Follow along as I build a high performance 914 engine
Making the Pushrods
I am now ready to cut the pushrods - I know which lifters to match with each valve, I know what my desired valve lift and rocker arm geometry is, and I've done all the calculations to figure out how long my pushrods should be.
The pushrods are a kit of 8 steel tubes and 16 pushrod ends (that get press-fit into the ends of the tubes). One side of each tube already has an end installed, so my job it to cut it to the right length, then install the other end.
There are many ways to cut the tube - ranging from a hacksaw/grinder, to a machine designed to cut arrow shafts for archery. I decided to use a parting tool on my lathe:
Now that I have it cut closely to length, I measure what I have with a caliper, and decide that I should take a few more thousands off - that's the beauty of a lathe! After the final cut (and a thorough cleaning), it's time to press on the other pushrod end. These ends aren't coming off... so measure twice - three times, if necessary! Then the end can either be installed with a press or hammered into place (use an old lifter so you don't hammer directly on the pushrod end). Here's a finished pushrod:
And here's the whole set ready to go!
To double check that I got my measurements right, I put the new pushrods into my engine assembly. I was pleased to find that all of my valve lifts deviate less than 1% from each other. This should help maximize efficiency because no single cylinder will be able to flow more (or less) air than another.
|All pictures and text copyright 2008|