Block Liner "Nip"

[markjonesx 1]

Having done some reading on 900 series engine builds, I have a question regarding the liner to engine block "Nip".

The manual says that you should have a "Nip" of +0.003 -0 to +0.005 in.

Do all the Liners come exactly the right size? if your our of tolerance what do you do?

[Sir Paolo 5]

In theory liners are supposed to be made to the right tolerances, so yes. But 3-5thou is about the thickness of a piece of thin paper, so the margin of error is minute.

After market liners may or may not be to the same standards, although I understand Westwood ones are OK.

I still had problems even though I bought genuine Lotus pistons/liners. I had to have the block deck skimmed by a specialist to bring nip within tolerances.

It depends it the nip is too high or too low on what course of action you take.

Liners do not all have to be exactly the same nip, the accepted difference betwen them as the WSM states is 1thou.

Another thing to be mindful of is to keep the heights uniform i.e. install the liners so that they go from high to low, or low to high (within tolerances of course), but not low to high to low or vice versa.

[910Esprit 548]

measure and record all the liners 'nip' in the one bore. Then use one liner and measure and reord the nip in each bore. You can then arrange the longest liner in the deepest bore to the shortest liner in the shorest bore. There are also 2 permutations of rotation for each liner. I've always got in spec using this approach.

[markjonesx 1]

There are also 2 permutations of rotation for each liner.

What does this mean?

[andydclements 790]

You can turn the liner through 180 degrees so that what was exhaust side is now inlet side. It works on the basis that there may be 1/2 or 1 tough of run-out around the base of the liner or block face that it mates to, so turning it may lower or raise the top of the liner slightly.

[markjonesx 1]

What sort of gauge do you use to check the nip?

Normal DTI? Anyone got a pic/link?

[lotus4s 24]

There is a specific tool for the job which is basically a dial indicator and bar mount but lacking that, you can use a straight edge across the bore and feeler gauges.

[910Esprit 548]

I use a DTI, with the stand simply located on the head surface of the block adjacent to each bore in turn. A bit fiddley, but perfectly repeatable.

[Sir Paolo 5]

I'd avoid using feeler gauges, there too fiddly when trying to achieve such critical measurements.

I use a depth micrometer and a machined flat bar with holes that line up with the liner and block, when in position.

[yeller77 114]

Reading this thread with interest as I've now finally got my block on a stand after being in bits for ages and the nips are all over the place!