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|T O P I C R E V I E W|
|melle||Posted - 04 May 2017 : 17:12:20|
I wonder what the weight difference is between 1.5 and 1.7 balance shafts. I've weighed a few 1.7 balance shaft on more or less accurate kitchen scales and they all weighed in at 2014 grams (including the woodruff key). I didn't have accurate scales handy when weighing what I assumed was a 1.5 shaft, but it weighed roughly only 20 grams less. I'm confused: were my scales that inaccurate, did I accidentally weigh another 1.7 shaft or is the difference in weight between 1.5 and 1.7 balance shafts indeed negligible?
|8 L A T E S T R E P L I E S (Newest First)|
|melle||Posted - 06 Oct 2018 : 11:23:08|
That would be my guess as well.
|Dynorog||Posted - 06 Oct 2018 : 10:52:52|
Hi Melle I would guess that the holes would be in different locations due to inconsistencies in their casting , different amounts of flashing and maybe slightly different densities of the metal?
|melle||Posted - 06 Oct 2018 : 10:25:24|
I couldn't find any difference in the counterweights, apart from the holes drilled to balance them. Couldn't detect any logic there either, some shafts with the same part number have holes in different positions.
I've weighed con rods in the past, iirc they were within 6 or 7 grams from each other. Max acceptable weight difference according to the factory manual is 13g, so not too bad.
|Jon||Posted - 05 Oct 2018 : 16:53:59|
The overall weight of the shaft isn't important, what's important is the weight of the counterweight that opposes the counterweight of the crankshaft.
As for the differences in total weight: if we take the average weight of the 5 balance shafts to be 1995 grams, then +/- 45 grams is a highly acceptable manufacturing tolerance for a 1960s cast iron component.
Another interesting game would be to weight the connecting rods on the same engine :-O
|melle||Posted - 10 Apr 2018 : 15:40:04|
Got the chance to weigh a few more, all from engines I've broken myself, so I'm sure of their origin.
All weighed including woodruff key.
1933 gr. (from 1.5, no part no)
1982 gr. (from 1.7, no part no)
1993 gr. (from 1.7, no part no)
2028 gr. (from 1.7, part no 405 889, Ford parts book says this is for a 1.2-1.5)
2042 gr. (from 1.7, part no 405 889)
I've now weighed about a dozen in total, lightest so far is 1928 gr., heaviest 2042 gr. I compared the 1.5 and the 1.7 balance shaft design and I can't tell any difference, counterweight positions look identical to me. Still none the wiser!
|melle||Posted - 12 Sep 2017 : 16:11:46|
Right, I've weighed five balance shafts, all on the same scales as I used to weigh the 1.7 shafts I did earlier, and they all had different weights.
In the pic:
1928 gr. (no part number)
1990 gr. (part # 405 889 = 1.2-1.5 according to a '74 Ford parts book)
2024 gr. (also # 405 889 iirc)
All counterweights are identically positioned, but have different balancing holes drilled. I didn't have a known 1.7 balance shaft handy to compare the designs.
The other two I weighed didn't have part numbers and were 1930 and 1962 gr. (one had a woodruff key fitted, can't remember which one. The woodruff keys are 4-5 gr. apiece). Some have a date mark and they also have different stamped numbers like "8" or "14". This is something I noticed on camshafts as well, does anyone know what these numbers mean?
|melle||Posted - 04 May 2017 : 19:10:41|
Because they had the 1.7 LC engine I suppose? You're right in that the S&R guide advises the lighter 1.5 balance shaft for tuned 1.7 engines, I guess to diminish reciprocating mass?
The 1.5 balance shaft is Saab part number 88 11 333 and Ford part number 405 885.
The 1.7 balance shaft is Saab part number 88 48 301 and Ford part number 436 208.
|Woody||Posted - 04 May 2017 : 18:59:52|
I have understood that the balance shaft was common to both engines as it is stated in SS&R guide. Not sure what info in Saab W/S manual.
Now you have prompted the question, checking the parts book shows another shaft listed from 96.6000 /95095 for USA models. But why?