Getting proper piston liner height when liners are flush

[Delorean Industries]

Kris, from the above measuring pictures and dimensions you have given once the block deck surface has a high micron finish applied for true up and gasket sealing you will be within spec. I would advise having this finishing process done prior to your shim measurements as .003-5 will be removed during this. We have switched over to a one size fits all shim process as posted elsewhere on this site and achieve protrusion based on what is required in the block spec true up process and touching the face of the liners.

[David T]

This is terrible.

I have done "top jobs", cylinder heads, on several Deloreans but never the whole motor. I think it shows the durability and longevity of the basic PRV. On many other old cars it is common to have to completely rebuild the motor, not so on Deloreans. On one Delorean I found and restored, it had been sitting for many years. The motor, at first, would not even turn over. After some lubrication and careful movement, I got it loose and it had great compression and oil pressure. My point is, the PRV is a pretty good little motor and most of the time does not require a full rebuild. That said, if you really cook the motor and overheat it badly, it should not be a surprise when it requires a full rebuild. Luckily most (but not all) can be fixed by only doing the heads. It also seems that once you rebuild a PRV, the chances of it leaking coolant seem to be very high unless you really know what you are doing. I see this not from my own experience, but from the posts on this forum over many years. IMHO the motor is the most durable part of the car (if you don't overheat it!).

[Ron]

Assumptions aside , is the negative nip at cylinder 2 or 5?

[bunni]

... once the block deck surface has a high micron finish applied for true up and gasket sealing you will be within spec. I would advise having this finishing process done prior to your shim measurements as .003-5 will be removed during this. We have switched over to a one size fits all shim process as posted elsewhere on this site and achieve protrusion based on what is required in the block spec true up process and touching the face of the liners.

Thanks for the info. After a few conversations with people locally, a touchup sounded like the ideal path. But with the engine being somewhat uncommon I wanted to see if there were other options or to confirm that surface touchup of the block was viable. The deck has not been touched at all since it was originally opened so this would be the first time anything has been taken off (to my knowledge).

I assume that the deck surface prep is something you've done successfully a number of times without issues? Also presuming I follow up with the valve clearance process (again) as well.

... On many other old cars it is common to have to completely rebuild the motor, not so on Deloreans. ... My point is, the PRV is a pretty good little motor and most of the time does not require a full rebuild. ... It also seems that once you rebuild a PRV, the chances of it leaking coolant seem to be very high unless you really know what you are doing. ...

My rebuild was a combination of "I did it wrong" (liners ended up moving), "while I'm in there," and "the experience." Not necessary, but here I am, and I want to make sure I do it right the first time. You highlight a very important point, "leaking coolant." Which is why I'm asking for things that are known working with this specific engine and not a shoot from the hip.

If it were purely a shim, then I'd have no issues stacking them. But they are also a gasket separating oil from coolant, which adds a lot more complexity to the equation. This is why I'm back to square one and want to make sure I do it right. I appreciate your knowledge, but offering an unproven suggestion for something that is the interior-most part of the engine, and one that you deem critical too, is potential waste of a lot of time for people. I know I'd hate to get done only to find that I've now got cross contamination that could now either be a head gasket or a complete rebuild. Having the confidence that the shims are done in a way that is known working makes any future troubleshooting that much easier.

Assumptions aside , is the negative nip at cylinder 2 or 5?

Cyl. 1 has a bit of a skew, one side is a hair under, the other is a hair above. Cyl. 2 is ~0.0005" under on one side, with just a hair under on the other side. Cyl. 5 is basically flush. Same with the rest of them.

I'm curious why 2 and 5 would be special here. I've not come across anything around here that would be a reason these would be negative.

[Ron]

Cyl. 1 has a bit of a skew, one side is a hair under, the other is a hair above. Cyl. 2 is ~0.0005" under on one side, with just a hair under on the other side. Cyl. 5 is basically flush. Same with the rest of them.

I'm curious why 2 and 5 would be special here. I've not come across anything around here that would be a reason these would be negative.

This is confusing because in post 8 you said, "The liner I just tested with is actually a hair UNDER the block, and the measurements with the indicator (and flashlight test) reflect that." Anyway, using the measurements above, you have neither -- All of these liners should be considered to be above the deck or level since you use the highest measurement.
If the nip was negative at the center bore of a bank (2 or 5), you would have to chase down a liner having a nip falling between those on the two ends, to maintain stepping. Otherwise, you could have used use any liner that has a nip <= to the adjacent one (center). (Although some of the manuals ignore step as long as the difference between adjacent cylinders is no more than 0.04mm, I would suggest rotating the high side of #1 toward #2 and the high side of #2 toward#3...)

Back to the shims- If you are still nervous about the shims, call Mike at DMCMW. They do this all the time and I'm sure he will also suggest that you use the yellow shims since the nips are so close. If that don't do it for you Josh had the best solution, imo.

Hope this helps...

P.S. FWIW, I thought you had an adjustable stem (clipped off in your pics...). Sorry for the assumption/confusion!

[bunni]

This is confusing because in post 8 you said ... you have neither -- All of these liners should be considered to be above the deck or level since you use the highest measurement. ...

I apologize for the confusion. I was referring to Cyl. 2 in that post which would be considered negative nip in that situation since the highest measurement is still (every so slightly) negative, correct? In the photos I was measuring liner 1, which was the one slightly above on one side and slightly below on the other, which would mean that during the shimming process, it would be still a positive nip, correct?

Back to the shims- If you are still nervous about the shims, call Mike at DMCMW. ...

Not a bad idea, didn't cross my mind to give any DMC shops a call since I don't usually call a mechanic and ask to troubleshoot on the phone. The only times I try to ask questions of DMC shops is either at tech events, on the forums here (if they respond), or if I'm about to actually send money their way and am asking about a product or a process for it. Though I've surely contacted someone and then later felt like an ass about it. Is calling up shops for things like this considered to be okay in the DeLorean circles?

[Delorean Industries]

Kinda like going to a house of worship. You are expected to tithe as a franchise will only deal with you while one hand is in your pocket. On the other hand, we are always more than happy to tell you the only proper way to do something right for free. But instantly wash our hands of any situation where said advice isn't implemented or continual polling of the internets at large ensues. Six of one-half dozen of the other I guess!

[Ron]

I apologize for the confusion. I was referring to Cyl. 2 in that post which would be considered negative nip in that situation since the highest measurement is still (every so slightly) negative, correct? In the photos I was measuring liner 1, which was the one slightly above on one side and slightly below on the other, which would mean that during the shimming process, it would be still a positive nip, correct?

NP!

Technically #2 has negative nip. But since the specs round at three decimal places, 0.0005" => 0.001, and a hair under is rounded to 0.000". I'd consider it flush and not worry about it because both of the adjacent cylinder's nip are flush = 0.000". I.E., the specs allow 0.0016" step so they will not interfere with the gasket material around #2 from getting the maximum compression when it is torqued down. (Fwiw, I prefer the torque once gaskets and strongly suggest you use them in any case.)

Not a bad idea, didn't cross my mind to give any DMC shops a call since I don't usually call a mechanic and ask to troubleshoot on the phone. The only times I try to ask questions of DMC shops is either at tech events, on the forums here (if they respond), or if I'm about to actually send money their way and am asking about a product or a process for it. Though I've surely contacted someone and then later felt like an ass about it. Is calling up shops for things like this considered to be okay in the DeLorean circles?

Hehe...I basically agree with Josh on that one.

Tithe where you are fed.