[Gach]

Originally Posted by steve25

Factory iron D ports can be ported to go 290 intake cfm at less then 190 CCs , so why is it so hard to believe that aftermarket aluminum D ports can go 330 when they start off at atleast 188 CCs if not 200?

I wasn’t going to get into this, but I just can’t let this statement go. Maybe on your flow bench. LOL

A lot of emphasis on flow numbers, which dose mean something but not a hell of allot. What it really boils down to when it comes to a d-port vs round port is what your goal and what your intentions are with a Car.

Yeah maybe can get 290 cfm on iron d-Port, but whats the air speed in the port. Just a little example a set of wide ports done by well known Pontiac engine builder when checked ( because he was very disappointed) in the performance was you ready 425 fps. Finally after going to a guy Who has one of the best reputations, he ended up dropping it to 325 fps. Car pick up a tremendous amount of power. There’s allot more it then air speed in port. But just goes to show how much flow number only matter if its a good port.

Oh yeah of course when he drop the air speed the flow numbers drop also, but he pick up 75 hp.

[Gach]

Bottom line when I see flow numbers posted I cringe. Because it doesn’t tell you anything about the port. A d-port whether it’s an ion D-port or aluminum d-port has its limitations. Yeah we can boast all we want about the flow numbers oh they flow 320 cfm.

[steve25]

Here’s a 290 cfm iron #13 head with a 2.14” valve .
But, yes if you do not know how to check for core shift and take certain measurements then your far safer at 260 to 270 cfm. Plus it takes a lot less porting finesse then 290 cfm.

[steve25]

Well your going to have to let it go Lou because right now I have a a set of Ford Boss 302 heads that flow 288@28” and a BBC factory rectangular port Aluminum heads flowing 297@28”, and the head the I posted pictures of is right there with them.

If you where here I would be glad to slap all 3 on the bench within 30 minutes time of each other and show you.

[steve25]

Most folks I see on here with there street cars with ported aftermarket round port heads are way under utilizing them.
Either there not running enough lift and or duration.

Enough cid .

Or as a sub group of not enough cid, not enough rpm.

[steve25]

Most folks I see on here with there street cars with ported aftermarket round port heads are way under utilizing them.
Either there not running enough lift and or duration.

Enough cid .

Or as a sub group of not enough cid, not enough rpm.

[Stan Weiss]

Originally Posted by Gach

I wasn’t going to get into this, but I just can’t let this statement go. Maybe on your flow bench. LOL

A lot of emphasis on flow numbers, which dose mean something but not a hell of allot. What it really boils down to when it comes to a d-port vs round port is what your goal and what your intentions are with a Car.

Yeah maybe can get 290 cfm on iron d-Port, but whats the air speed in the port. Just a little example a set of wide ports done by well known Pontiac engine builder when checked ( because he was very disappointed) in the performance was you ready 425 fps. Finally after going to a guy Who has one of the best reputations, he ended up dropping it to 325 fps. Car pick up a tremendous amount of power. There’s allot more it then air speed in port. But just goes to show how much flow number only matter if its a good port.

Oh yeah of course when he drop the air speed the flow numbers drop also, but he pick up 75 hp.

Gach,
Are the air speed numbers you are quoting average port speed or a measured localize air speed?

Stan

[Steve C.]

I had a set of '69 #16 d-ports race ported years ago by Jerry Goodale and when tested on my engine builders bench at the time they flowed 291 at .600 lift (28").
Intake valves were 2.125".

Looking back I suspect that number could be a bit generous. A few years ago I sold the heads to Paul Knippen, on his bench they were 278-282 cfm at .600".
(he tested 8 ports)

However different flow benches, and the type of bench, and with different operators you can and do get different numbers. Sometimes all over the map !

.

[slowbird]

Originally Posted by Gach

D-ports will never make power of a round port. My headers are coated and are 28 years old, never rusted. The flanges are separated never any header leaks. D-ports are ok, if you want to use stock manifolds for a nice street cruiser.

You have to drive it for the headers to rust.

[Gach]

When CV-1 where first introduced, it was established that they flowed 380 cfm out of the box. Which by all means out flowed a wide port head. Pontiac Dude was doing a pump gas builded. Long story short he ran a 10.20 maybe even 10.10.

I went with Wide Port. Both same size motor. Trust me we went back and forth on this. He hong up on me a few times..and I on him…LOL My second pass with wide ports I went 9.80. I had a set of CV-1’s. But went with wide ports. His thing was he kept saying these heads flow 380 cfm. My wide ports only flowed 362 cfm. But at 750 lift.

Finally when he got his CV-1’s to Gabby..Gabby calls me, he says yeah they flow 380 cfm, BUT! The air speed in the port is only 252… so to make up for low air speed he’s going to need a minimum of 275-285 duration. My cam is or was 265/276 hey it was a learning process for both of us, but I already new what air speed was. When Dude would shift that thing into second gear the rpms would drop almost 1000 rpms. Its like the motor wouldn’t recover.

Of crouse theres allot more to it then just air speed in the port.

[Gach]

Originally Posted by slowbird

You have to drive it for the headers to rust.

I was wondering how long it was going to take you…The trolls are out..Stan your next..lOL oh wait Stan beat you to it. Next !!

[Stan Weiss]

Originally Posted by Gach

When CV-1 where first introduced, it was established that they flowed 380 cfm out of the box. Which by all means out flowed a wide port head. Pontiac Dude was doing a pump gas builded. Long story short he ran a 10.20 maybe even 10.10.

I went with Wide Port. Both same size motor. Trust me we went back and forth on this. He hong up on me a few times..and I on him…LOL My second pass with wide ports I went 9.80. I had a set of CV-1’s. But went with wide ports. His thing was he kept saying these heads flow 380 cfm. My wide ports only flowed 362 cfm. But at 750 lift.

Finally when he got his CV-1’s to Gabby..Gabby calls me, he says yeah they flow 380 cfm, BUT! The air speed in the port is only 252… so to make up for low air speed he’s going to need a minimum of 275-285 duration. My cam is or was 265/276 hey it was a learning process for both of us, but I already new what air speed was. When Dude would shift that thing into second gear the rpms would drop almost 1000 rpms. Its like the motor wouldn’t recover.

Of crouse theres allot more to it then just air speed in the port.

Stan

[Gach]

Originally Posted by Stan Weiss

Stan

Tolling Stan

[Gach]

Its funny you two make way to obvious.

[Scarebird]

The 366 that was supposed to replace the 350 and 400 was a round port.

So to me if you are starting from scratch (no hedders, manifolds) I would go round.

[Stan Weiss]

OK, so Larry Meaux owns a flow bench and ports cylinder heads, he owns a dyno and builds engines. He also writes computer software (PipeMax) This is from his software.

Everybody has their own opinion. David Vizard who I authored a flow bench software program with likes to see around 300 fps.

Stan

[chiphead]

So is it just CFM? When you need more than 260CFM from the exhaust port, (80% of 330CFM intake) you go round port exhaust? Is the chamber any different between a edelbrock round port and the Eddy D-port? Is one chamber better than the other?

How much can a D-port exhaust port realistically flow?

If you had a D port and a round port that had similar flow numbers and port velocities, would they make similar power?

[hurryinhoosier62]

Originally Posted by mgarblik

I recently had to deal with this exact dilemma on a personal car. Had already bought round port E-heads for my Catalina. But the log jam was the damn exhaust manifolds. Especially with a street Pontiac, with the great manifolds they had, why deal with the continuous aggravation of tube headers on the street? The endless exhaust leaks at the flanges, rusting out every 3 years, maybe 6 years if coated, extra noise, heat, fitment issues, poor ground clearance and so forth. But the problem is, the round port exhaust manifolds are made of unobtanium. After waiting nearly 2 years I finally gave up, sold the heads and bought a set of D-port Edelbrock heads instead. They do not flow as well, especially over .300 lift, but at least ram air and long branch manifolds are available. D-port heads are more difficult to improve the exhaust port, and probably cost me 20-25 HP. But at least I can drive my car.

If I was going to run tube headers, I would certainly use round port heads.

Tom S. and I had this discussion years ago. I do believe Tom has more hands on experience running street engines with round port heads than anyone else here. When the man tells me to run long branch exhaust manifolds on a street engine I listen. If you really think you need extra exhaust flow you can always have the exhaust manifolds extrude honed. Mike, I agree: if you are going to run headers ( we have the problem of simply finding someone to fab headers for a ‘61-‘64 “B” body; Mad Dog stopped producing these headers years ago) I would go with the round port heads.

[Stan Weiss]

Remember air speed / port velocity is not a constant. This is CFM and velocity based on numbers from Edelbrock.

Stan

[Gach]

Originally Posted by chiphead

So is it just CFM? When you need more than 260CFM from the exhaust port, (80% of 330CFM intake) you go round port exhaust? Is the chamber any different between a edelbrock round port and the Eddy D-port? Is one chamber better than the other?

How much can a D-port exhaust port realistically flow?

If you had a D port and a round port that had similar flow numbers and port velocities, would they make similar power?

I think chambers are just about the same. The exhaust on D-ports are kind of their down fall. Can’t remember exhaust flow numbers on D-ports but I do know round port can go 270 cfm. Maybe more not sure.