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I changed p&c and head in engine - No valve gap!! WHY??

Hi,

Well, I replaced the pistons and heads in my bug, and now when I adjust the valves, I find I'm running out of screw and on one valve in particular, it is the rocker arm that is pressing against the valve spring with a gap 0.004. My engine is a Mexican engine I bought Mahle forged pistons, stock size. I bought new stock size heads which turned out to be made in Brazil ( seemed kind of cheap as compared to the Mex heads with 3/4 inch deep plug holes, and seemingly more solid casting) I replaced the pushrods with EMPI steel rods which when I compared to my "stock" pushrods they looked to be the same length. I put the rubber gasket on the rocker arm studs, and re-used the Mex rocker arms. Everything was torqued properly Now when I go to adjust the valves @ 0.006, I find that the adjusting screws for each valve are just about backed out all the way, just litte threads are noticed through the rocker arm. One of the adjusting screws is all the way out and the rocker arm itself is giving about 0.004 gap to the valve cap. Ok, so I put the engine in the car and ran it with the hope that this would somehow give me some more play, but the valves just got tighter. SO I learned that lesson - car ran great though.

It seems for things to give no or very little valve lash - it would have to be,,

1) pushrods are too long - don't think this is the case - they are seem exact by eye compared to the original ones. 2) The distance between the block and the outside of the head is shorter - but why would this be? Could it be cheap quality heads? - not having the correct flycut depth? ( into the piston too far?). I would think the pistons are the correct length.

Are the rocker arms now of an improper size with this combination?

How can I solve this? What would be the consequence of putting a thin shim under the rocker arms - where it bolts to the head? That should afford me clearance - argh.. but something is not right? Am I missing something?

Thanks so very much!

Matt S

Reply to
Matt S
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i seem to recall that there are actually shims that are made to go under the rocker arms- sort of a wave washer? it's been a while but what you describe makes sense... shorter cylinders... or deeper cuts on the heads-

jjd

Reply to
jdowling

Try using the stock pushrods. They are better anyway. The new ones might seem to have the same length, but the ball ends might have slightly different diameters, so the pushrods don't seat properlly in the rocker pocket or the lifter pocket. Also check that they were properlly seated in the first place.

If you find that you have the same problem with the stock pushrods, then you will have to cut the pushrods to the correct length.

Bill, '67 Bug.

Reply to
Vassilis Spiliotopoulos

could it be that I do not have them seated properly in the lifter pocket? Is this something that has to be paid attention to when installing the pushrods? I thought once you put them in, they "automatcially" go right into the pocket without any trying to get them there.

Thanks

Matt S

Reply to
Matt S

They usually go right into the pocket, but sometimes they bind. Since you ran the engine, I believe that they have seated all the way in.

To check if they are properly seated, remove the valve covers, and when the valves are fully closed (at the adjusting position), try to rotate the pushrod with your fingers. It should rotate easily without any signs of grinding.

Why don't you try the old pushrods? You will know imediatelly if it is a problem with the new pushrods, or if you have to cut new pushrods to the correct length. If the old pushrods behave exactly as in the old engine, then use those. They will result in a correct valve geometry and thus the valve guides will live longer and you will have better performance. If you discover that you have to cut new pushrods to the correct length, then you have to read about setting valve geometry first.

Another thing you must keep in mind if you insist on using steel pushrods, is that steel pushrods have different thermal expansion rate than aluminum pushrods (such as the stock ones) and need different (a bit tighter) adjustment than stock ones. You will have to find the best adjustment for your engine, in other words you must really know what you are doing. Then note it somewere visible on the engine, so that if a valve adjustment is to be performed by someone else in the future, he'll know where to set the valves to.

Bill, '67 Bug.

Reply to
Bill Spiliotopoulos

Bill, Thanks for your note, I will try the old pushrods, and see how they fit. Thanks for the info.

Matt S

Reply to
Matt S

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