468 motor build. Opinions.

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nordicjet

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« on: February 13, 2019, 10:57:32 AM »
Iím getting ready to build a 468 for my 18ínordic jet.  These are the parts that I have and would like to use for the build to keep costs down. But I want 625-650 hp.  Let me know it you guys think itís reasonable.  454 .060 over 2 bolt main studded. Forged 454 crank.  Scat H beam rods. Flattop trw forged pistons.  Havenít got a cam yet but going to do a solid flat tapper. 630-650 lift 270-280 duration 108-110 centerline.  I have closed chamber sq port heads. Stainless valves.  2.19/1.88.  Weiand tunnel ram with 2- 660 holleys just redone.  Upswept rewarder wet headers.  Also a top speed with this combo?  Hoping for 85/87mph.  Berkeley split bowl. Stainless impeller with hardened shaft and inducer. Ride plate full droop and FTN place diverter.  Stage 2 bowl porting and rebuild. GS marine. Bottom is getting blueprinted and a rail kit install  also March 1st.  Are my projections realistic on power and speed?  I know aluminum heads and a roller cam would do it for sure but I already have these parts and I want it running by the end of April.  Thanks in advance!




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« Last Edit: February 13, 2019, 11:02:33 AM by nordicjet »


nordicjet

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« Reply #1 on: February 15, 2019, 04:10:22 PM »
Wow. No opinions???


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TrollerDave

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« Reply #2 on: February 15, 2019, 05:51:09 PM »
Yeah the site doesn't get too much traffic anymore. I don't know much, but I think that combo should get you to your goal no problem. It might take some fine tuning with your jet and ride plate.
Do you know how heavy your hull is?  Weight is a big factor with jet boats.


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« Last Edit: February 15, 2019, 05:53:37 PM by TrollerDave »

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« Reply #3 on: February 16, 2019, 03:49:29 AM »
I think your alil optimistic on power, the tunnel ram thing, and we've all done it cuz it looks bitchin,  I think will kill your goal, tunnel rams work in a 3500 to the moon power curve, and your combo will never realize that, I think and Im nobody, but a good single plane  single carb intake and a plate nitrous system will get you everything and more than what  your looking for... and be alot of fun and simple.. jmo..

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gomo1980

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« Reply #4 on: February 16, 2019, 09:24:19 AM »
Why is a single plane intake manifold preferable to a dual plane if you are trying to increase hp and performance for a jet boat?


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mash on it

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« Reply #5 on: February 16, 2019, 01:43:41 PM »
Why is a single plane intake manifold preferable to a dual plane if you are trying to increase hp and performance for a jet boat?


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A dual plane manifold helps promote low to mid range torque, for 'pulling' a gear, ie: vdrive, mercruiser, tow truck, Motorhome, etc.

Low end torque Is not needed in a jet application. Ie: 200 hp @ 3000 rpm, a lowly 305 chebby can do that. High rpm requires high airflow, hence tunnel rams and single plane manifolds.

A properly set up tunnel ram will have MORE horsepower than a single plane manifold, but tuned improperly could be less than a single plane. Also, a single plane is easier to get to work right.

Dual planes are for tow trucks and motorhomes.

Just my $0.02

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gomo1980

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« Reply #6 on: February 16, 2019, 01:52:36 PM »



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mash on it

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« Reply #7 on: February 16, 2019, 02:07:58 PM »
Wow. No opinions???


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Yes.

Bad Ass.

628.371 hp, +/- 2

Speed? 10 minutes. You'll be at the beach 10 minutes before me, save me a spot.

I have the beer. :beer:

And the bbq grill.  :sly:

Dan'l

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aquaholic72

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« Reply #8 on: February 16, 2019, 04:59:35 PM »
A dual plane manifold helps promote low to mid range torque, for 'pulling' a gear, ie: vdrive, mercruiser, tow truck, Motorhome, etc.

Low end torque Is not needed in a jet application. Ie: 200 hp @ 3000 rpm, a lowly 305 chebby can do that. High rpm requires high airflow, hence tunnel rams and single plane manifolds.

A properly set up tunnel ram will have MORE horsepower than a single plane manifold, but tuned improperly could be less than a single plane. Also, a single plane is easier to get to work right.

Dual planes are for tow trucks and motorhomes.

Just my $0.02

Dan'l
Perfect explanation! 

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chrisx2

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« Reply #9 on: February 18, 2019, 01:23:55 PM »
Maybe a Victor w/ 1k cfm up top,

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nordicjet

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« Reply #10 on: February 18, 2019, 03:42:42 PM »
Yeah the site doesn't get too much traffic anymore. I don't know much, but I think that combo should get you to your goal no problem. It might take some fine tuning with your jet and ride plate.
Do you know how heavy your hull is?  Weight is a big factor with jet boats.


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Bare hull 540 lbs. thanks for the feeedback. 


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nordicjet

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« Reply #11 on: February 18, 2019, 03:46:03 PM »
Yes.

Bad Ass.

628.371 hp, +/- 2

Speed? 10 minutes. You'll be at the beach 10 minutes before me, save me a spot.

I have the beer. :beer:

And the bbq grill.  :sly:

Dan'l





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nordicjet

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« Reply #12 on: February 18, 2019, 03:49:28 PM »
Thanks for the feedback.  I have had good luck with tunnel rams.  And a single carb with nos.  But I have a tunnel ram setup.  So Iím gonna try it.  But it may end up with a dominator and a big shot if my goals arenít met.  See you on the river this summer!


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TrollerDave

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« Reply #13 on: February 18, 2019, 08:04:17 PM »
Thanks for the feedback.  I have had good luck with tunnel rams.  And a single carb with nos.  But I have a tunnel ram setup.  So Iím gonna try it.  But it may end up with a dominator and a big shot if my goals arenít met.  See you on the river this summer!


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Look forward to hearing how it goes once you get everything dialed in. Iím betting you make the 85 mark. Good luck.


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nordicjet

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« Reply #14 on: February 19, 2019, 07:04:24 AM »
Look forward to hearing how it goes once you get everything dialed in. Iím betting you make the 85 mark. Good luck.


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   Thanks bro!  I hope so.  Have put a lot of $$$ in the jet & motor.   


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« Reply #15 on: March 09, 2019, 01:28:54 PM »
If you are going to run a single plane, try a 1000cfm carb, with a 1" four hole spacer over top of a 1" open spacer. Get a carb with a smooth radius on the intake, or put a plastic radius adapter on top. It all helps with mixture distribution and power. I did this on the dyno and the engine picked up 55 hp.

nordicjet

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« Reply #16 on: March 13, 2019, 01:49:50 AM »
If you are going to run a single plane, try a 1000cfm carb, with a 1" four hole spacer over top of a 1" open spacer. Get a carb with a smooth radius on the intake, or put a plastic radius adapter on top. It all helps with mixture distribution and power. I did this on the dyno and the engine picked up 55 hp.
Thanks for the tip!


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« Reply #17 on: March 13, 2019, 09:56:52 AM »
Why are you doing a flat tappet over a roller?  I know they are cheaper but for what you are doing a solid roller would be nice.  Got burned years ago on a new build that ate a flat tappet and cost lots of money to repair then buty a roller in the end LOL.  Also some nice hydraulic rollers out there.  I run a .632 lift hydraulic roller in my 548" offshore boat and it dyno'd at 621HP with a single plane and a 800cfm carb.  Sometimes you can find some nice low hour take outs for lifters and cam.
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« Reply #18 on: March 13, 2019, 12:24:56 PM »
I run a flat tappet 468  basic motor close chambered heads made 400hp and 489 torq and she runs 80 in my tunnel hull.



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nordicjet

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« Reply #19 on: March 13, 2019, 05:16:36 PM »
Why are you doing a flat tappet over a roller?  I know they are cheaper but for what you are doing a solid roller would be nice.  Got burned years ago on a new build that ate a flat tappet and cost lots of money to repair then buty a roller in the end LOL.  Also some nice hydraulic rollers out there.  I run a .632 lift hydraulic roller in my 548" offshore boat and it dyno'd at 621HP with a single plane and a 800cfm carb.  Sometimes you can find some nice low hour take outs for lifters and cam.
I

I really want a solid roller cam.  But itís the cost holding me back.  And I hear hyd rollers have troubles also.   I want it running by May.  So I will prob do cnc ported aluminum heads & roller next winter.  Fingers crossed with my solid flat tappet. 


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nordicjet

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« Reply #20 on: March 13, 2019, 05:38:58 PM »
I run a flat tappet 468  basic motor close chambered heads made 400hp and 489 torq and she runs 80 in my tunnel hull.



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Nice. 


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