1971 Fiat 850 sedan

A little stumble backwards. I tried to coat the pistons. These are just a used set of 903 pistons I picked up from another fiat owner. Sandblasted and washed in acetone, scrubbed with a toothbrush until they couldn't be any cleaner.

The directions said to only spray on enough ceramic coating to leave a thin wet layer. Well that didn't seem like enough at all so I laid a little more on. It sure looked great

So I put it in the oven and after an hour...disaster


Did a bit of googling and found out that I just laid it on too thick. I can sandblast it off and try again but the dry film lubricant that was shipped to me came as a powder and it was supposed to be a liquid. Not sure if it dried out in transport (would it be a powder then?) or if I should try to mix it with a solvent. Waiting on response from the seller. The DFL should go on before the ceramic so I am just waiting now.

So I started in on the mods to the block. The 850 engines use a centrifugal oil filter system and lack a pressurized center main bearing. Since the 60's people have been modifying them to use an external oil filter element and to pressurize the center main. There is not a lot of info out there on how to do this anymore. I am going off scans of photocopies made in the 80's, spanish forum posts with dead images and the info over at scuderia topolino. Turns out that once you look at everything assembled it really is simple.

start at the center main. Install a late 903 bearing with the appropriate oiling hole and mark its position.

Drill into the bolt hole down at an angle

Then go to the outside of the block and remove the plug from the oil galley. that oil passageway runs pressurized oil from the pump to the cam bearings and the upper end of the motor. The hole I need to extend is already drilled most of the way so I just need to extend it an inch to meet up with the other side of that bolt hole on the center main.


So, Now the oil will come from the pump and get sent out the side of the block where the oil pressure relief valve use to be (the valve and its hole are in the lower right of that pic above) through a fitting I have yet to decide on, through a hose pipe to an oil filter on the firewall and back in to the motor via that drilled out plug. That will pressurize the 3 main bearings and everything else. But this leaves me with no pressure relief. I probably should just import an oil pump for any of the modern fiat 903 motors but I have a good pump so....

Take the line that used to run the oil to the crankshaft and turn one end into a plug and on the other end weld the pressure relief valve on.

Now I just need to tap the side of the block for whatever fittings I end up with and fill in the hole on the end of the crankshaft.

Just one or two more things before I can send the block out to be bored.

I can't belive that I have missed this thread, so much awesome DIY stuff going on!

I am at a very similar stage with my imp, the engine has become too much for the gearbox to handle, so I need to find a solution, however the orientation makes it very difficult. It has made me walk away from the project for a few months, just too much stress

This thread is making me perk up though, nice to see someone else overcoming similar problems.

Keep up the sterling work, and I will get back on mine

J

Thanks Ditch! There are plans afoot, another gearbox to get going with and some more minor engine mods

Very neat indeed, I did mine in a similar fashion but using the far less accurate dremel technique!

Success!


Skirts coated in dry film lubricant, tops in ceramic. Cured in the oven at 350 for 2 hours and no bubbling. Not perfect. I might redo them but these are technically ready to install after buffing the DFL with scotchbrite.

A few weeks with the moustach and I am warming to it but I still think I prefer it without


Still haven't taken the block to the machine shop. Waiting on some funds to roll in. Loaned out my MIG so I can't shave the rest of the holes.... Just taking it slow for the time being.

Its Norwegian, but the ad is actually Danish

Time to learn a new skill.

I have been thinking about the valves a lot lately. Wondering just what all is involved in a simple 3 angle valve job and how difficult the actual act is and what equipment is neccesary.

I have a co-worker who is some kind of idiot savant/mechanical genius/epic bodger. In his current list of cars is a Vespa 400, 53 Studebaker pickup, 78 Corvette, a 50's Studebaker Hawk and a 69 Camaro. He also collects antique tractors and all sorts of other vintage things. If anyone had the info I needed it would be him. I asked about valve seat grinding and the next day he showed up at work with this box

This awesome 1950's cantilever box is stuffed full with equally old valve seat grinding tools.

The grinder itself is just an old drill motor.

The arbors are pretty much what I expected them to be

The pilots were a bit of a suprise. They wedge themselves into the valve guides. Since this setup is so old it does not have any pilots that would fit a 7mm valve guide. So I cannot use this, but I can learn from it.

And the stone shaper is simpler yet better than I had imagined.

I aqcuired a few items earlier when I decided to try this

The Die is a very odd size. That makes them either very expensive or very cheap. I got lucky and found it cheap. 9/16"-16 to suit grinding stones made for old black and decker valve seat grinders. A 1.125 stone, a new 7mm drill bit and some 7mm drill rod.


Some scrap 1.125" aluminum rod sacrificed itself to the lathe to become my arbor

Put it all together and I have this


Ready the junker cylinder head.

Eeewww! Yet another 850 head that was stored for decades uncovered outside with no carb.

I did a bit of googling and found this picture of the three angles


Shaped the stone to 30 degrees and made a cut


Next was 45 degrees and some Dykem


And finally 60 degrees and some more layout fluid to show where I am removing material


And finally all three angles after removing the dykem


I used a rough "general purpose" stone and I think for the good head I would step up to a finer finishing stone.

I am going to take this head to some more knowledgeable people than I to get their opinions on the viability of my homebrewed valve job and hardware. I am pretty convinced that I can do this. Hell I already have, but I think I might need to learn a bit more about the angles and their locations/widths.


OK OK I know that these days valve seats are cut with carbide and no longer ground to shape, but a neway carbide cutter itself costs several orders of magnitude more than my total engine rebuild. Yes I am sure that grinding is far inferior for many super awesome reasons but This has cost me about $25 so far and looks to be working just fine.

Comments? I am interested to hear peoples opinions of this.

BLOOD HELL! what a build thread, is there anything you cant do What a awesome build.
Good luck with it but looking at hwo its going you don't seem to need it !

^What Seth said.

I understand that the 30 and 60 degree angles both help the gasflow and reduce the width of the 45 degree seat. The thinner the seat, the better the valve seals. However, the exhaust valve seat should be wider than the inlet valve seat - the wider area allows more heat to flow ffrom the valve into the head when it's closed.

It's well worth making sure that the diameter of the port behind the 60 degree section is as big as possible while still allowing a suitable width of 60 degree angle - that diamater is often very restrictive on stock engines, although it doesn't look too bad on your test head.

I did find a few suggestions on seat width on the internet a while ago - but I suspect that there are as many suggestions for width as there are engine builders/tuners...

And I've just read through the whole thread - it's a brilliant car, with a lot of very thoughful modifications. It's a credit to you, and I really like it.