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Hydraulic valve tappets 16V 1978

 
Old 06-30-2019, 11:04 AM
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Ad0911
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Default 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.
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Old 07-10-2019, 05:34 AM
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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!



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Old 07-10-2019, 05:46 AM
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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.
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Old 07-10-2019, 06:21 AM
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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.
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Old 07-11-2019, 12:12 AM
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Alternatively make a bushing with oil holes for the SOHC cam Housing to reduce it from 38-35mm to use DOHC lifters.
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Old 07-11-2019, 05:22 AM
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Originally Posted by V2Rocket View Post
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.
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Old 07-11-2019, 02:59 PM
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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?
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