AFR LT1 heads Question
04-26-2010, 12:04 PM
#41
XD
Even the small casting AFRs pass 300cfm while keeping an NA friendly chamber size. Using the goal of reaching 2hp per cfm for a very efficient combo, you have a theoretical max of 600 flywheel horsepower all motor.
Now of course you wont get it with a cc306 and a stock intake only revving to 6K - that is assuming a large, properly specced cam, and all the supporting mods for an engine that size(electric waterpump, longtubes, throttle body, single plane, good exhaust, proper fuel system, etc), but when all is said and done 300cfm is enough for a modest revving 396.
The 227s are amazing but come with their own problems and are not bolt-on heads...valvetrain, valve covers, and intake all need to be considered. A head that size though and you really need a big cam and a lot of rpm to justify it.
**edit** Before someone else jumps in, there is a lot more to heads then just CFM...this was just a simplified example. Cylinder head efficiency and the velocity of the air moving through the head is extremely important, and is why a lower CFM LSX car can outperform a larger headed LTX with a similar cam. This is also why well ported stockers like AI heads can outperform local shop ported heads that have bigger CFM numbers, like the shitty hogged out heads used on my last build. They put a decent cfm, but lacked velocity.
Even the small casting AFRs pass 300cfm while keeping an NA friendly chamber size. Using the goal of reaching 2hp per cfm for a very efficient combo, you have a theoretical max of 600 flywheel horsepower all motor.
Now of course you wont get it with a cc306 and a stock intake only revving to 6K - that is assuming a large, properly specced cam, and all the supporting mods for an engine that size(electric waterpump, longtubes, throttle body, single plane, good exhaust, proper fuel system, etc), but when all is said and done 300cfm is enough for a modest revving 396.
The 227s are amazing but come with their own problems and are not bolt-on heads...valvetrain, valve covers, and intake all need to be considered. A head that size though and you really need a big cam and a lot of rpm to justify it.
**edit** Before someone else jumps in, there is a lot more to heads then just CFM...this was just a simplified example. Cylinder head efficiency and the velocity of the air moving through the head is extremely important, and is why a lower CFM LSX car can outperform a larger headed LTX with a similar cam. This is also why well ported stockers like AI heads can outperform local shop ported heads that have bigger CFM numbers, like the shitty hogged out heads used on my last build. They put a decent cfm, but lacked velocity.
04-26-2010, 01:19 PM
#44
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Man all it takes is for someone to put their brand bias in one of these threads and off it goes.
AFR has been making SBC heads for a vey olng time, before the AFR name they were called Brownfeild if I remember correctly.
I have a set of the crappy "old style" AFRs i bought back in the 90s they are the 190s version. My stock shortblock 93 T/A with these heads and a CC305 cam, 3000 stalll 3.73s and Hooker LTS ran 12. 20s @ 115 with a mail order chip designed for a stock headed car with the cam.
I paid 1095 $ for them.
I later cleaned them up and put them on my newer 97 T/A that had a 9.5 to 1 compression 383 and with full weight and 87 octane gas ran 11.30s @ 120 mph. On the street it was a maniac.
This was before most of these guys had nice packages that were all set together. (which back then I probably would have bought had they been available.
AFR has been making SBC heads for a vey olng time, before the AFR name they were called Brownfeild if I remember correctly.
I have a set of the crappy "old style" AFRs i bought back in the 90s they are the 190s version. My stock shortblock 93 T/A with these heads and a CC305 cam, 3000 stalll 3.73s and Hooker LTS ran 12. 20s @ 115 with a mail order chip designed for a stock headed car with the cam.
I paid 1095 $ for them.
I later cleaned them up and put them on my newer 97 T/A that had a 9.5 to 1 compression 383 and with full weight and 87 octane gas ran 11.30s @ 120 mph. On the street it was a maniac.
This was before most of these guys had nice packages that were all set together. (which back then I probably would have bought had they been available.
04-26-2010, 07:09 PM
#46
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The street is CNC in the chamber and partial port CNCs, the Competition is full CNC and the Race is even further work. But I would jsut talk to them in person and find out what ya need.
04-26-2010, 10:42 PM
#47
Seems like he actually cared how my build ended up in the long run, and not just about what companies parts I used.
04-27-2010, 08:18 AM
#50
. 
04-29-2010, 10:02 AM
#52
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07-25-2010, 10:22 AM
#53
Sorry to bump and older thread but I have to clarify something here.
ALL AFR heads are CNC'd before you get them. There are 3 levels of CNC'ing.
street=base, rough cut partially into the ports and some chamber work
race= finer cut all around
competiton= even finer than the race cut.
Typically from what i've seen in looking at all of the charts they have, there is quite a jump from going from the "street" version to the "race" version. There is not as much of a jump in going from the "race" version to the "comp" version, but the price does go up a bit. I haven't seen any true cc's listed for the particular versions of each head, but common sense tells me that a 195 street head will have a slightly smaller port than a 195 comp head, due to more material being removed from the finer CNC detail.
As for the OP wondering if an AFR 195 could properly feed a 396, here is what Golen sells, a 550hp LT1 based 396:
http://www.golenengineservice.com/sp...l/396_520.html
Those are the "street" version of the 195's as well.
Here's a nice article when the heads first came out. The AFR 195 street heads slapped onto a 388 inch sbc, with a few intakes tested put out 523hp. You could duplicate that on an LT1 with a single plane conversion on your 383 or 396.
http://www.chevyhiperformance.com/te...wap/index.html
07-25-2010, 10:39 AM
#54
thats the motor i have. just because it works, doesnt mean it works right. u can make those numbers with an ai top end on a stock shortblock.
afrs web site says the street flow about 280cfm anyone know what the competition will flow? thats what ill be getting eventually
afrs web site says the street flow about 280cfm anyone know what the competition will flow? thats what ill be getting eventually
07-25-2010, 11:24 AM
#55
07-25-2010, 01:02 PM
#57
From the relatively few engine dyno to chassis dyno results we have seen which are mostly Golen a 25-7% loss seems to be typical. All of a sudden 520-550fwhp is less impressive that considered and even a 550hp motor ends up putting less to the ground than some of the nicer stock shortblock setups. I will say that IMO a piece of this is "happy" engine dynos, whether it poorly designed, poorly operated or flat out manipulated for advertising purposes I could not say..
Keep in mind there are multiple examples of well done hydraulic 383s using ported LT1 heads through stalled 4L60Es some even with 9" rears putting down in the 440s rwhp.
Keep in mind there are multiple examples of well done hydraulic 383s using ported LT1 heads through stalled 4L60Es some even with 9" rears putting down in the 440s rwhp.
07-25-2010, 01:34 PM
#58
From the relatively few engine dyno to chassis dyno results we have seen which are mostly Golen a 25-7% loss seems to be typical. All of a sudden 520-550fwhp is less impressive that considered and even a 550hp motor ends up putting less to the ground than some of the nicer stock shortblock setups. I will say that IMO a piece of this is "happy" engine dynos, whether it poorly designed, poorly operated or flat out manipulated for advertising purposes I could not say..
Keep in mind there are multiple examples of well done hydraulic 383s using ported LT1 heads through stalled 4L60Es some even with 9" rears putting down in the 440s rwhp.
Keep in mind there are multiple examples of well done hydraulic 383s using ported LT1 heads through stalled 4L60Es some even with 9" rears putting down in the 440s rwhp.
http://www.gmhightechperformance.com.../photo_08.html
5 different 195cc heads tested on an LT1. The AFR heads dominated, even over a hand ported set of TFS heads by TEA. Some of the other heads weren't even close. They were down 20-30hp everywhere. Those weren't even the good AFR heads, those were the basic "street" heads. The comps would have made a lot more power. The Ai stuff is impressive but i'd take a set of comp ported AFR 210's over a set of Ai TFS 215's any day. Both are roughly $2400ish (actually the AFR's are cheaper, but you have to ask, lol). I'd rather have an aftermarket cylinder head that is thicker and has porting potential than a stock ported set with god knows how many heat cylces through it.
07-25-2010, 03:11 PM
#60
Not usually one to be so blunt, but frankly AFRs, even mildly ported, will blow anything stock casting out of the water.
Compared to modern options, the basic shape of the port in a stock LT1 head is just not an efficient high performance port, and porting it generally just makes it a bigger ineffecient port.
Unless you are adding material while porting to completely redesign the shape of the port you will not see the performance of a high end aftermarket casting.
Not to say AI and LE don't do amazing things with them, but give them a better foundation like TFS or AFRs and you will be even more impressed.
Compared to modern options, the basic shape of the port in a stock LT1 head is just not an efficient high performance port, and porting it generally just makes it a bigger ineffecient port.
Unless you are adding material while porting to completely redesign the shape of the port you will not see the performance of a high end aftermarket casting.
Not to say AI and LE don't do amazing things with them, but give them a better foundation like TFS or AFRs and you will be even more impressed.