Inliners International Forums General Discussion Hi Performance Doubt about connecting rods...

Hi...

I found a forged connecting rod for a good price but is for sbc 2.1 crank pin so I would like to know if is possible adapt in a 250 chevy... I tried to find some special bearing or something like that but didnt find any reference...

Crower makes nice connectiong forged rods for our 194-150 engine.

http://www.crower.com/

I think Eagle makes some also.
http://www.eaglerod.com/
http://www.eaglerod.com/index2.php?
pg 9

option=com_flippingbook&Itemid=38&book_id=5


MBHD

I suspect you can use the original SBC bearing as a shell, bore it to the L6 rod ID and insert the L6 bearing - but I can't find someone who's done it.

Crowers I-beam rods are nice parts. I am using a set of Crower 6.0 floating pin in my stroker. I am also now building a 250 with Crower 5.7 press pin rods.

I too thought about altering small block chevy 2.1 big end rods to run on 2.0 journal. I am well equipped to do machine work so it would not cost me much to do but frankly, I could not come up with a good plan so I gave up and bought Crowers. If you are determined enough I'm sure it could be done.

SBC rods are also too narrow to use on a 6 cylinder crankshaft as well. Scat also makes them for the 194-250 engines. There are a good variety of aftermarket rods for the 194-250 engines, so you don't have to try and use something that isn't designed to work in them. For the difference in cost to modify SBC rods, it will be of no benefit to do that since there are many choices for rods that bolt in with no other mods required.

Thanks guys for replies are really helping...

I really understand when you say that you guys say why adapt something that its not design for the engine when there is one that is made for it.

But the point is that Im building an engine to produce about 350hp
and all those rods are the top line (about $500) and can support much more HP that Im intend in this project. Furthermore Im from Brazil so I have to convert the money and pay the taxes... Every $$$ I can save is very important, and I just need something intermediary...

So my question now is...

Earliers Sbc had small bearings with same size of 250.
Despiste the narrow botton of the rod I would like if there is something else that makes impossible use connecting rods like these? (much cheaper) http://www.ebay.com/itm/SIR5700SPLW-SB-C...500a96e&vxp=mtr

Thanks...

I believe the narrow big end is the only feature you need to deal with to make those parts work.

Guys:

Some months ago, I had a set of 6.200" h-beam full floating rods made up for a future 250ci inline project. I provided the manufacturer with an OEM rod as a template to be sure all the critical dimensions were correct. In doing so, I got a bit of an education about the inline rods being different in several ways from a "small" SBC rod since I too thought the V8 rod might be OK to use:

First, as CNC-Dude pointed out, the SBC rod's big end is way too narrow at 0.940" when compared to the six at 1.030. Not sure but I suspect too much oil would be lost out the sides to properly suspend the rod bearing. If that's true, bad things would happen in short order.

Second, the SBC rod's "beam" is slightly off-center between the big end (and small end?) when viewing the rod from the side. The inline six rod is precisely centered. Don't know if this would be a problem or not but I'm guessing the GM engineers designed the two rods with this difference for a reason.

Finally, since two rods share a common crank throw on the SBC, there is no chamfer on the connecting rods where the face each other, and there is a chamfer on the outsides to clear the crank pin radius. The six cylinder rod has to be chamfered on both sides. I would imagine failing to provide for clarence on both sides of the rod would result in considerable damage to both the rod and the crank.

My understanding is that failing to orient the SBC rods correctly regarding the crank pin radius and rod chamfers is one of the mistakes folks make when rebuilding small block Chevys that quickly result in a catastrophic failure.

Russ

I have talked w/old school roundy round track car racers back in the day & they would run SBC rods in there inline Chevy 250 engines w/the extra rod side clearance & all.

They would say it worked fine & it just splashed extra oil all over inside the engine.

Not saying I would do it, but it's been done before.

MBHD

For the HP level he is seeking, the stock rods will be fine with good bolts and the beams polished.

I think the two rods are the same forging. The V8 rod is off set and narrow because one side is machined so two rods can fit side by side on a common crank pin. Both engines use the same bearing. Like Hank I have talked to someone who ran V8 rods in a six with no problems. I have heard of welding and machining the journal to fit the narrower rod.