Head Games-AFR
11-02-2003, 07:22 AM
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Head Games-AFR
Have you guys seen the Head Games article in the Dec/Jan issue of Family& Perf Boating magazine?
I have been toying with the idea of installing a different head assembly on my stock '98 502MAG MPI. Dennis Moore's book suggested such a thing for more torque and HP's.
Not being a Tech guy, I do understand the concept, I have been hoping for an article on this subject.
Excuse my ignorance, but what is the difference between a 502 GM crate engine and my 502 MAG?
According to the article the stock crate motor pulled 530HP's on the dyno? Then the AFR head, cams and intake swap added about 200HP's.
Can one assume similar results on a stock 502MAG 415Hp's to net 600HP's +?
What else would/should need to be done, an exhaust header would make sense to me. ECU calibrations? What else?
How much is something like this going to cost?
Thank you in advance for any input.
Jamal
I have been toying with the idea of installing a different head assembly on my stock '98 502MAG MPI. Dennis Moore's book suggested such a thing for more torque and HP's.
Not being a Tech guy, I do understand the concept, I have been hoping for an article on this subject.
Excuse my ignorance, but what is the difference between a 502 GM crate engine and my 502 MAG?
According to the article the stock crate motor pulled 530HP's on the dyno? Then the AFR head, cams and intake swap added about 200HP's.
Can one assume similar results on a stock 502MAG 415Hp's to net 600HP's +?
What else would/should need to be done, an exhaust header would make sense to me. ECU calibrations? What else?
How much is something like this going to cost?
Thank you in advance for any input.
Jamal
11-06-2003, 05:21 PM
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Anyone?
Is this a stupid/ignorant question or has no one read the article.
If it is an old beat to death topic, please let me know.
Thanks,
Jamal
Is this a stupid/ignorant question or has no one read the article.
If it is an old beat to death topic, please let me know.
Thanks,
Jamal
11-06-2003, 06:24 PM
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Jamal,
I read this article also and I figure they started with a 502/502 HP crate engine from GM Performance parts. I am not an engine guru by any means but I would think that your engine would respond to these heads quite well. I would think that the power output would be limited by the efi intake manifold your 502 mag has. I know that John Lingenfelter used to work some magic on the 502 EFI's but his work does not come cheap.
I read this article also and I figure they started with a 502/502 HP crate engine from GM Performance parts. I am not an engine guru by any means but I would think that your engine would respond to these heads quite well. I would think that the power output would be limited by the efi intake manifold your 502 mag has. I know that John Lingenfelter used to work some magic on the 502 EFI's but his work does not come cheap.
AFR
11-06-2003, 07:44 PM
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I'm building a pair of Dart 540's with AFR 315 CNC heads. I usually use Dart CNC heads. The castings are nice, better than the AFR SBC castings I've used in the past in automotive applications. Out of the box, their flow is hard to beat, and the thick decks are nice, especially in a marine application. I bought mine bare, but fully CNC'd with copper-berrylium valve seats and hard anodized. There was alot of nice detail work, including hand plending of the seats to to ports and around the guides.
I'm putting them on the flowbench with some different intake combinations, so I will be able to verify AFR's flow/cfm claims. Actually, I'm using Del West valves, so I'm expecting a few cfm better than what AFR claimsI should have the engine's on the dyno by Thanksgiving, we'll see how they do.
I'm putting them on the flowbench with some different intake combinations, so I will be able to verify AFR's flow/cfm claims. Actually, I'm using Del West valves, so I'm expecting a few cfm better than what AFR claimsI should have the engine's on the dyno by Thanksgiving, we'll see how they do.
11-07-2003, 06:33 PM
#7
Jim V, Can you improve on these AFR heads?
The difference between the crate502 and MPI502 is the heads and cam and the EFI. You are best to stay with a proven package for the MPI. If you change the heads and or cam then you will have to change the ECU program. The question is will some off the shelf ECU reprogramming work with this combo. Who knows.
The difference between the crate502 and MPI502 is the heads and cam and the EFI. You are best to stay with a proven package for the MPI. If you change the heads and or cam then you will have to change the ECU program. The question is will some off the shelf ECU reprogramming work with this combo. Who knows.
11-07-2003, 08:58 PM
#8
I read the article and I don't think the dyno testing that the magazine did wasn't thorough enough. It was a little mis-leading and not really fair because they didn't test the heads back to back on the same engine. They removed the stock heads and then added the AFR's but then they added several OTHER hi-perf modifications/components to the test engine as well and it showed the AFR's making 200hp over the stock heads---------and that is fine BUT they should have also done a HEAD SWAP-----A HEAD SWAP ONLY! I wrote the editor a letter about it. It wasn't as informative as it should/could have been. My .02 of course 
11-08-2003, 08:49 AM
#10
Marty
A 2.300 intake valve should flow about 400 cfm @ 700 lift. The exhaust about 300 cfm. I dont remember what the AFR heads flowed on my bench. Many don't understand the difference between a marine head and a drag race head. A drag race head is designed to flow at 800 lift and higher. Most cnc heads are cut for drag racing or max flow at 800 lift. To get this the venturi area has to be larger. The venturi area in a marine head should be smaller to maintain air speed and to peak at a max lift of maybe 650.
The same with the exhaust port example the Canfield heads flow a butt load of air at .850-.900 lift but are dead at lower lifts. Im not flaming Canfield or AFR, they make a great product but I dont think they have a different cnc program for marine applications.
A 2.300 intake valve should flow about 400 cfm @ 700 lift. The exhaust about 300 cfm. I dont remember what the AFR heads flowed on my bench. Many don't understand the difference between a marine head and a drag race head. A drag race head is designed to flow at 800 lift and higher. Most cnc heads are cut for drag racing or max flow at 800 lift. To get this the venturi area has to be larger. The venturi area in a marine head should be smaller to maintain air speed and to peak at a max lift of maybe 650.
The same with the exhaust port example the Canfield heads flow a butt load of air at .850-.900 lift but are dead at lower lifts. Im not flaming Canfield or AFR, they make a great product but I dont think they have a different cnc program for marine applications.
