The porting is over

[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.

[LGAFF]

Sweet numbers.....was that ported heads also?

Congrats!

[Jim Nolan]

That was the heads also. I originally sent the injector housings and plenum to Locobob last year for porting and Haibeck for the e-prom, it was good but not enough.......I guess I just got addicted. The part that suprised me most was Arron at SGC said he had to take more out of the injector housings to match the heads.................and with the Dana 3.91 gears I actually used 6th gear on the drive home. It's going to take a while to get used to the headers, noise. I told him if i had a few more grand to throw his way I would have went for the stroker.

[Locobob]

Jim, the intake port work I did for you was designed for use with the stock 33mm primary head ports. I funnel down the primarys in the bottom half of the injector housings to make a gradual transition to the factory head port diameter - you don't want to suddenly go from 36mm to 33mm. Also were I to enlarge the bottom of the injector housing ports to 36mm without having the heads I would run the risk of screwing up the port alignment between the injector housings and heads. The parts must be done together to get proper results. Hope this explains the situation.

[Jim Nolan]

I never intended to slam you, being a little ignorant of the whole process after you ported I didn't think there was much left to port. I was impressed with what you did and my performance definately increased, but I wanted more and was suprised there was more to give to match the modified heads.

[Locobob]

No problem Jim
I guess the larger point I'm trying to get across here is that there is no such thing as one size fits all port-work. When I do a port job for someone I try to tailor it to the motors current state of tune. I can and have done more aggressive stuff, guess I need to spend more time communicating with folks in regards to expectations and future plans.

[Paul Workman]

Originally Posted by Locobob

No problem Jim
When I do a port job for someone I try to tailor it to the motors current state of tune. I can and have done more aggressive stuff, guess I need to spend more time communicating with folks in regards to expectations and future plans.

I agree w/ you Bob. W/o the heads to match the porting to, it would be up to whomever installed the IHs to grind out the ports in the heads using fully ported IHs. But, not everyone is willing to grind their own heads - 36+mm out of the IH into a 33mm head would impose serious impedance to the flow dynamics. So, without the heads being port matched (at all - i.e., stock) there is no way to realize the full potential of the IH porting potential, and no way someone such as yourself should have done differently, IMO.

P.

[LGAFF]

With regard to the "port matching" I was speaking to someone and they pointed out that this is really not an issue as the air is being pulled...not pushed, as with a forced induction. Conventional wisdom says reversion is an issue in this case.

Any thoughts.....

[Paul Workman]

Originally Posted by LGAFF

With regard to the "port matching" I was speaking to someone and they pointed out that this is really not an issue as the air is being pulled...not pushed, as with a forced induction. Conventional wisdom says reversion is an issue in this case.

Any thoughts.....

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.

[LGAFF]

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