Cam upgrade.... Any thoughts"
Grand HDF Member
Joined: Dec 2012
Posts: 3,782
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From: river
I'm concerned about the size of the carb as I know from running radical street cars a too large carb will tend to be soft on the low end. I worked in a speed shop and kids always came in wanting to put a 950 Holley double pumper on their 302. Couldn't tell them it was way too much carb.
Something to think about with the larger cam. A radical cam in a smaller engine will tend to be well, more radical sounding whereas that same cam in a larger engine is more streetable. Definitely something to consider. I don't want it to be unridable.
What ignition are you running?
Thanks again for your input, you're as crazy as I am...
Something to think about with the larger cam. A radical cam in a smaller engine will tend to be well, more radical sounding whereas that same cam in a larger engine is more streetable. Definitely something to consider. I don't want it to be unridable.
What ignition are you running?
Thanks again for your input, you're as crazy as I am...
I'm running a factory nose cone to set my timing and have an external Daytona twin tech for adjusting advance. I've ran crane nose cone, Daytona twin tech nose cone, Screamin eagle nose cone. Same chit to me.
In my honest opinion, a cam over 625 range is for race 1200s. Hammer has put down over 110 hp with 600s on street bikes. Not to many street 1200s are putting power down like that. I had to grind case for the 600s to fit. One other thing, if you get bigger, you'll need new lifters cause factory ones don't have the travel, and prob in the market for roller rockers. That's about 800 bucks
Grand HDF Member
Joined: Dec 2012
Posts: 3,782
Likes: 1,202
From: river
Redshift, hammer, tman, woods, andrews all make some big azz cams, but you also need the correct compression ratio to match the cams and youll need some mean flowing heads with big valves to support the cams. Ive watched guys over the years put huge cams in and I would walk away with my 536 or 575 screamin eagles because i my head porter had everything working together.
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Road Master
Joined: Nov 2012
Posts: 867
Likes: 15
From: South Central Pennylvania
A 42 mikuni will run just fine on a stock 1200 without any low end issues. It will also support a 105 hp build with ease. Hammer has had good luck with 585s and 600s and crush head work with big valves and a 45 mikuni without giving up any low end issues.
I'm running a factory nose cone to set my timing and have an external Daytona twin tech for adjusting advance. I've ran crane nose cone, Daytona twin tech nose cone, Screamin eagle nose cone. Same chit to me.
In my honest opinion, a cam over 625 range is for race 1200s. Hammer has put down over 110 hp with 600s on street bikes. Not to many street 1200s are putting power down like that. I had to grind case for the 600s to fit. One other thing, if you get bigger, you'll need new lifters cause factory ones don't have the travel, and prob in the market for roller rockers. That's about 800 bucks
I'm running a factory nose cone to set my timing and have an external Daytona twin tech for adjusting advance. I've ran crane nose cone, Daytona twin tech nose cone, Screamin eagle nose cone. Same chit to me.
In my honest opinion, a cam over 625 range is for race 1200s. Hammer has put down over 110 hp with 600s on street bikes. Not to many street 1200s are putting power down like that. I had to grind case for the 600s to fit. One other thing, if you get bigger, you'll need new lifters cause factory ones don't have the travel, and prob in the market for roller rockers. That's about 800 bucks
Carb is a little more tricky. Just to kick around, what do you think of dual carbs? Probably won't do it but just for conversation..
This is what I found on the mikuni website about their carbs and cfm rating.
"The stock Harley CV40 carburetor flows about 185 CFM (cubic feet of air per minute) when flow is measured at a pressure difference of 12 inches of water. All the Mikuni HSR series flow considerably more:"
Stock Harley: 185 CFM
Mikuni HSR42: 213 CFM
Mikuni HSR45: 237 CFM
Mikuni HSR48: 270 CFM
I don't know what size Harley motor they were talking about but using the formula I've always used the 120 inch motor cfm rating is right around 190 cfm. And that is not taking into account the volumetric efficiency of a normally aspirated engine which is usually calculated between 0.70 and 0.80 percent, give or take. We are talking stock motor here.
The formula I use is as follows:
Engine size X RPM Divided by 3456.. then X 0.70 - 0.80 v.m. rating.
120 Cubic inch motor X 5500 RPM = 660000 divided by 3456 = 190.97 cfm
Then using 0.75 V.M. Rating X 190.97 = 143.23 cfm
Of course for all out racing you'd probably want to double maybe almost triple that number. ...
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Road Master
Joined: Nov 2012
Posts: 867
Likes: 15
From: South Central Pennylvania
Road Captain
Joined: Jun 2012
Posts: 533
Likes: 2
From: Virginia
RE: Carbs - for most street 1200s, a properly jetted CV40 is fine. If you're building more than 100HP into your engine, then one of the Mikuni's or the larger CV44 is probably a better choice. Just like your car engines, you need to match the flow requirements - you don't put a Holley 1100 (yeah, I'm dating myself) on a 300HP street car and expect it to have nice street manners.
Taking the time to ensure that each component is optimized to complement the entire combination is where you get the bang for the buck, and that's where Aaron's advice is invaluable.
He's modeled our engines, and can calculate what a given combination will do before the first shavings have been cut out of a head.
As to pipes, also note that he almost exclusively recommends 2-1 pipes for street use.
Taking the time to ensure that each component is optimized to complement the entire combination is where you get the bang for the buck, and that's where Aaron's advice is invaluable.
He's modeled our engines, and can calculate what a given combination will do before the first shavings have been cut out of a head.
As to pipes, also note that he almost exclusively recommends 2-1 pipes for street use.
Road Master
Joined: Jul 2011
Posts: 1,030
Likes: 65
From: Calgary AB
if 120 ci -> 190 cfm, then a 76 ci (1250) -> 120 cfm. An HSR45 is almost double that.
I'm amazed at the numbers these guys are making, almost 1.5HP / ci, just over 1# torque / ci.
I'm amazed at the numbers these guys are making, almost 1.5HP / ci, just over 1# torque / ci.
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Joined: Dec 2012
Posts: 88
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From: Denver
As for pipes, since you are going so performance oriented I would check out the D&D bobcats. 2 into 1 for sportys. Great performance pipe with rave reviews. They aren't cheap, but they are a great set of pipes.
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Joined: Jul 2006
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From:
If your are not putting a good 2 into one on dont both with cams.Iput the n4 in with sceaming eagle pipes i hated lost so much down low.so i had to put a sampson powerflow on and what a difference drive and pulls like a dream.