Solid tappet conversion

[Henka]

I've seen alot of people going to soild tappets, not on this forum though. Now, to convert a ABY for instance, couldn't you just use the tappets from a older VW/Audi engine that had solid tappets?

What would the performance gain be? I've seen cams being sold that are "only for soild tappets" or "only for hydraulic lifters/tappets" - is there a difference? Are the cams made for hydraulic tappets compensated for the deviation of the tappet, meaning a conversion to solid tappets would give them toooo much lift? How much more lift is so?

How would you adjust them?

[AnLe]

I've seen alot of people going to soild tappets, not on this forum though. Now, to convert a ABY for instance, couldn't you just use the tappets from a older VW/Audi engine that had solid tappets?

What would the performance gain be? I've seen cams being sold that are "only for soild tappets" or "only for hydraulic lifters/tappets" - is there a difference? Are the cams made for hydraulic tappets compensated for the deviation of the tappet, meaning a conversion to solid tappets would give them toooo much lift? How much more lift is so?

How would you adjust them?

vw orginal solids have different diameter on cam than hydro. And the adjustment is done below the follower, motorsport peopple usually wants them to be adjusted from above, if I remember correctly.

Cossie lifters in Mercedes 2.3 16v engine, and maybe the real cossie has same diameter in lifters, there may be source for "bolt-on" solid head parts.

[~Delta]

Solid and hydraulic tappets on the VAG engines (1980 - 1998) have the same diameter. They are however not directly interchangeable, the cylinder head of the ABY needs some machining IIRC, as the solid lifters are deeper measured from the shim to the contact point between the valve stem and the underside.

There isn't really a performance gain, though the maximum safe RPM is increased and the valve timing remains stable (hydraulic lifters don't like sustained high RPM as you'll find out after an extremely spirited thrash in the lower gears - they rattle on tickover till the air pockets in the lifters disperse).

The camshafts for solid lifters is different to hydraulic items. The Sport quattro (KW) engine ran solid lifters. The original Audi S8 also had different cylinder head castings with solid lifters.

Either way, not a cheap exercise, I would be careful whom I entrusted to carry out the cylinder head modifications to run solid lifters, get the combination wrong, i.e use the wrong camshaft, the valves will be mashed into the pistons.

[AnLe]

I said too generally, I mean the camshafts diameter is different, so the lifters "height" is different, need longer or shorter valves to use them, or change cams.

[AnLe]

As toying around same idea, I went straight to ETKA to see S8 followers, and yes, 220kw engine has compensation pieces 0,05mm increments listed, but as far as I can use google and etkas atp search, the actual followers are hydraulic but still uses mechanic-kind-of compensating.

exhaust and intake has different followers:
intake: 077 109 309 J
exhaust: 058 109 309 E

Would love to see what is written in factory repair manual about these.