So I'm building a 351w, it's a 1970 with D008 Heads. The engines pretty much together except for my push rods and rockers, and i'm seriously confused.

I have a peformance Lunati cam for it, Flat tappet with hydraulic lifters.

The cam has a larger lift, and the actual lifters are a little bit taller, therefore it messes my push rod length up. I'm still running the factory stud mount rockers, with the ball and cup design. Wanted to go roller, but out of money!

I made a spare lifter a solid lifter, and I have and adjustable pushrod.

Question #1
How do I go about setting the preload and measuring the correct pushrod length.

Question #2
I don't understand how the rocker torques down to the stud, does the nut just run to the end of the threads and stop or am I missing something?

I know there's tons and tons of information about this on the web, but it's all about roller motors and adjustable rockers, I don't have any of that, It boggles my mind. Thanks

 

I'm not a valve-train expert, so no schooling from me... but a couple questions on your questions...


1.) Pre-load is set on a hydraulic lifter by running the nut down on the stud until all slack is taken-up, then an additional 1/2-turn or so is added to pre-load the spring inside the lifter. You can't do this on your solid-lifter, as you could bend the pushrod.


2.) When you say factory stud-mount rockers. That says to me they are adjustable - unlike factory "bolt-down" rockers where you just run the bolt all the way down and torque to spec. (This setup is adjusted by shims.) If you actually have stud-mount (like an old non-roller 289 or 302) the nut either has nylon or is slightly deformed on the last few threads to make it "stick" to the stud once adjusted. (It gets tight so it stays in-place once adjusted.)


If you are using the factory "sled" rockers that just slide on the valve-stem, the adjustment is not a critical - as there's no roller to fall off the stem.


How much taller are the new lifters over stock? If you have the adjustable stud setup with sled-rockers, my guess would be to get pushrods that are longer by the difference between your stock and new lifter.


A picture would be nice!

 

Do you have a Chilton's or Haynes manual?

1. What does Lunati's instructions say about preload? 0.020" - 0.030"? Actually, the lifter's plunger bottoms out at around 0.180" so you have plenty of play - you could go almost up to 0.090" (about half of the plunger's depth) and still be ok.

Set the preload:Take the spark plugs out. With the intake cam lobe on the base circle, your solid lifter in place, the adjustable pushrod in place, and the rocker torqued down to specs, adjust the pushrod such that there's no side to side and up/down play. You should just barely be able to turn the pushrod in a circular fashion. Take it out and measure the length. Add what ever preload is needed. Remember, there's plenty of play in the lifters in case you get an oddball number.

Example - stock pushrods are what, 8.2", end to end? Say your measurement is 8.0." Add the desired preload (0.030" ?) You need a pushrod 8.030." I would bump it up to 8.050" - I don't think Summit, Comp, etc makes them off the 0.050" or 0.100" mark. I'm supposing the int/exh lifts are the same. If not, measure the exhaust, too. Although you should be able to use the same pushrod for both.

2. Once you have the correct pushrods, follow the torquing specs - snug the rockers down first, then torque. Each cylinder should be close to the base circle when torquing the rockers. A manual would give you the cylinders that are on base circle when #1 is - there's more than one.

Make sure you have break in oil with plenty of ZDDP. Use a 0.50" drill to pre-lube every thing before you set in the distributor using the dizzy rod from the oil pump.

Valve train geometry isn't that critical using oem rockers.

 

D0OB head casting number prefix: 1970/71 Galaxie/LTD/Fairlane/Torino/Mustang/Cougar 351W heads

 

There are shim kits to buy to put on the stud to lengthen the push rod. Had a 400 blocl decked and heads milled so shims had to be used.

 

All 351W engines use "rail" rocker arms. The valve end of the rocker has a pair of tabs which fit down over the valve stem to keep the rocker aligned on the valve. These are NO GOOD for a performance engine. These can chew up the valve stem, or with a higher lift cam, the ends of the rails can hit the spring retainer,push it down, allowing the keepers to pop out,causing the valve to drop into the cylinder. Good bye engine! These rockers were mounted on "positive stop" studs.The nut is tightened down until it contacts the shoulder on the stud. These do not allow any adjustment. They should be replaced with screw-in studs,guide plates, and hardened pushrods.

 

I needed .030 so this is what I used.
https://www.summitracing.com/parts/c...70-1/overview/