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OHC6 230 to 250 crankshaft conversion

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Joined: 20 Mar 2015
Posts: 8
Location: 4540 Laute Dr Pahrump NV 89061

1966 El Camino

PostPosted: Fri Jun 05, 2015 9:00 am    Post subject: OHC6 230 to 250 crankshaft conversion Reply with quote

66-67 Pontiac 230 Cube one barrel can be turned into a 250 cubic inch with a 250 Cheve crank. If it has a 230 1v head the compression ratio will be 10.5 to one. With Felpro head gasket which is thicker than factory it will drop to about 10 to one. If you have a 230 4v head the compression will be about 11.5 to one. It should run on premium if timing is factory at 5 degrees before top dead center. The Cheve connecting rods are about 15 Grams lighter than 230 Pontiac rods and can be ground lighter to look more like motorcycle connecting rods, same with Pontiac rods. The 250 Pontiac rods look like boat anchors and there is no reason to run them unless you have a blower or turbo charger. If you wish to add 3 cubes, have the rod journals ground to .030 under and move the stroke about .025 up which also will go down about .025. There are .040 under bearings available. I got 250,000 miles out of my last rebuild. The 250 Cheve crank is the same nose diameter as the 230 Pontiac which will run the single pulley Pontiac 230 balancer. If you want 2 pulleys, get a bolt on pulley...VERY light. That is what I am running. A Cheve 2 groove harmonic balancer will run if you put a spacer behind the balancer .400 inch thick to put pulleys in the proper location BUT you need to JB Weld the harmonic balancer when using the Cheve 2 groove pulley, never the cam belt gear. The Cheve crank nose must drilled and taped to 5/8 N.F. The fly wheel end is turned down to Pontiac fly wheel diameter unless you run a 153 tooth Cheve flywheel which is lighter. I run a 10.5 Pound aluminum Cheve fly wheel with a 6.5 pound starter motor. 250 Pontiac harmonic balancers are boat anchors and I have yet to find a replacement for 250 balancers. The 250 Pontiac belt gears are also hard to find. So find a 230 1v and be glad you did. Richard McDonough 775 727 0881 Always run synthetic from minute one. PS There are 3 points in the block that must be moved to allow the crank to rotate. This is detailed in a dvd I have produced. It is a chance to see if the filter media has been removed by boiling the block in acid done in yester year.
OHC6 engines since 1970. Parts, tech since 1985. DVD set on OHC6 on ebay. 775 727 0881. Over sized cam journals fitted to .001" clearance, synthetic oil will run at least 200,000 with ZERO wear. Worth welding journals over sized. Kanter dealer.
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