'80 SN 351w RR performance upgrades

Hi, (Thanks CCF.com for a great forum)

Just bought a refurbed '80 Ski Nautique very nicely redone about 10 years ago with engine overhaul 4 years ago. First owner SN and during first week somehow overheated the engine during normal operation and have a knock now. Raw water impeller is good and 160 deg thermostat also good on the stove test. Jury is still out on root cause of overheating. don't have much history from previous owner, other than I never had any problems...

Long and short, need to rebuild or buy long long block. Was considering the following performance upgrades to get more RPM's out of the engine for more top speed for reverse rotation 351w with firing order 18456273 and 1:1 Velvet drive tranny:

* roller cam with marine grind
* roller rockers
* GT40P heads
* aluminum intake
* already has newer Holley 600 marine carb
* already has newer Mallory marine distributor

Called a long block supplier and he says can't get too 'radical' with a RR roller cam due to reversion and can't get full benefit of GT40P heads with normal marine cam.

The 1:1 tranny and and 4 blade prop tops at roughly 40-42 now. Any thoughts CC Fans!?

I want reliable solid running engine with no issues. Need it to idle well and low enough through no wake river I spend a bit of time on.

Thanks!

There are dozens of threads on it around here, you have found the first limit which is the lack of great cam choices.   A roller would be spectacular but in reverse rotation its going to need to be a custom job and it would cost more than most will bite. That being said some 1.7 roller rockers have been known to wake up a stock cam. The gt40p heads are a no brainer they yield actual horsepower and are not much more expensive than rebuilding stock heads. After that an intake helps... that gets you through the easy stuff. A good acme 540 propeller will yield the biggest bang for the buck in terms of performance increase with your boat which was not running real great at n40-42, 45-47 would be more correct for a stock 80.   The above should have you in the 50+ range done well.

Good luck with it. It'll be a screamer when re assembled.

I am considering the same power upgrade as I have one externally cracked head. Reluctant to pull it apart as it runs so well.

Paul,

Been that way all summer ha. No leaks. Cracked half moon shapes below two exhaust ports. I attribute it to high hours and the heads being used in brackish water for 4 years or so.

Castings have somewhere between 1600-1800 hours on them.

Guys, thanks for the responses, finally able to get back to responding.

JoeinNY, nice ride and holeshot video!!

I've got an ACME 208 13X12.5V RH 1" 4-blade prop. Could this be some of the reason for the lack of top end speed?

You're recommending an ACME 540 3-blade. After a little research including your thought, I'm finding that the 3 blade is a better fit for my 1:1 drive setup, although being told that an OJ 4-blade 13X13 is stock for my boat and offers less rooster in the wake and relatively same performance at $120+ bucks more than 540 at $375....

I'm installing 1.7 Scorpion roller rockers on GT40P heads and have PCM exhaust manifolds, any recommendations on taller valve covers that don't interfere with exhaust manifolds?

Any thoughts here would be mucho appreciated.

Thanks!

EagleEyedOne wrote: I'm installing 1.7 Scorpion roller rockers on GT40P heads and have PCM exhaust manifolds, any recommendations on taller valve covers that don't interfere with exhaust manifolds?

I can confirm the FMS/Crane 1.7s fit under the red PCM aluminum valve covers, but the baffles need to be modified and I used some 5/16" valve cover gaskets for more clearance. I believe the steel ones have more room, my aluminum ones were really low.

Gaskets

Thanks for the great feedback!

It's getting real now, just got the short block, GT40P heads, RPM AirGap intake, CRC holeshot cam, and other goodies! Getting ready for assembly.

Now that things are being removed, noticed the mufflers look original, any reason to consider upgrading exhaust to either stock new or something a bit higher performing? Recommendations?

Will summarize the full project in a future post.

Thanks.

The Air Gap is a pretty high intake might have some clearance issues with the engine cover.

1980 would be 1:1 tranny, it can be indexed to go lefty but doubt you want to do that. Plenty of discussions on here about turning these boats with a lefty prop.

EagleEyedOne wrote: Thx gun-driver: It is a 1:1 Velvet drive tranny and could be swapped but read/was told the reverse rotation torque of the engine counters the drivers weight keeping the wake even and boat level.

It's the prop ration that counters the drivers weight. Engine has minimal effect. That why they were able to switch the Regular Rotation engines in later SN 2001s but kept the prop spinning RH.

When you say CRC Holeshot cam, what are the specs on that cam? Have you got it assembled and running yet? I am looking for a rr cam for my 351W that I have apart right now.
Thanks.
Matt

Sounds interesting. This is a slider not a roller correct?

JohnB - this is not a roller cam.

Duane/Matt - I think I paid $260 for the cam at CRC.

While I have everyone's ear, or hopefully anyone's ear, do recommend a particular dealer or site for a rebuild kit? I have an '87 351w rr, and see several kits out there but not sure which mfg's to avoid. Nothing crazy, .30 over, I assume my crank will get .10, so pretty standard stuff. I will probably be picking up a CRC cam, so that obviously wouldn't be needed with the kit. Thanks in advance for the recommendations.
Matt

Hi,
Does anyone have a spare prestolite alternator with part number alk 6220Y-1N? I know they're hard to come by and the order I placed earlier today was cancelled. I need something quick if possible. Going on vacation with this boat project finally coming together... thanks for any suggestions!