of page
http://www.proheads.com/Brodix_LS3.html.

Smokey B

This is what's used to pick the correct head. Not some BS 250 - 260cc and it flows a chitty 350 or 390cfm.

http://www.wallaceracing.com/chokepoint-rpm.php
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/flow-rpm.php
http://www.wallaceracing.com/calc-cfm-head.php
http://www.wallaceracing.com/ca-calc.php
http://www.wallaceracing.com/csa-calc.php
http://www.wallaceracing.com/calchpaf.php

Port centerline length, Needed for some formulas
https://www.yellowbullet.com/forum/s....php?t=2569811

Smokey B

Bortous you get this and you don't have to call asking what's needed. You can state it as a FACT the formula Don't lie.
2.9 csa is needed for a Ls7 head and a 408 @ 8000. 370cfm is needed for 800+ and same cid.
Heads matched 1000% So wtf it has a 275cc runner.



Read the quote. i Asked all this already. Real porter would tell you this as to learn mine did.

bortous

I just checked it all out.
I don't really understand it.
What would the choke point of my CNC LS3 heads be I wonder.
From the numbers i put in i got 7000rpm but unsure if that's accurate or not.

Smokey B

Oh it's pretty accurate....went and did it for Chris Frank Ls3 heads and Darin Morgan Ls7 heads both match what's required for a 7500 & 8000 rpm engine with 408 ci..

Busy cooking. What is the RPM wanted and HP looked for? Aftermarket does not give you the csa .... Do the math.. Runner centerline length x CC of head= csa. We don't have exact numbers cause U don't have a head. You can know for a head if the CSA matches your Rpm and CID... A 260 cc head doesn't work for every 416. Example: You may need a 3.2 csa ls7 head = 285 cc cause your wanting 9000 rpm with 416ci. if 750hp needed how much cfm is needed from the head and what's the csa, for the CID and RPM? Work it out step by step.


Head made to application

bortous

I want 7000rpm.
I have a ls 408 with a 4.030 bore with a set of those Higgins LS3 heads in the picture.
Can you work out what max rpm these heads will rev too?

Smokey B

Honestly factory ported Ls3 heads cover alot of bases.
They have better castings like LIBERTY 11°degree 255cc ls3 heads for $400 each

Smokey B

Ok i will, but as is they sound good. My ls3 heads are around 2.8 i'll double check..cooking

Smokey B

Minimum CSA for a 408 and 7000 rpm is a: mcsa of 2.62
The ls3 port would come out to be 256.49 cc's with a 2.8 mcsa x 5.591 ls3 port centerline length.


You GOOD with room to grow in rpm...... Rough #'s but very much on point.

bortous

Thanks bro