85 900 Notchback arrives in Vermont

[Crazyswede]

ok, Noted. do you know which 2.3 crank the swedes were running? I think the 2.3's in the 9000's are considered the "long" blocks while the 2.3's in the 900's or was it 9-3/905's are considered the "short" blocks.

[Luke]

I think its 90,91,92 cranks that can be made to work. I believe you have to use a 2.1 block for this as well, due to clearance issues, and there is still some amount of grinding in the block to allow for clearance.
A couple years back a local mechanic had an 2.3 crank out on the bench and a stripped down 2.0 C900 block nearby. I had stopped by and suggested we try to mate the two up. The crank dropped right in, all the journals and flanges lined up perfectly and without pistons rotated fine.
I didnt think to much about it for a while, but then a year or two ago a swedish guy was posting here about the 2.3 8V motors they build in sweden for rally. I had a somewhat lengthy email exchange with him afterwards trying to get the details. Basically, they grind down the standard rod journals to chevy small block (the early smaller journal version) bearing size. Then you can use a huge range of chevy aftermarket rods that are available at ridiculous prices for very strong and light rods. Its about a .020 grind to get down to the chevy size, a local shop quoted $175 for this including polishing and radiusing the journals and oil holes. A nice short skirt lightweight piston is spec'd with the appropriate wirst pin height to match up... They are getting close to 200 HP from these things with 8V head ( all that the class rules there allow)
I would think for under a grand you could build an awesome torquey, nice reving powerplant that would be perfect for mixed competition.

[Crazyswede]

I am pretty sure that the 2.1 blocks are just overbored 2.0 blocks. There are 2 oe 3 2.1 blocks at Chris's shop. So I'll start playing with components and see what I can come up with.

[airsweden]

I think I've mentioned it here before. A few years ago I had a chance to spin a 2.3 crank in a 2.1 block. It appeared to fit til I started attaching the rods. The places where there was contact all seemed easy enough to grind down. I do recall that there might have been a clearance issue with the 900 trans case as well.

[Crazyswede]

I think I've mentioned it here before. A few years ago I had a chance to spin a 2.3 crank in a 2.1 block. It appeared to fit til I started attaching the rods. The places where there was contact all seemed easy enough to grind down. I do recall that there might have been a clearance issue with the 900 trans case as well.

I think some of this goes away with the longer Chevy rods which help reduce the extremety of the angle change in the rod. I guess we will just have to pull a 2.0 and 2.1 block apart and play around with a crank and see if we can make it fit.

[Jordan]

I always thought the problem was with transmission clearance. Since there is that pesky primary chain drive there it wasn't a particularly easy way to space it out, so you'd have to do some sort of crank or transmission clearancing which sounds sketchy.

edit: saw this on saabnet...

It's been done but it requires crankshaft counterweight modifications and clearancing of the trans for the crankshaft counterweights. You would use a mid year ('91-'93) 9000 2.3 crank. As far as pistons both your 2 ltr 900 and the 2.3 ltr 9000 use the same 90mm bore but the crank / rod combination in the 9000 utilizes a 6mm taller block so you have to go to a custom piston with a shorter pin height. The downside to this besides all of the clearancing is that the 2.3 cranks already require balance shafts mostly because there wasn't enough room to get enough counterweight mass for the increased stroke. Granted an inline crank's dynamic balance Isn't effected by the mass of the counterweights however the more stroke the more mass is needed unless the manufacturer cheats their design by going with balance shafts. We work around this by lightening the crank within the rod journals themselves like you see in after market race cranks. If I were to do another early block 2.3 conversion I'd add heavy metal (tungsten) to the counter weights to make up for the counterweight to trans clearancing of the crank and of course do my rod journal lightening which makes the counterweights think they are in fact heavier. You can't replace your 90mm pistons with 93mm pistons as you wouldn't have any cylinder walls left. You can however use a C-900S '91-'93 2.1 block that is already 93mm as you'll need custom made pistons anyway. For 2.1 forged pistons we've come up with an only plus 3 thousands oversize piston to keep the already thinner cylinder walls as thick as possible for a turbo application. If I remember correctly we used the C-900 rods for this setup. Dave at SPG9

[Luke]

I think I've mentioned it here before. A few years ago I had a chance to spin a 2.3 crank in a 2.1 block. It appeared to fit til I started attaching the rods. The places where there was contact all seemed easy enough to grind down. I do recall that there might have been a clearance issue with the 900 trans case as well.

Part of the advantage to using the aftermarket rods is that they are available with lower profile bearing caps, which helps the clearance issues. Also the longer rods reduce angle that the rod swings through, which allows for a higher revving motor.

[airsweden]

So what's the actual displacement of a 2.1 block with a 2.3 crank and the pistons/rods people have been using?

[Jordan]

I think its close to 2.5.

It sounded to me like the clearance issue was more with the counter weight part of the crank and not the rods themselves. That's what I thought was kind of sketchy, trying to mess with re-balancing the engine.. maybe its not that important or not that hard to figure out

[Crazyswede]

I always thought the problem was with transmission clearance. Since there is that pesky primary chain drive there it wasn't a particularly easy way to space it out, so you'd have to do some sort of crank or transmission clearancing which sounds sketchy.

The primary chain would be an issue with one of the vertical blocks out of a later 900/9000 but this project will still use the stock angled 900 block so the primary chain distance remains the same. the main journals on the 2.3 crank do not get ground but the rod journals do.

So it sounds like balance on the crank might become something to address. All good info. Thanks for the Saabnet clip. I shot "Ric" an email because I think he had something to do with all this.

[airsweden]

I think he meant too bad you can't put a spacer between the 900 block and the trans to give the crank some room to spin.

[Crazyswede]

I think he meant too bad you can't put a spacer between the 900 block and the trans to give the crank some room to spin.

Well it would be very easy to draw up a spacer that gets squeezed between the transmission and block. it wouldn't even be that hard in the grand scheme of things to cut the primary housing and raise the top gear...then just have some longer chains made up. Then, worst case, you reshape the hood for clearance....a la WRX hood scoop. Guess it all depends on how much you need for clearance. So then I might ask....if we ran a vertical 2.3 block with aftermarket rods and pistons could we eliminat the need for a spacer and then use a stock transmission?

[Luke]

Theres no need for any spacers or chain cutting etc... From what I was told with the right parts its a light relief on one part of the gearbox casing and nothing more.

Also the post from saabnet dosen't make complete sense to me. You can't make up for a 2nd order harmonic imbalance (due to the non-perfect sinusodial phasing of the pistons throughout the stroke) with more crank counterbalance. Thats why the longer rods are needed, to minimize that effect somewhat. Counterweights are for the first order balancing and thats pretty easy to get right.

[Crazyswede]

Well maybe I'll see what it takes to drop a vertical block onto an older transmission.

[Crazyswede]

Theres no need for any spacers or chain cutting etc... From what I was told with the right parts its a light relief on one part of the gearbox casing and nothing more.

Also the post from saabnet dosen't make complete sense to me. You can't make up for a 2nd order harmonic imbalance (due to the non-perfect sinusodial phasing of the pistons throughout the stroke) with more crank counterbalance. Thats why the longer rods are needed, to minimize that effect somewhat. Counterweights are for the first order balancing and thats pretty easy to get right.

I was reading that they were suggesting the addition of tungsten to the counterweights to make up for some of the material that had to be removed from the counterweights for clearance.