1980 Chevy Corvette FAQ - Techin' In With Fletch

Tech Questions For Fletch!

Dan Fletcher Feb 1, 2009 0 Comment(s)
Sucp_0902_02_z 1980_chevy_corvette_faq Chevy_faq 2/2

Have a tech question you need answered? Send it to questions4fletch@yahoo.com, fax them to 201/712-9899, or snail-mail 'em to Super Chevy, 365 W. Passaic St., Rochelle Park, NJ 07662.

What Head Is This?
I have a '67 Chevy II, two-door post that I use for drag racing. It has a 355ci with a Powerglide. The suspension is stock except for a Ford 9-inch with 4.56 gears. I run around 11.0 in 2,000-ft air. The motor has cast iron heads, casting No. 840292. They have 64cc chambers, angled spark plugs, 2.05 intake and 1.60 exhaust valves, and 180cc intake runners. I have heard these called Turbo 292 heads and that they were built by Chevrolet in the '70s and never put on a production car. Can you tell me about them? Where did they come from? How rare are they? They must be good heads because they make good power.
-Jim Wiford
Clarkston, Wash.

I spoke with one of my engine builders, Gary Hettler, and he said that they're "the best 23-degree casting ever made by GM." They were produced from the late-'60s through the mid-'70s, and went through seven or eight configurations over that span. They are pretty rare, indeed.

They were never put on a production vehicle, but instead were sold over the parts counter by GM. Hettler told me that guys like Grumpy Jenkins used them in Pro Stock back in the day because they were the best flowing piece they had to work with. They originally came with a 2.02 intake and 1.60 exhaust valves, so someone must have put the 2.05 in yours.

He's Missing Something
Let me start with what I have. It's a 1980 Vette that I put a 383 in running 10.5:1 compression ratio, AFR aluminum heads (227 race-ported 64cc chamber) with 1.6 stainless rockers (a bit heavy). The cam is a Doug Herbert solid roller 244/244 duration @ .050, .567/.567 lift with the 1.6 rockers, and a 106 centerline. I use a Victor Jr. manifold with a 1-inch spacer and an 850 Speed Demon mechanical secondary carb. For a fuel pump, I use a Holley black with a 1/2-inch line run to the regulator, which is set at 8 psi. Two 3/8-inch lines run from the regulator, one to each fuel bowl on the carb. For ignition I run a 6AL to a Flamethrower distributor and MSD cap, rotor, and wires. The timing is set at 36 total and comes in at 3,000 rpm. The car has a five-speed Tremec and 4.09 gears.

Now the problem. In first and second gears at WOT at about 5,300 rpm, my engine misses bad. If I take off slowly, I can bring my rpms up to 6,500 with no problems. If I'm cruising at, say, 2,500 in third gear and floor it, the engine goes right up to 6,500 rpm. When the engine starts to miss my fuel pressure is rock-solid, but my air fuel gauge starts to lean out.

First I put jet extensions on my Demon, as well as a larger needle and seat, and raised the float level with no help. I changed my timing up and down, used different plugs and gaps, and changed out carbs. I ohm'd out my wires and checked the cap for cracks. I don't know what else to do. This engine has some serious cajones but I can't harness all of them.
-John Wilson
Via email

It certainly sounds like a fuel issue to me, no doubt about it. That said, you've done, checked, adjusted, or otherwise verified most of the places I would have suggested going. How about this thought-do you have a fuel cell or the factory tank? If you're using the factory tank, without the aid of proper baffling, fuel could be running/sloshing away from the pick-up. This would kind of fit what you're describing, where it seems to be running out of fuel under hard acceleration. Has the suction line from the tank to the pump been upgraded? Having 1/2-inch line from the pump to the regulator doesn't help if the line feeding the pump is smaller.




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