SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: eliminator18 on June 13, 2019, 07:34:46 AM
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im planning on building another bbc motor, but am looking for some useful information for this build.
Boat: 76 eliminator 18ft with Berkeley jg pump
engine block: 454
I want my boat to be able to do 70+mph
the info im looking for is:
* do I bore and stroke the motor or leave it std with higher comp pistons
* where does the hp/tq peak need to be in rpm for optimal performance?
im just looking for some helpful info to get me in the right direction. in my head I have planned to go 496 w/ 10.1 comp hyd roller cam brodix heads and 950cfm dp carb.
thanks for any helpful insight
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You will also need to know what impeller you have to know Hp and RPM you need to reach your goal.
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it currently has ''A" impeller, bowl stuffer, droop snoot, and hyd. place diverter
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All Chevy jokes aside, I don't see how you don't get 70 out of that. Even for a Chevy. Ooops, sorry.
What was the specs on the last engine and what rpms/go/mph did it do?
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This might help
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LAST ENGINE WAS BORED .031 OVER WITH 781 HEADS 9.5:1 COMP XM HYD. FLAT TAPPET CAM AND 750DP CARB
BOAT TURNED 5400RPM AND GPS READ 59MPG, I THEN REPLACED WITH NEW ALUM "A" IMPELLER AND SS WEAR RING AND RAN IT AGAIN
WHICH RPM DROPPED TO 5K MAX AND GPS READ 65MPH.
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If the bottom end is solid you could bolt on a set of edelbrock oval port aluminum heads, a single plane high rise intake, a good carb, roller cam, lifters, and rockers and a good distributor and go have fun. Also check your bottom for hook and that the jet intake is set properly. Sounds easier said then done. Set up right this should give you 600 plus hp and be pretty solid.
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Cool thanks for the info
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The cam is the heart and soul!
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MY NEXT QUESTION IS, WHAT CAM ARE MOST OF YOU GUYS RUNNING IN YOUR JETBOATS?
HYDRAULIC ROLLER OR SOLID ROLLER CAM? IM THINKING OF HYD. ROLLER, JUST BECAUSE OF THE FACT ITS SET IT AND FORGET IT, I DONT WANT TO BE ADJUSTING VALVES EVERY TRIP
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HOW MANY OF YOU RUN AN INDUCER ON YOUR PUMP? I HEAR ITS MAINLY FOR HEAVY BOATS, ANY PROS/CONS ON PUTTING IT ON AN 18FT ELIMINATOR, OR IS IT A WASTE OF MONEY
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MY NEXT QUESTION IS, WHAT CAM ARE MOST OF YOU GUYS RUNNING IN YOUR JETBOATS?
HYDRAULIC ROLLER OR SOLID ROLLER CAM? IM THINKING OF HYD. ROLLER, JUST BECAUSE OF THE FACT ITS SET IT AND FORGET IT, I DONT WANT TO BE ADJUSTING VALVES EVERY TRIP
I'm running a hydraulic roller cam.
Howard's Cams.
.567", .578", 224°, 232°.
427 truck heads.
454, .030" over.
9.0:1, trw's
Victor Jr rpm.
Holley 750, vs
Logs and snails.
505 hp @ 5000 rpm.
Spinning an American Turbine AA
That's all I got.
Dan'l
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In my opinion build a 496 and stick with pump gas, 10.1 full roller with a good set of heads you should get probably 80+ depending on how good the pump and your set up is. If your not racing it stick with pump gas a lot more enjoyable when your not paying a fortune at the pump, just my 2 cents, good luck with your build either way
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See how with a tighter pump you gained 6 mph and dropped 400 rpms. A good flowing pump and less wetted, even surface is key to jet boats. You can make a lot of HP but if you can’t transfer it out the pump and you’re plowing through the water, you loose speed.
You’re not too far off 70. You might just need to work with the jet configuration. Some boats like a droop, some might need some wedge to change the angle. Have you tried checking speed at different diverter angles?
An inducer helps to get you out of the hole quicker. Not known to do much for the top end. Some smaller boats notice quite a difference, some don’t.
If you want to just build more HP, tunnels and K-034 and you have good ideas.
For a 70-80 mph jet boat, peak HP is usually 53-5600 rpms. Just depends on the boat and set up. Your impeller will need to match.
What kind of exhaust are you running?
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