Back again

After ruining my rebuilt engine I started looking out for a replacement piston. This proved pretty difficult because early 16vs had a different combustion chamber shape. In the end I found a later style B202 taken from a 9000 with 87k miles for only £120 delivered, which is great!

The 9000 engine isn’t a straight fit in the 900, all of the ancillaries are mounted differently due to the fact the engine is transverse with an end-on gearbox in the 9000. Basically the block end plates, manifolds, oil pick up pipe and all ancillaries must be swapped over but the bare block, head and internals are identical.

Pre ’92 9000 B202 Engine

Thanks to lockdown it was a while before it could be delivered, but on a freezing day in February it arrived and I was stripping and cleaning it. It had been stored with the cam cover off so at the very least I was planning to replace all of the gaskets and thoroughly clean out the head.

A bit cleaner

Unfortunately, once I removed the head I found that the bores were bizarrely worn. I’ve had the head off these engines with 200k+ miles and still been able to see the crosshatching in the bores, but for some reason these bores were worn smooth. I was told it was running great when removed, but I didn’t want to have gone to all of this effort for a worn out engine, so it was full rebuild time. Again.

Worn bores

Both blocks and cranks were taken to the machine shop for them to choose whichever they felt was the easiest to save – scored from the cracked piston or generally worn.

I was out of service for a day or two after lugging these in and out

In the end, happily the machine shop felt that the original block would be fine with another honing and no need for oversized pistons, while the new engine’s crank was the better starting point for polishing. I also had them skim the new engine’s head (which must be paired with the pistons due to the different combustion chamber shape – hence why I couldn’t keep the old head) after I cleaned and lapped in the valves.

So now it was time to build the new engine’s internals into my old block. Nothing much to note about that, it’s becoming pretty frustratingly familiar by now.

Once the engine it was in, I ruined the slave cylinder again at first startup (I’m getting good at this trick) by forgetting to remove the clutch spacers, which meant the piston over extended, popped out and mashed up it’s seal. Not hard at all to replace but pretty frustrating.

All back together

Other than that setback, it started up first time with good oil pressure so I’m running it in on base boost before I can start to tune. There’s a list of snags to sort but nothing too major.

And finally back on the road


How to ruin a rebuilt engine

So, on the very first drive after the engine rebuild I was gradually increasing the boost when I suddenly felt the power drop. A glance in the mirror and I couldn’t see anything behind at all but steam – the head gasket had failed in a big way. Cut the engine straight away, coasted into a lay-by and called the breakdown company.

Yup, that’s blown

Pulled the head, replaced the head gasket which had blown on cylinder 1 and she was running again, but making huge smoke once she started warming up. The compression was about 30% lower on cylinder 3, so I thought perhaps I’d cracked the head. Embarrassingly it was weeks before I realised that the smoke was because the rear silencer was saturated in coolant. Flushing it with a hosepipe solved it, but she still wasn’t running right – running lumpy at anything above idle.

I decided to instead concentrate on fixing a little hole by the right front side jacking point:

Eventually I decided I was going to have to pull the engine back out and tear it down.

The first ring had broken on piston 3, chewing up the piston and the bore and somehow also cracking the lower ringland?! To boot, even the bearings and crank are scored, presumably either from bits of ring, or perhaps I didn’t get every bit of crank sprocket.

The cause of all this? Turned out in my rush to get the car back together, I’d refitted the crank position sensor in the original position, not the one I worked out it should be in when I did the T5 conversion. So, the ignition timing had been 18 degrees too far advanced.

Currently I’m just waiting for the engine shop to reopen so I can find out what can be salvaged.


Saab 900 Engine Rebuild

With the engine bay sorted it was time to start on the engine rebuild. I bought an engine stand and mounted it up.

A quick clean up later…

Stripped and wrinkle painted a spare cam cover:

Stripped the engine down to find no visible head gasket failure, but pretty tired bearings.

The block, crank and head went to the machine shop where the head was skimmed, block honed and crank journals polished. New standard size bearings and piston rings were sourced, along with a full timing kit. The chain guides had to be sourced from Sweden at great expense. I had a spare later head from Erika that I considered fitting but learned that the later heads have a different combustion chamber which combined with my earlier pistons would reduce the compression ratio. Keeping the existing head meant sourcing new plastic nipples for the cam oiler tubes which the later heads don’t have. These tiny bits of plastic were really hard to find, and I ended up having to pay £80 for them.

Turns out early cam covers have a different sized rubber chain guide, which I was unable to source so I trimmed down a later one to fit.

Had a bit of a disaster during the rebuild. I’d fitted the head and the cams but not the cam sprockets, when for some reason I thought I’d fit the crank pulley. As the torque wrench clicked at 180nm I realised my error. I’d just turned the engine over without the timing chain connected. Assuming I’d bent some valves, the head came off to assess the damage but in fact the loose timing chain had bunched up and instead stripped the tips of some teeth from the sprocket. So, the only damage was a new crank sprocket, a new head gasket and another set of head bolts.

During this I dragged the supposedly good spare gearbox that came with the car out of the back of the garage. I’d never looked at it so was really disappointed to find it completely seized and basically ruined. Tried to free it off and eventually got the diff turning and gear selector working but still no drive, so £1500 later a freshly rebuilt box was sent from TR Autos in Cornwall. This box got a steel diff cover fitted to hopefully help it handle the power.

Didn’t get many shots to document this, but the original oil cooler was looking tired. Drop in replacements are really expensive, so after some measuring I bought:

  • Two M16x1.5 – AN6 adapters to go on the oil filter housing (use dowty washers on the M16 side)
  • A cheap 9 row AN10 oil cooler
  • Two AN10 to AN6 reducers to go on the cooler
  • And a few metres of AN6 braided line along with a load of fittings

The generic oil cooler dropped into the stock housing after some modification to the mounting tabs. A complete replacement for ~£100, instead of ~£280 for the DO88 kit.

Turbo upgrade

The old standard Garrett T3 turbo was also pretty tired, and for the price of a rebuild kit I lucked out on a Chinese 60 trim T3. Turned out this was much bigger than the standard one! The standard hard oil drain and feed pipes wouldn’t quite fit, so I made up some flexible ones with AN fittings. To make the drain fit the block I welded a AN bung to the cut down stock drain, with a tab to fasten it to the gearbox bolts.

I also made a 3″ downpipe…

And 3″ intake pipework:

And that’s it! All back together.


Front suspension refresh

While tidying the engine bay, I’ve had all suspension components, engine brackets etc soaking in citric acid to remove the rust. This was my first time using citric acid and I was really impressed with the results:

Apparently the rally guys like to reinforce the lower wishbones, so I couldn’t resist having a go myself:

Cleaned up the aluminium wishbone mounting blocks and painted in the cheesiest colour possible:

And an obscene amount of money was spent on new old stock genuine SAAB engine mounts and Powerflex poly bushes.

Saab 900 engine mounts

And finally, painted with POR-15.


Engine bay welding

Since pulling the engine out, progress has been a bit slower than I’d hoped during lockdown but I’ve still got a fair chunk done.

The right driveshaft tunnel has had a repair patch before but now the arch above was pretty thin…

Then I cut out the battery tray since I’ve relocated it to the other side (before realising I could have simply unbolted it) which revealed quite a lot of thin metal. Decided I’d be best to cut out the box crash structure to do the repairs, so took a lot of measurements and did this:

There were a couple of other patches around the bay, such as the front crossmember:

You can see here the angle iron added for strength where metal was cut away for the front mount intercooler.

After that, time for paint!

I’ve also coated the underneath and arches with Bilt Hamber Dynax UB, which is a thick black wax, and injected their Dynax S-50 wax into the box sections, which is a much thinner consistency.