Pushrod length,

Post by **Coops** » Sat Nov 14, 2015 9:23 am

Has any one got a step by step guide on how to measure pushrod length with adjustable roller rockers and hydraulic lifters?

Im going to need it myself in the coming weeks as my new build starts taking shape but I can also make it a sticky topic to help others in the future as we have done with many step by step guides.

thanks guys

Blown v8 · Post by **Blown v8** » Sat Nov 14, 2015 4:28 pm

This may help,
http://www.hotrod.com/how-to/engine/ctr ... od-length/

Triumph-V8 · Post by **Triumph-V8** » Sat Nov 14, 2015 5:13 pm

Step one is to buy an adjustable dummy pushrod from COMP.

Step two is to set engine that cam lobe is fully closed and
the dummy is set into the place to be measured.

Step three is to open the dummy pushrod until the lifter
is compressed 1mm.

Step four is to make the pushrod in the proper length and
fit it to the engine.

Should you swap to adjustable pushrods you have finished
with step three.

I have pretty nice pushrods from Real Steel in use,
they consist of lower and upper cup to be pressed into
a very stiff steel tube that must be cutted to proper length.

mgbv8 · Post by **mgbv8** » Sat Nov 14, 2015 10:03 pm

You not going for a mech cam and solid lifters Coops ?

Why Not ??

Triumph-V8 · Post by **Triumph-V8** » Sun Nov 15, 2015 9:14 am

Blown v8 wrote:This may help,
http://www.hotrod.com/how-to/engine/ctr ... od-length/

I think this is fully wrong, maybe somebody else
may look on this because English is not my language.

What I do is to place rocker shaft in the proper height to valve
that at half lift the angle between valve and contact point to
rocker axis is rectangular.

After that I place the rocker shaft in the proper distance to form
the contact area between valve tip and rocker in the middle of tip.

The pushrod length is the last thing that must follow the setup
before and can not be changed from the required length

Cobratone · Post by **Cobratone** » Sun Nov 15, 2015 9:34 am

I did it similar to the hot rod link insomuch as colouring the valve tip with ink, fitting the valve gear and pushrod (bought an adjustable checker one) and then rotating the engine. Checking the pattern "rubbed away" in the ink then increase or decrease the pushrod length and do it all again. Here is a picture of my penultimate attempt so you can see the pattern. Hope this helps.

sidecar · Post by **sidecar** » Sun Nov 15, 2015 9:40 am

I've only read part of the article in the link but when the guy said tha the pushrod length controls where the roller on the tip of the rocker sits on the valve stem I stopped reading because it is just wrong! This is controlled by the design of the rocker and the height of the shaft that is rotates on. I guess the installed valve height will have a small effect too (But very small).

Once the correct rocker height as been established so the the roller is in the correct position on the stem of the valve suitable pushrods of the correct length would then be fitted.

bigaldart · Post by **bigaldart** » Sun Nov 15, 2015 8:16 pm

That Hot Rod quote is accurate when you consider that most American V8's use trunnion mounted rockers and valve clearance or pre-load is set by raising and lowering the pivot point of the rocker. With shaft mounted rockers like a Rover then this must be addressed separately. The statement is not incorrect it just relates to a different rocker arm set up.

Alan

sidecar · Post by **sidecar** » Sun Nov 15, 2015 9:24 pm

Yep but it's the raising ang lowering of the pivit point of the rocker that is changing the contact point of the roller on the valve stem, then after that the pushrod just has to be the right length for where ever the rocker ends up being.

stevieturbo · Post by **stevieturbo** » Mon Nov 16, 2015 10:32 am

All those factors come into play...it really depends on quality of parts used, and how close/far to spec they actually are.

With adjustable parts, aftermarket parts, machined parts...you introduce lots of variables.

Ultimately the wipe pattern is what you need to work towards, keeping it as small and central over the valve tip as possible.

You may need different pushrods, to adjust the rockers, or even raise/lower the entire rocker gear. The latter being the most difficult if it was needed.