AFR heads out perform GT40X heads even after porting, polishing, milling & cam swap

Jimbocobra · #1 (**permalink**) 11-02-2010, 10:42 AM

Wow, 537 hp from a simple heads swap on an otherwise stock Ford crate 392 stroker, 107 hp over the advertised rating and 75 hp pick up on the dyno from a $1500 bolt on. I was suprised that it out performed even after the porting, polishing and milling the GT40X heads and adding a larger cam to the stoker vs. just installing the AFR 185 heads.

http://www.airflowresearch.com/artic...e004/A4-P1.htm

I somehow missed in my last post of the 10 article links: Ford Crate 392 Stroker GT40 Heads Actual HP Documented in Magazine Articles

blykins · #2 (**permalink**) 11-02-2010, 10:44 AM

AFR makes some good stuff that's for sure....I use them on a lot of my engines.

Excaliber · #3 (**permalink**) 11-02-2010, 11:05 AM

I'm not surprised, from my "reading research" and listening to others comments AFR are difficult to beat with the one exception being absolute upper rpm flow limits in some cases. But for low to mid range power and even into the higher rpm ranges they are about the best around. They would certainly be my first choice.

Hotfingrs · #4 (**permalink**) 11-02-2010, 11:15 AM

AFR is all I used, until I switched to 18 degree heads.

Excaliber · #5 (**permalink**) 11-02-2010, 11:29 AM

18 degree heads? Can you enlighten us as to what those are?

From the flow numbers I've seen there are a few heads that will outflow the AFR's at high rpm. But those that do show poor numbers when compared to AFR in the lower and mid rpm range's.

blykins · #6 (**permalink**) 11-02-2010, 11:32 AM

There are quite a few heads that will outflow the AFR's....however they will be Yates based heads with huge ports or fully CNC ported heads.

And you're absolutely right....to get the big port volume and flow rates, you usually lose the low/mid lift flow numbers.

Also keep in mind that advertised flow numbers are just that. I bought a set of Trick Flow TW-R heads to go on a 445 ci Windsor. They were advertised to flow 340cfm. On a real flow bench, they flowed 320 and I had to port them to get the 20cfm back.

petegtsv10 · #7 (**permalink**) 11-03-2010, 08:35 PM

My Claytonized 427 (429 now) has AFR225s and although I barely have my break-in miles done, I can tell you the low end feels very potent. I was a little worried about drivability, even though Cory assured me it would be fine, but it's already more drivable than before. Even with the big heads and solid roller cam, it actually gets better mpg than when it was only 375 rwhp.

COBRANIP · #8 (**permalink**) 11-04-2010, 12:02 AM

"18 degree heads? Can you enlighten us as to what those are?"

18 degree heads are....er....well....they are....er.....you know....well...
let's just say they are not "Ford" related and let it go at that.

P.S. "18 degree" refers to the angle of the intake valve (stem centerline) to the centerline of piston travel.
Original heads had a 23 degree angle on this (cough, cough) manufacturer's small block engine.

.........O.K. I'm coming out of the closet here.....I LIKE small block Chevy engines! There, I said it!

albertpaul68 · #9 (**permalink**) 12-03-2010, 02:19 AM

I'm not surprised, from my "reading research" and alert to others comments AFR are difficult to exhausted with the one barring getting complete high rpm breeze banned in some cases. But for low to mid ambit ability and even into the college rpm ranges they are about the best around. They would absolutely be my aboriginal choice.

MOTORHEAD · #10 (**permalink**) 12-03-2010, 06:25 AM

I'm not surprised, from my "reading research" and alert to others comments AFR are difficult to exhausted with the one barring getting complete high rpm breeze banned in some cases. But for low to mid ambit ability and even into the college rpm ranges they are about the best around. They would absolutely be my aboriginal choice.

WTF? English, please !

dcdoug · #11 (**permalink**) 12-03-2010, 02:46 PM

Quote:

Originally Posted by MOTORHEAD

I'm not surprised, from my "reading research" and alert to others comments AFR are difficult to exhausted with the one barring getting complete high rpm breeze banned in some cases. But for low to mid ambit ability and even into the college rpm ranges they are about the best around. They would absolutely be my aboriginal choice.

WTF? English, please !

I'm sure that was a bot/spammer since it was a first post. Either that or a drunk member from our downunder contingent talking about his "aboriginal choice".

scottj · #12 (**permalink**) 12-03-2010, 07:25 PM

Quote:

Originally Posted by Excaliber

18 degree heads? Can you enlighten us as to what those are?

The 18 degree Chevy head was approved by NASCAR in 1990 to replace the original 23 degree cylinder head. The 18 degree head was never on a production vehicle, nor was the SB2 that replaced the 18, nor the SB2.2 that replaced the SB2, nor the R07 that replaced the SB2.2

While cylinder head development for NASCAR abandoned the in-line valve configuration when it went to the canted-valve SB2, many other forms of racing continued to develope the 18 degree design. The 18 evolved into the 16, 15, 13, 13/11, 12.5, and now 9 degree head.

Most AFR heads (Ford and Chevy) are designed to be bolt-on replacements for original production car heads, maintaining factory port locations and such. Essentially, they are refined production car based heads with limited power potential compared to the more exotic race-only cylinder heads.