Not a "Build Thread," just my motor...
Extreme HDF Member
Joined: Jun 2014
Posts: 11,448
Likes: 2,299
From: NW Ohio
Good stuff. Thanks!
I know the 585 cam wants something like 10.5:1 static compression. That was my starting point. I'm not sure what a practical limit is for compression on a street build running 93-ish octane and a custom advance curve. I was thinking of pushing it a bit higher...11+
I can get decent fuel, the tank is lifted, I have an oil cooler, and it never gets terribly hot here so I feel like I can push it a bit. The current 88 never pings, even on 87 octane.
I know the 585 cam wants something like 10.5:1 static compression. That was my starting point. I'm not sure what a practical limit is for compression on a street build running 93-ish octane and a custom advance curve. I was thinking of pushing it a bit higher...11+
I can get decent fuel, the tank is lifted, I have an oil cooler, and it never gets terribly hot here so I feel like I can push it a bit. The current 88 never pings, even on 87 octane.
Road Master
Joined: Jun 2013
Posts: 1,181
Likes: 98
From: north of the south pole
I've had hsr45, cv44 & hsr 42 on my 95". What I noticed was more low and mid punch with 1st the hsr42 then the cv44.Probably because the smaller ports pack the combustion chamber better at low to mid range as the port velocity is higher. The hsr45 had more top end than the other two.
These were on 10.5-1 95" pistons.
These were on 10.5-1 95" pistons.
Last edited by fxdlx; Feb 3, 2019 at 10:01 PM.
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,921
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From: poway
Few things to note here.
. Longer stroke does not make a motor torquier. Displacement does. A longer stroke makes the rod to stroke ratio change (lower). This can be an advantage on higher compression motors as it shortens TDC dwell time but a lower rod to stroke ratio reduces the ability to crate torque mechanically. Mechanically, you loose torque if you stroke over bore and not increase rod length..
You should pick a carb that complements the flow of the heads. In other words a bigger carb won't help a head that don't flow much..
A bigger cam does not necessarily need a bigger carb assuming fuel flow is good. You may pick up power with a smaller one as the intake tract overflows the motor and you get reversion.
. Longer stroke does not make a motor torquier. Displacement does. A longer stroke makes the rod to stroke ratio change (lower). This can be an advantage on higher compression motors as it shortens TDC dwell time but a lower rod to stroke ratio reduces the ability to crate torque mechanically. Mechanically, you loose torque if you stroke over bore and not increase rod length..
You should pick a carb that complements the flow of the heads. In other words a bigger carb won't help a head that don't flow much..
A bigger cam does not necessarily need a bigger carb assuming fuel flow is good. You may pick up power with a smaller one as the intake tract overflows the motor and you get reversion.
Extreme HDF Member
Joined: Jun 2014
Posts: 11,448
Likes: 2,299
From: NW Ohio
Good stuff, Max. Thanks.
I'm talking to Hillside and VeeTwin and will follow whatever suggestions they give me once I settle on a shop and a build plan.
Ported and flowed heads are a given. So is high compression. I'll leave the details like CC volume, valve sizes, cam selection, etc up to the pros. I can bolt together parts like a mad man but I don't have the spell book for selecting complimentary engine parts and specs.
I'm talking to Hillside and VeeTwin and will follow whatever suggestions they give me once I settle on a shop and a build plan.
Ported and flowed heads are a given. So is high compression. I'll leave the details like CC volume, valve sizes, cam selection, etc up to the pros. I can bolt together parts like a mad man but I don't have the spell book for selecting complimentary engine parts and specs.
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Outstanding HDF Member
Joined: Mar 2015
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From: Philly Suburbs
Chris, your plan is basically exactly what I did. The shop that did my headwork felt my build would be right on the line between favoring an HSR42 or 45, and described the difference basically the same way that fxdlx did above. The decision to go with the 42 was mostly made because it's what I already had, so we opened/matched the manifold and went that way.
Extreme HDF Member
Joined: Jun 2014
Posts: 11,448
Likes: 2,299
From: NW Ohio
Some basic numbers and anecdotal evidence...
98" engine can pump between 140-170 CFM at 6200 RPM, Depending on volumeteic efficiency.
Carb flow rates at 12" of water...
Stock CV40: 185 CFM
Mikuni HSR42: 213 CFM
Mikuni HSR45: 237 CFM
Mikuni HSR48: 270 CFM
Some Googling shpws me that...
HSR42 has supported 110+hp
HSR45 has supported 130+up
HSR48 has supported 150+hp
Seems like the 42, like you said, is right on the edge for a strong 95-100". Thw smaller carb would likely have better street manners bit might cost a couple ponies at the very top. I'll take the instant response on the road. I had a healthy 427" with around 460hp that only a 750 cfm carb on it. A lot of guys say you need an 850... The 750 was a blast on the road.
98" engine can pump between 140-170 CFM at 6200 RPM, Depending on volumeteic efficiency.
Carb flow rates at 12" of water...
Stock CV40: 185 CFM
Mikuni HSR42: 213 CFM
Mikuni HSR45: 237 CFM
Mikuni HSR48: 270 CFM
Some Googling shpws me that...
HSR42 has supported 110+hp
HSR45 has supported 130+up
HSR48 has supported 150+hp
Seems like the 42, like you said, is right on the edge for a strong 95-100". Thw smaller carb would likely have better street manners bit might cost a couple ponies at the very top. I'll take the instant response on the road. I had a healthy 427" with around 460hp that only a 750 cfm carb on it. A lot of guys say you need an 850... The 750 was a blast on the road.
Last edited by cggorman; Feb 8, 2019 at 07:58 PM.
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,921
Likes: 8,027
From: poway
Some basic numbers and anecdotal evidence...
98" engine can pump between 140-170 CFM at 6200 RPM, Depending on volumeteic efficiency.
Carb flow rates at 12" of water...
Stock CV40: 185 CFM
Mikuni HSR42: 213 CFM
Mikuni HSR45: 237 CFM
Mikuni HSR48: 270 CFM
Some Googling shpws me that...
HSR42 has supported 110+hp
HSR45 has supported 130+up
HSR48 has supported 150+hp
Seems like the 42, like you said, is right on the edge for a strong 95-100". Thw smaller carb would likely have better street manners bit might cost a couple ponies at the very top. I'll take the instant response on the road. I had a healthy 427" with around 460hp that only a 750 cfm carb on it. A lot of guys say you need an 850... The 750 was a blast on the road.
98" engine can pump between 140-170 CFM at 6200 RPM, Depending on volumeteic efficiency.
Carb flow rates at 12" of water...
Stock CV40: 185 CFM
Mikuni HSR42: 213 CFM
Mikuni HSR45: 237 CFM
Mikuni HSR48: 270 CFM
Some Googling shpws me that...
HSR42 has supported 110+hp
HSR45 has supported 130+up
HSR48 has supported 150+hp
Seems like the 42, like you said, is right on the edge for a strong 95-100". Thw smaller carb would likely have better street manners bit might cost a couple ponies at the very top. I'll take the instant response on the road. I had a healthy 427" with around 460hp that only a 750 cfm carb on it. A lot of guys say you need an 850... The 750 was a blast on the road.
One thing to mote is that the CFM requirement for the motor is an average demand. Peak can be 3 times higher. The number you post is good if you have a giant plenum with a throttle body or carb on top.
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Extreme HDF Member
Joined: Jun 2014
Posts: 11,448
Likes: 2,299
From: NW Ohio
I didn't think of that. Good point! V-Twin...tiny (no) plenum...
I was wondering why so many people were reportng improved performance with what I considered to be HUGE throttle bodies on their EFI builds. That would help explain it.
I was wondering why so many people were reportng improved performance with what I considered to be HUGE throttle bodies on their EFI builds. That would help explain it.
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