Push rods for solids are aluminium, just like the block. Push rods for hyro lifters are steel!

 

Al has roughly 2x steels coefficient of thermal expansion.

 

After some quick calcs....

 

With steel push rods, The cold intake valve clearence goes from 0.25mm cold (as per factory specs) to around 0.47mm hot!! (i.e. the al block expands twice as much as the steel push rod as it heats).

 

Hence why my engine was so noisey when hot. Changed the lifters over (not a fun job) and its 768% less noisey, 457% nicer to drive in, and 3% less likely to wake me up if someone is stealing it.

83 turbo should already by hydro??

 

I guess I'm not following you here.

 

Using solid lifters with steel rods..... well as long as nothing gets bent I don't see why you couldn't. It wasn't done initially because it wasn't needed, and the push-rod is the "fuse" in case something goes wrong. The steel ones will not bend, and with a solid lifter you risk breaking something in a serious way.

 

GD

83 turbo should already by hydro??

 

I guess I'm not following you here.

 

Using solid lifters with steel rods..... well as long as nothing gets bent I don't see why you couldn't. It wasn't done initially because it wasn't needed, and the push-rod is the "fuse" in case something goes wrong. The steel ones will not bend, and with a solid lifter you risk breaking something in a serious way.

 

GD

 

Originally it was hydro. Someone before me rebuilt it (did an awful job) and replaced hyros with solids. Left hydro rockers and push rods in. When i rebuilt it, i kept that setup. It got terrible valve tap when hot.

 

What i've said below explains why you shouldn't use this setup - the different metals expand different amounts as they heat up, causing the tappet clearence to INCREASE as the engine heats up. 0.47mm is far too large a valve clearence.

 

They should slightly decrease with aluminium push rods due to the steel valve stem and the higher temp of oil than coolant. Thats what you want - the engine is a bit tappy when cold but quietens out as it heats up.