Hydraulic valve tappets 16V 1978
 

I am in the process of assembling my engine. It is a 1978 4,5L 16V. Recently I acquired a spare 1977 engine with a one cylinder head taken off and reconditioned. I noticed that I could push in the central shaft of every hydraulic tappet. This is not possible with the tappets from my own engine. How is this supposed to be? I can push in the shaft by using a clamp with lots of force but by far not as easy as the tppets from the spare engine. How is this supposed to be? I always thought that this would cure itself if the engine is running again perhaps this is wishful thinking. Can anyone share their experiences. In the picture ther left one is the '77 tappet, the right one is the '78 tappet from my engine.
https://cimg0.ibsrv.net/gimg/rennlis...16b681a93a.jpg

I have had a lot of recent "experience" freeing up my lifters. All of the lifters in my engine (M28/12 4.7) were solid!
I bought a few used ones from 928 International (if you need some, get them as they are very cheap - new lifters are a few hundred $ each!!)

Anyway I soaked mine for various lengths of time and in various solutions with limited success! Maybe 2 or 3 freed up, and this was with lots of effort (I tried soaking them in petrol, acetone, mentholated spirits, a mix of acetone and transmission fluid, and so on), but I did not get the success that was needed!
Plus rotating the piston and trying to compress (by hand).

My last "resort" was to apply pressure (similar to what you did) by putting in a crude press. This worked and I was able to free up all my lifters! I think the length of time that they soaked did help in the end, as they freed up quite easily with the pressure applied - I did measure the movement and I think it was 3 or 4mm (don't quote me, I will measure again...)

The surface of the lifter is coated, and this is called parkerizing, a very hard coating, a very light polish can clean these up if needed, careful not to scratch or mark it though!
I now have a good selection of lifters to use and will pick out the best ones for my engine.

Exploded view, one came apart while cleaning, they are very simplistic in their design, just bloody expensive!

https://cimg6.ibsrv.net/gimg/rennlis...71803233e0.jpg
https://cimg7.ibsrv.net/gimg/rennlis...6d29607b99.jpg
https://cimg8.ibsrv.net/gimg/rennlis...6d3783bc3a.jpg

I will add to the above in that while soaking the lifters in various solutions I did flush out all the old oil and lots of carbon/ oil deposits as well - a lot came out and this would have led to them being able to be freed up.
It took a lot of effort to get the fluids in the tiny holes and then into the central chamber...….

I plan to try and refill them by "cooking them" in engine oil, an old pan on the stove full of oil and compressing the piston.

Yes, the 38mm hydraulic lifters for the 16V engine are extremely expensive. So far I have not tried to free up my lifters but the four punch marks are there to avoid the small plunger to fall out. The punch marks need to be removed by grinding/machining in order to get the plunger out. I know Lindsey Racing did offer a service of disassembling/cleaning of the 16V lifters (same lifters in 944 SOHC engine) but they do not do that anymore. I have found a Mercedes 40mm hydraulic lifter that possibly can be used but machining of the lifter bores will be necessary. There are also 42mm lifters for Ford available. Have not been able to source another 38mm hydraulic lifter. The 32V engines have smaller 35mm hydraulic lifters.
Åke

Alternatively make a bushing with oil holes for the SOHC cam Housing to reduce it from 38-35mm to use DOHC lifters.

There is a reason why the 16-valve engines do have larger diameter lifters. I have not checked but it may be a problem the cam lobe will ride on the edge of the smaller lifter. If that happens the cam lobe will wear down quickly. It will be less work to bore out the lifter bores for 40 mm oversize lifters than fabricating and installing bushings.
Åke

If I understand correctly, the hydraulic lifter should be compressable by hand (thumb) but they are stuck quite often. There is no proven method of freeing them but to get them moving it can be achieved with big force (clamp, vice). Soaking them has moderate results.
But will they ever return to normal?

So now I have some extra lifters. The ones I already had from my old engine have been hot soaked in degreaser, after that they were dried and hot soaked in engine oil. During the cleaning process a lot of crud came out. The central shaft or pin or plunger or whatever it is called can be pushed in with big force from a vice and they will come back in their original position, albeit a bit slow. The extra set I have can be pushed in by thumb. So the big question is:

Which are the good ones? This is importnat for me because I am at the point of assembling the camshaft towers and put them on the engine.

Hi

What conclusion did you reach on this?
I'm about to reassemble the cam towers and i'm debating what i should do with the lifter. All of them move freely after soaking in degreaser and then rinsing with clean oil. I'm therefore concluding that they should move freely initially vs dampened? I tried forcing oil in by placing the lifter in a sealed jar with engine oil in and then creating a vacuum - the aim being to stimulate what would happen when engine oil pressure did this in normal operation as the engine warmed up. This worked ok as i could see bubbles coming out of the holes but only made a slight difference to the pressure required to compress the piston, i concluded that the test method simply wasn't creating enough pressure to force the oil in.
I purchased a couple of extra's from a breaker and was planning to try dissembling them by dremelling the stake marks and removing the piston - the aim being to see if i could clean them as per the later 32v versions which don't have the stake marks and are therefore easier to clean. Not sure if i should bother or not though!

Interested in your experience with this.

I tried cleaning them by injecting degreaser in the hole and immersing the thing in degreaser in a heated ultrasonic bath. Some dirt came out. After taking the degteaser out by heating them with the hole down I then put them in a heated oil bath to absorb some oil. The plunger still feels very stiff. I can push itt down slowly with force bu not with my thumb. Another set I have is easier. These I can push down by thumb. I still don't know what it should be like

I soaked mine for many weeks, even months in mainly petrol or acetone, all the while turning them and tapping them to remove all the debris inside. I then broke the seal/ seize with a vice/ press and all now feel the same and are very easy to depress by hand - there is no difference between the used ones I bought and my original seized ones. I picked out the best 16 and put back into my car.

The original Porsche 38mm hydraulic lifters (INA 420 0009 10) are very expensive.
I have sourched a Mercedes 40mm lifter (INA 420 0001 10) that could be used. I have to look further into the matter.
However machining of the lifter bores in the cam houses will be necessary.
Åke
https://www.ebay.com/itm/Ventilstose...QAAOSwSXFeLLWo

I now have the curious option of having to choose which lifters to use, since I have a double set. The lifters from my 1978 engine (70,000 miles on it) are all very hard to compress. I need a vice to do that. But the plunger does compress and retract. This engine appeared to have been taken good care of by the 1st owner. Engine was rather clean inside and out. Hardly any carbon buildup around the rings and on top of the pistons. I could wipe it of with a cloth or brush and degreaser. The fuel tank was clean inside. The second owner screwed it all up by quick fixes here and there.
The other set I have is from my spare 1977 engine. This engine has a lot more miles done by the looks of it (very dirty) but has been put into storage somewhere approx 10 years. These lifters can easily be pushed in using my thumb.

What is the best choice here?

Soak the original ones in a cleaning solvent over many days/ week. Keep rotating them, lightly taping them on a soft piece of wood (or the like) until you get some of the built up residue out, keep compressing them. Eventually they will get the same as the ones that are easy to compress.
Then pick out the best ones based on outside condition, especially the faces.
Mine have been back in now for almost 1000km and running well.