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-   -   Some carb / intake info (https://www.offshoreonly.com/forums/general-q/341807-some-carb-intake-info.html)

Black Baja 10-07-2016 03:59 PM


Originally Posted by bck (Post 4489497)
I was talked into going with the 4150s by the original engine builder because of the improved driveability. In retrospect I should have gone with the 4500s and matching intake from the beginning. Peak horsepower with the first cams and 4150s was 56-5700. The final 4500 and cam combo peaked at 5600 with 1in spacer and 5700 with the 2 in

With that small of a head you really want the largest intake you can get your hands on.

bck 10-07-2016 04:09 PM


Originally Posted by Black Baja (Post 4489500)
With that small of a head you really want the largest intake you can get your heads on...

I'd tend to agree, but like I said I couldn't buy just to test with and I wanted to know without a doubt I would gain power before I spent $. I considered going larger with the entire induction setup including heads but it was a huge expense. I wanted a money back guarantee on the power I was promised and I wanted the power under 6k rpm, not over. Of course no one would make a promise like that so I went with what was free and then purchased what I could.

getrdunn 10-07-2016 05:34 PM


Originally Posted by Black Baja (Post 4489496)
Just an FYI cause I know your using a solid lifter cam. The bushing type rollers will nock 25hp right out of the motor.

50/50.
Where do you draw the line... with open spring pressures? Good and bad with both needle and bushing.

Black Baja 10-07-2016 05:54 PM


Originally Posted by getrdunn (Post 4489526)
50/50.
Where do you draw the line... with open spring pressures? Good and bad with both needle and bushing.

I don't draw the line as far as spring pressure. I've ran up to 1250# open with titanium valves. Really depends on the entire valve train package...

bck 10-07-2016 07:52 PM

Now, those original builds with the smaller cams / 4150s walked all over the dominator combo at lower rpms. They were even at 4600 and then the dominator combo pulled away from 4600 to the end at 5800. I really wish someone had the skills or program to overlay all these graphs.

bck 10-07-2016 08:10 PM

1 Attachment(s)
Here's the graph of the 2 4150 pulls. One with spacer and one without. You can see the spacer improved everything. Also this combo with the smaller cam / 4150 easily outperformed the dominator combo up to 4600 then the Dom combo pulled ahead till the end at 5800. Notice this graph has torque on the right on a different scale than hp.

bck 10-07-2016 08:15 PM

1 Attachment(s)
Here is the Dom with 1 in. spacer graph.

getrdunn 10-07-2016 08:21 PM


Originally Posted by bck (Post 4489560)
Now, those original builds with the smaller cams / 4150s walked all over the dominator combo at lower rpms. They were even at 4600 and then the dominator combo pulled away from 4600 to the end at 5800. I really wish someone had the skills or program to overlay all these graphs.

That comes at no surprise. Combo/application. Twins vs single... Sacrifices will always be made to achieve maximum hp but not necessarily always ideal for every application. I think you ended up extremely well. Sure more time and more money might have gotten you a few more ponies but give you credit for doing what you did. Going to dyno to jet and look for leaks and go home is not worthy in my opinion.

getrdunn 10-07-2016 08:22 PM


Originally Posted by bck (Post 4489568)
Here is the Dom with 1 in. spacer graph.

Nice

bck 10-07-2016 08:28 PM

The boat tended to like to cruise @ 45-4600. I didn't spend much time below that so it was a decent trade off for the top end. Even with all that low end torque with the original combo the boat just didn't seem to like cruising at 3500


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