wjb21ndtown

I'm having trouble figuring out some compatibility issues and benefits (different info from different people), so I figured I'd throw it out here and get some advice.

I have an 85 Baja Force 320 with (I believe) stock Gen IV 454's. I'm not sure if they're the 330's or 370Hp motors, but I really don't care either way as both motors need power upgrades if you ask me. The boat runs fine and is decently fast, but I'd like to get a little more out of the boat (another 5-10 mph would be perfect).

I was thinking about removing the old oval port heads and intake manifolds and installing newer style rec. port heads. I was planning on using Gen V 502 heads, and Edlebrock Performer Air Gap intake manifolds and new Holley 4150 850 cfm marine carbs.

My questions are as follows:
Will the Gen V 502 heads fit on my Gen IV 454's?
Why do current high performance manufacturers still produce oval port stuff when rec. port stuff seems so much better?
Am I going to have any other issues switching from oval port to rec. port?
What kind of benefits should I see from the intake/head swap?

Any help would be greatly appreciated!

handfulz28

It matters what you have now because if you have 370s, you won't notice much by your planned changes. If you have 330s, you'll make them approx 370s.

If you have large ovals right now, get the oval Air Gap manifolds and do bigger valves in the heads. Throw in hotter cams and finish the heads off with good rockers and springs. As always, exhaust suited to the cam also has to be done.

Oval port heads make more torque and efficient HP for the range you're in. I don't know why so many people think rect ports are preferrable.

And I'm guessing you're pushing TRS drives? You're gonna need a lot of power to pick up 5-10mph with those anchors.

tms1155

If you have oval port heads now they are 330HP. If they are rect. they are 370 or 400.

getrdunn

iTrader: (7)

As mentioned above you need to know what you have for heads currently. If you have the larger oval port heads and not the peanut port heads you'll want to keep them and upgrade the valves to 1.88 and 2.19's. Chance are there will be 1.72 and 2.06's. Have a little chamber and port work done and call it good. With your heavy boat you'll need all the torque you can get. Rectangular port heads are not necessary better heads in every application. There are just a lot more of them available than that of the larger oval ports. Most common heads you'll find now a days are the peanut port or rec. port. Pull your valve cover off and look at the last 3 casting numbers. That will determine what you have. I know for sure the 049's are OK but don't recall at the moment the others. Regardless at best even with the rec heads or larger oval port heads, cam, intake and carbs you may see 3 to 4 MPH at best. Also deck your heads or change your pistons to get your comp up. Comp. ratio is huge when it comes to making power. Just don't go over 9.5 to 1.

To get the gains your looking for you should consider after market heads with a good port job and roller cam. Also a stroker kit. If you have peanut ports and all you plan to do is the cam, intake and carb thing I would almost even consider keeping them. Oval port heads on your boat will be a plus. Without the cubic inches the rec head will be a little lazy so to speak.

Check out the threads on "330's on roids" and so on. You'll get a lot of info.

Good luck,

jeff1000man

+1

speedreeder

wjb, I have recently done this exact same thing you are wanting to do. I had 330's in a 29' powerquest it ran good at 63 mph. I put on old closed chamber, large oval heads.All of the bottom end is still bone stock. The heads were port matched to an air gap intake,The chambers were cleaned up, With a stock deck height. The valves are still stock other than S.S.. A regular hydraulic cam was used. I run a 750 holley with stock merc t-bolt ignition. I put this set up in and gained.....12 MPH !!! I have a TON of torque and went from a 23 pitch to a 27+..Let me know if I can help you out any further..Rob

jeff1000man

It's because of the closed chamber that you got the increase in compresion to go with the cam. That would have given you a huge advantage.

Good job.

speedreeder

YES, That was what I was looking for...More compression without changing pistons! Very inexpensive

getrdunn

iTrader: (7)

Very impressive 180 to 210 HP gain per side, 510 to 540 HP. Very curious what flat tappet cam and comp. ratio is.

Job well done... The last 454/330 upgrade I did I was a little less fortunate at only 482 HP @ 5800 RPM. 9.5 to 1 comp. 465 HP cam, Air gap, Holley 800, Dart oval ports 2.25/1.88 valves, 265cc int. runners ported and flow benched. Supervised by Valako.

jeff1000man

Not really because those closed chamber heads are pretty hard to find. What we have been talking about is the 049, etc casting GM big oval port heads. Those are 118+- heads. I don't know the chamber size on the closed, but they are considerably smaller. They will work on a 330 because a 330 is a flat top piston.

Others will be able to contribute more.