Push rod length

[Anonymous]

I have just put a 2V head (shaved) on to my 221 bottom end and noticed that the 221 push rods are shorter than the 250 push rods that come with the head. Which push rods should I use on my motor?

Any help you could give me would be great, thanks.

 

[xctasy]

Grab a bear or a nice warm drink, and read through this very carefully....

It's been 7 years since I've had a 221 appart, and I think that from 1968, the 221's got earlier adjustable valve gear, not the same as the 250. One of addos posts confirmed it. This means the 221 has a "cup to the rocker gear, and a ball to the hydraulic lifter" pushrod. The rockers were designed to have a 3/8" (9.525 mm, 0.375") ball, while the 250 had a ball on the pushrod and a cup on the rocker.

Stock factory log and 2v 250's are quoted as 9.682" std (ball to ball) Thanksalloydave for your info,

Stock 221 info, tanks to XT 500 (Cameron). He has measured his old XT 221 pushrods at

approx 8.05" from top surface of the cup to bottom of the ball end,

or 7.875" from the top surface of the cup to centre of the ball.

That is 8.238" cup to ball, by my calcs.

When you go to a ball to ball rod, you add the half the 3/8" ball to the length, and I get 8.61" That's what I think you need.

Anyone else can confirm that?








(*One thing I can tell you is that the 221 deck height is 0.955" [24.25 mm] lower. Stock 221 pushrods to suit a 250 2V would have to be about 0.955" shorter. However the cam is mounted out further than the 221, and the lifter design changed.

There were a vast raft of changes from 1967 to 1971, with massive changes in engine deck height and valve gear. Hydralic lifters didn't mean non adjustable valve gear, so there are many different combinations out there. From 68 to 70, 221 had the same valve gear and pushrods.

Use the 221 pushrods. They should be a straight bolt -on. Make sure the 221 rods have cupped ends to suit the 250 head.

Earlier 144/170 and 200's had adjustable ball and cup ended pushrods, at 7.875" and are way to short.)

 

[Anonymous]

Thanks for that info I checked them today and the 221 push rods are just over 8 inches long and the push rods that came with the head are just over 9 inches long and both sets have a ball on one end and cup on the other (measurements are a bit rough because I only had a tape measure). I installed the short push rods and torqued the rocker gear down and now i'm up to setting the tappets. Does anyone know approximately what measurement to set the tappets too as the three books I have here all have a different measurement. If anyone know the measurement in mm it would be a huge help as I only have metric feeler gauges at the moment.

Once again any help you can give is much appreciated.

 

[addo]

How good are the lifters?

First, rotate the motor until the balancer timing notch is lined up with the pointer on zero. Both valves for #1 should be closed position. If not, rotate 360° until they are.

Loosen the adjusters for #1 until you can juggle the pushrods up and down. Tighten gently until this stops. Then add one turn to each. Mimic this setting for the other pots by measuring the exact amount of adjuster out the rocker bottom.

You should be good to go. Of course, if your lifters were stuck down, you've just ruined the cam, so make sure they were pumped up before you started!

Cheers, Adam.