Failed design

[Michael C.]

Why don't you think this hood treatment for 67 tri-powers never made it to production? Anyone tried to fabricate this?

[Michael W.]

Re: Failed design

They needed all the BB hoods they could get for SB cars.

[Michael G.]

Re: Failed design

My guess, since it was drawn on April 14, is that the design was initially proposed on April 1 to fix the tri-power's kneuten valve N87 nitrogen leakage problem....

[Duke W.]

Re: Failed design

My guess, since it was drawn on April 14, is that the design was initially proposed on April 1 to fix the tri-power's kneuten valve N87 nitrogen leakage problem....

I think this was discussed a few years ago and the reason may have been that it failed GM's severe water intrusion test.

I had a friend years ago whose Scirocco experienced hydraulic lockup after a truck next to him doused the car with water going through a big puddle. I guess VW's test wasn't as severe as GM's.

Duke

[John H.]

Re: Failed design

I think this was discussed a few years ago and the reason may have been that it failed GM's severe water intrusion test.

That's correct - I was in the Corvette Group at the time, and I remember when the prototype hood failed the Proving Grounds Water Ingestion Test; it was a foregone conclusion (just from examining the design) that it would fail, and the test confirmed it. Sales loved it, Engineering didn't (just like sidepipes).

[Michael C.]

Re: Failed design

Was it similar to the L88 in design theory? Just triangular instead of round? I find this stuff fascinating. Thanks for share the history.

Mike C.

[Richard M.]

Re: Failed design

That's correct - I was in the Corvette Group at the time, and I remember when the prototype hood failed the Proving Grounds Water Ingestion Test; it was a foregone conclusion (just from examining the design) that it would fail, and the test confirmed it. Sales loved it, Engineering didn't (just like sidepipes).

If they setup a trap door with a water exit could it have worked? Cost prohibitive probably, but it's a cool design and too bad it didn't get used. A true uniqueness and we'd have another thing to pay big bucks for when restoring the 400's or the 435's.

What about the Chevelle Cowl Induction? How did that work against water? I'm unfamiliar with it's design.

Why didn't engineering like the sidepipes? Was it performance loss issues?

[John H.]

Re: Failed design

Was it similar to the L88 in design theory? Just triangular instead of round? I find this stuff fascinating. Thanks for share the history.

Mike C.

Mike -

Nope - the L-88 drew air from the rear of the hood - the cancelled design drew it through the opening at the front of the stinger.

[John H.]

Re: Failed design

What about the Chevelle Cowl Induction? How did that work against water? I'm unfamiliar with it's design.

Why didn't engineering like the sidepipes? Was it performance loss issues?

Rich -

The Chevelle cowl induction hood drew air from the rear, like the '69 ducted hood option on the Camaro. Engineering didn't like the sidepipes due to the restriction caused by the 1-7/8" core pipes, which were actually 1-5/8" across the peaks of the perforations; the stock under-car exhaust was much less restrictive.

Opening the front of the stinger was useless anyway from a performance perspective - there was no "ram-air" effect until well over 100mph, as the opening was in the boundary layer of essentially static airflow (which is why Pro Stock cars have their scoop intakes 18" above the hood surface). The only benefit of a functional surface-level hood scoop is from ambient instead of underhood air; colder air in the intake charge is generally worth about a 1% power increase for each 10*F reduction in air charge temperature.

[Duke W.]

Re: Failed design

I'll add that the actual static pressure on the hood is negative, but postive at the base of the windshield, and this was known at the time though at legal road speeds it's only a few inches of water. Given the front opening and water ingestion issue, it was just a bad design, period.

The Chevelle cold air induction on the hood just forward of the windshield has a vacuum valve that I believe only opens it up at WOT.

Duke

[Michael C.]

Re: Failed design

John, I see. Seems like the design should have been the same as the L88 with the only difference being a triangular air filter. Still pull air from base of windshield. Too bad they cancelled it.

[Robert R.]

Re: Failed design

It would be similar to the 73-75 Corvette Cowl Induction system, correct?
Did that setup yield any extra hp?

[Michael J.]

Re: Failed design

This is very interesting, especially since numerous other manufacturers, like Mopar and Ford, had many "Ram Air" cars in the day. I have two of them, and they handled the water intrusion simply and effectively.

[Duke W.]

Re: Failed design

It would be similar to the 73-75 Corvette Cowl Induction system, correct?
Did that setup yield any extra hp?

SAE net rated output is the same with or without cold air induction because it's always corrected to specific atmospheric conditions.

Most of the time with under the hood induction, power will be less because the induction air is hotter than ambient,
and less dense than SAE standard air density.

Cold air induction means that actual output depends on actual ambient air density, so cold, dry air will definitely make more power than SAE standard air density.

Air density varies most with temperature over short time periods, and the rule of thumb is one percent more power for every 10F drop in inlet air tempeature.

Duke

[Jeff P.]

Re: Failed design

John,

I'm looking at the Hooker Super Competition Sidepipes Design and can't see the Restriction problems if the GM Engineering Team would have used this Design. All the Header Pipes are the same length, meaning Tuned Exhaust dumping into a 4" muffler for anti reversion and noise reduction. Big increase in horsepower and Torque using individual pipes at the Heads instead of a Stock Restricted Exhaust Manifold, is the way they are designed today on the new vettes. Yes the small horsepowered cars like the stock manifolds. The Failed Design of the Air Induction could have been redesigned for street and Race Design.