approximate horsepower!
 

Hey all you engine guru's, I have a question for you. I had my engine rebuilt year before last by a mercruiser master mechanic. It's was a Mark IV 330 HP 454and I upgrade to 461 CI with speedpro coated hyperutectic pistons, Isky flat tappet cam with 230 intake and 236 exhaust @.050 with 515 lift on 110 lobe separation angle. It is topped off with Edelbrock RPM oval port aluminum intake and edelbrock 750 cfm marine carb with GM large oval port heads, (230cc I think) with stock valves. It also has crane roller rocker arms and us still using the stock exhaust straight out the transom. I know it's not a race motor and I don't treat it like that but I was just courious about how much HP it may have if I go to sell it in a year or two.

400 hp.

Does not matter it will not last long with that cam and stock exhaust. You need aftermarket exhaust with long risers or you will be sucking water back in. You may even need dry exhaust with the 110 LSA.

I just saw you have run it a whole season with that setup. What did the oil look like when you changed it?

I'd be surprised if that cam didn't revert water with the stock exhaust. Even if it does not, the stock exhaust will choke down the better flowing intake manifold, cam, and heads you have. No point in putting that combo together then running stock exhaust. That cam is also a bit large for a 461CI with cast internals, like the 330HP has. You really want to keep the rpm 5000 or below, and that cam will probably not make any more power below 5000rpm than one with about 10* less duration. Less cam would probably make more usable power, idle better, and not revert.

I'm guessing here, but with your stock exhaust, and specs you have given, Im gonna say 350-370HP at 5000.

But it was a Mercruiser Master Mechanic that built it so it must be right. :lolhit:

Ya, that scares me almost as much as the drag racer car engine guys!

Not suggestion that a "Merc master mechanic" is a bad thing, but reminds me of the guys working at midas, being ASE certified techs. Doesn't necessarily make you a engine builder by being a mechanic.

I went to General Motors training school for 18 months when i was younger. I can still F-up a spark plug swap. :party-smiley-004:

I ran a 233/241 Ultradyne cam for several years without a problem. 330 bottom end, rectangle heads, stock exhaust. Ran great for what it was.

And there are many guys who have run less cam and reverted water and milkshaked their motors and killed exhaust valves. It might work, but why risk it when you gain nothing. I'd bet a few bucks that a cam with less duration and a 112-114* would make as much if not more HP for his application throughout the powerband. HP500 cams were notorious for reverting water even with GIL exhaust, and they had less duration than his.

Dont get me wrong, nothing better than a great sounding cam idling, but nothing worse than a crankcase full of nestle quick! :drink:

I'm not saying reversion is impossible maybe I was just lucky. How does the reversion water turn the oil to Nestles Quick without hydro locking it.

I don't think that cam size and duration is a high probability reversion candidate, the LSA is close to it but not quite. I do agree that the engine should make 400-425HP with this combination-EXCEPT FOR THE EXHAUST!-
As others said here, a good breathing power making engine needs to breathe on the exhaust side so invest in a good exhaust upgrade and get the power the engine is capable of making.

Best Regards,
Ray @ Raylar

Those cam numbers are strange. Lots of duration and and not that much lift. Not a very good cam selection, especially with the 110 lob sep. Probably making about 380hp at 5000rpms.

Wow, you guys are killing me here! The builder has a great reputation and has re-built many "blue motors" here in the Louisville area. I was planning on changing the exhaust to something like Stainless Marine but as of right now, the motor may have about 6-8 hours on it since it was rebuilt. I have checked the oil after every trip and so far no "milkshake"! I will check the cam card again to make sure I gave you guys the right specs. I believe I bought it the cam, intake and carb from CP Performance a few years back.

Did you edit your original cam specs? Because I could have swore i saw ultradyne, with like 236/[email protected] on 110* orginally...????? Unless my mind is going, which it surely can be..

GPM posted the ultradyne specs.

Just trying to be honest, I blew mine up from reversion several years ago. I was using a crane cam with similar duration specs and more lift and 112 LSA. I trashed my oil, spun berrings and broke a crank. I had moisture under the valve covers, lifter valley and behind the timing chain.

At this point, i'd try to get a nice set of stainless marine, gil, imco, EMI, or similar manifolds with extended risers. The exhaust will let them breath, and help eliminate reversion chances.

I do like the oval port setup for what you have.

Im in the Ray camp on this one from personal experience

I wouldnt think you'd have that much problem with that setup, but you would really "wake it up" with any good aftermarket exhaust system. Id say that setup on a dyno with headers would probably make about 420 HP.

I ran an engle flat tappett cam with a 110 lobe sep in my 500 hp small block for years with no ill effects and in some ways the loss of valve control at higher rpm kept me from blowing it up as I came out of the water when I was a "punk kid".

Get yourself a good set of headers or at the very least a quality manifold with as high of a riser as you can fit under the hatch and just run it.


Uncle Dave

I would like to see the rest of the numbers on that cam, I don't know that the .050 numbers on a cam that size would have as much affect on reversion as seat timimg. I agree with the exhaust change for better power.

Hey guru"s, will the EMI Thunder system work with the 3" taller risers? My stock cast manifolds have the 3" spacers on them now so that's why I ask. They go straight out the transom and have an old set of Gil tips that don't work anymore them and I keep them closed most of the time. $2150 seems to be a reasonable price for this.

390HP + or - 10

Cam Specs revised!
 

O.K. so a mind is a terrible thing to waste! It has only been a couple of years when this thing was rebuilt and apparently my memory is NOT what it used to be. Here are the CORRECT specs for the cam in my 461:

Lunati #30206
Valve Lift INT 525 EXH 525
Lobe lift INT .309 EXH .309

Adv Duration INT 285 EXH 300
.050 Duration INT 230 EXH 235
Lash INT.000 EXH .000
Lobe Centers INT 108 EXH 112
.050 Timing
BTC 7
ABC 43
BBC 50
ATC 6
LSA 110
Grind SPB1-285-300

Better or worse than originally posted?

Thanks for the help!

Ted

In answer to the question of how much power will it make....not enough :coolcowboy:
How big were her hooters? not big enough :coolcowboy:
It's never enough...we're retarded..that's why we're boaters

Not that much different. .010" more lift and basically the same duration. The extra lift will be in your favor but it's nothing your going to see.

Not a good marine cam, fire the person that recomended it. :eek::eek: