I have a 1978 25ft Magnum heavy lay up.It has a 365hp Mag BB chev with rec port heads. TRS drive, would I see any improvment in acceleration or wot mph gain if I swiched to oval port heads? I get 61 mph at 5050rpm now with a 23p re- piched to 24p, old quicksilver cleaver.

hmmmm thats odd. As far as i know teh rectangle port heads are bigger than the performance (large) ovals so i woudl tend to hink smaller ports might just slow you down.

You coudl pobably have your curent heads worked a little to make them flow more air andtheat might help you pick up some HP and speed.

You might call and talk with JimV. He can put 'wedges' in your heads and mild port work and really wake them up.

Just read an article in Family and Performance boating that said they tested 2 identicle motors 1 with rec ports and 1 with oval,,, the oval porst made more HP and torque, and in a more usable power band.

Jim Valekeo did my heads. I am running the stock GM rec. port and Jim put the wedges in them and 2.3 intake valves and a bunch of grinding later and my engines really came alive. Jim can set you up with a complete package deal....

I've been doing a LOT of research on this because I'm thinking of putting some different heads on my motors. What I've come up with is the oval port high performance heads have smaller intake ports but they make more torque & horsepower at lower rpm's. Unless you plan on running above 6,000 rpm's you will make more horsepower with them & go faster. If you do buy new heads somethings I would look for are heads with intake port volume around 260cc, combstion chamber volume around 118cc, valve size 2.19 intake & 1.88 exhaust, and as long as you have them off I would get them mildly ported, unshroud the valves a little, clean out the bowl & runner area, & make sure the intake & exhaust line up. As far as aluminum vs cast I think I'm going with the cast because of the price difference & because I've heard a few stories of head gasket & corrosion problems with the aluminum. Did you have a particular head in mind ? Please keep us posted! good luck !

obnoxus,

what type of oval port heads did they use for the test??

What generation block are you using?? If its a Gen V, then going to GM large oval ports won't work. If it's a Mark IV then they'll be fine. On a Gen V, you would have to go with an aftermarket heads.
Most of your performance increase would be in the lower and midrange area, with maybe a slight increase on the top.

CR max,
they were Edelbrocks,,, the bare casting prt # was 7161 which did include valves,, I did not get a price,,,, for complete heads with Inconel exhaust valves ready to bolt on were just under $700 a piece,,, like $683 I think,,,, did not get p`ricing on cam and injection work yet.

I saw an article by Teague in PB a few years ago. They pretty much agreed with Bo. Better midrange with the ovals. And unless your pushing over 500hp, there wasn't much of an increase in hp with rec. port. They also mentioned that even in higher hp applications they liked to stay with oval ports on single engine boats for the added low/mid range torque.
Gary