Classic cars forum & vehicle restoration.

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I stripped all the tin work off the engine today and it is fairly evident that the cylinder base gaskets are leaking on both cylinders also the is a small amount of leakage on the push rod tube cylinders so it makes sense to replace the gaskets and seals and give the head a decoke. The engine was running well and no odd noises so I don't want to touch the crank other than replace the front seal.

Another question for Peter! How easy is it to get the cylinders and rings back into the cylinder? I have never taken the cylinders off before. Also is it worthwhile replacing the rings whilst it is all apart? I guess it makes sense to take the cylinders off and see what condition they are in first? Anything else you would do whilst it is apart?

Tony

[colwyn500]

It really would be not that much more difficult or long winded to completely disassemble and rebuild it you're going that far, to include replacing timing chain and gears. Just as a matter of course if taking the barrels off and assuming no significant wear or scoring I think many people would hone the barrels (easy job with a simple tool and electric drill) and fit new rings. It is more fiddly with the con-rods already connected to the crank but you can refit the barrels like that. It's only five minute's work to remove the sump and detach the conrods anyway. (fit new lock-nuts). I didn't spend much on the engine rebuild apart from the new pistons and rebore.

I re-used the main bearings, I think the cam bearings are integral with the block anyway, fitted a new set of standard big-ends without any work to the crankshaft, one valve and new springs (very worthwhile) all new seals and gaskets. It resulted in a super little engine (so far )

Ask the Fiat Forumers and I am sure they will extend my suggestion significantly to a reprofiled cam, bigger pistons, skimmed head, smoothing out the ports etc. etc. and look, you needn't even get cold.

KNO_6884 by peterthompson, on Flickr

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Yes you are probably right about going the whole hog, there really is not a great deal left after taking the cylinders off and the cost is fairly minor to replace the big end bearings, rings, etc if needed, less than £50 it's preventative maintenance if you like.

I am sure I would be met with loads of replies on the Fiat forum about upgrading and polishing things if I were to pose the question on there, which I why I came to the voice of reason. 80mph in a 500 really!!!!! It would scare the life out of me and it's not what the car is meant for.

[colwyn500]

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Yes I don't quite understand the thought patterns of some of them.

TBH I am beginning to think that maybe I should change the engine casing for the other one I bought for a 650 with a hole in for the distributor. The last thing I want to do is start drill additional holes in the bodywork to accommodate the additional electronics for the ignition and it won't sit right anywhere or look right. The only problem maybe the camshaft if it has the gear for a distributor, I will find out tomorrow.

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As you said Peter it really is simple to strip down and takes no time at all.

The cylinder base gaskets were virtually non existent you can just see what's left of them next to block.

The cam and crank are still attached to the block until I decide which block to use the existing one or the one with a distributor hole.

The cylinders and pistons look really good no scoring at all.

When you said you replaced the nuts on the con rod, did you have nylock nuts on them as the ones I removed were just plain nuts and no washers?

[colwyn500]

That all looks very familiar, even down to the OSB that you have it all on
You've got me with the nuts; they were definitely plain with no washers when they came off, but they may have been Aerolite nuts that went back on but I'm not sure; I also used threadlock for good measure.

The main things I struggled to keep aware of were keeping the piston and rods with the correct barrels and making sure everything faced the correct direction. I got there in the end.

PS. Just thought to put the cat amongst the pigeons. I think you should rebuild the engine as is. Using another block there will be lots of minor differences from wear, settlement and even the slight differences in the original casting and machining. Also, I think you would have to replace the main bearings and I don't know if the block has its own cam but if not, there will be a mismatch swapping over casings. You would really be having to get things machined with oversize bearings etc.

You seem to have a tidy little engine and that ignition system sounds perfect. If I had that setup, originalist though I am, I wouldn't stress trying it in the 500.

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Yeah you are right about the blocks, especially when you think they were made in different factories, countries even. There are sure to be some tolerance differences. There is no cam with the other engine block, I would have to buy one which would be additional cost and TBH the other block looks like it hasn't had the best of lives.

I think under all the oily grime it is in pretty good nick.

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I just had a thought about what you said about making sure about pistons and cylinders were kept in the correct order and facing the right direction. I took great care with the pistons and marked them up then labelled them. But I just took the cylinders off and didn't really think about making sure it was with the right piston!!!!!! So I was desperately thinking I hope I can match them up, and suddenly it occurred to me I can match them up by the oil staining on them from the picture above and breath again!!!!! Pays to take pictures.

So another question did you put the pistons into the cylinders then just offered them upto the block and then connected up the con rods?

[colwyn500]

So another question did you put the pistons into the cylinders then just offered them upto the block and then connected up the con rods?

That's what I did and it's one of the great advantages of detachable barrels.

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Peter another question when putting the Pistons and rings back in the cylinders. The manual refers to "turn the piston rings round so that their gaps are on the far side of the piston from its slit. The piston slit is on the lightly loaded side, the thrust is the other". These pistons don't have a slit on them?

Did you put the gaps on the rings in any particular position?

[colwyn500]

Your pistons look totally different and have cutaway skirts so I guess don't need slits. They won't expand the same way as the 500 full pistons. I followed the unusual instruction and all ring gaps were on the side of the piston nearest the exhaust. Still try not to align them with each other.

There may be a stamped number 1 and 2 on the conrods and that would probably be on the side that the ring gaps should be. That asssumes the pistons haven't been taken off the rods.

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Thanks I found another manual which said the slot that I don't have is normally on the camshaft side and that the number on the conrods is normally on the same side as the slot. So working on that theory I put the ring gaps on the opposite side which would be the exhaust side.

Well I say I put! I managed to get the first two rings in the barrel using my fingers but I can't get the third thicker one in. Did you use a ring compressor?

[colwyn500]

I no longer have a ring compressor so I must have managed without. The best I can imagine is I cobbled one up out of a tin can and jubilee clips or cable ties. I think I got them in without tools though.
Are they new rings and if so have you checked the gaps?

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No they are the original rings. The barrels are in really good condition and the rings are in spec using a feeler gauge for the various measurements. I'll have a go tomorrow with some cable ties as it the bigger oil ring I maybe able to get a really small tie across half of it????