How to I.D. heads

[Mykeys Toy]

EA81 types from other OHV heads. I have a two heads hanging out in the back of a fixer beast and thought I may be able to put them to use if I knew what they belonged to.. big thing I think would be solid or hyd lifters?

 

Mike

[TomRhere]

The way I understand it, the heads themselves are basically the same between Hydro and solid lifters, (if both heads are of the large valve type). It's the lifters, pushrods, and rocker arm assemblies that are different between the two, camshaft may be different too.

 

Hydro rockers look the same as the solid ones, but the Hydro ones have a locking tab under the adjusting nut, where the solid ones do not. You just need to use the rocker assembly for the type of motor you're putting the head(s) on.

[GeneralDisorder]

Hydro rockers look the same as the solid ones, but the Hydro ones have a locking tab under the adjusting nut, where the solid ones do not. You just need to use the rocker assembly for the type of motor you're putting the head(s) on.

 

The locking tabs come with a good gasket kit, so you might see them on some solid lifter engines as well if they were added later. Best way to tell hydro from solid is to look at the end of the pushrod itself - the solid's have aluminium pushrods with steel "caps" on either end which can be clearly seen with the valve cover removed. The hydro's have a solid steel pushrod with no cap.

 

I'm not entirely sure about the way to tell small-valve vs. big valve heads apart - the best way is to measure the valves of course. The intake valves are 2mm larger on the big valve heads. The casting differences may also indicate small valve if there are two bolt-holes on the bottom of the head for 10mm bolts that bolt to the older block castings. Later solid lifter blocks (83/84) and all hydro blocks do not have the large boss on the block casting for those bolts.

 

I don't have any small-valve engines at the moment so I can't get pictures of these differences. If someone wants to take pictures of the head/block mating area from under the vehicle on their 80-82 small valve engine then I could supply comparison pictures of the larger valve varieties.

 

GD

[TomRhere]

Isn't there something about the shape of the valve cover between the two? Thought I read on here that the small valve ones had rounded corners where the large valve ones had the angled corner.