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air gap rpm to box stock SCJs. They are going on a 10.2:1, 521, custom hydro flat tappet for a sterndrive boat. Should i match the ports, D shape them(like I have read to do for a victor), or leave them alone??
 

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Generally when dealing with standard port style heads, I don't think there's much benefit, but the mismatch from an intake with standard ports to the SCJ/P-51 heads is significant. Hold up a CJ gasket to the ports of the intake and you'll probably find yourself covered in aluminum chips.
 

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Generally when dealing with standard port style heads, I don't think there's much benefit, but the mismatch from an intake with standard ports to the SCJ/P-51 heads is significant. Hold up a CJ gasket to the ports of the intake and you'll probably find yourself covered in aluminum chips.
LMAO!....aaah, a man after my own heart!
Rob
 

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IMO... port matching is ALWAYS better than an untouched casting...
Not so sure I would agree that port matching is always better then not port matching. I think it depends on the combo and the intended application....or what one defines as "port matching," I suppose.

Paul
 

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C'mon Paul, you know it's always better to "HOG 'EM OUT"!!
 

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IMO... port matching is ALWAYS better than an untouched casting...
There are cases where cutting on an otherwise good port to make it match can reduce flow.

It is common practice to use the gasket as a template for matching. While that is handy, there is nothing sacred about the size, shape, and location of the port openings in the gasket.
 

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There are cases where cutting on an otherwise good port to make it match can reduce flow.

It is common practice to use the gasket as a template for matching. While that is handy, there is nothing sacred about the size, shape, and location of the port openings in the gasket.
Like Cutaway said, nothing says all gaskets will match each other.
 

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Still.......I LOVE seein' them chips fly and hearing that burr going GRRRRRRRRind! LOL That being said......I've ruined some ports in my "younger" days........Who said knowledge is free?? LOL
Rob
 

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Always match to the ports, not the gaskets.

Here's a pic showing the difference between standard ports and SCJ.
 

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Port matching is often over rated. Flow testing might prove certian walls should be matched and anothers not.
My suggestion would be to use the Torker II on your combo. The Air gap will cost you a bunch of power. I have owned quite a few stearn drive boats and built several engines for others. In one big block aplication I had a chance to run a air gap, RPM and a torker on the same BBC in the same boat back to back. The engine was a stock 330 HP with the only change being pocket ported Edelbrock oval port heads. Three different size Holly carbs were also tested on each intake. All three intakes were as cast.
Results carbs were out of the box. A 750, 830, and an 850 Holley. The carbs didnt make much differance with any of the intakes. One might have got better economy or performace tuned but I was looking for seat of the pants change not a 5 HP differance only seen on a dyno.
The boat base line was stock peanut port heads with the RPM and Holley 830.
Top speed all day most any load 75 MPH on GPS. A good amout of bow rise nothing outragious.
Heads changed to the pocket ported Edelbrocks mentioned and RPM intake installed with the 830 Holley. There was no percieveable differance in its performance compaired to the base line combo.
The Air Gap was installed next no differance in feel compaired to the base engine or the edelbrock head version other than the chunk of cash out of my pocket for the Air Gap.
Feel of the boat was the same amout of bow rise out of the hole .Acceleration no better off plane or on plane.
The Torker totaly different story. The boat jumped out of the hole no bow rise. Acceleration to 75 was amazingly faster on or off plane. Like having a 100HP shot of NOS. If the boat was reproped think the top speed would have been mid 80's.
 
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