The porting is over

[Locobob]

Originally Posted by Paul Workman

Yeah...********!

Suction as a force (to "pull") is a misnomer. Actually, it's all push. Air is forced into the heads via relatively high atmospheric pressure vs. the low pressure inside the cylinder. "Forced induction" simply enhances the ambient air pressure, and flow is flow.

The fluid dynamics of that portion of the air column coming in contact with a "reflective surface" (e.g. an 90º one at that) will cause impedance to that portion of the affected column. But, more important, the air molecules will be reflected back at the same angle of incidence they had striking the miss-matched port. The reflected air then collides with the rest of the air stream. The result is a static pressure wave on the same plane as the obstruction - that virtually narrows the port beyond the actual obstruction. This further impeds the air column beyond that portion occupied by the over-hang of the mismatch. (This can be witnessed when observing the ripples in a fast flowing stream. As the water encounters a submerged rock, the resulting ripple erupts at the surface, well above the top of the rock(s) - evidence of deflected flow affecting the rest of the (water) flow, in this case.)

Sir Isac Newton can do a much better explanation than I. Matching reaps benefits beyond the mere dimensions of the unmatched surface, is my point

P.

Wow, didn't know you were such a super genious Paul... My brain started to hurt in the second paragraph

[Locobob]

Originally Posted by LGAFF

I agree matching is better.......but curious as to whether or not matching is detrimental.

Airflow generally does not like changes in size or direction, nor does it like sharp objects in it's path. If you don't port match you are creating all three of these conditions.

[xlr8nflorida]

Originally Posted by Jim Nolan

I picked up my '92 today from South Georgia Corvette today and I am satisified with the results. The before and after dynos show a definate improvement. The one thing that I was most pleased with was the dyno results. With the full porting, headers and the dyno tuning it pulled 394.5 hp and 354.9 torque, at peak. The most impressive part was the fact the peak occured at 5,500 rpm and never fell off up to 7,000. The horsepower on the other hand kept climbing up through 6,500 rpm before it leveled off. The big plus was once they peaked they never dropped off.

My pre-mod dyno numbers showed a peak about 5,300 and dropped off torque from 349.4 at 5,300 to 286.7 at 6,500 and horsepower from 357.8 at 5,300 to 319.1 at 6,500 rpm.

The temp that was 91.

Are these typical numbers for cars that have had the heads done? I thought the dyno number looks about right for cars without heads ported?

What Hp do you get from the heads ported? I thought it was an extra 25-35.

[LGAFF]

Maybe he meant the heads were ported at the intake surface....port matched. My 92 is running 391rwhp with ported intake/port matching.

[flyin ryan]

Originally Posted by Locobob

Wow, didn't know you were such a super genious Paul

Paul's not as dumb as he looks . Seriously Paul knows he's not the smartest guy out there but he does his homework & that's all good.

[flyin ryan]

Originally Posted by Locobob

When I do a port job for someone I try to tailor it to the motors current state of tune.

That's exactly right, I do the same for my customers. I get guys who want me to go all out on a part, heads, intake etc., right now because they want to step up the combination at a later date. I'll tell them, unless down the road is two months, just optimise the combination for now, as it sits, rather than living with something horrible for three years or more, not worth it .

[Paul Workman]

Originally Posted by flyin ryan

Paul's not as dumb as he looks . Seriously Paul knows he's not the smartest guy out there but he does his homework & that's all good.

Thanks! (...I think)

P.

[tomtom72]

I gotta say that I thank you guys, the "Porting Brain Trust", for having disscussions like this! I'm learning valuable insights, and valuable facts.


sorry for the hi-jack Mr. Nolan...

[Aurora40]

Originally Posted by xlr8nflorida

Are these typical numbers for cars that have had the heads done? I thought the dyno number looks about right for cars without heads ported?

What Hp do you get from the heads ported? I thought it was an extra 25-35.

It may depend a lot on what kind of dyno they used. I know my car on a Dynojet made about 15whp more than on a SuperFlow. If he was on something similar, that would mean he was making around 410whp, which sounds about right for a dual-mass full ported 350ci.

I assume SGC knows what they are doing, and that it's just a matter of different dynos.

[Jim Nolan]

Looking at the sheets it was a Dynojet.

I didn't ask it so fess up,..Who owns the twin turbo ZR1 SGC is putting together. The paint on the motor is beautiful and Aaron said it should dyno at about 900hp.

I don't care about the hi-jacking I like the info, but I have to admit some of the dynnamics is over my head.