4.3 mercruiser roller cam

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machz1000

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does anyone know what year mercruiser started using roller cams in their 4.3 and what the profile is on it thanks
 
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machz1000

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Re: 4.3 mercruiser roller cam

I have a 1991 baja 204 i am putting vortec heads on it and am going to do a cam swap while i have got the motor apart and would like to know before i pull it so i will have the right cam
 
Bondo

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Re: 4.3 mercruiser roller cam

machz1000 said:
I have a 1991 baja 204 i am putting vortec heads on it and am going to do a cam swap while i have got the motor apart and would like to know before i pull it so i will have the right cam
Click to expand...

Ayuh,... Basically,... Whatever cam grind Chevy was using in their pickup truck motors that particular year,...
Is the Same cam Mercruiser was using in their 4.3l boat motors...

Don't get to stupid pickin' a cam,...
Boat motors do Not like Hot Rod cams at all...
Ya gotta think truck/ RV, Idle to 4800 rpms...
If it's big enough to lope,... she'll be junk in no time....
 
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machz1000

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Re: 4.3 mercruiser roller cam

i was looking at a .457 lift intake @exhaust
duration @.050 218 intake @ exhaust
108 lobe seperation
i figure i will be plenty safe with this
 
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joewithaboat

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Re: 4.3 mercruiser roller cam

The major cam companies have marine specific stuff. If i were doing the vortec conversion i would at least use the biggest factory cam or a little bigger to get the most out of it. It is well worth the call to a tech line.
 
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dollarten

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Re: 4.3 mercruiser roller cam

Bond-o said:
Ayuh,... Basically,... Whatever cam grind Chevy was using in their pickup truck motors that particular year,...
Is the Same cam Mercruiser was using in their 4.3l boat motors...

Don't get to stupid pickin' a cam,...
Boat motors do Not like Hot Rod cams at all...
Ya gotta think truck/ RV, Idle to 4800 rpms...
If it's big enough to lope,... she'll be junk in no time....
Click to expand...
Well said . It seems the temptation is always there to put in a loopy cam . I like to call them "ratchetty " When that is done you are bleeding of cylinder pressure and killing the low end . The power and torque is swapped off to the high RPM end . an area that marine engines do not operate well in, not with a stock bottom end on an a extended run
 
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machz1000

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Re: 4.3 mercruiser roller cam

the cam i want to use is the same as in jeg's marine crate engine 262 horsepower 300lbs of torque.makes 280lbs at 2600rpm that engine has basically a flat torque curve looks to me to be a good choice.The boats a baja 204 it weights about 3000lbs I find the boat to be a little slow on the bottom end.It will rev 4800rpm at wot hoping this will wake her up
 
zbnutcase

zbnutcase

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Re: 4.3 mercruiser roller cam

The GM p/n for the roller 4.3 cam is 10134321
 
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TomB985

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Re: 4.3 mercruiser roller cam

machz1000 said:
the cam i want to use is the same as in jeg's marine crate engine 262 horsepower 300lbs of torque.makes 280lbs at 2600rpm that engine has basically a flat torque curve looks to me to be a good choice.The boats a baja 204 it weights about 3000lbs I find the boat to be a little slow on the bottom end.It will rev 4800rpm at wot hoping this will wake her up
Click to expand...

So you want to gain at a minimum 40+ horsepower on a stock engine? Probably not a good idea. Remember that unlike a car these engines are operated at max load for extended periods of time. This is why the specific power of a marine engine is much lower than most modern car engines.
 
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machz1000

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Re: 4.3 mercruiser roller cam

i did not say anything about a car engine.The cam i am using is the same cam jegs are using in their 4.3 liter v6 marine specific crate engine that has vortec heads
 
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joewithaboat

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Re: 4.3 mercruiser roller cam

TomB985 said:
So you want to gain at a minimum 40+ horsepower on a stock engine? Probably not a good idea. Remember that unlike a car these engines are operated at max load for extended periods of time. This is why the specific power of a marine engine is much lower than most modern car engines.
Click to expand...

Stock marine 4.3's went from 175hp to 230hp, he will be fine. The stock higher hp engines had much better heads, roller cam, roller fulcrum rockers, more carburetor and intake. They are tough little engines. Basically a 350 with 2 cylinders cut off.

that jegs engine shows...

Camshaft Specs:
# Lunati Hydraulic Flat Tappet
# Duration @ .050'' Lift: 218 Intake / 218 Exhaust
# Lift: .457'' Intake / .457'' Exhaust
# Lobe separation: 108?

Personally I would use a roller cam. Im also surprised it is making that much hp with that flat tappet.
 
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Tail_Gunner

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Re: 4.3 mercruiser roller cam

If i may ask what are you looking for in a cam besides performance....aka water sports ..economy..top end. Your approach is right the 4.3 big enemy was always induction or breathing. Marine cams are very mild...actually weak but safe. There are a few new grinds out there that will do quite a bit for the motor. One thing try to stay AWAY form cams under 110 and over 112 lsa 109 is a very odd cam design....



Here have a read some awfully good info there http://forum.grumpysperformance.com/viewtopic.php?f=52&t=5154&sid=0f3c786b92aa52daba99e9f528c4dea3
 
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machz1000

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Re: 4.3 mercruiser roller cam

I am looking for more power for getting on plane quicker and faster top end speed at the same time not turning it into a gas guzzler.Its not a v8 i am not expecting huge gains from this engine
 
Bondo

Bondo

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Re: 4.3 mercruiser roller cam

I am looking for more power for getting on plane quicker and faster top end speed
Click to expand...

Ayuh,... Then go with the factory cam...

Ya need a cam that's cut for Idle, to 4800rpms....
Aka; a Marine/ RV/ Truck cam....
 
Tail_Gunner

Tail_Gunner

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Re: 4.3 mercruiser roller cam

As in any engine using todays tech. You can expect huge gains....First and most simple stop is trim tabs.. about 125 that will effect your launch...Its very simple and much more to come
 
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