I have just pulled down my SSS L-18.
Looked into the bores and saw nice cross-hatching (is it one word?)
or so I thought......
I looked a bit harder (not that much harder but hey ) and noticed that on all 4 cylinders on the outside edge (bore closest to side of block) there was NO cross-hatching!
It is "polished" for about 20mm, and runs down the bores, then there is clear cross-hatching again on either side.

The motor did use up oil (it is a datsun after all) but not a lot.
It pulled strong and blew no smoke. (well it blew a "bit" but I swear it was mixture )

Now I'm pretty sure that that part of the bore wouldn't be sealing properly right ???

Anyone have any clues what the effects of these "polished" bits would be ??? (I'm thinking not good)

What could have caused this ???
(Improper honing of the bore when last rebuilt ?, Improper running in when last rebuilt ?)

I took some pictures and will post em up post haste.

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1975 P610/180B SSS ex PRC3 Rally car (parts car)
1974 P610/180B SSS (parts car)
1972 P510/1600 Currently sitting untouched
1977 P610/180B Wagon Daily Driver

You really need a dial gauge to see if the bore is perfectly round. If its elongated lengthways then that will be why the hone marks are still there but not on the sides.

I think.

Dave

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USA Daily: 2014 Nissan GT-R, very minor modifications for the track
USA Project: 1978 280Z, minor suspension upgrades, VK56DE conversion in progress. SOLD
AUS Race Car: 1973 240Z, L28ET, Autronic, GT35R. SOLD
AUS Project: 1972 1600, 3200km old S15 SR20DET, ground up rebuild. SOLD

When my present FJ20ET was built we noticed that adjacent to each stud in the bores up the top, the rings had not been sealing in an area about the size of a thumb nail. This was due to block distortion caused by tension on the head bolts.

To try to eliminate this a heavy boring plate was bolted to the top of the block when it was bored for oversize pistons. The FJ block is a pretty solid lump too.

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Richard... http://www.youtube.com/watch?v=rqM9_Wq-TKc

The area you describe would be the area where most bore flex is experienced (or comes from) wouldnt it? As it takes more of the crank shaft loading, and hence the rings bite into the bore more in this area?

Meh, i'm probly wrong.

I always thought a block was supposed to be bored with a torque plate and main caps/girdle in place and torqued to the specs it will be assembled at, and operating temperature coolant being run through it?

Dave

_________________
USA Daily: 2014 Nissan GT-R, very minor modifications for the track
USA Project: 1978 280Z, minor suspension upgrades, VK56DE conversion in progress. SOLD
AUS Race Car: 1973 240Z, L28ET, Autronic, GT35R. SOLD
AUS Project: 1972 1600, 3200km old S15 SR20DET, ground up rebuild. SOLD

In an ideal world they do.
You wont get this service unless they have a plate & your prepared to pay extra.

_________________
A little knowledge is a dangerous thing.
www.datsport.com

"R.I.P. Baz. 29 April 2022. Thank you for all your contributions to the Datsun community over the years. You will be missed." - OZDAT

Dave, thats the area of most load on the bore when the rings are forced against the bore on the power stroke.
If thats the only point then its not abnormal for a revving engine.
how may Ks has it done since the rebuild?
chrome rings?

_________________
A little knowledge is a dangerous thing.
www.datsport.com

"R.I.P. Baz. 29 April 2022. Thank you for all your contributions to the Datsun community over the years. You will be missed." - OZDAT

Yeah thats what I thought was the correct procedure.
But doesn't mean it is always done. I'm sure not many machine shops have a torque plate for a L-block.
The pistons currently in are ACL +1mm os, so at some point in it's past it has been rebuilt.
I just hope the damage done isn't to severe. (like cracks somewhere)

thanks guys.....big help.

_________________
1975 P610/180B SSS ex PRC3 Rally car (parts car)
1974 P610/180B SSS (parts car)
1972 P510/1600 Currently sitting untouched
1977 P610/180B Wagon Daily Driver

Yeah Baz that is the only place on the bores with that surface (ie. polished smooth)
I really have no idea when it was last rebuilt.
Would this smooth area cause a lose of compression / blow-by etc ???

You have a nice torque plate don't you Baz ?

_________________
1975 P610/180B SSS ex PRC3 Rally car (parts car)
1974 P610/180B SSS (parts car)
1972 P510/1600 Currently sitting untouched
1977 P610/180B Wagon Daily Driver

Dave, there is likely to be some blow-by, as cyl wall distorsion(sp) is evident. And of course your rings will not seal as well, on the polished area (has it become glazed?) as they will not be able to bite into it.

Dave a run thro with a plateau hone & a set of cast rings should be all thats needed.
would need to check it first of course.

Uless you want to build up a new motor. then ditch the acl slugs

Yes we do have an excellent torque plate its 108mm thick

_________________
A little knowledge is a dangerous thing.
www.datsport.com

"R.I.P. Baz. 29 April 2022. Thank you for all your contributions to the Datsun community over the years. You will be missed." - OZDAT