My 2.5 L rebuild was prompted by a "spun" #3 rod bearing. Because the bearing had spun,
it was doubtful that the #3 stock rod could be reused.
This prompted me to order a set of Pauter rods through a friend of mine who is a distributor for
I did not really get the Pauters because I thought they would be better than the stock rods.
By many accounts the stock rods are strong enough to withstand a beefed up 2.5 L S14. But buying a new
set of Pauters was actually cheaper for me than trying to acquire and recondition a used set of stock
rods. And although the stock rods work well, once you hold a nice custom rod in your hands it is difficult
to resist. Also the Pauters are lighter than the stock rods which is a plus at high RPM's.
The Pauter rods come with ARP rod bolts. There is little doubt that
are among the best in
the industry. And rod bolts are probably the single most stressed fastener in any high revving engine. Thus
it makes sense not to cut any corners in this area. A good set of rods with a strong big end and a quality
set of rod bolts will go along way towards letting your engine stay in one piece as the rev's climb. There is also a high
probability (in my opinion) that the rod bearing failures which S14's are known for are at least partially caused by detonation.
A strong bottom end will stand a much better chance of surviving occasional detonation.
The general specifications for the Pauter rods were written on a card which came with my order. These values
are apparently measured for every set of rods that they produce - truly custom. I have included the mass
values for the stock BMW S14 rod as a comparison point:
Pauter Rod Specifications
| Big end mass
|| 409 gm
|| 466 gm (stock)
| Total mass
|| 579 gm
|| 665 gm (stock)
| Center-to-center length
|| 5.670 in
| Small end diameter
|| 0.8667 in
| Big end diameter
|| 2.0472 in
| Small end width
|| 0.941 in
| Big end width
|| 0.940 in
Here we see my original BMW connecting rods, which I brought to my trusted machine shop
so that they could check the big ends for "out-of-roundness".
I figured that one rod would be bad but maybe the other three could be salvaged. The machine shop said that
indeed one of the big ends was slightly out of round, but that it was no big deal to fix. They felt the damage
was not nearly bad enough to warrant throwing the rod away. The way they fix the big end is to machine a very
small amount off of rod cap. This has the effect of making the big end ID undersize.
Then they bore/hone the big end back to its nominal ID, but in such a way
that the hole is offset, away from the pin area. In this way they maintain the original rod length to within
0.0005". I had the rods reconditioned at a very reasonable cost. But there is a strong feeling among the
experienced S14 engine builders in this country that once a bearing is spun, the rod is junk.
Thus, whether I would ever use that particular rod again is unclear. A new set of rods is not "that" expensive -
$1000 will buy you a very nice set of rods from several respected manufacturers (Pauter, Carillo, Crower etc.).
Pauter rod compared to stock unit »