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Author
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Topic: AFR 165cc Street Heads Question
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DocVoodoo
Gearhead Posts: 164
From: Plainfield CT USA
Registered: Feb 2003
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posted 11-17-2006 10:48 PM
 
OK I am going to go with the AFR 165cc Street Heads. I want to have them port matched to my Intake while I was at it I was thinking of having them cut down to
54 cc rather then the 58cc that they come in. If I don��t have them cut how much compressions will I loose from the 9.7 -1 I have now? If I do have them cut is there any worry about valve clearance since the original heads on there now are 54 cc with 351 valves in them? http://www.jdsperformance.com/index.asp?initemuid=330&fcmd=item&inmake=0
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1966 GT light blue VERT
1966 GT light blue Convertible
Blue Standard Interior A code
I am running a 289 with a comp Cam 270HR roller , C9OX COBRA Intake , Holley 650 DP Mechanical Secondarys , Tri Y headers , roller tiped rocker Arms and over sized 351 Valves that are in 289 heads that have been polished and ported. Hooked to a T-10 4 speed and 3.25 traction lock 8 inch rear end.
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fasteach
Journeyman Posts: 28
From: miami Fl.
Registered: Jul 2006
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posted 11-18-2006 03:37 PM
well...in the absence of real experts, i guess i can point you in the right direction.
the standard rule of thumb for our engines is, 6cc's = 1 point of compression.
another general rule of thumb is .006 milled for every 1 cc. (six thousandth of an inch milled from the face of the head removes roughly 1 cc of volume from the combustion chamber volume) hope that helps.
Duke
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DocVoodoo
Gearhead Posts: 164
From: Plainfield CT USA
Registered: Feb 2003
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posted 11-19-2006 04:58 PM
So it will bring it down to around 9-1 give or take ? ------------------
1966 GT light blue VERT
1966 GT light blue Convertible
Blue Standard Interior A code
I am running a 289 with a comp Cam 270HR roller , C9OX COBRA Intake , Holley 650 DP Mechanical Secondarys , Tri Y headers , roller tiped rocker Arms and over sized 351 Valves that are in 289 heads that have been polished and ported. Hooked to a T-10 4 speed and 3.25 traction lock 8 inch rear end.
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fasteach
Journeyman Posts: 28
From: miami Fl.
Registered: Jul 2006
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posted 11-19-2006 06:17 PM
yep...4cc's is 2/3 of a compression ratio.
On the plus side...i'd trade airflow for compression ratio ANY DAY. 
Duke
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indyphil
Gearhead Posts: 3394
From: Senoia, G.A. USA
Registered: Jul 2002
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posted 11-20-2006 08:00 AM
Stroker kit will get you that compression back!
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fasteach
Journeyman Posts: 28
From: miami Fl.
Registered: Jul 2006
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posted 11-20-2006 12:05 PM
a stroker kit would bring compression back to where it was before the swap...and also render the heads and cam too small for the application, depending on displacement...JMHO.
Duke
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ga289stocker
Gearhead Posts: 129
From: Sugar Hill, Ga
Registered: May 2006
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posted 11-20-2006 01:06 PM
DocVooDoo have you ever run your car at the track?.We have very similar combo's, i just bought the 165 AFR's and will be putting them on this winter. I'm not going to mill them any though and know I'll loose a litte compression but i'm sure the flow rate and new cam I'm installing(282s) will more than make up for it.. just curious..thanks. ------------------
1965 2+2
289 A code 4v, 4spd, stock heads 3.80 posi, 13.84 @ 100.65http://i22.photobucket.com/albums/b320/ga289stocker/yard2.jpg
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indyphil
Gearhead Posts: 3394
From: Senoia, G.A. USA
Registered: Jul 2002
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posted 11-20-2006 01:06 PM
quote:
Originally posted by fasteach:
a stroker kit would bring compression back to where it was before the swap...and also render the heads and cam too small for the application, depending on displacement...JMHO.
Duke
It was really a tongue in cheek comment. Stroker kits are an expensive way to raise compression. but even so, I dont agree. If an engine runs good by itself, it will only run better if stroked. Stroking an engine without changing the heads does mean you end up leaving some power on the table, but with MORE power and a MORE streetable engine than before, youre getting the best of both worlds. Its not like there will be a driveability problem. I was tongue in cheek, but before machining a good set of heads think about the long term plans for the engine. If you stroke it later you may not want the heads milled, and its not easy to undo that. I would live with the lower compression and consider a stroker kit as a long term idea (perhaps next time you rebuild the engine?) A 331/347 with AFR 165s isnt a bad package, itll have awesome low RPM grunt, probably still make over 400hp with a streetable cam.
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fasteach
Journeyman Posts: 28
From: miami Fl.
Registered: Jul 2006
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posted 11-20-2006 02:52 PM
the "tongue-in-cheek" was recognized...
AFR calls the 165cc head suitable for 289-302 engines up to 6000rpms...they call the 185cc head suitable for 302-351 engines up to 6500rpms.
Disagree with AFR all you wish, i'm not offended.
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indyphil
Gearhead Posts: 3394
From: Senoia, G.A. USA
Registered: Jul 2002
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posted 11-20-2006 04:31 PM
quote:
Originally posted by fasteach:
the "tongue-in-cheek" was recognized...
AFR calls the 165cc head suitable for 289-302 engines up to 6000rpms...they call the 185cc head suitable for 302-351 engines up to 6500rpms.
Disagree with AFR all you wish, i'm not offended.
AFR doesnt say that their 165s cannot be used on a 331/347. If you do use 165s, you will give up a little higher RPM power to the 185s but youll have better off idle performance and more low end grunt. 185s are not for everyone, he cant buy 185s now and stroke later, the 185s have the larger valves and dont fit the stock type pistons on his current short block (without cutting the pistons). My comment was to inspire DocVoodoo to think about his long term aspirations. Cutting the heads is permanent, and isnt easily reversed. think of the possible paths, stroker kits, blowers etc.. Its all a matter of planning. but once you cut them down then your stuck with it. I think Alex said that a full point in compression is worth about 20-25hp? I have a 331, and I reckon Im between the 165s and the 185s when it comes to what I really want. The 185s will make more power but the 165s will have better off idle performance. Im all about driving around on the street. And I havent decided which chamber volume to get yet because I think I may add a few PSI of boost someday.
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DocVoodoo
Gearhead Posts: 164
From: Plainfield CT USA
Registered: Feb 2003
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posted 11-20-2006 08:16 PM
Well I want to stick with my 8 ich rear end so to much power is a problem. Its allso an original factory GT and the block is original to the car . What ever I do need to be easyly undone and to radical could take out an original block . But your right I should allso think about rsale of the heads incase I want to go back to stock .------------------
1966 GT light blue VERT
1966 GT light blue Convertible
Blue Standard Interior A code
I am running a 289 with a comp Cam 270HR roller , C9OX COBRA Intake , Holley 650 DP Mechanical Secondarys , Tri Y headers , roller tiped rocker Arms and over sized 351 Valves that are in 289 heads that have been polished and ported. Hooked to a T-10 4 speed and 3.25 traction lock 8 inch rear end.
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fasteach
Journeyman Posts: 28
From: miami Fl.
Registered: Jul 2006
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posted 11-20-2006 08:34 PM
wow...where to begin?
Just so this doesn't stray even FURTHER off topic for DocVoodoo...yes, 9.7:1 compression ratio with 54cc heads will yield 9.03:1 compression ratio with 58cc heads, all else being equal.
AGAIN i must say that i would GLADLY trade airflow for compression ratio, ANY DAY.
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