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308 bore size?

Started by _darrenmark1_ , Jan 15 2009 08:25 PM

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#1 _darrenmark1_

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Posted 15 January 2009 - 08:25 PM

i bought a 308 today with a bore size of 102.5mm any idea if that's 40 thou over?

#2 rodomo

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Posted 15 January 2009 - 08:40 PM

Yeah, what he says below, sorry to scare you :D
I'm building a shed at the moment and 100mm = 4 inches.

Edited by rodomo, 15 January 2009 - 08:54 PM.

#3 TerrA LX

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Posted 15 January 2009 - 08:45 PM

Bore Size: 102mm/4in
Stroke: 78mm/3in

102.5 is approx. 020 thou over.

#4 _gtr2600S_

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Posted 15 January 2009 - 08:49 PM

i bought a 308 today with a bore size of 102.5mm any idea if that's 40 thou over?


102.5mm = 4.0354" So, simply subtract the difference from a standard bore size (whatever that is) to determine the oversize.

308 standard bore = 307.81 ci
308 +.010 = 309.32 ci
308 +.020 = 310.84 ci
308 +.030 = 312.37 ci
308 +.040 = 313.89 ci
308 +.060 = 316.96 ci
308 +.065 = 317.73 ci 5.206 litres

Capacity is determined by the radius squared X pi X the stroke X the number of cylinders

#5 rodomo

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Posted 15 January 2009 - 09:00 PM

http://www.convertun...om/mm/to/inches

#6 _gtr2600S_

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Posted 15 January 2009 - 09:05 PM

http://www.convertun...om/mm/to/inches


Yeah, this is OK...or 'google' Josh Madison and download a small freeware application, Convert..looks like it converts 'everything'.. :D

#7 _darrenmark1_

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Posted 15 January 2009 - 09:12 PM

with my calipers

4 inches = 101.6mm
4.0355 inches = 102.55mm
is 10 thou .25mm of a inch?
or is .5mm 10 thou of a inch?

#8 _gtr2600S_

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Posted 15 January 2009 - 09:19 PM

with my calipers

4 inches = 101.6mm
4.0355 inches = 102.55mm
is 10 thou .25mm of a inch?
or is .5mm 10 thou of a inch?


.010" = 0.254mm

0.5mm = 0.019" (nearly 20 thou)

If you download the small application, you can do the conversions yourself.

Here: http://joshmadison.c...rt-for-windows/

Cheers, T

Edited by gtr2600S, 15 January 2009 - 09:23 PM.

#9 _darrenmark1_

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Posted 15 January 2009 - 09:27 PM

right then

so it would be 40 thou out!!

ACL say a standard bore is 102mm is that the case or is that just for ease as 4 inches in 101.6mm
so by that calculation 102.5 is 40 thou over.
Thanks
now i will figure out what to do with it. i would prefer 20 or 30 thou out for a rebuild.
i was gona put it in my sons LH 3300 SLR. Duno now.

after 40 there is only 60 and i rekon thats to far, any idea what resleeving costs?
It has a good date code or i would just go and get another block.

#10 TerrA LX

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Posted 15 January 2009 - 09:33 PM

:wtf:

020 thou over

#11 rodomo

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Posted 15 January 2009 - 09:35 PM

Did it come with pistons? The size should be on the top.
.060" is O.K. for a streeter, just get the block sonic tested for piece of mind. It doesn't cost much.
Also, if it is just a street motor, a good engine builder can bore to the wear to maintain wall thickness.

#12 _darrenmark1_

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Posted 15 January 2009 - 09:38 PM

Ok I'm a idiot!
the guy i bought it from said it was 40 thou out, but maybe he meant it needed to go to 40 thou out.

I'm old and its all very confusing to a senior citizen.

Metric to imperial. thou to mm

if its 20 out that's all good

#13 _darrenmark1_

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Posted 15 January 2009 - 09:41 PM

Did it come with pistons? The size should be on the top.
.060" is O.K. for a streeter, just get the block sonic tested for piece of mind. It doesn't cost much.
Also, if it is just a street motor, a good engine builder can bore to the wear to maintain wall thickness.


nah no pistons. if it did i would look at them. and read the size. just going by what the guy told me.

Its a 308 with a 74 date code 20 thou out(so we have figured out) for $200 bux. Not bad

#14 _SS Hatchback_

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Posted 15 January 2009 - 09:41 PM

is the block already been machined? if it hasnt then the machinist will let you know how far it will have to go then you can decide, if it is already machined then 102.5mm going by above posts is 20 thou

#15 rodomo

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Posted 15 January 2009 - 09:42 PM

You can't be that old if you can still read your verniers :spoton:

#16 TerrA LX

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Posted 15 January 2009 - 09:43 PM

No offence, was spelt out over three times tho.

At this point you may get away with a clean up with the present 020 depending on the bore condition or choices are 030 040 etc etc.
030 is good for a stocker or if you going all out then 040 will have the biggest range of pistons AFAIK.

Edited by ALX76, 15 January 2009 - 09:44 PM.

#17 TerrA LX

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Posted 15 January 2009 - 09:47 PM

Actually come to think of it the sales person could be right, if ur using verniers you may want to measure it with an inside mike or bore gauge as .05mm may be hard to pick up on the verniers.

#18 _darrenmark1_

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Posted 15 January 2009 - 09:58 PM

i spun it around in all eight bores (different sides etc.) they were all the same. 102.5. and i had to use my monicle to see it.
haha

#19 TerrA LX

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Posted 15 January 2009 - 10:02 PM

I think you may have an 040 thou over block sorry.

#20 _darrenmark1_

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Posted 15 January 2009 - 10:10 PM

i thought as much..

any idea on a re sleeve?

How much

Thanks

#21 _82911_

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Posted 15 January 2009 - 10:53 PM

IF you have been acurate with your measurements then your bore size is = 4.035" or .035" overbored.
IF you are using a .030" oversize piston then you have a piston to bore difference of approx .005".
When measured accuurately this will probably drop to around .003". Which would indicate a cast OEM type piston, or your initial measurement is slightly inacurate and your bore size is actually a little larger than you measured....
Either way..... it is .030 over.
If it will clean up with a hone, then that's the end of it. If not go .040 over.

Cheers Greg..

#22 GML-31

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Posted 15 January 2009 - 11:21 PM

the amount most of time most of these cars are driven most of us will be dead before they need another rebore
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