Port match or not

[Scott Liggett]

I have an Edelbrock RPM intake whose ports are somewhat smaller than the intake ports on my Victor Jr heads. I realize this isn't as bad as having a larger intake than ports on a head, but I was wondering if I am losing a considerable amount of HP this way. The Vic Jr head ports would be a spot on match on a Vic Jr intake, but I don't want to lose that much bottom end torque.

I've been considering upping to a RPM Airgap intake and wonder if I should open it up to match the ports on my heads.

What do you guys think?

[TheSilverBuick]

Re: Port match or not

If you're careful with a grinder why not gasket match or close? Careful, aluminum cuts like butter with a die grinder bit meant for iron :P

[TC]

Re: Port match or not

All match porting will do is move your powerband about 500rpm higher in the rpm range. So in theory you should pick up a couple/few HP. ;)

[JeffMcKC]

Re: Port match or not

If you rework plenums and runners 20 to 30 HP is found if done right, done wrong they will kill HP faster than anything, gasket matching is over rated unless they are way off

[Bamfster]

Re: Port match or not

When I bought the new victor jr fot the chevelle I was able to order one pre port matched to a felpro #1205 for a few more $$$. It just so happened that my dart heads were also sized to a #1205 gasket. Do they offer this in the air gap?

[squirrel]

Re: Port match or not

The Vic Jr head ports would be a spot on match on a Vic Jr intake, but I don't want to lose that much bottom end torque.

There's your answer right there. If you make the intake match the heads, properly, you'll lose too much bottom end torque.

I suggest you just leave it alone, and buy the right manifold when you decide you want a higher rpm engine.

[JeffMcKC]

Re: Port match or not

You wont feel the difference in the seat of your pants.

[SpiderGearsMan]

Re: Port match or not

needs more gear

[CDMBill]

Re: Port match or not

As Jeff points out you are more likely to hurt something than help if all you would do is a flare out to the gasket size at the flange. A properly shaped blend back to plenum is worth the expense if you or whomever does ti knows exactly what they are doing.

A lot of folks feel that the slight lip is actually good for controlling reversion, especially wet flow reversion on the long side of the port wall. The worst thing that people do is create a double bell shaped depression in the pats on both sides of the gasket.

[JeffMcKC]

Re: Port match or not

ALWAYS MORE GEAR!!!!

This is the one thing in the days of overdrives over looked !!!

[milner351]

Re: Port match or not

Scott
From what I learned on diyporting.com (mostly in reference to modifying stock ford e7te mustang heads) the real advantages are to be had in the bowls and just under the valve seats in the heads....
not much of any measured gains were discovered by enlarging or matching the port sizes at the intake/ head.

Given that your engine has heads that are "too good" for the street application you're putting them in, I'd think the best compromise would be the airgap intake - they seem to do well in every dyno comparison on every engine - they always seem to have the "most area under the curve".

If you've got the $ and the hood clearance - I'd go with an air gap and see what difference that makes. I don't think I'd touch it with a die grinder either - just run it as is out of the box.

[Eric68]

Re: Port match or not

Don't gasket match it for sure. All you do is create a "buldge" in the runner. The engine doesn't know that the intake and runner in the head are two different parts -- you want a smooth transition all the way from the plenum to the intake valve with consistent cross-section (no bulges or steps) all the way.

If you want to enlarge the exit of the intake runners to match the port in the head, make sure you make it a smooth transition and go back into the intake runner a ways. A lot of the intakes neck down at the exit so if you cut back an inch or so the port in the intake gets bigger.

[urwurznitmahre]

Re: Port match or not

Don't gasket match it for sure. All you do is create a "buldge" in the runner. The engine doesn't know that the intake and runner in the head are two different parts -- you want a smooth transition all the way from the plenum to the intake valve with consistent cross-section (no bulges or steps) all the way.

If you want to enlarge the exit of the intake runners to match the port in the head, make sure you make it a smooth transition and go back into the intake runner a ways. A lot of the intakes neck down at the exit so if you cut back an inch or so the port in the intake gets bigger.

if he doesn't match, it will be a step..
and won't the air/fuel stall when it gets to that "step"
I'd think even a slight buldge would be better, than a step.
the fact that reb. is worried about the low end..
I'd think the step making the air stall would hert the low speed flow than a slightly inlarged port opening

[TC]

Re: Port match or not

Like Eric said when match porting the intake you'll want to work up into the runner so that you don't end up with a pinch in the intake runner. Now saying this you also what to keep as much of the roughness on the walls of the intake runners as you can. It is that roughness that helps keep the fuel suspended in the incoming air and stops it from puddling on the walls of the runners.

[Caveman]

Re: Port match or not

I'd say do a half - match.

If the flow meets a wall (the intake runner is smaller in that spot than the intake manifold) then give it somewhere to go... i.e., knock down the wall.

But I wouldn't open up the intake manifold at all....