Checking for Pushrod length

-
Okay I understand what you mean now. I know I need at least a thread sticking out on the adjuster though, otherwise the pushrod cup gets really close to the rocker arm. And the instructions were very vague, all they said was to adjust to measure for proper pushrod length and tighten to zero lash, and then go a full turn from there.

Also my rocker arms oil a bit differently, the adjuster bolt is just a bolt with a ball on the end, and there is a little hole behind the adjuster that oils the cup and ball. I was told that the adjuster had to be down far enough so it squirts oil on it properly.

And about the geometry, I originally checked with the pushrods that were too long and all the contact patches seemed to be pretty good, so no worries there.
 

Attachments

  • photo 2 (1).JPG
    32.2 KB · Views: 282
  • photo 1 (1).JPG
    35 KB · Views: 263
Okay so I think I figured it out! (Hopefully lol) As you can see there are about 1 and a bit threads showing on the bottom of the rocker arm.

I put the old push-rods in place and as you can see its way too long! the new one seems much better.

That isn't taking into account the lifter pre-load as stated. You think it looks good so I can order push-rods?
 

Attachments

  • photo (1).jpg
    36.6 KB · Views: 300
Pushrod length won't affect the contact patch on the valve with shaft rockers, because the pivot point of the rocker (the shaft) doesn't move up or down like stud rockers. The only way to change the valve contact patch with shaft rockers is to either shim the shafts, put lash cams on the valve stems, or change the valve lengths.

The checking pushrod length in your photo is acceptable. Ideally you'd probably want to wind the adjuster in one more turn so that no threads are showing. Then you can measure your pushrods with zero lash (as per the instructions) and order them.

Once you install the new pushrods, you'll need to add another 1/2 to 1 turn of preload. So by the time you have done that, you should have 1 or maximum 2 threads showing from each rocker.

However, the most important thing is that the pushrod cup clears the rocker (as you have rightly mentioned), so if it's getting too close, err on the side of caution.

It's also a good idea to seat all your rockers (no threads showing) and measure every pushrod length - all 16. I know it's a pain, but there will be some slight variance in the measured length of each pushrod. You want to select the shortest pushrod as your final length, as that will ensure none of your pushrods are too long.

For example, on some cams the intake and exhaust lobes are ground on different base circles (if there's a big difference in lift), which means the average reading for each exhaust pushrod would be slightly longer or shorter than each intake.

This was the case with the cam I have in my engine now, and I ordered two different length pushrods for the exhaust and the intake. The exhausts were .025" longer than the intakes, as there was a .020" difference between the lobes.

You probably don't have to worry about this much unless there is a big difference in readings. Just select the shortest pushrod measurement and you should be fine.

I know this all seems a little complicated - after all, they're just pushrods (LOL!) - but the secret to building good engines is to CHECK EVERYTHING. And then CHECK AGAIN. It is time-consuming and exacting. But it is also rewarding when you get it right and can enjoy the fruits of your labour.
 
Yeah I know the closer the better. I'm going out in a bit to double check the measurements and measure all 16 like you mentioned. I think I can shorten them slightly, but the pushrod cup gets close and like mentioned I'd like to know that they can't touch.

Thanks for the help! I think I've almost got this figured out.
 
No worries. Just remember, the pushrod cup will move closer to the rocker as it moves, so make sure they don't touch - even at full valve lift.

If you do that, and then use the shortest pushrod as your ordering length, you shouldn't have any problems or nasty surprises from overlength pushrods. Once you wind that preload in, you'll gain a bit more pushrod/rocker clearance.

Another tip: if you order stocking pushrods (off-the-shelf, as opposed to custom) and find they are a size in-between, order the closest length that is slightly shorter - not longer - than your measured length. You can order either oiling or non-oiling pushrods (with or without oiling holes at each end), as it won't make any difference to your engine. The oil has nowhere to go inside the pushrod. This should give you more pushrods to choose from. I like Trend pushrods myself, but that's personal choice.
 
I made a solid lifter by putting some washers in an old lifter so I could check the clearance at full lift (didn't use to measure for length) and found that I have lots of clearance even when the rocker adjuster is seated, so no issues there.

I found that I could bring the adjuster in slightly and after measuring all 16 like you mentioned I think I found the shortest one. The first picture is of zero lash, the second is a half a turn (preload), about a thread and a bit like before are showing. (I think I had it before but I measured at zero lash but that was where it should have been after taking into account the preload) it looks like I'm low enough for proper oiling and not too far out, I think I finally understood all of this and determined the correct length that I need!

And I think I'm going to order custom pushrods, I've looked and haven't found any that are close enough, ohh well, I guess now I'll have ones that are exact length.
 

Attachments

  • image.jpg
    31.4 KB · Views: 239
Couldn't get both pictures on one post for whatever reason from my phone!
 

Attachments

  • image.jpg
    34.5 KB · Views: 271
Excellent! Glad to hear that! And I think I ended up with 7.110, everything is written down in the garage though, but I think that's it.

And it's a fairly small cam, comp XE268-h. This build isn't anything more than a few steps up from a stock engine, just street use. My first motor that I've built thats mine so it's kinda exciting now that the end is near.
 
Sounds like a 7.100" pushrod should fit the bill. If you can find a ball/cup assembled pushrod in that length, all good. But most of the stocking pushrods are ball/ball, so you'll likely have to go custom. No biggie, as they're not that expensive.

Smith Brothers have some nice two-piece pushrods. Part # NH54A is a custom length 5/16" x .049" cup/ball heat-treated pushrod with no oiling holes for $8.81 each. NH58A is a 5/16" x .083" cup/ball for $10.35 each. The cheaper pushrods will work with your cam, but the .083" wall thickness pushrods will leave a little room for upgrade (assuming you can use the same pushrods!). General consensus is to get the strongest pushrod you can to do the job (obviously within reason), as it will ensure valvetrain stability. But talk to the manufacturer first, as they will know exactly what you need.

[ame]http://www.pushrods.net/pdf/SmithBros_catalog_2013.pdf[/ame]
 
Yea unfortunately I haven't found any. And I was actually planning on getting some smith bros ones, I've been told they are good as well.

And I still haven't decided which ones I want, I'll probably just end up going with the standard ones but I'll see what I do when I order lol

Glad this is finally figured out! Now I've gotta get the motor finished and start driving the car!
 
You must log in or register to reply here.
-

Back
Top