Technical Valve Seat Recession 110 Engine With Unleaded

[fiat500]

Following the recent incident where my engine stopped working because an inlet valve seat dropped out, I have now stripped the head and drawn some conclusions about what happened.
It turns out that the affected cylinder is the same one in which a seriously burnt exhaust valve was found to be the the most likely cause for the car having been taken off the road years before and which then lead to it becoming (cover his ears) a basket case. Here is what it looked like then:
KNO_5846 by Peter Thompson, on Flickr
Obviously I put a new valve in at the time, but I didn't consider it necessary at the time to have the seat re-cut...maybe I should have done? So it was thoroughly ground-in, which possibly was a mistake.
Today I had to tap the inlet seat back in to allow me to compress the springs to get the valve out. But then the real culprit was obviously this same exhaust valve. It has really badly recessed the seat and burnt away at one side. I think that some of the crusty deposits in the combustion chamber might even be melted metal.
MAL_3578 by Peter Thompson, on Flickr
MAL_3586 by Peter Thompson, on Flickr
So for me running the number of miles at the speed have been doing without an unleaded conversion to the head was a mistake. I will definitely have the conversion done if I rebuild the engine and for any future engine jobs.
It explains the strange putt-putting noise the exhaust started making a few months ago, how I was so overly intrigued that my rebuilt engine had such a nice sound in comparison and why the engine had become such a pig to cold-start.
It doesn't explain why only a few days prior to giving up on me, the engine seemed to be running better than it had ever done.

 

[IanEmery]

I feel sure the width of the exhaust seat face contributed to this; it is good engine build practice to have the valves lapped in so that the seat contact patch is about the width of a pencil line to minimise heat transfer. When an alloy head gets hot enough the seats will no longer be an interference fit.

Regarding the possibility of valve seat regression, or burning, caused by lead free petrol maybe this explains why you've had to reset your tappet clearances so often? I have read varying views on whether lead replacement is necessary for our engines but maybe this swings opinion towards it. I've always used Millers lead substitute but I know some other wners feel it unnecessary.

Whatever, I hope you can get this sorted quickly and soon be back on your travels with Murph.

 

[fiat500]

Whatever, I hope you can get this sorted quickly and soon be back on your travels with Murph.

We will be; the latest trip to Orkney didn't feel right without him,

 

[fiat500]

I have read varying views on whether lead replacement is necessary for our engines but maybe this swings opinion towards it.

It does, but I have found something that swings it further. Someone has already done the research and found a Fiat publication which gives their opinion on it. It lists the 126.000 and the 126A1.000 engine (among many others) as being "Vehicles which must only use 4 star leaded petrol.". As the forerunner to these engines it seems extremely unlikely that the 110.000 engine will be any different.
http://www.sportingfiatsclub.com/forum/topic.asp?TOPIC_ID=1108
There are some Fiat engines which are not designed for unleaded but are intermediary in design and can be used so long as "rapid acceleration and constant high speed are avoided" So even if that was the case for the 500, I haven't followed that advice nor could I.
Maybe there has been some confusion as the 126 BIS can use unleaded petrol. I know there was some Haynes advice recommending leaded to be used every fourth tank.
So I am going for the best of the best lead substitute additive, but I will be getting the 500 head modified ASAP.

 

[Vitesse]

I think you are unique because of the amount of miles you clock up. I doubt there are any other 500's in the U.K., possibly in the world? That clock up as many miles as you? I think for occasional weekend use most will be fine. Also considering the fact that it looks like there was a problem originally with that exhaust valve, it has just compounded the issue.

I still use an additive despite my meagre miles, probably a 200 miles per annum max. I use Castro Valve Master Plus and I used to run my Vitesse on it, which certainly clocked up a higher annual mileage and I had no issues. There were a lot more valves to worry about as well seeing it was a straight six.

 

[fiat500]

I think for occasional weekend use most will be fine. .

True.....but what use is that to me? :bang:

200 miles a year? That's 75 years' worth of driving I've used up already.

 

[Vitesse]

True.....but what use is that to me? :bang:

200 miles a year? That's 75 years' worth of driving I've used up already.

I can't get all my tools in a 500 maybe I should trade it in for a Giardiniera, so I can use it for daily use??????

How many miles did Murf have on him when you first got him? How many have you added?

Luigi in 50 years has 79,000 miles on the clock, I would imagine some of that time it had a broken speedo cable as well, so that works out at 1500 odd a year, you are doing 10 times that in 2 years!!!!!!!!

 

[fiat500]

I can't get all my tools in a 500 maybe I should trade it in for a Giardiniera, so I can use it for daily use??????

Now you're being silly............Giardinieras aren't proper Fiat 500s .....they're too big to be really useful.
We've gone from just over 32K to just under 48K miles in less than two and a half years. Even so that means I've stll only done about one third of all the miles the car has ever done and it was reportedly only used for about five years before its long lay-off. So someone used it as a proper car prior to me.
What can I say? It must be obvious that I really like driving the car and I could never envisage ownership for ceremonial purposes only. So I'm determined to continue as before until the next incident.
Currently Murf's shivering on the lawn wondering why his backside first went light and has suddenly got a bit heavier than before. We should be on the move again tomorrow.

 

[Vitesse]

Now you're being silly............Giardinieras aren't proper Fiat 500s .....they're too big to be really useful.
We've gone from just over 32K to just under 48K miles in less than two and a half years. Even so that means I've stll only done about one third of all the miles the car has ever done and it was reportedly only used for about five years before its long lay-off. So someone used it as a proper car prior to me.
What can I say? It must be obvious that I really like driving the car and I could never envisage ownership for ceremonial purposes only. So I'm determined to continue as before until the next incident.
Currently Murf's shivering on the lawn wondering why his backside first went light and has suddenly got a bit heavier than before. We should be on the move again tomorrow.

Oh right so from 1974 he was parked up in a leaking garage rotting from the top down until you bought him, so he must have sat for 30 odd years. Did you buy him through eBay?

 

[fiat500]

Murf was an eBay purchase over the Christmas/New Year period, 2008/2009. He cost £700 and I was told that he sat for 30 odd years. The engine had a Lucas, screw-thread, sports coil, which I later sold for £11. A spark plug was broken and seized and that valve was goosed. So it's obvious that someone experienced troubles before me.

 

[jjacob]

Hi Peter,

Anytime you have valve recession or a valve burn, the valve and seat must be replaced. Looking at your picture the valve seat margin is way too wide, a clear indication that the seat has been pounded out. This will lead to further recession and constant valve clearance changes.
Best to have the head professionally rebuilt with hardened valve seats, new valve guides, and new valves, and the head surface just ever so slightly skimmed to make sure it is flat. The parts are all remarkably cheap.
Others have gotten away with not replacing their valve seats and using an additive to the fuel to help protect the valve seats. My opinion is that this works fine for light use of the car. However, that does not include you! You use your car as a daily driver and put lots of miles on it. In this case a head with proper hardened valve seats is necessary.
Fiat did not have hardened valve seats until late in the 126 run. I posted this information recently. https://www.fiatforum.com/500-classic/445683-engines-hardened-valve-seats-unleaded-gasoline.html
John

 

[jjacob]

One other thing. The area around the intake valve seat does not look good (grinder marks). Your intake valve seat coming loose is an indication maybe that this head is shot. You might look for a good used head that can be rebuilt or buy a new head.
If you are putting in the 600 or 650 engine you have, you might think about having hardened valve seats put in the head unless it falls into the range of engines that came with them from the factory.
John

 

[fiat500]

Thanks John everything you said aligns with my thoughts and plans. I think the head is reusable and next time that I'm in town I'll be putting it in front of the professionals to see what the possibility and cost would be.
I am going to run the
650 somewhat less aggressively and using the best lead substitute​ ALL THE TIME. Even so I am sure this will haunt me again.
The synchro box does seem to have a slight but noticeable higher gearing so perhaps that will help

 

[Vitesse]

John's post is interesting as I didn't read it properly before. My 650 is a very late 1997 and has a serial number starting 692------- so I guess it has hardened seats, which I wasn't aware of. It does look considerably different to a standard head as well, which I believe gives it higher compression.

 

[fiat500]

John's post is interesting as I didn't read it properly before. My 650 is a very late 1997 and has a serial number starting 692------- so I guess it has hardened seats, which I wasn't aware of. It does look considerably different to a standard head as well, which I believe gives it higher compression.

SNAP!
MAL_1778 by Peter Thompson, on Flickr

 

[Vitesse]

So is your engine number above the magic number? I assume it is?

 

[fiat500]

So is your engine number above the magic number? I assume it is?

......very well above, being in the 9 *** *** range, which puzzles me because I think it's 1987 and did they actually build that many? but the 594, as you would expect is down in the 4 *** ***.
I still am not going to hammer this engine and I will be taking with a pinch of salt, those past posts by various parties saying such as "will run all day at 60", "70 is easily possible in a 650"etc. Al true I am sure but at what price?
Maybe I should avoid lead substitute if the information about the head having hardened seats is true, because I supect that part of my carbon build-up was from the substances in the additive.
Sorry to offend the sensitive eyes of you perfectionists...I used whatever paint I had and as you can see...no polish whatsoever

[ame]https://youtu.be/hUPfPfMPvs0[/ame]

 

[Vitesse]

I think the 6------ figure is specifically referring to Polish built 126 engines, as John took that from a Polish website, so yours is proberly an Italian engine which is allegedly a better built one.

 

[fiat500]

I think the 6------ figure is specifically referring to Polish built 126 engines, as John took that from a Polish website, so yours is proberly an Italian engine which is allegedly a better built one.

It's now a Scottish-sourced, English-built engine
But I think it is actually Polish in origin; it had a Zelmot distributor and alternator and a FOS carb.

 

[jjacob]

I think all of the hardened valve seat 650 engines were Polish.

John