Another cam question
Tourer
Joined: Dec 2010
Posts: 372
Likes: 1
From: Denver Colorado
Leave it like it is until the warranty has expired. Then come back and see what the new designer cam is. Odds are the hot over priced ones you see now will be replaced with something purportidly better and certainly more expensive - then go buy the current day cam for half the price. If you want a high lift cam be prepared for the full deal or save for a major rebuild in the future. 
Grand HDF Member
Joined: Nov 2004
Posts: 3,917
Likes: 184
From:
The only thing about higher lift cams is they really don't come into play unless the heads are designed to benefit from the higher lift. In other words why run a 575 lift cam if the heads stop flowing at say 510. What benefit would you gain. I trying to think where I saw a chart on the cfm flow on stock heads at different lift, I'm thinking it was on another forum but it showed around 510 or so was about it at the time the chart was posted.
Here are the flow numbers for Dewys pro street ported heads with 1.900 in. and stock ex. @10" h20 multiply number times 1.67 to get @28"
ALL REAL NUMBERS
intake lift CFM Exhaust CFM
.100 = 37.4 / 27.1
.200 = 81.9 / 52.9
.300 = 123.9 / 87.1
.400 = 130.2 / 93.4
.500 = 127.0 / 96.6
.600 = 128.1 / 100.3
SAME DAY - SAME FLOW BENCH
STOCK HEADS NUMBERS are :
.100 = 33.8 / 26.1
.200 = 72.8 / 53.9
.300 = 107.1 / 74.1
.400 = 122.9 / 86.1
.500 = 117.6 / 88.4
.600 = 118.3 / 90.3 Now after head work the benefit cleary showed gains with the higher lift cams. Im just say'n.
Here are the flow numbers for Dewys pro street ported heads with 1.900 in. and stock ex. @10" h20 multiply number times 1.67 to get @28"
ALL REAL NUMBERS
intake lift CFM Exhaust CFM
.100 = 37.4 / 27.1
.200 = 81.9 / 52.9
.300 = 123.9 / 87.1
.400 = 130.2 / 93.4
.500 = 127.0 / 96.6
.600 = 128.1 / 100.3
SAME DAY - SAME FLOW BENCH
STOCK HEADS NUMBERS are :
.100 = 33.8 / 26.1
.200 = 72.8 / 53.9
.300 = 107.1 / 74.1
.400 = 122.9 / 86.1
.500 = 117.6 / 88.4
.600 = 118.3 / 90.3 Now after head work the benefit cleary showed gains with the higher lift cams. Im just say'n.
Last edited by Tn.Heritage; Jan 14, 2012 at 05:22 PM.
Road Captain
Joined: Jan 2009
Posts: 739
Likes: 2
From: St. Louis
The only thing about higher lift cams is they really don't come into play unless the heads are designed to benefit from the higher lift. In other words why run a 575 lift cam if the heads stop flowing at say 510. What benefit would you gain. I trying to think where I saw a chart on the cfm flow on stock heads at different lift, I'm thinking it was on another forum but it showed around 510 or so was about it at the time the chart was posted.
Here are the flow numbers for Dewys pro street ported heads with 1.900 in. and stock ex. @10" h20 multiply number times 1.67 to get @28"
ALL REAL NUMBERS
intake lift CFM Exhaust CFM
.100 = 37.4 / 27.1
.200 = 81.9 / 52.9
.300 = 123.9 / 87.1
.400 = 130.2 / 93.4
.500 = 127.0 / 96.6
.600 = 128.1 / 100.3
SAME DAY - SAME FLOW BENCH
STOCK HEADS NUMBERS are :
.100 = 33.8 / 26.1
.200 = 72.8 / 53.9
.300 = 107.1 / 74.1
.400 = 122.9 / 86.1
.500 = 117.6 / 88.4
.600 = 118.3 / 90.3 Now after head work the benefit cleary showed gains with the higher lift cams. Im just say'n.
Here are the flow numbers for Dewys pro street ported heads with 1.900 in. and stock ex. @10" h20 multiply number times 1.67 to get @28"
ALL REAL NUMBERS
intake lift CFM Exhaust CFM
.100 = 37.4 / 27.1
.200 = 81.9 / 52.9
.300 = 123.9 / 87.1
.400 = 130.2 / 93.4
.500 = 127.0 / 96.6
.600 = 128.1 / 100.3
SAME DAY - SAME FLOW BENCH
STOCK HEADS NUMBERS are :
.100 = 33.8 / 26.1
.200 = 72.8 / 53.9
.300 = 107.1 / 74.1
.400 = 122.9 / 86.1
.500 = 117.6 / 88.4
.600 = 118.3 / 90.3 Now after head work the benefit cleary showed gains with the higher lift cams. Im just say'n.
Thread Starter
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Road Captain
Joined: Mar 2009
Posts: 551
Likes: 2
From: Tallahassee, Fl
Leave it like it is until the warranty has expired. Then come back and see what the new designer cam is. Odds are the hot over priced ones you see now will be replaced with something purportidly better and certainly more expensive - then go buy the current day cam for half the price. If you want a high lift cam be prepared for the full deal or save for a major rebuild in the future.
Road Warrior
Joined: Aug 2010
Posts: 1,268
Likes: 8
From: Detroit, the asshole of America
Wow, those are some pretty poor flow #'s. I didn't realize that HD heads were so restrictive. (even with some porting) The flow stalls at a relatively low lift, too. I'm used to seeing automotive (LSX) flow numbers around 300 CFM+ for the intake and mid 200 CFM flow numbers for the exhaust. Is the basic design of the HD head the limiting factor? (port layout, valve angles, etc.) Or is there just not enough material to work with to make them flow well?
Road Captain
Joined: Jan 2009
Posts: 739
Likes: 2
From: St. Louis
2 things, one being that chart was measured at 10" instead of 28" so the numbers aren't what is normally reported, and the Harley heads after porting will get over 300 cfm on the intake side with porting and oversize valves. The stock valves are tiny compared to automotive applications.
Road Captain
Joined: Nov 2010
Posts: 502
Likes: 0
From: Roads of Idaho
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Road Captain
Joined: Jan 2009
Posts: 739
Likes: 2
From: St. Louis
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