Derek's 308 engine rebuild

My friend Niall came over to help with the cleaning (funny how my friends are far less available now that the weather is cold and the task is cleaning.) The combustion chambers that had been caked with coke (must have run rich for most of it's life) are now nice and clean, as are the sides of the heads and block. It was totally worth getting the soda blaster and it only took about 12-15 lbs of soda to clean everything. While the parts dry I'll start to put my ultrasonic cleaner together for cleaning all the small parts, carbs, and my wife's jewelry (hope it works on fake gold and glass
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Here's a better look at the block. I got it in just before a snow flurry!
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Kiwiokie,

My heads have since been on and off a couple of times so the first time they were hard to fit I gently ran a round file down the tubes to clean up the oxide which was catching and slowing the fitting/removal. The soda blasting (at around 60psi) worked well on the remaining traces of oxide on the head faces near the water jackets.

Rob,
Thanks for the heads up. You must have ESP as yesterday I asked Chloe at Superformance if I could change my mind and add back the standard head gaskets which she kindly agreed to allow and they are on their way (but not a few other parts that were 3-4 months lead time-- would have been nice to know when I ordered.) I decided that MLS gaskets were overkill and the extra work (and risk) to remove studs and then skim the block and heads was excessive given that so many people are running 10.5:1 and higher (or turbos) using the regular gaskets.

 

I picked up the 348 crank from the machine shop. I had it machined with the same dimensions as the original 308 crank (with the 62202 bearing pressed lightly 10.5mm into the crank and leaving 3.5mm proud.) They said it was really hard as the splines were obviously hardened.

I welded up the ultrasonic cleaner tank using a 0.7mm thick (22 gauge) stainless kitchen duct offcut and a 1.5mm (16 gauge) bottom. At first I put the 100W 40khz transducer on the side but the wall was too thin and flexed when full of water so the transducer glue cracked and only the central screw stopped it shaking itself off. I have now put the transducer on the thicker bottom and welded on some short legs. I will try it out in the next few days (after carving pumpkins and ordering some more parts.)

I'm still trying to decide if the 23-8N high temp valve alloy is worth the extra expense for the exhaust valves. I know that a couple of suppliers are selling 21-4N exhaust valves and they work ok but with some of our cars having air injection (and some being turbocharged), I'm tempted to go with the better alloy. Anyone have any experience of aftermarket exhaust valves wearing?
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Next time send it to me and I'll charge you a ton of money-- better to keep it in the family On a more serious note, I will not waste time scrubbing again-- soda blast it or find someone with a jet washer (about $60-120 for a wash here in Ottawa.) I think the soda gives a nicer shine-- perhaps closes or polishes some of the porosity.

 

I've been looking at the cam drive gears and bearing in my kitchen as it has been snowing a bit and it's warmer in the house than the garage. I don't know why they had a seal on the inside when the outer bearings are 2RS so there are two seals to go through before the oil would leak out? Perhaps the engine oil would damage the old standard NBR rubber seals and having viton/FKM would not require the inner seal?

I measured the shaft and it seems there is enough space for a double roller bearing like a 4203 (17x40x16 instead of the standard 17x40x12) which would take 54% more dynamic load but I haven't found a 2RS version yet with viton seals which would probably outlast the car. The seal lip has polished a line which is 3mm from the small step near the gear face (the step can be machined down if needed) and a new internal snap ring groove can be cut 4mm inboard of the old groove. The seal would still have 3.5mm of bore to press into which should be fine with a little adhesive for insurance. My preference would be to find some bearings with viton seals and omit the separate oil seal.

I got a few of the air injection plugs from the anodising and they look nice. The boy racer in me wants the red but the silver will look a bit more fitting for a grey/bald old git like me
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Thanks Martin! So the seals will stay. Any chance you can find a 4203 (or similar) with 2RS seals?

 

Simon, with the extra 4mm stroke you can get the extra compression without a bigger dome on the piston so that avoids the ever thinner "orange peel" combustion chamber. Also the combustion chamber hemisphere goes all the way up to the edge of the bore (unlike Jags) so you can get a bit of squish up into the chamber by bringing the edges of the new pistons up close to the hemisphere and matching its slope.

cheers, derek

 

So I was away for the weekend and was busy with getting parts ordered and getting some FEA optimisation on the cam pulleys the last couple of days. As I suspected, the cam pulleys available from some sources are far heavier than they need to be. A friend ran a few design optimisation rounds and he got it down to 255 grams with a minimum Factor of Safety at 3.5 and max deflection at 0.04mm. This is with 7075-T6 aluminium.

I will head down to Ogdensburg tomorrow to pick up a bunch of stuff including the Loctite high temp sealant for the liners. I should be able to get the liners in and torqued down for the mains measurement by the weekend and into the machine shop on Monday.

The regular head gaskets came from Superformance (very speedy service as before.) They are Elring gaskets so I will use some sealant around the water passages for insurance as I've read somewhere the Elring gaskets don't crush enough with the liner protrusion.
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Kiwiokie, read the earlier posts. The main problem is coolant migration from the liners to the studs. Not catastrophic, just harder for someone to get the heads off again in 20-30 years (assuming fuel is even available then and humans are allowed to drive.)

 

Thanks John, I sent Atmus an email as I'm still trying to solve the outer cam drive bearing weakness.

The high temp Loctite 5109 hasn't made it to Ogdensburg yet so I'll go down next week. On the brighter side the weather has dried up and will be a balmy 9-10C over the weekend so I will try to soda blast and pressure wash the transmission so I can bring it into the basement for a winter checkup.

Next week the body goes to the two gents in the forest who will seal up the old primers and fillers, prime it, block it and paint it. After lots of reading I think it's a bad idea to go all the way back to bare metal since the labour to get it back to the shape it is in now would be huge. Better to leave the lines as they massaged by the coachbuilders at Carrozzeria Scaglietti. They will also sand blast and paint the maze of tubes and layers of steel and fibreglass in the boot/trunk.

I don't want to put back all that rock wool in the trunk-- any suggestions for something light, insulating, and less hard on the lungs? Wear a mask if you ever work with the rock wool.

 

This is not glamorous work. I wish I'd taken a "before" picture of the transmission which was encrusted with decades of black oily crud, and an "after" picture of me once the pressure washer has transferred most of that crud onto me (in thousands of small, sticky clumps.)

While the transmission was drying in the sun, I checked the heads and block for flatness and moved them into my basement where I'll work on them. Hopefully the sealant will get to Ogdensburg today and I can install the liners in the next few days, torque down the heads with the old gaskets, and measure the installed diameter of the new bearings before taking the crank to the machine shop.

I went to check the age of my new Dayco timing belts and was very pleased to see how new they were, 2016 week 65!! It took me a few seconds to realize that there is no week 65 so sent off an email to Dayco asking how they now date code belts. I'm not holding my breath so does anyone have any ideas?
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The outer cam drive bearing research paid off! The best bearing available is the NTN 6203LLUA1C4 with L627 grrease (Mobil Polyrex EM, -20F-350F!) I found them from a Toronto supplier (ontariobelting.com) for about $16 and about $18 at my local bearing shop. They are special order.

I would suggest that anyone with the earlier design switches to this newer design to put the bearing closer to the pulley (that's why Ferrari did the change and then switched to the bigger 630647 bearing later. I looked at machining the old timing cover to take the bigger bearing but it wouldn't leave much support for the snap ring. Better to just put in the best bearing possible and check the play every time you change the belts.