turbo2256

Just port up the heads you have aftermarket would be way overboard for what you are asking.

traviss

if your goal is 300 hp.. you might as well go for 400 You might look into vortec heads for around $400 a set they are pretty decent. Dennis's book has alot of valuable information. I used alot of it for referance. And you won't have to worry about your alpha's they will be fine with that kinda hp even less stress with twins. I have over 410 hp in my alpha, always reaming the **** outta of it and have had zero problems. Come spring about 490-500 hp will be going through it

good luck bro, keep us updated



Travis

florida gator

What is Dennis Moores book that I have seen refferenced here?

martiniboat

A must read for any performance boater. (which pretty well means all of us)

jafo

Dennis Moore's book is called "Small Block Chevy Marine Performance" (HP Books, 2000). I got my copy from Amazon right after it was published, but I think Dennis has said on this forum you can order it directly from him.
As far as rebuilding/machining/porting the original heads used on the 260 engine, you will find more often than not that these "light-cast" heads either have hair-line cracks or are warped too badly to resurface. These heads were a weight-saving (bad idea) from Chevy, and were not made with performance in mind. You will miles ahead by using the Vortec or World Products.

BAD-HABIT

Very simple mods.....Ive seen several tests that report (Moores book seems to agree) that state stock Vortec heads w a 4 bbl will net 307hp @5000rps. You can get COMPLETE Vortec heads for about $400 per pair. I got mine from Salee performance (A GM dealer in Oregon)It wouldn't hurt that you would get the springs,valves and stuff all new and included either with 400hrs on the motor It wouldn't hurt to replace those anyways.....

turbo2256

For about 800 you can get a set of ported vortex heads

Iggy

Stock port Vortec heads will support a 400+ horse 383 SBC. If using a cam with over .480 or .490 lift the heads must be modified or the retainers will hit the valve giudes. Stock springs should be replaced too, spring pockets will have to be opened up to acommodate.
Scoggin-Dickey Chevrolet has a kit that includes an Edelbrock RPM Air-gap intake, modified Vortec iron heads for .550 lift, rocker arms, springs, retainers, head bolts and gaskets for $949.95.
Same kit for .570 lift roller cams is $940.95.

wwwTOPDJcom

I have a 350 mag 1992 what does it have for internals
and what kind of reliable power could be had for $1500 in work?
same here 400 hours I like the weight savings of the smallblock

bobl

I have a package I’ve been doing to the 5.7 Vortec engines that is working out very well. I port the Vortec heads and install 2.02/1.6 valves, small Crane hydraulic roller cam
(p/n 104224), Edelbrock RPM Air Gap intake and 600 CFM carb. This results in 340+ PSHP. I’ve seen a minimum of 5 MPH gain and as much as 8 MPH over the base 250 PSHP Vortec engine. The HP peak is about 5200 RPM. The Vortec engine has a stronger bottom end than the earlier 5.7 engines. If adding this package to a pre-Vortec engine the compression will be higher since they usually have flat top pistons. The Vortecs have a dished piston. I would limit the RPM to 5000 and run 93 octane gas. Timing should be set at 32 degrees total. I’ve also done this on a 350 Magnum. The gains weren’t as great since it already has a good intake system. I installed an adjustable fuel pressure regulator and raised the pressure about 5 lbs to compensate for the added air flow. It worked very well although the gain was only about 3 MPH. It would be something good to do if the engine had to come out anyway, but I’m not sure it would be worth the expense otherwise.