CAMS and HEADWORK MATCH?
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Intermediate
Joined: May 2012
Posts: 48
Likes: 0
From: On the road
Are those #'s for a specific cam?
HDF Community Team
Joined: Jun 2006
Posts: 12,776
Likes: 2,607
From: san antonio
It's not that simple. Those are flow numbers at .600" lift; which none of the cams previously discusse has. BTW, the Crane cams you referenced are not often selected but those that run them really like them.
Anyway, I digress. Flow at .600" lift means nothing, that is just what the heads are capable of flowing at that lift. Without knowing what the head flows at the lower lifts; you don't know anything. I also noticed that FLRH2000 didn't say whether those readings were at 10, 25 or 28 inches of water column. Don't get hung up on flow numbers; Bean doesn't provide flow numbers but many head porters do. That data only shows what those heads flowed on that head porters flow bench. Flow test them on another bench and I will guarantee the data will be different. Then your air filter must flow an equal amount; having heads that flow 260cfm doesn't mean much if your air filter only flows 210cfm.
Pick your cam, get your heads ported to match, get a good tune and forget about flow; it doesn't matter.
Anyway, I digress. Flow at .600" lift means nothing, that is just what the heads are capable of flowing at that lift. Without knowing what the head flows at the lower lifts; you don't know anything. I also noticed that FLRH2000 didn't say whether those readings were at 10, 25 or 28 inches of water column. Don't get hung up on flow numbers; Bean doesn't provide flow numbers but many head porters do. That data only shows what those heads flowed on that head porters flow bench. Flow test them on another bench and I will guarantee the data will be different. Then your air filter must flow an equal amount; having heads that flow 260cfm doesn't mean much if your air filter only flows 210cfm.
Pick your cam, get your heads ported to match, get a good tune and forget about flow; it doesn't matter.
Club Member
Joined: Jun 2007
Posts: 45,429
Likes: 2,898
From: Bedford UK
The bike in Prodrag's photo will have a competition valve job, designed to deliver maximum performance in a very particular rev range, probably using non-pump gas. A street port will give performance over a much wider engine speed range, to provide a wide spread of torque. Given two heads, one of each type, the differences will be pretty obvious, with bigger valves and ports in the one. I doubt if either of us would actually like riding Prodrag's bike...... 
Sponsor
Joined: Dec 2007
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The ports have been modified with this stuff people a "street port".
Reminds us of the "3/4 race" cams that J.C. Whitney used to sell.
Scott
Reminds us of the "3/4 race" cams that J.C. Whitney used to sell.
Scott
Road Warrior
Joined: Oct 2009
Posts: 1,251
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If someone uses the term 3/4 race cam with me in conversation with me, I'm simply walk away lol
HDF Community Team
Joined: Jun 2006
Posts: 12,776
Likes: 2,607
From: san antonio
You are comparing apples and oranges. There is no clear cut definition of a "street" port job. A BigBoyz street port retains OEM valves and springs, includes a "competition" valve job, new guide seals and reshaping the exhaust and intake ports. Other porters have their own configuration for a "street" port. For instance, some include a larger intake valve; some replace the OEM valves, etc. It is important to discuss the details of the head work with the porter so you can compare prices and work scope to make an informed decision for you particular build plan.
A competition valve job generally implies a multi-angle valve job which can be done on a set of stock, non ported heads; it's just a trick valve job.
A competition valve job generally implies a multi-angle valve job which can be done on a set of stock, non ported heads; it's just a trick valve job.
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Banned
Joined: Sep 2009
Posts: 3,569
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From: deland,florida
our street port consists of opening the bowls up for 1.900/1.615 valves and some port reconturing and includes valves & seals,our compitition valve job is fully radiused seat work performed on our SERDI 100 seat & guide machine (flows WAY better than any 3 or 5 angle seat).cant speak for others street ports,but ours flow 155+ @ 10",great for 100+ hp our of milder builds,our stage II & III headwork is for more aggressive builds
Intermediate
Joined: Mar 2007
Posts: 29
Likes: 0
>Are those #'s for a specific cam?<
dano,
Those flow rates work for a LOT of them (to many to list.) 95" to 103" CID.
Don't get hung up on the cam, focus on the fact your trying to feed a CID within a specified time interval. The CID will dictate the potential TQ, the RPM range the max TQ is made will show as HP. No matter what cam you use, 95" CID is always going to be 95" CID and the exercise of filling the cylinder to it's max never changes.
>It's not that simple.<
For real, it is.
>Flow at .600" lift means nothing, that is just what the heads are capable of flowing at that lift. Without knowing what the head flows at the lower lifts; you don't know anything.<
WTF? It means EVERYTHING the ONLY thing, without in increase in flow, material removal does nothing more then lower velocity. With that said, the importance of the flow rates at the higher lifts are indicative of the MOST IMPORTANT things when it comes to heads.
1st. The heads don't stall, won't stall, and/or flow backwards at the lifts lower then .6" to include .57" .51" .5" .498" etc...
2nd. EVERYONE KNOWS you can't have 260+ CFM @ .6" and NOT have 250, 240, 200,CFM etc at the lower lifts, what do people think, the head flows absolutely nothing until .6" lift then BANG 260? Nothing in between? So if you KNOW the head flows 260+ at .6" lift you KNOW what it flows @ .5", .4", .3", .2", .1" etc....and then you KNOW what it will do when harnessed to a specific set of supporting parts.
>I also noticed that FLRH2000 didn't say whether those readings were at 10, 25 or 28 inches of water column. Don't get hung up on flow numbers<
28", 260 @ 10" Would be 430+ and unachievable N/A in a stock cast TC head.
FWIW, ABSOLUTELY get hung up on flow numbers, when it comes to head porting, in spite of what you read on the internet, NOTHING else matters.......for real.
dano,
Those flow rates work for a LOT of them (to many to list.) 95" to 103" CID.
Don't get hung up on the cam, focus on the fact your trying to feed a CID within a specified time interval. The CID will dictate the potential TQ, the RPM range the max TQ is made will show as HP. No matter what cam you use, 95" CID is always going to be 95" CID and the exercise of filling the cylinder to it's max never changes.
>It's not that simple.<
For real, it is.
>Flow at .600" lift means nothing, that is just what the heads are capable of flowing at that lift. Without knowing what the head flows at the lower lifts; you don't know anything.<
WTF? It means EVERYTHING the ONLY thing, without in increase in flow, material removal does nothing more then lower velocity. With that said, the importance of the flow rates at the higher lifts are indicative of the MOST IMPORTANT things when it comes to heads.
1st. The heads don't stall, won't stall, and/or flow backwards at the lifts lower then .6" to include .57" .51" .5" .498" etc...
2nd. EVERYONE KNOWS you can't have 260+ CFM @ .6" and NOT have 250, 240, 200,CFM etc at the lower lifts, what do people think, the head flows absolutely nothing until .6" lift then BANG 260? Nothing in between? So if you KNOW the head flows 260+ at .6" lift you KNOW what it flows @ .5", .4", .3", .2", .1" etc....and then you KNOW what it will do when harnessed to a specific set of supporting parts.
>I also noticed that FLRH2000 didn't say whether those readings were at 10, 25 or 28 inches of water column. Don't get hung up on flow numbers<
28", 260 @ 10" Would be 430+ and unachievable N/A in a stock cast TC head.
FWIW, ABSOLUTELY get hung up on flow numbers, when it comes to head porting, in spite of what you read on the internet, NOTHING else matters.......for real.