Quote:
Originally Posted by charlie66
I found this online and copy an pasted it .
The ohc6 was based off of Chevrolet’s 230 cubic inch L-head six-cylinder engine but nearly all components were either modified or of a completely new design. The ohc6 had a bore of 3.875 inches and a stroke of 3.250 inches with a 9.0:1 compression ratio. The crankshaft was a cast nodular-iron design supported by seven main bearings and the block was extended well below the crankshaft centerline to provide greater stiffness, improve bearing life, and minimize vibration. The steel forged connecting rods were conventional in design and attached to cast aluminum flat-headed pistons of a slipper skirt design that contained deep recesses for the valve heads. The pistons did not include any expansion control devices which differed from those found in other engines.
Looks like these engines all came with forged rods ..
If so it think this engine would definitely hold some power.
I've been looking for what rod length they have because the stroke is a half inch less then a 8cyl . But i cant seem to find any information .
The fact that it has a short stroke really gets my interest..
My question would be, can you get a cam ground for this . If not , then you're stuck with the factory spec's. Which im sure will work but not what i would want to go off of. It does have a decent amount of duration right off the bat though.. .228 degrees is not bad..
I think if you got a low compression version like the 9.0:1 which makes around 175hp you could make 500hp with 25 to 30 psi. That would be with a stock motor right out of a car with no mods..
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If the pistons were a unique design, could pistons from a different engine with the same dimensions be made to work? Those Jeep I6 ones have close numbers and are forged.
Forged rods for the Chevy 250 are available in 5.700" and 6.000." I'm sure I saw on SpeedTalk.com a comparison of the Pontiac and Chevy rods. They were the same length but the Pontiac's were much beefier. Can't find it right now. Are the crank journals for the rods the same for the Chevy and Pontiac?
A new cam would be cut from a blank, right? Would the new cam be too hard a metal for the original followers? I wonder if roller followers could adapted or specially made. Would probably need to order more than just one set if so.
https://www.ebay.com/itm/142992244403
I messaged the seller of these to see what info I could get about them. I'll follow up if I get a response.
The short stroke like you say is good for turbocharging. Shorter stroke=higher redline. More rpms=more boost. The valvetrain has to live at that speed, though.
About compression, rule of thumb for V8s is 9.5:1 for N/A, 8.0:1 for boost on pump gas. But it's cylinder pressure under load that really determines preignition threshold. Are the combustion chambers on the I6 similar to the V8s? If they are, wouldn't they have the same cranking pressure tolerance? I've read that 160psi is the limit for iron heads. Wouldn't you need a considerable piston dish to run 25lbs of boost and not blow your engine?
https://forums.maxperformanceinc.com...d.php?t=852412. Asked about block strength in the boost section. Mr. Jack Gifford said he was told by Mickey Thompson's crew chief that the OHC heads would crack between the valves when they tried to run them. Races push their engines to the absolute limit, so I wonder how hard their engines went before failure.
So many unknowns, so many new things to learn!