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Old 08-27-2015, 08:24 AM
jberenyi jberenyi is offline
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What do GT40 Heads buy you?

I have a 351W 250 hp with 650 hours on her. Thinking of putting GT40 heads on her in the winter or have the heads get a nice 3-angle valve job locally for about $300. Anyone know if the engine performance and speed of boat would increase noticeably with GT40 heads and a nice aluminum intake?

Last edited by jberenyi; 08-27-2015 at 09:25 AM.
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Old 08-27-2015, 09:09 AM
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east tx skier east tx skier is offline
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It will get you close to 295--300 hp with the intake. Top speed probably won't crack 46. Get a nice CNC'd prop to go with it and you'll realize a lot of midrange torque.
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Old 08-27-2015, 09:26 AM
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etduc etduc is offline
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Quote:
Originally Posted by jberenyi View Post
I have a 351W 250 hp with 650 hours on her. Thinking of putting GT40 heads on her in the winter or have the heads a nice 3-angle valve job locally for about $300. Anyone know if the engine performance and speed of boat would increase noticeably with GT40 heads and a nice aluminum intake?
My 1st Mastercraft, was a Tristar 190. The preferred head is GT40P, I believe that head came off early 90s Ford Explorer V-8. It has a slightly smaller combustion chamber, mounting holes have to be drilled out. (Just tell the machine shop, you're putting them on a 351w, for marine use.) The slight increase in compression, is very small, so not a deal changer. They both flow the same.

Intake upgrade, makes a big difference. I used a Ford racing intake (got it on ebay, new $90.00)

Port match the intake, to the heads.

I use standard heads, which I ported, and matched.

My Tristar, was hitting 45 easy, with the CNC 541 three blade.
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Old 08-27-2015, 10:07 AM
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CantRepeat CantRepeat is online now
 
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How many hours did Kyle have on his motor when he grenaded the bottom end?

OP I bring this up because a well known TT member who is pretty good with motors did a top-end on his and IIRC blew the motor that same season.

So, if you are going to do this on a 650 hour motor you may just want to do the lower as well.
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Old 08-27-2015, 10:14 AM
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How many hours did Kyle have on his motor when he grenaded the bottom end?

OP I bring this up because a well known TT member who is pretty good with motors did a top-end on his and IIRC blew the motor that same season.

So, if you are going to do this on a 650 hour motor you may just want to do the lower as well.
Very good point.
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Old 08-27-2015, 11:21 AM
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Quote:
Originally Posted by CantRepeat View Post
How many hours did Kyle have on his motor when he grenaded the bottom end?

OP I bring this up because a well known TT member who is pretty good with motors did a top-end on his and IIRC blew the motor that same season.

So, if you are going to do this on a 650 hour motor you may just want to do the lower as well.
In Kyle's case...I think beer and girls, where involved.
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Old 08-27-2015, 11:21 AM
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Originally Posted by etduc View Post
In Kyle's case...I think beer and girls, where involved.
As per the norm with Kyle...
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Old 08-27-2015, 11:42 AM
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CruisinGA CruisinGA is offline
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Quote:
Originally Posted by CantRepeat View Post
How many hours did Kyle have on his motor when he grenaded the bottom end?

OP I bring this up because a well known TT member who is pretty good with motors did a top-end on his and IIRC blew the motor that same season.

So, if you are going to do this on a 650 hour motor you may just want to do the lower as well.
Good point!

I think it depends a little on intended use.
If it was my boat, I would want to do bottom end too, because I spend a lot of time at or near WOT footin.
If I was mostly wakeboarding/skiing/cruising etc I might not worry as much about new heads on a 650 hr boat because the real bottom end stress is at higher RPM's.
650 hrs isn't that many. Different story if we were at 900+ I think.
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Old 08-27-2015, 03:09 PM
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j.mccreight@hotmail.com j.mccreight@hotmail.com is offline
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Quote:
Originally Posted by east tx skier View Post
It will get you close to 295--300 hp with the intake. Top speed probably won't crack 46. Get a nice CNC'd prop to go with it and you'll realize a lot of midrange torque.
Me thinks your being a bit generous on that HP bump guesstimate with GT-40 heads, likely only give a 25-30 HP bump with 40 heads and an Eddy intake manifold, maybe 15 more with P heads and the Weiand intake. IIRC the OP already has a CNC propeller.
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Old Yesterday, 09:25 AM
jberenyi jberenyi is offline
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Quote:
Originally Posted by j.mccreight@hotmail.com View Post
Me thinks your being a bit generous on that HP bump guesstimate with GT-40 heads, likely only give a 25-30 HP bump with 40 heads and an Eddy intake manifold, maybe 15 more with P heads and the Weiand intake. IIRC the OP already has a CNC propeller.
How H.P. with just the intake change out do you think?
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