Engine builders....cam suggestions
10-26-2025 | 09:25 AM
#11
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Joined: Nov 2004
Posts: 14,154
Likes: 3,714
From: On A Dirt Floor
No engine builder here
nor jet boat person
nor 460 bbf petson
but what the heck, i’ll take a stab
the ol’ trusty comp cams 280h
230/230 at .050” 110 lsa
https://www.compcams.com/magnum-mari...d-429-460.html
nor jet boat person
nor 460 bbf petson
but what the heck, i’ll take a stab
the ol’ trusty comp cams 280h
230/230 at .050” 110 lsa
https://www.compcams.com/magnum-mari...d-429-460.html
10-26-2025 | 01:08 PM
#13
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Joined: Aug 2019
Posts: 1,249
Likes: 420
From: BC
The problem with jets, in regard to cam'ing, jet drive need high rpm to get the water flowing effectively. You end up with a high cruise rpm with a high vacuum. The engine doesn't work very hard, but it's inefficient.
Berkely impeller chart:
500 HP at 5400 rpm. That's if the A imp isn't already cut down to increase rpm.
450 HP at 5200.
Cam: HR mid 22x Int with a lower 23X Ex with 0.550" lifts.
Your LSA requirement will be dictated by the undervalved the BBF heads, and the conpression ratio. Essentually, how hard it is to have the int and exh ports interact with pressures/flow.
An example for large displacement vs cam duration:
The 365 Mag BBC (454) crate engines of the day, had a 224° single pattern FT cam with 0.510"lift, & 115.5° LSA. Peaked out at 390 hp (crank) at 5200rpm.
Large Rec Port heads and 8.6 CR.
Bottom line, the more accurate info you can generate, the more accurate your custom and/or shelf cam.
Berkely impeller chart:
450 HP at 5200.
Cam: HR mid 22x Int with a lower 23X Ex with 0.550" lifts.
Your LSA requirement will be dictated by the undervalved the BBF heads, and the conpression ratio. Essentually, how hard it is to have the int and exh ports interact with pressures/flow.
An example for large displacement vs cam duration:
The 365 Mag BBC (454) crate engines of the day, had a 224° single pattern FT cam with 0.510"lift, & 115.5° LSA. Peaked out at 390 hp (crank) at 5200rpm.
Large Rec Port heads and 8.6 CR.
Bottom line, the more accurate info you can generate, the more accurate your custom and/or shelf cam.
Last edited by Tartilla; 10-26-2025 at 02:55 PM.
10-27-2025 | 03:49 PM
#16
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Joined: Aug 2019
Posts: 1,249
Likes: 420
From: BC
Jones Cams Marine Cam Selection Sheet copy:
There's a drop down selection where it says 'Jet' for various drive systems.
Where it speaks to seat pressure etc, that would/could be prescribed by the cam suggestion...unless required to work with what you have etc.
Generally, when building an engine, you need to have the heads finalized and complete...to dictate everythkng else like pistons and dome requirements for intended CR etc.
There's a drop down selection where it says 'Jet' for various drive systems.
Where it speaks to seat pressure etc, that would/could be prescribed by the cam suggestion...unless required to work with what you have etc.
Generally, when building an engine, you need to have the heads finalized and complete...to dictate everythkng else like pistons and dome requirements for intended CR etc.
Last edited by Tartilla; 10-27-2025 at 03:52 PM.
11-03-2025 | 06:20 AM
#17
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Joined: Jul 2017
Posts: 1,740
Likes: 298
From: Sodus MI
I told him he is kinda putting the cart before the horse trying to get a cam before having the heads done compression fully figured. I think he is finally listening and will update when I have some more nailed down info. Thanks!
11-23-2025 | 01:15 AM
#18
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Joined: Sep 2025
Posts: 26
Likes: 9
From: Mississippi
Trying to help my old man out and figured I would ask the brain trust...he is getting a motor together for his jet boat and he's not looking to break any speed records just has some wants so figured I'd see what you guys thought....
460 ford(yeah I know lol)
Not a huge ford researcher so he said he's getting "the good" ford heads...apparently they have some castings that are pretty good from the factory I guess
Stock bottom end with all new bearings and seals of course
2x4 tunnel ram and will be running my Holley 2x4 EFI setup that I just took off my boat with ignition control
Full dry exhaust over the transom
He wants to stay hydraulic roller and wants to go as big as he can since he's running dry exhaust
Again not worried about ringing every single HP out of it just wants it to sound as mean as possible and whatever power he gets, he gets lol
It's a 19-20 ft beisemeyer jet boat that he will just be tooling around in annoying people on inland lakes more than likely hahaha
Thanks for the help!
460 ford(yeah I know lol)
Not a huge ford researcher so he said he's getting "the good" ford heads...apparently they have some castings that are pretty good from the factory I guess
Stock bottom end with all new bearings and seals of course
2x4 tunnel ram and will be running my Holley 2x4 EFI setup that I just took off my boat with ignition control
Full dry exhaust over the transom
He wants to stay hydraulic roller and wants to go as big as he can since he's running dry exhaust
Again not worried about ringing every single HP out of it just wants it to sound as mean as possible and whatever power he gets, he gets lol
It's a 19-20 ft beisemeyer jet boat that he will just be tooling around in annoying people on inland lakes more than likely hahaha
Thanks for the help!
Gotta know compression ratio to pick a cam
11-30-2025 | 11:40 PM
#19
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Joined: Jul 2019
Posts: 49
Likes: 44
From: Northern Virginia
What boattrubador said ... knowing the compression is key especially when you already know it is going to be "low" i.e. 8.5:1
With static compression in that range, a gnarly cam plus a tunnel ram and the 460's generous intake ports will be *extremely* lazy at planing and cruising RPM unless he's got a pretty small impeller cut.
With static compression in that range, a gnarly cam plus a tunnel ram and the 460's generous intake ports will be *extremely* lazy at planing and cruising RPM unless he's got a pretty small impeller cut.
