Bottom End Components - 99 v. C900 v. 9k v. 9-3 v. 9-5

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DrewP
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Bottom End Components - 99 v. C900 v. 9k v. 9-3 v. 9-5

Postby DrewP » Thu Mar 10, 2011 5:05 pm

Working at a SAAB service shop has many advantages, one of which is a very thorough supply of spare parts from just about any SAAB model commonly found in the states.

Luke's 16v rally build inspired this post, I was looking for a bit of a budget way to get lighter weight reciprocating pieces for my build.



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Turns out that factory 9-3 / 9-5 components may require only a moderate amount of work to fit to a C900 B202 block.

Rod bearings - SAAB used the exact same rod bearings for all C900 / NG900 / 9000 / OG9-3 / OG9-5 and all 2.0L 99's, 1972+.

Main bearings - All early 2.0L cars 1972+ 99 / C900 / 2.0L 9000 (1986 - 1990) use the same main bearings. Later 2.0L and all 2.3L cars 1991-1998 9000 / NG900 / OG9-3 / OG9-5 all use the same bearings.

All 2.0L and 2.3L engines use the same 90mm bore.



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'02 9-3 & 9-5 connecting rods are one-piece forgings, and have split fractured big end bearing caps. They are very slender, right now I don't have an accurate scale to see what they actually weigh, but they are little compared to the B202 turbo rods.

The B205 and B235 rods are marked on the big end '2.0' or '2.3' to designate which engine they came from.

2.0L B205 rods have a center-to-center length of 159mm.

2.3L B235 rods are 153mm.

They all have 56mm big end bearing receiving bores, and 24mm wrist pin bores.

I am going to try to fit a B2x5 reciprocating assembly into a B202 block, I won't have to cut the block deck down too much if I use 2.3L 9-5 rods and 9-3 pistons, rod length/stroke ratio is much better too, the later pistons have significantly higher wrist pin height and much longer rods.


This is a regular B202 setup next to a 9-5 piston on a 9-5 rod - much longer rod length and higher pin height, but only about a 5mm difference in deck height, and the stock 9-5 rings are those new fangled low-tension rings that are pretty thin, supposed to make a bunch less friction.

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Wrist pins are 10mm shorter (but thicker wall), and the pistons have reliefs around the pin rather than a full skirt:

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Nice hardware, and the crazy shear-fractured big end caps.

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The 9-5 / 9-3 pistons also have the crowns hard anodized, though the guys here like to clean them up during head gasket job and scrub most of it off.

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The small dishes are 9-3 pistons. They In the 9-3 block with B2x5 head they give an 8.8:1 compression ratio.

The larger dishes are 9-5 pistons, compression ratio is nominally 9.3:1. The CR is higher even though the dish is larger because the crown of the piston is 0.7mm higher than the 9-3, has a little more squish around the perimeter.

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Last edited by DrewP on Thu Mar 17, 2011 12:52 pm, edited 4 times in total.
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Jordan
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Re: 16 valve B motor - living the dream

Postby Jordan » Thu Mar 10, 2011 5:22 pm

Wait, what? That is how the main bearings are split??

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Re: 16 valve B motor - living the dream

Postby DrewP » Thu Mar 10, 2011 6:13 pm

EDIT: Some quick reading on the internet asserts that this method has several other benefits than manufacturing ease, it also positively locates the cap in relation to the rest of the rod, so there is no need for a) Locating bores on the bolts, or b) hollow dowels to locate the two pieces to each other.

It also prevents the two mating surfaces from fretting against one another, the tendency for the mating faces to slide (microscopically) across one another and chew up the surface, so it is no longer as smooth as it was when it was originally machined.

GM Development Paper on LS3 V8 wrote:"Rods with cracked or "fracture-split" big ends are common on modern engines. The fracturing creates a unique interface that "locks" together only one way and does so very precisely. The more accurate interface ensures a uniform big end diameter and shape."



**********************

Yup, rather than machine the rods & caps separately and then machine the mating faces and bore them, the rods are forged in one piece (good for grain flow around the fasteners I believe), scored on the inside, and then fractured. When the cap is placed back on it's already a perfect fit where the fracture occurs and is bolted back together and bored to finished size.

I had only even seen large diesel rods done this way, a friend worked for CAT in Peoria, IL on their little utility engine, something like a 16-litre straight 6, and he brought home a bent rod that was made that way, I had never seen one.

Little later on I got to tear down the Ford turbo-diesel V6 that goes in the European spec Jaguar S-type and it was the same deal, it wasn't until I started working here and tore down a 9-5 engine that I saw these in a gasoline application, but I imagine it's cheaper than manufacturing and machining the pieces separately, and guarantees a very good fit.

I never really read up on the process, but I imagine they fracture them at low temperature to make sure the fracture faces are nice and brittle to get the mating grain like that.


Cool stuff out there.
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Re: Bottom End Components - Info Post

Postby Luke » Wed Mar 16, 2011 10:07 am

I split off the info about the bottom end components Drew started to a new post as I felt it deserved its own thread so its not buried in 18 pages of other stuff.

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Re: Bottom End Components - Info Post

Postby Crazyswede » Wed Mar 16, 2011 1:41 pm

Ahh...I thought it was a strange first post in a new thread.
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Re: Bottom End Components - 99 v. C900 v. 9k v. 9-3 v. 9-5

Postby DrewP » Thu Apr 25, 2013 3:28 pm

Bump.

Does anyone have the center-to-center length of a C900 rod?

Asking because I stumbled on these, $130 for a set of 8 forged H-beam rods meant for a 4.6L Ford V8, they are 150mm c-c length but the small end bushing is a little small at ~23.1mm and doesn't look like there's enough room to bore it out. No mention of the big end bore diameter.... If the big end is close they could probably be made to work for short money.

http://www.ebay.com/itm/Ford-4-6L-Set-8 ... 8207163%26



EDIT: He just wrote me back, the big end receiving bores are 2.239 in. = ~56.9 mm, too big to be machined to take a Saab 56mm big end bearing, but there could be some off the shelf bearing shells that could work.
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Re: Bottom End Components - 99 v. C900 v. 9k v. 9-3 v. 9-5

Postby Geoff » Thu Apr 25, 2013 10:22 pm

Some of the guys in Sweden have Small Block Chevy rods in their cars. The cranks are machined down a bit to fit the smaller Chevrolet bearing.
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Re: Bottom End Components - 99 v. C900 v. 9k v. 9-3 v. 9-5

Postby DrewP » Fri Apr 26, 2013 11:38 am

I think what Dave Kennedy told me he used in the last motor he build for one of my customers was a Crower rod meant for a Ford, but I never got the details of which one and what was needed.

I'm a lot more willing to tweak things to work now that I have steady access to machine and measuring tools. These just popped up in my 'Suggested Items' box and thought they warranted a look.
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