looking to order some push rods for 302 with 289 heads with guide plates. ive noticed 3 different sbf lengths. one for the roller engine which im not using, 62-68 @6.804 and 69-85 or so @6.886. why the difference between the last two. is it a different deck height (thought that was a 72-76 thing there) difference in the fulcrum point in the head, valve stem tip higher or lower, or is it something different in the rockers. i need to know what the difference is so i know what to order.
help with pushrod length
- Thread starter ashford
- Start date
the best way to know is to buy a pushrod length checker. You put the checker where you would have your pushrod, and you adjust the length of the checker until the rocker stays on the valve correctly. This is the best way to account for milled heads/blocks, and other irregularities. Then order custom length pushrods. I don't know that I would want to use stock pushrods with guide plates. You want hardened pushrods.
69Rcode_Mach1
Active Member
Go with hardened pushrods for sure. I would also use a pushrod length checker and make sure to have the tip of the rocker arms on the center of the valves or you run the risk of mushrooming the head of the valve. Just draw on the top of the valve with a marker, then tighten down the rocker arm and see where it leaves a line, if it leaves it in the center you have the right length, and then you just have to order them.
The three different lengths are due to 1. roller cams use a short 6.25" length due to the taller lifters. The other two applications are due to the switch in april 66 to rail rockers and the required longer valve stems to gain clearance for the rockers over the retainers. But as the others have suggested the correct way to determine proper length is to use checking pushrods. You MIGHT get lucky with off the shelf lengths but you might not If you've got stock heads, valves and the block deck and heads haven't been milled too much, you may be OK with off the shelf ones. Only way to know is to assemble the engine and roll the crank around and observe how the rocker tip contacts the valve stem tip. The contact patch should be as close to centered as possible.
summit racing is having a clearance sale on trick flow hardened pushrods %40 off. hope i or can order them before they run out. im using 1.90 1.50 chebby valves on 67 289heads and either diecast roller tip or crane aluminum i have both. the crane's are the pos ones that share the same part # with chevy 1.6. so im sorta leery on using them again, think ill just pawn them off on one of my chevy friends.
