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cds02
06-04-2010, 11:37 PM
I dont think that i have even said hello to you helpful guys/gals on the forum, but hello and want to say that i have been a member for a while and enjoy reading and learning from all experiences. Anyway i have an 89 MC pro star 190 w/ the 351w and have decided to update the engine back up some. Got the boat last year and had it re-gel coated and had the interior redone and now doing the engine. Now im sort of new to MC's but have done quite a bit of mechanic work on regular engines, just not marine stuff. So need some help please, and i have read for the last 3 weeks about all this but you get a lot of mixed reviews from older posts, so work with me. LOL. I plan on putting gt-40p heads on it, rebuild the carb, edelbrock intake, and a custom grind cam from cam research. Also if anyone else wants to recommend soem general maintance items that normally wear out, i would love to hear b/c like i said i am new and learning.
The heads i am pretty much set on and have found lots of forum members get good results.

The intake, well some say the regular performer and some say the RPM version. Also when swaping intakes do you a different space plate???? Help here please.

The carburetor i have pretty sure is the 4160 correct, from what i can read, its pretty much good to just rebuild it instead of going aftermarket correct???

The cam, well i think i am going to get the heads and see what they flow and get cam research to cut me something.

1redTA
06-05-2010, 09:51 AM
Sounds like a nice plan, let us know how it turns out

I remember a mod to the intake where you cut a small "eyebrow" under neath the carb mounting flange onthe divider wall I believe it helps top end?

Laurel_Lake_Skier
06-05-2010, 12:15 PM
You'll need a plate like THIS (http://www.summitracing.com/parts/SUM-G1420/Application/?prefilter=1) to seal between the existing carb spacer and the new manifold (they are also available through Ski Dim but a few bucks more I think). It won't replace the spacer you have.....you'll still need to use that spacer as a connection point for your PCV system. The plate is needed to form a good seal since the walls of the performer manifold are much thinner than the stock cast iron.

cds02
06-05-2010, 04:57 PM
You'll need a plate like THIS (http://www.summitracing.com/parts/SUM-G1420/Application/?prefilter=1) to seal between the existing carb spacer and the new manifold (they are also available through Ski Dim but a few bucks more I think). It won't replace the spacer you have.....you'll still need to use that spacer as a connection point for your PCV system. The plate is needed to form a good seal since the walls of the performer manifold are much thinner than the stock cast iron.

Ok thanks alot for letting me know that. Ill order that as well when i order my intake.

cds02
06-06-2010, 05:07 PM
Anyone give any advice rather to use the regular performer intake or the RPM version??

dummy
06-06-2010, 05:27 PM
Performer vs RPM would kinda depend on your camshaft selection. With the GT-40 heads good flow characteristics I probably wouldn't hesitate to run a RPM if it were my boat. I'd also consider a hydraulic roller camshaft if the retrofit is in your budget. This one would be nice: http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=894&sb=2

Or, if flat-tappet something with specs similar to this: http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=876&sb=2

Here's some GT-40p flow specs: http://www.carbdford.com/tech/flowdata.htm
Seem to top out at .500 lift with decent mid-lift numbers.

I'd stick to a cam with 204-214 degree @ 0.050 on the duration since you want to keep the curves fat in the low ends. Chuck as much lift at it within these duration parameters as you can to take advantage of the GT-40's flow. They've got good velocity, so you don't really need to wind up the rpms to get 'em to move air. Up to you, really since it's your boat. :cool:

You won't really give up much if any low-end with the RPM. I've always felt they do a good job of balancing high rpm flow with low rpm port velocity. Like 1redTA says, if you use the Performer, drop the center divider about a 1/2-inch to allow the cylinders to share better at higher rpms. A 1/2-inch open phenolic carb spacer will also do the same thing.

cds02
06-06-2010, 09:56 PM
Performer vs RPM would kinda depend on your camshaft selection. With the GT-40 heads good flow characteristics I probably wouldn't hesitate to run a RPM if it were my boat. I'd also consider a hydraulic roller camshaft if the retrofit is in your budget. This one would be nice: http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=894&sb=2

Or, if flat-tappet something with specs similar to this: http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=876&sb=2

Here's some GT-40p flow specs: http://www.carbdford.com/tech/flowdata.htm
Seem to top out at .500 lift with decent mid-lift numbers.

I'd stick to a cam with 204-214 degree @ 0.050 on the duration since you want to keep the curves fat in the low ends. Chuck as much lift at it within these duration parameters as you can to take advantage of the GT-40's flow. They've got good velocity, so you don't really need to wind up the rpms to get 'em to move air. Up to you, really since it's your boat. :cool:

You won't really give up much if any low-end with the RPM. I've always felt they do a good job of balancing high rpm flow with low rpm port velocity. Like 1redTA says, if you use the Performer, drop the center divider about a 1/2-inch to allow the cylinders to share better at higher rpms. A 1/2-inch open phenolic carb spacer will also do the same thing.


Okay, as far as the intake goes is it alot more aggrevating trying to get the RPM to fit under the hood with the flame arrestor? That was my major concern with it. And has anyone pretty much found a good one that works and fits.

Also do you think its pretty much as good keeping the stock carb and re-jeting it, i fugred i would def. have too.

On the hyd. roller cam i would like to but dont know if my budget is going to allow me too.

Also with the Gt-40p heads do you all most of the time recommend to get them on a bench and flow them before ordering a cam?

JimN
06-06-2010, 10:17 PM
Make sure you specify marine gaskets for the heads and intake manifold and use new fasteners for them.

cds02
06-06-2010, 10:51 PM
Make sure you specify marine gaskets for the heads and intake manifold and use new fasteners for them.


Will do man, thanks for the tips.