Author Topic: 302 hemi prototype with crossram  (Read 5752 times)


william

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Re: 302 hemi prototype with crossram
« Reply #1 on: January 27, 2007, 08:15:50 PM »
That ad has been on ebay nearly continuously.

Those heads sure get a lot of attention considering they are no more than a failed engineering experiment. Chevy could not make them work; got Yunick involved. He couldn't make them work either. No race history, never sold to the public, no factory installations.

My68SS

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Re: 302 hemi prototype with crossram
« Reply #2 on: January 27, 2007, 08:47:47 PM »
What was wrong with them? They couldn't get the expected performance from them?
I was gagging at the price tag!   :o
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Jerry@CHP

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Re: 302 hemi prototype with crossram
« Reply #3 on: January 27, 2007, 08:58:11 PM »
You should have seen the mutt at Russo Steele that had a pair of these heads installed on the engine.  Also had an extra pair displayed with the car.  I think this Z28 did stupid money there.

Jerry

JoeC

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Re: 302 hemi prototype with crossram
« Reply #4 on: January 28, 2007, 04:31:46 AM »
also on ebay were the
FORD TRANS AM TUNNEL PORT CYLINDER HEADS
 
http://cgi.ebay.com/ebaymotors/FORD-302-TRANS-AM-TUNNEL-PORT-CYLINDER-HEADS-NOS_W0QQcmdZViewItemQQcategoryZ33617QQihZ015QQitemZ250047377225QQrdZ1

Chevy was working on the Porcupine head as a response to the Ford Tunnel port head. From what I read, they both made good power but at higher RPM so there was less low RPM torque for pulling off the corners and the higher engine RPMs hurt engine reliability.
 The Ford Tunnel port heads were not very successful and had a lot of engine failure so the Porcupine heads were not really needed.
It's amazing the extent that Chevy and Ford went to just to win in Trans Am


Jerry@CHP

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Re: 302 hemi prototype with crossram
« Reply #5 on: January 30, 2007, 04:11:16 AM »
Saw two more sets of these heads on an appraisal trip today.  I thought they were rare?  That's four sets that I've seen in the past two weeks.

I think it's safe to say there are more than five sets known to exist????

Jerry

william

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Re: 302 hemi prototype with crossram
« Reply #6 on: January 30, 2007, 06:15:32 PM »
Maybe Heartbeat reproduced them.

JoeC

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Re: 302 hemi prototype with crossram
« Reply #7 on: January 31, 2007, 12:01:18 AM »
In Smokey’s book, I think he claimed something like 200 sets of the porcupine heads were cast.
Not sure how many had final maching operations done, but Chevy would have to have a good number of heads in the pipe line if they planned to run this head configuration in Trans Am. The rules to homologate parts for TA stated that the items had to be available to the public in sufficient quantities. So Chevy had to make a pretty good amount of Z race parts such as cross rams, big sway bars, 4 wheel disk, hoods etc.
TA rules allowed service parts but they had to be pre-approved by SCCA.

VI009DZ

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Re: 302 hemi prototype with crossram
« Reply #8 on: January 31, 2007, 02:43:33 AM »
From what I had read about these heads, there was nothing "wrong" with them at all.  GM and Smokey worked the snot out of them and were unable to show that the gain in HP was going to be worth the additional tooling, engineering and production costs.  It seems that there was some kind of plateau they hit like 385hp with the Hemi heads on the 302.  Hemi is kind of a 'catch name' for them; they aren't a Hemi head in the traditional sense.  It's more of a splayed valve head like a big block chevy than a Hemi head.

JohnZ

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Re: 302 hemi prototype with crossram
« Reply #9 on: January 31, 2007, 03:46:03 PM »
That was the second time around for an aluminum hemi head for the small-block; Zora Duntov built several of them for the original 377c.i. Corvette Grand Sport in 1963, with twin plugs per cylinder, and it didn't work out very well either. Didn't make enough additional power to make the effort worthwhile, so they continued to develop the conventional wedge-chamber heads.
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Jerry@CHP

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Re: 302 hemi prototype with crossram
« Reply #10 on: January 31, 2007, 08:40:27 PM »
Guess Chevrolet had it right the first time.  I am getting 450-475hp out of stock 291 castings for my stock eliminator Z28 engine w/.485" lift camshaft.  Can't best that.

Jerry

lakeholme

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Re: 302 hemi prototype with crossram
« Reply #11 on: February 01, 2007, 04:04:21 PM »
It's an interesting thought, but Jerry and John are right in more ways than one.  In the five or so true years of the hemi muscle car era, they only sold about 11,000 of the big hemi engine cars.  Why would GM want to pay the big production costs for those results?  It's an interesting thought... But it's mostly hemi-hype.
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JoeC

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Re: 302 hemi prototype with crossram
« Reply #12 on: February 02, 2007, 12:18:53 PM »
The big hemi engine cars sold many many more cars then the ones that actually had a Hemi engine installed. It was called product promotion engineering and GM, Ford, and Chrysler all played the game. Projects like the Z/28 302, LT1, L88 ZL1 were built for racing homologation rules and the goal was to gain publicity from the racing exposure.
 I see the term “homologation specials” being used more often now for the American cars that were built to satisfy racing rules. Homologation specials have been around since the 1930s when special cars were built to race at Lemans.
Even the video game people promote the special built cars with games like "Sega GT Homologation Special"