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1360 bore and cyl wall measurements
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Author:  Kennomini [ Wed Apr 10, 2013 6:09 pm ]
Post subject:  1360 bore and cyl wall measurements
I'm looking at some blocks that are currently bored to 1360, around 2.834 and the cylinder walls are 1-2 0.195, 2-3 0.170, 3-4 0.195.
After some previous chats on here the issue about moving the bores outwards by 0.015 to even up the center cylinder wall. Also David Vizard says to move all the bores backwards by 0.010....by the measurements I have taken are these blocks suited to be 1360 (or bigger in the future) and still high comp 10:1 + etc.

Or should I steer clear of these ones?
Author:  drmini in aust [ Wed Apr 10, 2013 7:08 pm ]
Post subject: 
My 1360 is at standard bore spacing, and running 11.0:1 C/R on 98 unleaded. I have had no gasket or other problems. Ditto my 1412 stroker (73.0mm bore) running 10.6:1.

IMO you can just get away without bore respacing on a road 1380, but not if boring to 1400cc (74.0mm pistons).
Author:  Kennomini [ Tue Apr 23, 2013 10:21 pm ]
Post subject: 
(1) What is the ideal gap between the cylinder wall and the cylinder diameter? (eg 0.010thou)
(2) Also the piston should be measured at the base correct?
(3) And the ideal place the measure the bore is front to back?
Author:  mini_mad_matt [ Tue Apr 23, 2013 11:48 pm ]
Post subject: 
Ideal gap? well ideally as much as you can get? How small a gap can you go? Well you need something for the gasket to seal on, i can't give you a set figure, but there is "enough meat" and then there is "that's not enough meat" :lol:

To measure a piston, you measure the skirt adjacent to the gudgeon pin. Piston manufacturers might specify a certain height to measure at, but it is normally the height of the pin. As far as i know. (could be wrong)

The ideal place to measure the bore is all over the place. You can get special micrometers for measuring cylinder bores i think, but i just use a t-bar and measure that with a normal micrometer. It is easy to use the t-bar to measure from top to bottom and different sides.

However the place most likely to wear would be where the top ring comes up to the top of the bore.

If i'm looking at a block that i don't want to rebore, i will just run a hone similar to this http://www.google.com/imgres?um=1&sa=N& ... =39&ty=113 down it, and i can quickly see how much of a lip and any hollow spots etc. Then i can decide whether it will hone out or need a rebore. If it does hone out then i will measure it and see if it's still any good.
Author:  Kennomini [ Wed Apr 24, 2013 5:59 pm ]
Post subject: 
Quote:
EDIT (1) What is the ideal gap between the cylinder wall and the cylinder (I meant Piston) diameter? (eg 0.010thou)
(2) Also the piston should be measured at the base correct?
(3) And the ideal place the measure the bore is front to back?


I have access to two blocks one is already bored to "1360" the other is still standard.
My new pistons are Hypatec .094thou over (1360).
I'm happy to use the already bored block so long as it's suited, that way we don't sacrifice a std block (that can be used for another/someone else's smaller build).
That's why I want to get my measurements correct before I get ahead of myself.
Author:  mini_mad_matt [ Wed Apr 24, 2013 9:32 pm ]
Post subject: 
So you mean the piston to bore clearance?

That really depends on the piston, if you have new pistons in a box it should say on the box. I think hypatecs are 1.5thou. That's for a new standard rebore, it's not going to be a big deal if you are running a few thou more.

So i measure the piston with a micrometer first, then i get a t-bar and measure the bore. I then measure the t-bar with the same micrometer as before. I then double check the piston with the t-bar's measurement too just because i'm special.

Noting that the skirt of the piston has a larger diameter at the bottom of the piston, so where you measure the piston diameter actually matters.
Author:  Kennomini [ Sun Apr 28, 2013 11:31 am ]
Post subject: 
Just checked/measured the block 2.840" and pistons 2.870" and the box says 0.0015 minimum clearance.
So I'd say I'm good to go with a bore/hone to get it spot on and then it's build time :D .
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