Fiat TC 1592/1608 bore spacings

Road-race engines and ancillaries - general discussion
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Lee67
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Fiat TC 1592/1608 bore spacings

Post by Lee67 » Thu Feb 16, 2017 7:16 pm

Hi all

I know there are bore spacing differences between the 1438/1608 blocks and the 1592/1756/1995 blocks but does anyone know how much difference there is??

Could a crank from one "family" be used in the other? i.e. 1608 crank in 1592 block or vice versa?

As always...thanks for any comments/info

Lee
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Spider 1969
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Re: Fiat TC 1592/1608 bore spacings

Post by Spider 1969 » Fri Feb 17, 2017 7:14 pm

Hi Lee,

Did some measurements on a 1756 and 1608 engine today. As you probably know the 1592 and 1756 share the same crank and block dimensions but the 1756 has an 84 mm bore and the 1592 has an 80 mm bore. I measured from the centre between cylinder #2 and #3 towards the rear and front. See attached picture. The total length of the 1608 block is 390 mm and the length of the 1756 is 397 mm.
I did not measure whether the centre between bore #2 and bore #3 is the centre of the block itself, it seems it is not.

As crank shaft journals are different diameters I would say cranks are not interchangeable. Also spacing may be an issue but as the sumps are still on I did not measure this.

Hope this is of help.

Why would you want to interchange crank shafts? Do you have one that's out of specification?

Regards,

Charles
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Bore spacing comparison-001.JPG
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Lee67
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Re: Fiat TC 1592/1608 bore spacings

Post by Lee67 » Sat Feb 18, 2017 11:40 am

Hi Charles

Thanks very much for doing this, much appreciated.

I was certain of the 91mm bore centre distance on the 1592/1756 block but your measurements on the 1608 block confirm what I thought and what we both suspect - that the 1592 crank won't work in the 1608 block.

The reason I'm asking is that a friend has a 1608 engine (125A block) with what he is certain is a 1592 crank in it. He's had the crank measured and it has a 79.2mm stroke which is indeed the stroke of a 1592 crank but I fail to see how this would ever work in the 1608 block. And furthermore why would anyone ever try to make it work?

Considering there's only 0.8mm difference in stroke between the 1608 and 1592 cranks I think it's likely to be an error in measurement more than anything. I've also passed on crank journal measurements for the 2 cranks for him to check which should help determine what he actually has.

Again, thanks for the info and input...thank you.
Lee
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