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Finnsdad
12-01-2009, 12:13 PM
I know that when new, the non HO 351 was 240 HP. The HO motor (gt40 heads) was 285. From what I have read, the gt40p heads are a little better, about 15 hp more. If I were to add a Performer (or Performer RPM) intake, what additional impact do you think it would have on the hp? 10, 20, 30 extra?

Jim@BAWS
12-01-2009, 01:22 PM
I know that when new, the non HO 351 was 240 HP. The HO motor (gt40 heads) was 285. From what I have read, the gt40p heads are a little better, about 15 hp more. If I were to add a Performer (or Performer RPM) intake, what additional impact do you think it would have on the hp? 10, 20, 30 extra?

The manufactuer of the intake would be your best bet


Jim@BAWS

east tx skier
12-01-2009, 02:28 PM
The performer specs about 10--15 hp. What you will notice is mid range torque. In my experience, it was a nice compliment to the stock GT40 heads.

xstarplease
12-01-2009, 02:31 PM
I would recommend the Performer for a boat. I think the Performer RPM is gonna give up some on the bottom and have more than you will use on the top. I think a 15hp gain would be a good guess. Probably not enough for a noticeable seat of the pants difference.

Finnsdad
12-01-2009, 02:40 PM
How much taller is the performer over the stock intake?

xstarplease
12-01-2009, 04:58 PM
How much taller is the performer over the stock intake?

The difference in install height between a Performer intake and stock should be negligible. The Performer RPM is enough taller to possibly make a difference.

east tx skier
12-01-2009, 09:04 PM
If you are putting the plain old performer on a 91 and up boat, you are going to be really close to the motorbox, even with a low profile flame arrestor that is fairly hard to come by these days. You could lose the spacer under the carb if applicable. I found myself carving a channel in the noise reduction foam to get some head space.

One suggestion that I never got around to trying is putting a collar on the bottom of the motorbox to raise it up. Seems like a cheap and somewhat easy solution.

Laurel_Lake_Skier
12-01-2009, 09:39 PM
How much taller is the performer over the stock intake?

A little over 1 1/2 inches higher.....I was just able to make it under the motorbox of my '91 without any changes.

Finnsdad
12-02-2009, 08:11 AM
Thanks, I'll have to go to my stg unit today and check... I have something other than a MC

east tx skier
12-02-2009, 11:03 AM
Thanks, I'll have to go to my stg unit today and check... I have something other than a MC

If it begins with an N, those motorboxes are pretty big and will accomodate things well.

Finnsdad
12-02-2009, 11:11 AM
It begins with an S and a B

DooSPX
12-02-2009, 01:29 PM
ski brendella?

Finnsdad
12-02-2009, 02:50 PM
yes, it is a 91 Shortline

TRBenj
12-02-2009, 03:01 PM
I know that when new, the non HO 351 was 240 HP. The HO motor (gt40 heads) was 285. From what I have read, the gt40p heads are a little better, about 15 hp more. If I were to add a Performer (or Performer RPM) intake, what additional impact do you think it would have on the hp? 10, 20, 30 extra?
The P's are better than the GT40's, but I wouldnt say theyre 15hp better. An intake is generally worth around 10hp. Go with the RPM if you can fit it- it should be about 2.5" taller than stock. You should be right around 300hp with those mods. Add a cam to bring it all together and you'd likely see 320.

Anyone who says that ski boats "only need low end torque" or that an aggressive dual plane intake manifold will hurt performance is an idiot. Where are you getting this info and what modifications have you done? Misinformation at its finest.

east tx skier
12-02-2009, 03:01 PM
Cool boat!!!!!

Finnsdad
12-02-2009, 03:02 PM
Thanks Doug!

east tx skier
12-02-2009, 03:03 PM
Anyone who says that ski boats "only need low end torque" or that an aggressive dual plane intake manifold will hurt performance is an idiot. Where are you getting this info and what modifications have you done? Misinformation at its finest.


Whew, glad I said that he would probably notice the increase in mid range torque. :) I agree though, you're out of the low end range before you even plane out.


How have you been, Tim?

DooSPX
12-02-2009, 03:20 PM
yes, I never see the underside of 3000 rpm unless I easing into the throttle.
dont know how the wake or tracking is on those boats, but I always thought they looked cool!!! Nice boat

xstarplease
12-02-2009, 04:36 PM
Anyone who says that ski boats "only need low end torque" or that an aggressive dual plane intake manifold will hurt performance is an idiot. Where are you getting this info and what modifications have you done? Misinformation at its finest.

Who exactly did say this? If you are referring to me, all I said was the performer RPM had a higher RPM range than he needs (6500 RPM) This extra on top is gained at the sacrifice of some down low. While it may not be a noticeable difference, why sacrifice anything at all on the bottom when the Performer has a high enough RPM range to catch idle to wide open throttle on an inboard. I've had cars with both intakes, and there is a difference off idle.

PS I'm sure sure I've been called worse than an idiot if you were indeed talking to me. Either way, no worries.

Finnsdad
12-02-2009, 05:55 PM
Well, I went to the stg unit and I have 2.25" if clearance. If I lose the spacer I could gain a little more. Think the Performer RPM will fit?

TRBenj
12-03-2009, 02:59 PM
I've had cars with both intakes, and there is a difference off idle.
No such thing as "off idle" on a ski boat. As long as your power starts coming in by 2500-3000 RPM's, you're fine. The Performer RPM and equivalent dual plane intakes hold a nice advantage over the standard Performer from midrange on up, as Doug mentioned.

Doug, all good here... lots of projects to keep me busy this winter. I take it youre staying out of trouble? Hope you poke your head in over on the "other" site every once in a while!

Finnsdad
12-03-2009, 03:02 PM
Tim- Do you think it is worth it to get the "air gap" intake?

east tx skier
12-03-2009, 04:44 PM
Doug, all good here... lots of projects to keep me busy this winter. I take it youre staying out of trouble? Hope you poke your head in over on the "other" site every once in a while!

Oh, sure, I'm over there pretty regularly. Trying to stay out of trouble, but had a fuel issue during the last set of my last outing. Hoping it's the antisiphon valve, but won't play with it until I dewinterize. If that doesn't fix it, I'll start trying to figure out fuel pressure and give the pump a hard look.

Finnsdad
12-03-2009, 04:50 PM
Tim- I really like the exhaust manifolds on your motor, so I went to the manufactures website and there is your motor... cool!

http://www.hitekmarine.com.au/ford.htm

xstarplease
12-03-2009, 09:51 PM
No such thing as "off idle" on a ski boat. As long as your power starts coming in by 2500-3000 RPM's, you're fine. The Performer RPM and equivalent dual plane intakes hold a nice advantage over the standard Performer from midrange on up, as Doug mentioned.


That's good to know. I need to quit trying to bring my hot rod experience onto teamtalk. There is obviously a much bigger difference between fast cars and ski boats than I realized. It is still hard for me to wrap my mind around not needing power to come in until 2500+ rpm. I drive my boat below that rpm a fair amount when easing from place to place.

Now I have a question. Would the airgap benefit him at all? I was always under the impression that the moving air through the intake cooled the air/fuel mixture producing more power. Would a boat have enough airflow to make any difference at all?

DooSPX
12-03-2009, 09:59 PM
That's good to know. I need to quit trying to bring my hot rod experience onto teamtalk. There is obviously a much bigger difference between fast cars and ski boats than I realized. It is still hard for me to wrap my mind around not needing power to come in until 2500+ rpm. I drive my boat below that rpm a fair amount when easing from place to place.

Now I have a question. Would the airgap benefit him at all? I was always under the impression that the moving air through the intake cooled the air/fuel mixture producing more power. Would a boat have enough airflow to make any difference at all?

for one, there is no air hardly at all in the motor box.

xstarplease
12-03-2009, 10:18 PM
for one, there is no air hardly at all in the motor box.

Exactly what I was thinking. He asked if he should get the airgap. I didn't see this helping at all on a boat with no air flowing through the engine compartment.

thatsmrmastercraft
12-03-2009, 10:51 PM
At the risk of joining into the receiving end of flying names, the Performer would be the better choice as xstarplease said due to the RPM operating range being more compatible. The Performer RPM could cause a low rpm hesitation that should be able to be overcome, but why ask for it.

As far as removing the carb spacer, that could also cause a vapor lock issue. Its there to absorb and dissipate some of the heat.

I like the idea of building a base for the engine cover to sit on. A person could construct it out of 1" x 3" Starboard and cover it with carpet to match the existing carpeting. That would give plenty of clearance and would look like the 190/197 for the last bunch of years.

I have the Summit version of the Performer on my boat and am very happy with the operation. I plan to add the P heads this summer for a few extra ponies.

DooSPX
12-04-2009, 09:01 AM
At the risk of joining into the receiving end of flying names, the Performer would be the better choice as xstarplease said due to the RPM operating range being more compatible. The Performer RPM could cause a low rpm hesitation that should be able to be overcome, but why ask for it.

As far as removing the carb spacer, that could also cause a vapor lock issue. Its there to absorb and dissipate some of the heat.

I like the idea of building a base for the engine cover to sit on. A person could construct it out of 1" x 3" Starboard and cover it with carpet to match the existing carpeting. That would give plenty of clearance and would look like the 190/197 for the last bunch of years.

I have the Summit version of the Performer on my boat and am very happy with the operation. I plan to add the P heads this summer for a few extra ponies.

by chance, did you notice a nice boost in torque with the stock E7 heads after the intake?

thatsmrmastercraft
12-04-2009, 11:05 AM
The boat came with the intake so I never operated it with the stock form.

Finnsdad
12-04-2009, 03:59 PM
If the spacer is an important part, you can get a shorter one for cheap.

markb
12-09-2009, 07:16 AM
Gentlemen, you all seem to know a lot about jacking up the HP on our 351's so, I have a question for all of you. I have an 88 ProStar, Powerslot, 351 with about 700 hours. I have the GT40P heads, not installed yet. I plan on getting the Performer or Performer RPM. There is 2 1/2 inches of clearance above the flame arrester. My questions relates to the heads. Any recommendation on what rocker arms to use AND do I need to purchase new pushrods??

Thanks,
Banger

Laurel_Lake_Skier
12-09-2009, 11:37 AM
You should be able to use the rocker arms and pushrods from your old set-up. The only issue here might be if the P heads have been reconditioned and shaved down a fair bit.....at that point you would want to take some measurements to check if new pushrods or shims for the rockers would be in order.

TRBenj
12-09-2009, 01:38 PM
^^LLS nailed it.^^

Tim- I really like the exhaust manifolds on your motor, so I went to the manufactures website and there is your motor... cool!

http://www.hitekmarine.com.au/ford.htm
Ha, thats news to me. I recognize the other engine (to the right of mine) as well. Too funny.

At the risk of joining into the receiving end of flying names, the Performer would be the better choice as xstarplease said due to the RPM operating range being more compatible. The Performer RPM could cause a low rpm hesitation that should be able to be overcome, but why ask for it.
Thats just not gonna happen. Ive driven a few ski boats with modified engines sporting tall single plane intakes... no hesitation there either. The RPM is still a fairly tame manifold for a ski boat- if you've got the room, run it.

I dont know whether it would be advantageous or not to run an air gap vs. a regular RPM. Id like to try one. There isnt a lot of airflow throught he engine compartment, but I dont see how it could hurt. I wouldnt want to try and keep it clean, though!

markb
12-10-2009, 07:22 AM
Thanks for the reply. The heads are remanufactured from Promar Engines out of Patterson NJ. They have GT40P heads listed under Ebay. I'll have to take the measurements this coming spring and after the 17.5 inches of snow we just got Tuesday night in Madison, spring seems a long ways away!