64post

iTrader: (5)

This is interesting.
http://www.airflowresearch.com/260cc-ls3-cylinder-head/

64post

iTrader: (5)

Those numbers are pretty impressive and ok for 4.00" bore and 12* valve angles.

G Atsma

I noticed a reference to a 245cc street head.
The intake port is referred to as 260cc.
So what is meant by the 245cc reference?

64post

iTrader: (5)

I think that's a typo, I saw that too.

G Atsma

Knowing AFR and their capabilities, I was kinda hoping a 245cc would happen, as it would possibly flow as much or a little more than the OEM head, which would increase flow velocity a BUNCH over stock, thereby kicking low-end torque up a BUNCH.
But that's just me.... lol

64post

iTrader: (5)

Yes, 245, 260 and 280cc. 245 for the 402-416 builders.

G Atsma

Hey, AFR does many different cathedral heads, so maybe variations of this one are coming down the chute too. Someday....
I think a 245 would give a stock LS3 a much needed low end kick. Couple that with a conservative cam, and a sleeper is born!

KW Baraka

iTrader: (7)

I just think it's about freakin' time AFR did a lil' somethin' for the LS3!

KW

Tuskyz28

I personally think runner sizes are overated when it comes to selecting the cylinder heads. I go by real world results instead of what a salesman say.....
Its a guy on here running a ERL 427ci motor in a heavy GT0 running 10s naturally aspirated with AFR 205 heads and a Fast 92mm intake .... 230s on the cam. On paper the AFR head dont look like it have enough to support a 400 plus cube motor but again track results never lie.
Bigger the port the lazier the head becomes as far as air speed and throttle response.
Hell Tony Mamo 454ci motor did great with a cathedral 245cc head. So did Tooleys. Tooley 454ci motor went 9s naturally aspirated.
I was inform on Tuesday by a well respected guy that spec cams for a living about cylinder heads. He shows no favoritism at all!! He basically said when running a rectangle head you need a single plane intake to take advantage of thr largr intake runners. No need in running a big head if you not go let the engine breath/rev high.

G Atsma

You're right! It's about getting a small runner volume to flow huge numbers, like this new LS3 head. The runner is 260cc's exactly stock size, but it flows WAY more than stock, which means flow velocity has to be huge, which contributes to low and mid-range power. This head should do well!

KCS

iTrader: (20)

The volume is the same as stock but the min. cross section is larger than stock. Stock LS3 heads have about 2.75 square inches. AFR says their head is 2.875 square inches.

G Atsma

Which then sounds like it would "slow the flow". With the 12*valve angle, is the port then shorter? Then, with the same volume, it would be "fatter" compared to stock. Not as good as I thought.

big hammer

Didn't mast and trick flow do this some time ago already? And I see AFR flowed them on a 4.155 bore

big hammer

I think mast makes a 240-ish cc ls3 head

G Atsma

You are correct. It is an 11* small bore head. Does not flow big numbers, but that might be because of the 3.89 bore they flowed it on.

big hammer

I think they're one of the best flowing 3.89 bore heads out there. But yes mast tends to advertise flow numbers on the bore they're designed for. And the 240 mast heads will still outflow stock ls3 heads by a lot

G Atsma

They are good heads! AND they're awfully proud of them! lol
Yeah it makes sense to flow on the intended bore. Truth in advertising! If it were possible to flow a stock head on a small bore, it would not show good numbers either.

KCS

iTrader: (20)

Yeah, generally speaking, but at some point you have to increase the CSA to get the flow numbers that you're after. At 28" of H20, where most flow tests are done, you aren't going to get more than 145CFM per square inch.

If I had to guess, I would think it would be a little longer. With the valve laying flatter to the deck at 12 degree versus 15 degrees, the backside of the port would get longer. It just depends on what axis the valve is rotated on.

They probably shrunk the port in key areas that may have been dead spots, which are areas in the port where there isn't a whole lot going on. You can fill in these areas without hurting flow or causing excessively high velocity.

G Atsma

Thank you KCS! Yeah, maybe I was backwards on the port/angle relationship. An incredible amount of science goes into head design, and it is fascinating to see how it all works together. I haven't seen AFR screw too many things up lately, so it will be interesting to see how the long-awaited LS3 head does.

MuhThugga

They also make a head for 4.000" bore engines. A guy over on LS1GTO installed them and the numbers were inline with what a set of factory milled heads would do. Again, just one instance, but for the pricetag, I'd be pissed.