Hi all,

Happy to join, thanks for having me!

To kick things off, I have a question that some of you will probably have no trouble answering. A little background first:

I'm rebuilding my brother's 350 TBI for his G20 Van. We tore the block down completely, bored it, new pistons, rings, bearings, cam, lifters etc. The block was decked and the heads too. Here is where my question lies:

Because of the decking of the block and the heads, I know that I need to adjust my pushrod length, so that the rocker arms will push down straight onto the valves. I did the marker test on the valve stems to see where the rocker arms hit the valves. It was a little off, as expected. So, I bought the Comp Cams push rod length tool to find the right length.

The thing is, when I install the tool (and also with the regular pushrods), after I found zero lash, I turn the rocker arm nuts another 180 degrees as per manual. When I then turn the engine to see where the marks of the rocker arms on the valves will be, I notice that the pistons of the hydraulic lifters are pushed inwards when the cam lobe comes up to open the valve. In normal operation however, the oil pressure should prevent the lifter piston to be pushed completely to my knowledge. So, the reading on the valve stems I get now, would not be an accurate reading to my reasoning, as in normal operation, the hydraulic lifters would be pressurised, causing their pistons not to be pushed all the way in, which will have an effect on the rocker arm geometry.

My question is; how do I make sure that I gain an accurate reading to determine the right pushrod length?

I thought about priming the oil pump in order to pump up the hydraulic lifters, which might be closer to normal operations. However, opinions on whether to pump up the lifters for setting valve lash is much debated.

I would really appreciate your thoughts on the matter! Many thanks in advance!

Regards, Joost