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Old 04-09-2018, 06:59 AM   #8
D13
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Join Date: Feb 2007
Location: Memphis MI
Posts: 1,851
Re: inline 6 250 std rocker arms question

Summit's catalog was typed in in error. Small block chevy rockers are not compatible with the 250. The ratio is off and the distance from the stud to the valve is off. The ratio was driven by the block geometry and there are no factory alternatives.

If you replace the rocker studs with screw in big block studs you can run big block rockers, and get access to some different ratios. Almost all of these will be LARGER as this technique is usually used to increase lift at the valve. Also note that these will not not fit under the valve cover so you would need a custom cover.

Your theory of lower ratio means lower lift is correct, but that will not negate the need for proper break in lube. The cam to lifter is the critical problem area and that will be under high pressure no matter what. You have to have some valve spring to make the motor run. A better bet would be to use stock springs for break in then upgrade the springs if desired.
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1987 2 ton
1982 250/TH350 beater in progress
Dad's 1981 3/4 L6 3 on tree posi and no options, awaiting restoration or scrapping
Plus a mess o' tractors
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