3.0 using 2.7 Rods??

[914obsession]

I tore apart my 3.0, the case had never been split before. Everything inside looked really good, the bearings were in great shape, only reason for the rebuild was 2 broken head studs. I ordered some rod bearings, the GT3 coted version and noticed that my rods are slightly wider, which causes the bearings to be off set a bit. It turns out that the rods seem to have a 2.7 part number except for the weird S symbol at the end - 911.103.105.OR (S). Looking at the pictures in the Bruce Anderson book, the rod looks like a 3.0 rod and not a 2.7 due to the casting. (See photos) I'm lost... I was told the only real difference between the 2.7 and 3.0 rods was the fact that the 2.7's were about 2mm wider at the crank.

If it turns out that I have 2.7 rods, my question is, can I use them for my 3.0 rebuild? I'd have to get a set of 2.7 rod bearings.

My other question- if these are 2.7 rods, how did they get in there?

Any help would be greatly appreciated.










Dan

[Flat6pac]

The only time that 2.7 rods were actually used was for the Carrera 3.0 which for all practical purposes . was a 2.7 crank, rods and ignition.
Your 3.0 from 78 will use different rod bearings. True the length is the same but 2.7 items do not cross with the 78 and later 3.0.
The rods of the time for 930 part numbers was used on the 3.3 turbo.
Bruce

[914obsession]

Based on the photos and part numbers listed, are those 2.7 Rods, I didn't think that any of the 2.7 Rods has the (S) after the part number.

If they are 2.7s can I use them, assuming that I buy the correct 2.7 rod bearings? Is there actually a width difference, if so will it effect anything on my 3.0?

Thanks

[tom1394racing]

Those are 2.4/2.7 connecting rods.

[914obsession]

That's what I started believing until I looked at the pic in Bruce's book (pg. 65). These rods are identical in casting (except the part number) to the 3.0 rods, they look different than the 2.7. For instance the lip around the bearing surface has the arches that the 3.0 has, the casting around the wrist pin has the flat spot near the center and the casting around the rod bolts is identical to the 3.0 and not the 2.7? Also, what's with the (S) after the part number, the 2.7's listed in Bruce's book do not have this. I'm starting to go crazy here...

Bottom line, if these are 2.7s can I use them? How did they get in there???

Dan

[john walker's workshop]

how many flywheel bolts?

[914obsession]

That's what I started believing until I looked at the pic in Bruce's book (pg. 65). These rods are identical in casting (except the part number) to the 3.0 rods, they look different than the 2.7. For instance the lip around the bearing surface has the arches that the 3.0 has, the casting around the wrist pin has the flat spot near the center and the casting around the rod bolts is identical to the 3.0 and not the 2.7? Also, what's with the (S) after the part number, the 2.7's listed in Bruce's book do not have this. I'm starting to go crazy here...

This is a 9 bolt crank.

Bottom line, if these are 2.7s can I use them? How did they get in there???

Dan

[tom1394racing]

Dan

See these pics...When you lay a 2.7 and an SC rod side by side there is little to tell the difference between the two. The difference is in the bottom end as the pics show. The 2.7 rod has a wider bottom end and is the darker rod in each pic.

I checked and found that a stock 2.7 rod at this width does not fit between the counterweights on an SC crank.

[sc_rufctr]

Originally Posted by 914obsession

Also, what's with the (S) after the part number....

Dan

That looks like a manufacturers mark to me.

[Henry Schmidt]

Casting marks quite often cross manufacturing model lines.
Early 3.0 rods may have used the same forgings.

One other thought is that 2.7 rods can easily be narrowed and used on a 3.0 crank. We did it all the time when 3.0 rods were hard to find.

[john walker's workshop]

Originally Posted by john walker's workshop

how many flywheel bolts?

i'll ask again.

[Fast Corners]

Originally Posted by john walker's workshop

i'll ask again.

Originally Posted by 914obsession

This is a 9 bolt crank.

Dan

Sheeesh! Kidding of course

[356RS]

I think John was hoping to hear that it was a 6 bolt crank. That would have been a nice find.

[Henry Schmidt]

I hate to quote myself but when Yoda speaks, the world should listen.

Originally Posted by Henry

Casting marks quite often cross manufacturing model lines.
Early 3.0 rods may have used the same forgings.

The rods pictured below a factory 3.0 rods. Note the casting numbers.

Cheers

[Henry Schmidt]

Originally Posted by 356RS

I think John was hoping to hear that it was a 6 bolt crank. That would have been a nice find.

A 6 bolt crank would mean a 3.0 turbo or 3.0 Carrera case but the crank would just be the same as a 2.4-2.7.
That is of course if it wasn't an RSR crank. But that would be like finding rocking horse s**t.

[914obsession]

Thanks everyone for the help! I was in disbelief, but these rods are definitely for a 2.7, I'm trying to track down my correct rods from the machine shop...

[john walker's workshop]

Originally Posted by Henry Schmidt

A 6 bolt crank would mean a 3.0 turbo or 3.0 Carrera case but the crank would just be the same as a 2.4-2.7.
That is of course if it wasn't an RSR crank. But that would be like finding rocking horse s**t.

and that would explain the 2.7 rods, but it's a 9 bolt crank apparently.

[tctnd]

Seems to me I read somewhere that some early 3.0s used 2.7 rods that the factory narrowed by trimming one side only, thus explaining the slight asymmetry you see. If the factory saw fit to use them and all appears to be well why not reuse them and use the money saved for better rod bolts or head studs?
regards,
Phil