I'm going to build either a 468 or a 496. I want to get the horse power up in the 500 to 600 range. Now I'm torn between using either a Closed chambered Rectangular port head, 3919840 that's been poslished, ported and has 2.19 / 1.88 valves size. The other is an opened chambered oval port head, 353049 that's also been polished, ported, bowel blended and 2.19 / 1.88 valves size. Keep in mind I haven't bought my piston's yet and I want to build a Street/ Strip motor. Thanks guys smile.gif

anytime you mention the word "street" and the engine is under 500 cubes, then go with oval ports.

You'll need a domed piston with the large open chamber 049 heads, I bought SRP pistons for use with the 049's. Speed pro has a good one that will work with pressed fit rods and give you about 9.5-1. I have H-beams with floating rods so opted for the SRP's. IMO the psiton manufacturers are really lacking a good selection of 9.5-10-1 pistons for the 4.310 bore 4" stroke engines, not much to pick from when you're running the 049 size chambers.

Have you determined the operating range? Either will work clearly, with the ovals doing more in the 3500-5000+ range, and the rectals 5000+.

I'd use the 049s and SRP slugs as Bob recommends.

Oh also I am building this motor for a 4 speed car with 411's. I've been looking at piston's, What's the difference between a Floating pin and non floating i guess Piston pin that is) :confused:

Buy TRW/Speedpro 12,5 pistons and remove the high side of that twin dome.

That will give you 10,4 in a 119cc head with 0,42 gasket and zero deck.

This dome is not a hollow one.

Ran my pistons since 97 and bought them used then.

Sprayed 300hp N20 last 3 years. and 225 before that. Mayby 100 n2o runs. Works great.

Or a new set of bare cast-iron Merlin ovals b/c they are ready to go after you just assemble them with whatever valve train parts you need to run.

But they are 119 cc chambered or thereabouts...

pdq67

Or bump compression up and run 310cc rect canfields new assembled for 1399$