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j.mccreight@hotmail.com
10-20-2010, 01:24 PM
Hey Guys,
I'm looking at doing some engine changes this winter. Would like to change camshaft, does anyone know the factory cam specs. What brands and how large a cam I could install without changing valve springs etc, Also is the cam a flat tappet or a roller. I am not changing the cylinder heads. I already replaced the intake manifold with the Weiand Stealth Dual Plane which is equivalent to the performer rpm. Boat is a 1989 tri-star 351w, I don't think its a HO or has the gt-40 heads since it had a 4160 carb on it. Thanks for any info.

DooSPX
10-20-2010, 01:37 PM
the 285HP HO started in 92.
the cam is a flat tappet and you NEED to change springs anytime you install an after market cam or even another factory cam for that matter. here is why, the springs are wear items (meaning they wear out) period! they get weak, so even a factory cam can stress the springs enough to brake. after market cams ALMOST ALWAYS have more lift than factory and the stock springs can barely handle stock lifts. changing to a after market cam you may need to install new push rods because the lobes are difference and change the height that is needed for the push rods.

Kyle has a thread floating around here some where of the factory HO 285HP cam specs... it is larger than you would think...
the difference between the 240/250HP 351W and the HO 285HP is the cam and heads...

the bottom end will need to be in great shape before you start to add power, but a set of GT40P heads (off a V8 explorer of the mid 90's) drill the bolt holes out to 1/2 inch and install brass freeze plugs. (the P's flow a little better than the standard GT40's, smaller chambers = more compression and better spark plug angle too. a Performer intake while your at it (the intake will even help a little on a standard 240hp too)

personally, a CNC prop will be your BIGGEST BANG for your BUCK you can get...
if you call Eric from OJ and tell him what boat, engine, trans ratio you have and what you do with the boat, he will get you a prop that will turn it into a completely new boat.

I would not do JUST a cam swap along, but do the heads and intake.... much bigger difference than a cam swap alone on the E7 heads...
but you have the $ and time, a cam/heads/intake swap will make a HUGE difference compared to what you are used too...

Kyle
10-20-2010, 01:43 PM
Your boat is not a HO. I recomend to take the engine and tranny out and rebuild the bottom end as well. I did not and you can see from another one of my threads what happened when I increased the compression.

You will need to get cam and heads to make it the HO engine. I have the factory gt40 cam spec sheet. If you are looking for heads the gt40's are high. You can go get the gt40p head wich is a 305 head out of explorers. Have a machine shop do a valve job and deck it. Also have them drill out the 7/16 head bolt holes to 1/2 inch and put in brass freeze plugs. Then the p head will work better than the gt40 head. The p head has a different spark plug angle and will have a little bit more hp than the standard gt40. Your exhaust manifolds will be fine with the p head. I am running them on mine.

Heads about $400
Cam about $200
Lifters about $75
Gasket set about $100
Timing set about $50

Look at spending a grand and you will then have a stump pulling tractor to ski behind.

DooSPX
10-20-2010, 01:45 PM
Your boat is not a HO. I recomend to take the engine and tranny out and rebuild the bottom end as well. I did not and you can see from another one of my threads what happened when I increased the compression.

You will need to get cam and heads to make it the HO engine. I have the factory gt40 cam spec sheet. If you are looking for heads the gt40's are high. You can go get the gt40p head wich is a 305 head out of explorers. Have a machine shop do a valve job and deck it. Also have them drill out the 7/16 head bolt holes to 1/2 inch and put in brass freeze plugs. Then the p head will work better than the gt40 head. The p head has a different spark plug angle and will have a little bit more hp than the standard gt40. Your exhaust manifolds will be fine with the p head. I am running them on mine.

the P's are 302 cid. ;) :D
just messin' with you kyle! :D

Kyle
10-20-2010, 01:50 PM
Yes I ment 302 miss print my bad. Guess I need to slow down.

Here is the link http://www.mastercraft.com/teamtalk/showthread.php?t=36324


Page 5 post #45 is the cam spec sheet.

The P heads are rated 20 more hp than the gt40 standard head. You should be just over 300hp. With the performer intake you should be around 315 to 325 hp.

j.mccreight@hotmail.com
10-20-2010, 01:57 PM
The best thing for me is to make it a HO with the gt-40p heads and camshaft?
I have changed the prop to OJ 4 blade

Kyle
10-20-2010, 02:28 PM
The best thing for me is to make it a HO with the gt-40p heads and camshaft?
I have changed the prop to OJ 4 blade

Yes. I found my heads at a machine shop here locally who just rebuilds the gt40p heads and has them in stock.

Print out the cam spec sheet and call comp and order one. The rest is gravy.

You will really notice a difference. I am a footer and it has made a huge difference on my boat.

41 used to be my max speed with no skiers and when footing long line I would pull it down to 36 to 37 on gps. Now 2 footers long line and we are at 44 to 45 just grippin and rippin. 45 or 46 is max without skiers on gps.

DooSPX
10-20-2010, 02:43 PM
do the heads/cam/intake and have your self a bad little boat! :D

j.mccreight@hotmail.com
10-21-2010, 11:23 AM
will the stock rocker arms and pushrods all work without being replaced?

DooSPX
10-21-2010, 03:00 PM
will the stock rocker arms and pushrods all work without being replaced?

your rockers should be fine, but I would do the push rods to be on the safe said. when you call comp, order a set of pushrods to their specs.

Kyle
10-22-2010, 05:48 PM
Pushrods are cheep. Replace them also....

DooSPX
10-23-2010, 11:38 AM
Agreed, Like I said, ALWAYS replace the springs and pushrods at the least with a cam swap, no matter if its a upgrade or not.

j.mccreight@hotmail.com
10-24-2010, 10:04 AM
thanks for the input, now to make some calls.

DooSPX
10-24-2010, 11:05 AM
Keep us up to date! Good luck with your winter project :)

1redTA
10-24-2010, 03:29 PM
remember on flat tappets you shouldn't reuse the lifters!
definatley replace the springs and make sure the lift does not the coils close to binding
I would roll the pushrods along a straight edge to make sure they are not bent, if not and are the correct length they go back in.