Reply With QuoteIt will help a bunch if you know what size your impeller is and what rpm range you want to turn and the size of your boat.
I have a 73 Kona jet with a Jaccuzi pump.The pump Has had a race mod,to accept a berkley impeller(am told this was an old drag race trick).I have My engine at themachine shop,and am about to have it built up.My question is on what kind of cam,valve train,intake and carb works best for jet boats.It is a 454 .will be punched to.20 or .30 over.It will be a stroker with a 4.25 inch stroke.What Rpm range should i run.is roller vs solid better.I will want to do some river racing and a little skiing.I would appreciate the help so i can describe to the engine builder,what i want.The block is being taped for studs right now and after that we want to get started with the build.
Thank's a bunch.
It will help a bunch if you know what size your impeller is and what rpm range you want to turn and the size of your boat.
It is an 18 footer .I do not know what size impeller it has but could probobly find out.I think the previous owner said it was a berkley a impeller,but would not swear to it.As for rpm range i am looking for advice for what range is best.
not knowing ur budget...nor any facts about ur mtr as far as what u already have...its hard to tell u what to do to it...every1 has there own ideas...i personally would bore it .030 & with the 4.250 stroke u get 468 c.i. ...a very good choice & reliable combo...i would call Comp Cams & tell them what u want to do with the boat & they can set u up with the complete valve train (cam, lifters, springs etc)...i would go with a hyd cam...use a good roller timing chain...a good HP oil pump...a HP mechanical fuel pump (GM, holley, edelbrock)...a good HEI ign system...i would use a dual plane manifold (better torque & driveability)...maybe a RPM Performer or Air Gap...i would use a Holley 850cfm or Edelbrock 750cfm carb...i would shoot for around 5300-5400 rpm...thats plenty...what u want is a "very" reliable mtr that u can fire up with n/p's & go have fun & not worry about it or work on it all the time...u will prob get alot of replies to ur ?? on the build-up...these are just my .02 cents worth & what i would do
Ron (fastrat)
p.s. u can buy alot of parts on this site or on Racingjunk.com or from Summit or on EBay
468 is with a 4 inch stroke. 30 over with a 4.25 will get you 489.
Before we can give you ideas, we need to now your budget and goals. Hopefully your builder knows the tricks to make a marine motor live.Clearances are different because of the environment, more rpms, more water, better cooling available. Use these things to your advantage to build the best power.
That 1/4 inch stroker will add a bunch to the cost of your build up. The rewards are small, especially in a jet that has its own RPM limits built in. A 4.25 in a prop boat will pay off alot more. Save the bucks, build a strong 454-460-468, with the stock 454 stroke. Cheaper crank, cheaper block preparation, cheaper pistons etc etc. To use a leg in a jet is kinda like wasting money unless it is for full out racing, and then add about 5K to make the jet work to match the extremely expensive "stroker" motor..............MP
The block is a standard bore 454.The casting #'s say it is a 73 modle block.The heads are large oval port's,and is a two bolt main.mechanical fuel pump.hei distributor .My budget is 5-6 grand for the motor .My guy says he can do it within that budget.
My goals are to go atleast 80 mph,some river and lake racing,while still being able to ski behind the boat to.
I want a reliable engine with a good idle and great throtle responce and torqe.
I am not familiar with the rpm range for jet boats ,so I don't know what to expect.
I want to go fast ,but I don't want to have to wrench on it when I go to the river.
I don't know a whole lot about chevys. But you should get 550 to 600 HP. In that boat with the right set up should be at least 80 mph..
Here's my setup, hope it helps for comparison sake.
Original Indmar 454, stock bore & stroke. CAST crank & pistons (IMO, unless you want to live arround 6,000RPM, you don't really need a forged one. You can put a LOT of muscle on the cast crank at 5K+)
Compression is still 8.5 to 1 My budget prevented a piston replacement.
I replaced the 3/8" rod bolts with ARP Wave-locs, 8740 Chromoly version, had rods resized.
Cam, Iskendarian kit from DuaneHTP on the board here, .565" lift, 280* duration, flat-tappet hydraulic. Isky 7,000 RPM Superlifters, Isky Springs, shims, steel retainers, Poly-locks. I'm still running the stock style stamped rockers.
Changed to 3/8" pushrods & guides from the 5/16 pencils I had. Speed-Pro's
Comp Cams 9-keyway all billet double-roller timing chain setup.
Clevite 77 bearings
Speed-pro double molly rings.
Fel-pro gaskets top to bottom
Heads are "049" large oval port cast iron with the "small" valves (2.06/1.76 I think) I think the large ovale are the way to go unless building a 8kRPM race-motor where the rectangles would be better.
Edelbrock Performer RPM Air Gap Dual plane manifold. works great. Keeps the torque available while letting her breathe on the top end.
Still running Niccson Logs. Installing Lightning thru-trans. headers this winter as well as 4" outlets.
I'm running 350HP / 412LbFt Q right now, should be pulling 400+ / 460+ LbFt Q this spring after the headers, 470+ HP / 480+ Q after NEXT winter's head porting. Head shop said those are some great heads for that motor.
I've been running (courtesy of dad) a 75HP Nitrous setup since 1979 (he uwned boat since showroom new). I am replacing it with 150 HP max tunable Sniper setup this winter. May not run it over 125 but I can if I want to.
I'm spinning an "A" berk @ 4800 RPM right now, running about 64 or so on a scarred up hull. (hull work this winter (Project #III) I am running a Pro-loader from DuaneHTP as well (his shop is close to my employer, fortunately haha).
She had been radard in the day by dad at 72 on the stock engine, +N2O, with him alone, probably arround '79 or so.
I'm anticipating an RPM level of 5800 max if I push her to 600HP on the gas. the imp. will become an Agressor B this winter.
She's turnkey to run & drive, great throttle response, pulls tubes & skiiers HARD, launches even harder when some bassmaster decides to show me how it's done. She is cold-blooded in the first start of the day, but just bump the key after that. You can drop the hammer all the way to the carpet from an 850RPM idle and she never misses a beat.
Holley model 4150, 700 CFM, Primary power valve (6.5"), jetted 66/76. Twin accel pumps, 10cc Pri/50cc Sec, center-hung brass floats. Actually automotive carb, not a marine but original to the 1978 boat. Flawless operation.
I'm still running the prestolite points distrib but upgrading THAT to a Mallory Flamethrower setup this winter along with the Nitrous & headers.
I just finished up a 489 for my boat. By the time I added up all the machining costs it was only $500 dollars more to go with a stroker kit, Crank, rods, forged pistons, bearings etc.
I'm running a solid roller comp single pattern 246@50 .622 lift. I'm running the 049 oval port heads, with chamber work and the exhaust valves unshrouded with 2.19/1.88 stainless valves. An air gap and a 900 HP holley, electronic ign, Berkley JG pump with a AA impeller, droop, plate and diverter.
What I quickly found out is that the pump is too sloppy to handle the motor. I have to severely pedal it out of the hole . Since it is a stroker, the torque is better and I run substantially more vacuum as I am cruising, thus better mileage. That's good at over $3 a gallon.
Before I put this set up together, I did the same thing you are doing in terms of asking for help. I found a few guys running similar set up and I am pleased as punch. My only limitation on motor output is exhaust. I went from 2 7/8 logs to 3.5" logs - lightnings and the pump are next.
Make sure you put a good pan on. Well worth the money.
Just my experience, but I am happy with the combo. Given your budget, I think this can be accomplished. My only advice is to find a builder familiar with not only boats, but jet motors specifically!!
Gugs
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