460 jetboat build

[disturbthepeace1]

My newest prodject, So far:

460 +0.060
.005 deck
stock crank champherd
truck rods bal, polished, ARP bolts
Speed pro forged dished -22cc
Edelbrock perf RPM heads 75cc chambers
Stealth intake matched port 1in spacer
850 dblpmpr
100hp edelbrock nitrous plate kit


questions:
I want to bush the rods for floating pins, but he pistons are press only. Has anyone had a shop cut grooves in the piston for spiral locks?

What is th max HP for these rods(polished balanced, and fitted with bolts)?

Also, what about smoothing out the dish do you think that might help combustion? Im going to cut a little off the head deck to get the ratio to 10.3:1.

I want about 560hp on the motor and RPM range of 2500rpm-6300rpm with a C jet.. Im thinkin of 240ish @.050 and 550+lift..

Its a 19ft jet that will only used to go fast..

I know there some guys in here with boat motor experience and since this is my first goat motor build any advice would be welcome........

[Big Dave]

I see you plan on buying forged pistons which are generally designed for full floating pins. Stock rods (with bronze bushings inserts) can be machined to full float, and since you are having them resized any way (with ARP bolts) it wouldn't be that much more expensive. Since you are boring the block to get 0.060" over and presumably having to buy new pistons, just order the forged full float with either flat tops or dished depending upon you final combustion chamber size after you surface the heads.

I see you are going after market on the heads which is a good move. Before I even finished reading your post I was going to suggest a set of CJ heads as they would do well here if you can find a 428 CJ lying around unmolested after all these years with good heads that just happen to be lying around. A nice marine cam would work well (they usually have a larger LSA angle than street car motors to get a flat broad torque curve) and they are chosen by desired RPM and your impeller type (A or B).

Exhaust is always a problem with marine applications. If it is below deck and enclosed you have to run marine cast iron water cooled manifolds (log type not exactly high tech by racer standards). If your motor is fully open (no sump) you can use tube type headers as there isn't the fear of an explosion with an exhaust leak igniting explosive fumes in the sump.

Always a chance of a fire onboard with any inboard engine, but explosions are worse. Play safe, and don't forget the life jackets(real CG approved ones; not inflatable toy water wings).


Big Dave

[disturbthepeace1]

The piston that i want to use come in press pin only that is why i was wondering if anyone has had the grooves cut to accept a floating type pin. I feel this important due to the fact there will be sustained rpm at high cruising speeds...

The headers are upswept open exhaust(water injectd)

The motor came with a set a "CJ" heads on it but when i checked casting #'s I found them to be the worst casting availible with a 100cc open chamber. By the time I find a set of bare good CJ's($600 was the cheapest i found), fill them with good valves,have them cut for dual springs, studs guidplates, and porting; Im almost at 1600.00..... Edelbrocks are 1800.00 complete

[Big Dave]

You do know that the only reason people use floating pin pistons is for maintenance on the motor. The fact that it can be torn down in the pits without the need to press pistons off and on the rods; makes emergency repairs possible. There isn't a horse power difference in the two means of mounting pistons and the lack of a floating pin makes the motor more durable (one less thing to go wrong, such as pushing out a spiral lock.)


Big Dave

[disturbthepeace1]

I have always believed that by switching over to a foating piston it would do a couple things.

Less heat since there is more wear surface to distribute the energy.. making it use less energy to move at sustaned RPM's

If a piston pin wear surface got damaged do to metal debri, heat it would still move do to the extra movement between the pin and the rod end..

I think a piston would have to crack or a lock would have to be install incorecctly for a spiral lock to fail.. I have used them for years with out any failures...

[clay]

I guess it would make emergency repairs possible, but not easy with the double spiro-lox - they are a PIA. I would have thought floating pins would be more durable also in addition to the possibility of emergency repairs. If the pin started to gall in one area, it could spin in the other for a while to let the other one cool off. Now granted, this durablity woudln't be even remotely justified in a street or even drag race setup, but in a boat I can see some serious abuse taking place. Just a thought. Clay

[Hanz]

Properly installed locks have no business coming out, or they wouldn't be used in high dollar/high performance engines. When was the last time you saw a piston being replaced in a circle track pit?

But with that said, I wouldn't hunt down a shop to machine grooves, and hope they were machined correctly.

Don't forget that you would then either have the pins shortened, or buy new pins. I am *guessing* that if you did find someone to machine the grooves and shorten/replace the pins, you would be talking a good $300 if not more.

If you insist on full floating pins, I would take this $300 and the money that the Speed Pro pistons cost, and buy another brand piston with free floating option already in place. Maybe Wiseco, JE, or Ross, I'm home now and don't have my catalogs here. If they are a shelf item you might be talking $600 or so.

If you decide to stay with the Speed Pros and press them on, make sure the shop hones the piston pin bores for extra clearance, and you won't have the seizing or tightening problem.

Hanz

[af2]

I myself have run wire locks in the past and I am still using them with the Mahle pistons I am running and have never had one come out. Wire locks are great when you eventually have to disassemble to refresh the motor and almost everyone running F1 uses them.
I am talking wire v.s. spiral. Spiral will never come out if installed correct and the same with wire locks. Spiral is the worst to remove. Always damage the piston when finished!

[disturbthepeace1]

Another sulution would to go with flat tops that are $120 more but come in pressed or foating. I would need to get the 95cc perf RPM's heads, block deck to 0.00, and mill the head from 95cc to 86.6 cc..

How to you find out much head surface to take off to achieve a given chamber cc? Or is this something the machinist would find out as soon a he made a first cut and mesurement..

[af2]

[disturbthepeace1]

This would put the head closer to the piston and in order to get clearence I would have to notch the pistons... -xcc's...

I think some of these manufactures know how to get you to spend the extra money on the parets that dont cost that much more to manufacture then lower performance pieces.......

[Big Dave]

I personally have never had a pin come out either. But it was a report of what used to the industry standard of double snap ring failures that have prompted people to try Teflon buttons and these accursed Spiro-locks. I have thought long and hard about getting a set of custom pins and pistons made up that again use snap rings just to rid of Spiro-locks. That is how fond I am of them.

I do not believe there would be enough surface area to sustain continued operation of the engine should a pin seize in the piston. Additionally floating pins rely upon splash lubrication, something most of us are trying to get under control with baffles, and scrapers and deep sumps (for those not running dry sumps).

Big Dave

[af2]

I aborted my own post! Anyway, What the hell is the piston doing when going UP? It is sucking oil and that is lubricating the pin. There is a positive and negative thing going on all the time!

[af2]

[af2]

Not true if running a dome! DOH