calculating lifter rod length and preload

onefastmustang · #1 (**permalink**) 10-07-2009, 07:09 PM

I got my replacement lifters for my windsor today. This time I opted to go with some Ford Racing ones with lifter bars. bye bye spider.

Anyhow they are the same height as the ones I pulled out but I still want to make sure I have the right length rods in there. I have Comp Cams 7643 rods that I got from KC. I put them and tighten up the rockers (pedestal) and I can't rotate the rod. I have heard that you should be able to rotate the rod when tightened. I am doing this with the cylinder in the rested position with both valves closed. Also I have a Comp Cams 7901 length checker. I placed the rocker on the intake port side, checked it for alignment on the valve and it was in the middle. I then expanded the 7901 which came out four turns until I saw the lifter start to go down a tad. I am not 100% sure on what the preload should be but I read somewhere around .020. Is that right?

Gaz64 · #2 (**permalink**) 10-08-2009, 12:27 AM

Quote:

Originally Posted by onefastmustang

I got my replacement lifters for my windsor today. This time I opted to go with some Ford Racing ones with lifter bars. bye bye spider.

Anyhow they are the same height as the ones I pulled out but I still want to make sure I have the right length rods in there. I have Comp Cams 7643 rods that I got from KC. I put them and tighten up the rockers (pedestal) and I can't rotate the rod. I have heard that you should be able to rotate the rod when tightened. I am doing this with the cylinder in the rested position with both valves closed. Also I have a Comp Cams 7901 length checker. I placed the rocker on the intake port side, checked it for alignment on the valve and it was in the middle. I then expanded the 7901 which came out four turns until I saw the lifter start to go down a tad. I am not 100% sure on what the preload should be but I read somewhere around .020. Is that right?

You should still be able to rotate the pushrod after "zero" preload albeit a bit firmer than the "spin with your fingers" prior to zero lash.

Unless you have already filled up your lifters, then they may be firm to turn.

20 thou (.020) is ok to shoot for, for preload.
Hydraulic lifters can run anywhere in the 10/20 - 60 thou zone for lifter preload.
Some guys even run their hydraulics at zero.

You'll be going for custom length pushrods from your pushrod checker if you haven't got adjustable rockers.

onefastmustang · #3 (**permalink**) 10-10-2009, 07:32 PM

Thanks.. I put it all back together today.. It is noticeably different sounding then before. Before I had a spider, dog bones and ford lifters. Now I have ford (crane cams) lifters with link bars and the engine sounds a bit different. I set the preload on every lifter per spec of between .020 and .060. I ended up having to use a shim on every rocker, probably because the block had been shaved the last time it was in the machine shop. But it did fire right up after 3 turnovers and ran smoothly, just different sounding. Now to take it for a ride in the morning.