Thread: Cosworth bore size??
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Old Mar 4, 2009 | 07:53 PM
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B16CVH
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From: West Mids
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Originally Posted by BigErn
Did a quick search but nothing jumped out at me so sorry if I missed it.

I measured my block today for the Sapph Im rebuilding and just wondered what size was standard, so I know if I need to get it .25 or .5 etc.

The measurements I took were, as if you were stood lookng into the bay of the car, from left to right in the bore and front to back to check for ovalling too.

This is what I got anyway.....

Cylinder 1. L-R = 90.80mm F-R = 90.40mm
Cylinder 2. L-R = 90.65mm F-R = 90.60mm
Cylinder 3. L-R = 90.49mm F-R = 90.71mm
Cylinder 4. L-R = 90.62mm F-R = 90.61mm

Those sound about right or do you think Im doing something wrong??
There is a slight lip at the top of the bore and now I come to think of it thats where I measured from, do I need to measure under the lip?? If so, how??

If it makes any difference Im using one of these http://buy1.snapon.com/catalog/item....re&dir=catalog


I also measured my head too while I was on and got...

Front - 139.15mm
Rear - 138.92mm
STD bore size is 90.8mm so in guessing thats what yours is. Measuring the lip will give you a good indication of the size as this will be the "original" bore size as it has had no wear. You will get a larger size left to right as the bore do oval over time on the faces that recieve the most punishment (L&R). First oversize will do just fine.
A bore guage is better for measuring but what you have used is good enough to get some figures.
Last edited by B16CVH; Mar 4, 2009 at 07:55 PM.
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