Intake port cc question for 5.7l sbc

[carlos515]

I was all set.....Ordered a set of Jegs vortec heads and intake. Then the might as well hit. I cancelled the order.
I am now wanting to get a set of Dart Iron Eagle heads. They offer a 165cc intake port and 72cc combustion chamber. This would put me at 9.68:1. This is where I get confused , or over complicate things . The Dart catalog mentions Marine use when they list a 180cc intake port and 72 cc combustion chamber.
On a relatively stock 355 with stock roller cam , stock intake , can I use the 165cc ?
Also , is it wise to stay with the 1.94 intake and 1.50 exhaust ?
Thanks,
Carlos

 

[carlos515]

Ok going forward......165-170cc intake runner is said to be fine for a stock 355cid with my marine cam according to Dart. This will breath much better than the stock heads.
Carlos

 

[Scott06]

Ok going forward......165-170cc intake runner is said to be fine for a stock 355cid with my marine cam according to Dart. This will breath much better than the stock heads.
Carlos

Yeah i would think the smaller volume intake port would better match a stock ish marine build.

 

[Scott Danforth]

I wouldnt waste Dart heads on a boat motor unless you are running a surface drive or jet drive. Stock vortec are 174cc with 64cc chambers

 

[Tail_Gunner]

As Mr Danforth says. Running a marine motor above 5/5500 rpm gets very expensive. But you seem to shooting for more HP one would assume.

Carbed engine I assume?

 

[carlos515]

Thanks all.
I don't want to run more than 5000 rpm . I am looking for max torque. My deck clearance is .017 ,with 64cc heads I was just concerned about being at 9.8:1 on the less than stellar marine gas. For the cost up here in the great North , especially with Covid pricing and availability , The Dart heads are good priced. Summit has a set of Vortec , but may need the springs replaced .
I do not have a set of heads currently , but will also need a new intake if I go the Vortec route .

Thanks

 

[Scott Danforth]

You are over thinking it. If you have stock flat tops with the 4 piston reliefs, stock vortec heads and .045 quench (0.017 deck clearance and a .028 head gasket) you can run 87 octane pump swill.

Change cam to something better than the stock bump stick for bigger returns than dart heads below 5000 rpm

If you want more torque than that, build a 383 stroker.

If you just want to fatten up the midrange, use a 2" carb spacer

 

[carlos515]

Thanks Mr. Danforth .
That makes sense . I figured I was over thinking.
Carlos

 

[apw30534]

FYI... those Vortec heads will outflow a set of Chevy Bowtie heads from years ago. They are excellent heads right out of the box and designed to work best at lifts under .500" and with 1.94/1.5 valves.
I'm currently building a mild 355 from a worn out 602 circle track crate engine...(350/350hp) and using very similar parts. Only big difference is that I'm upgrading to a Comp Cams XM270 hydraulic roller. The flat top 4-relief pistons should put me around 9.7:1 with 64cc heads.
These Vortec heads have very efficient combustion chambers... so they dont need alot of timing. 32 degress total should be about perfect with 91 octane marina gas.

 

[carlos515]

Thanks,
I am flip flopping between the Summit and the Jegs vortec heads right now. My machine shop can get me a set of Dart , but they are double the money. I was just looking for the best bang for the dollar. But as pointed out earlier....I am making this more complicated then necessary .

 

[Scott Danforth]

Thanks,
I am flip flopping between the Summit and the Jegs vortec heads right now. My machine shop can get me a set of Dart , but they are double the money. I was just looking for the best bang for the dollar. But as pointed out earlier....I am making this more complicated then necessary .

best bang for the dollar is to call machine shops near dirt tracks and oval tracks. a used set of heads, ready to go with screw in rockers studs modified valve guides, etc. all set up for about $400 a set. any machine shop that serviced the track would have had a few dozen sets on the shelf then the rules changed allowing better heads to be used on the track. so now they want to liquidate the stock vortec heads. My old machine shop used to have not only vortec heads, however pre-done rotating assemblies as he serviced 4 different tracks and sponsored 19 racers.

If you are buying new, any GM dealer, GM performance, Summit, Jegs, etc. pre pandemic, the heads were $800 a pair complete. now they are a bit more. the summit brand is an off-shore head compared to the GM heads