Different length pushrods on the same side

[Spaceman]

Howdy engine experts,

I'm putting my valvetrain together, and the left side went in without any issues. Now I'm working on the right side and I've stumped myself. I just measured and trimmed all four pushrods for the right side. I used the adjustable length tool at the #4 intake valve location to determine the length. Anyway I trimmed all four, but with everything installed I've realized they are too long for both valves on cylinder #3. On both #3 valves, I can't back the adjusters out far enough to get any clearance.

I used the tool again on the #3 valves, and found that I would need pushrods about 1/8" shorter than what I cut for the #4 valves. Is that an excessive amount of difference?

I asked Sonex and Kerry said his first thoughts were did I shim both cylinders the same and is the head seated squarely on both cylinders... I checked those things and all looks good. Also, with the crank/cam positioned for all valves on that side closed, the ends of all four pushrods appear to line up. So I don't think there's anything wrong with the lifters being seated or anything like that.

Should I just try to get my hands on two new pushrods and trim them to a shorter length, or could this indicate some other problem?

Thanks!

[Area 51%]

There is a very narrow band of degrees that the camshaft isn't opening or closing something. The two cylinder next to each other have very different things going on at the same time. Use TDC on a single cylinder to set the pushrod length, then try that length on the other cylinder at IT'S TDC.

If that brings you no joy, try swapping rocker arms and see if the problem follows the change. Also, make sure the threads on the adjusters go all the way to the ball sockets. If they don't, the adjuster will not screw all the way into the rocker causing a tight condition. I have pictures of that phenomenon. Had to buy another set.

If you ultimately find it is indeed the pushrod length, I have a couple of spares you can have. Half of the pushrods that came in my kit wobbled badly when rolled across a glass table, so I had to buy another set. Ergo....spares.

[Spaceman]

Also, make sure the threads on the adjusters go all the way to the ball sockets. If they don't, the adjuster will not screw all the way into the rocker causing a tight condition. I have pictures of that phenomenon. Had to buy another set.

After looking at it some more I think this is at least part of the problem. One of the adjusters doesn't back out quite as far as the others. The other one is very close to the other two though (on the good cylinder), so that might be part of it but maybe not the whole issue. I'm going to PM you about those pushrods though!

I held a straightedge up to the ends of the four pushrods as they stick out of the engine with the rocker shaft removed, and they're all flush! The ends of the valves are also all flush, so the problem has to be just inconsistencies somewhere in the rocker assembly I guess.

[lutorm]

There are only three possible sources: the lifters, the adjusters, or the valves. If the valve stems are all in a line, it's either the pushrods or the adjusters. However, like A51 said, I don't think there's actually a crankshaft position that has all the valves completely closed. When you say they're too short, I assume you've checked the cylinders in sequence and turned the crankshaft so that cylinder is at TDC on the compression stroke.

The easiest way to figure out what's causing it is to just exchange an adjuster that's tight with one that's not. If the problem follows the adjuster, well then it's the adjuster.

[sonexsteve]

I’m far from an engine expert, but offer the following experience I had building my AeroVee a couple of years ago....

I had great trouble getting the rocker arm action to produce consistent results after setting it all up correctly, then rotating the engine, whereupon I’d immediately find that the setup had changed and I had to start out all over again.

After weeks of attempting to get it to work correctly I decided to disassemble the entire valve/rocker arm/push rod assemblies and inspect everything in detail. This showed that 2 of the rocker arms had been drilled for the shaft hole way off centre, something like 20 degrees off straight. Very poor quality control somewhere, and whoever had assembled the 2 sets must have been asleep or blind during that process.

I’m not suggesting this would be the source of your problems, but a detailed examination of all components disassembled for your own quality control inspection might pay dividends

Steve Moody
Leamington Spa, England
Sonex A #1383, AeroVee #847.

[Outlaw6]

To get both valves on a cylinder at zero lift at TDC it has to be TDC between the compression and power strokes. If your at TDC between the exhaust and intake strokes then the intake valve has already started opening for the intake and the exhaust valve hasn't fully close until after TDC into the intake stroke.
All four valves in a side are never all closed at the same time while one of the cylinders is at TDC.