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088 vs AFR 265 dyno comparison

Old 07-11-2013, 10:07 PM
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Default 088 vs AFR 265 dyno comparison

Here is a great article comparing the AFR 265 heads to a factory set of GM 088's.

http://www.carcraft.com/techarticles...t/viewall.html
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Old 07-12-2013, 01:31 AM
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That is a good article. I just wonder if a guy took a basic 502 longblock in to the builders these car magazines use & had them build an engine on specifics like 6-700hp. general operating rpm 3500-5500rpm must be able do this non stop day after day, with as minimal maintenance possible. Not telling them it would go into a boat what kind of set up they would come up with? Of course it also has to have a broad, flat torque curve from above idle to redline, capable of running 200hrs or more with no major teardowns. Then put it side by side on a dyno with an engine that was built especially for marine use & see what happens. Randy
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Old 07-12-2013, 08:11 AM
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Good article Mike. Pretty much gives one a idea on how crappy the GM rect heads flowed on the exhaust side.

Also interesting, is that the Air Gap intake beat the victor jr, up until 4700RPM. Then the Victor JR. took over. I always read on here that using a dual plane in marine is the way to go. Maybe merc was on to something when they installed single planes on the 454/420', HP500's, etc.
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Old 07-12-2013, 08:55 AM
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It is a good informative piece. The one thing I wish they did was use a Vic Jr on the 088's so it was more of an apples to apples test. Also the Vic Jr on the AFR's was port matched were as the Air Gap was not, even still the Air Gap was within 15 hp at 5700 rpm. On my 439 that I build a few years ago with the AFR 265's I used a Weiand Stealth, with unlike the Air Gap it has the plenum divider cut to within 1/4" of the floor where as the Air Gap is only notched a 1/4 on the top. Plus the Stealth as larger runners which combined should allow it to make a bit more power on top. Either way there is some good info and comparisons.
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Old 07-12-2013, 09:02 AM
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Good article.
Those numbers are almost identical to my dyno numbers when I changed my old Merc 420's with GM rectangle port heads to old iron Merlin rectangle heads the JimV filled the floors on (Wedged) and extensively ported the exhaust side. I like the cam split 242/248, with with the better flowing exhaust side. I am no cam expert but when I was picking out my cams this summer I talked quite a bit with Bob and Jim about this.
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Old 07-12-2013, 09:14 AM
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This winter I need to do something different with my engines which are lightly modified 420's. I think the Rectangle port heads are only good to a point then just stop making power unless you really port them, at which point its cheaper to just get new heads. I need to talk to Bob again soon, and have him get me two sets of 265's and new cams.
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Old 07-13-2013, 11:50 AM
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I'm curious, what do you think the size of the jets were in the Holley 950?
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Old 07-17-2013, 02:01 PM
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Originally Posted by MILD THUNDER
Good article Mike. Pretty much gives one a idea on how crappy the GM rect heads flowed on the exhaust side.

Also interesting, is that the Air Gap intake beat the victor jr, up until 4700RPM. Then the Victor JR. took over. I always read on here that using a dual plane in marine is the way to go. Maybe merc was on to something when they installed single planes on the 454/420', HP500's, etc.
MT, I touched on what you are asking and linked the same article several weeks ago. No one really responded to my question on that one, but this thread kind of brings it up again. Is it better to make all that power down low and swing a bigger prop, even if it means you drop off in power above 4600 RPM and maybe struggle to swing that prop at those speeds?

http://www.offshoreonly.com/forums/g...4k-5500-a.html
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Old 07-17-2013, 02:03 PM
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Originally Posted by endeavour32
It is a good informative piece. The one thing I wish they did was use a Vic Jr on the 088's so it was more of an apples to apples test. Also the Vic Jr on the AFR's was port matched were as the Air Gap was not, even still the Air Gap was within 15 hp at 5700 rpm. On my 439 that I build a few years ago with the AFR 265's I used a Weiand Stealth, with unlike the Air Gap it has the plenum divider cut to within 1/4" of the floor where as the Air Gap is only notched a 1/4 on the top. Plus the Stealth as larger runners which combined should allow it to make a bit more power on top. Either way there is some good info and comparisons.
I traded a couple of emails with Tony from AFR, and he told me that both the Victor and the Air Gap were port matched to the AFR heads for the test.
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