If you have a meter test the leads and also test the plug extensions. I had a similar problem . The coil was getting hot and stopped working. when it cooled down it ran again . The extra resistance was making the coil hot because it was having to overcome a high resistance in the extension.
Technical Strange Issue
- Thread starter Labman
- Start date
Currently reading:
Technical Strange Issue
lazylobster
Established member
I’ve had a bad plug that broke down when hot. Meter showed high resistance. So worth running your leads, plug and coil over a meter 
OP
OP
Well guys, bad news for me. I did a compression check and cylinder one has zero compression. Cylinder two was around 90 psi. I had the head reconditioned about three years ago after a valve seat broke on that side. My thread on it is here somewhere. So it seems the repair didn’t hold or maybe it’s something even worse. I won’t know until I take the head off again. Not looking forward to it as it was a PIA getting that head off. So if I’m correct and the valve seat is bad again, I will be looking for a new head. Not interested in having it reconditioned again. If anyone has one or knows where I can get one please let me know. This is of course it’s just an issue in the head and not the piston ring or something like that. It’s for a 1970 500F.
Thanks guys.
Thanks guys.
- Joined
- Apr 1, 2017
- Messages
- 361
- Points
- 137
Bummer
....get the engine out and head off, don't get down hearted everything is repairable...….
Both Mr. Fiat and Van der Laan have 600 and 650cc heads. OEM 500 L and F heads are on ebay.
OP
OP
Found out the cause of my “strange issue”. Catastrophic engine damage. As I feared, the head I had reconditioned and a new valve seat was fitted, failed. The ring must have came loose and got ground up and ruined the head and piston. This explains the backfiring issue too. The valve was not sealed correctly on compression stroke. Now I have my work cut out for me. Engine will most likely come out and be dropped off at a shop because this is beyond what I can handle. So I most definitely will be needing a new head. Please send me links as there are none available here in the US. Will be needing bunch of other new parts as well [emoji35]
Last edited:
This post contains affiliate links which may earn a commission at no additional cost to you.
Hi Labman,
Whoever 'reconditioned' that cylinder head should imho be held responsible for the cost of repairs.
If this is the standard of workmanship available to you locally, can you really feel confident in similarly 'competent' people carrying out the engine repair?
DIY, imho, is often the best course of action on older cars nowadays. Many modern Mechanics don't understand older engines and don't seem to care.
You say the repairs now needed are beyond what you can handle.
I say rubbish.
You've already managed to remove the cylinder head, I believe you can continue and complete the repair correctly. It's not that complicated.
You sound like you're feeling overwhelmed by the magnitude of the repair job facing you. To give you some perspective, as a former Fiat dealership Mechanic, I would have been expected to have your car in and out in 2 days max. incl. waiting for the new cyl. head to arrive (next day delivery). Even now, in my old age, with a new head/valves/gaskets etc. to hand, I'd knock that out on a Saturday morning or an evening, no big deal. No need to remove the engine either, wouldn't have been allowed in a dealership 'shop. Just remove the engine lid and raise the car on jackstands/blocks for convenience, if you want.
I wouldn't go ordering a new cylinder head just yet - always best to strip, clean and examine properly first. Imagine ordering a new cylinder head and then finding a lot more damage/wear, necessitating a replacement engine?
Your existing cylinder head could likely be repaired and be completely reliable but the cost of such work (machining, welding, re-machining, fitting new seats, new guides, more machining, new valves, skimming etc.) would probably cost a lot more than a new cylinder head plus valves. Or would it? I'd check before ordering a new head.
You might pull the cylinder barrel from the damaged cylinder and check for any damage to the piston e.g. crushed crown (top) or trapped/broken rings. Also check the cylinder bore for any damage (might not be any). Before doing this, turn the engine so that the piston is at the top of it's stroke (tdc), lift the cylinder barrel a little so that it comes free from the cyl. block (crankcase) and stuff some rags into the crankcase mouth to prevent any broken piston rings (just in case there are any broken) from falling in, then remove the barrel fully to inspect the piston.
Doing this will allow you to decide if a replacement cylinder head will fix the problem or if more extensive work will be necessary.
If you decide to have a go yourself (and I hope you do) remember there's lots of people here to help you, just post your questions and pics if possible.
There's lots of info incl. pics on this forum from others who have done work on their cyl. heads/engines, if you care to do a search.
What have you got to lose?
Al.
Whoever 'reconditioned' that cylinder head should imho be held responsible for the cost of repairs.
If this is the standard of workmanship available to you locally, can you really feel confident in similarly 'competent' people carrying out the engine repair?
DIY, imho, is often the best course of action on older cars nowadays. Many modern Mechanics don't understand older engines and don't seem to care.
You say the repairs now needed are beyond what you can handle.
I say rubbish.
You've already managed to remove the cylinder head, I believe you can continue and complete the repair correctly. It's not that complicated.
You sound like you're feeling overwhelmed by the magnitude of the repair job facing you. To give you some perspective, as a former Fiat dealership Mechanic, I would have been expected to have your car in and out in 2 days max. incl. waiting for the new cyl. head to arrive (next day delivery). Even now, in my old age, with a new head/valves/gaskets etc. to hand, I'd knock that out on a Saturday morning or an evening, no big deal. No need to remove the engine either, wouldn't have been allowed in a dealership 'shop. Just remove the engine lid and raise the car on jackstands/blocks for convenience, if you want.
I wouldn't go ordering a new cylinder head just yet - always best to strip, clean and examine properly first. Imagine ordering a new cylinder head and then finding a lot more damage/wear, necessitating a replacement engine?
Your existing cylinder head could likely be repaired and be completely reliable but the cost of such work (machining, welding, re-machining, fitting new seats, new guides, more machining, new valves, skimming etc.) would probably cost a lot more than a new cylinder head plus valves. Or would it? I'd check before ordering a new head.
You might pull the cylinder barrel from the damaged cylinder and check for any damage to the piston e.g. crushed crown (top) or trapped/broken rings. Also check the cylinder bore for any damage (might not be any). Before doing this, turn the engine so that the piston is at the top of it's stroke (tdc), lift the cylinder barrel a little so that it comes free from the cyl. block (crankcase) and stuff some rags into the crankcase mouth to prevent any broken piston rings (just in case there are any broken) from falling in, then remove the barrel fully to inspect the piston.
Doing this will allow you to decide if a replacement cylinder head will fix the problem or if more extensive work will be necessary.
If you decide to have a go yourself (and I hope you do) remember there's lots of people here to help you, just post your questions and pics if possible.
There's lots of info incl. pics on this forum from others who have done work on their cyl. heads/engines, if you care to do a search.
What have you got to lose?
Al.
Last edited:
Don't forget about www.mrfiat.com , who are in the U.S. and have lots of parts for the 500, also have downloadable parts catalogs.
They have engine parts, +complete engines but I only see cyl. heads for the 500R/126 (600/650cc).
Also in the U.S., C.Obert & Co.@ www.fiatplus.com have lots of 500 parts including some cyl. heads.
Might save you some time/money on some of your parts requirements.
Remember that for items such as cyl. heads, many parts suppliers charge a core deposit, refundable on receiving an undamaged, re-useable part, i.e. it might actually be cheaper to buy from a U.S. supplier....
Al.
Last edited:
OP
OP
Thanks for the replies. The person who reconditioned my head certainly seemed like he knew what he was doing a he worked on VW engines for many, many years and had a huge workshop with all kinds of equipment. He was an old guy and took forever to get the head back to me. This was back in 2016. Not sure how the valve seat he repaired broke again but the head is so badly damaged, it cannot be rebuilt as far as I know. So I think the biggest obstacle I am going to face here in the US is finding a 500F head. Hobbler is on the lookout for one for me and if any of you out there can source one for me that doesn't need a core deposit, please let me know. Back in 2016 someone here had two NOS heads that I could have (and should have) bought instead of having my head rebuilt. I contacted him and they are long gone now. Luckily I have a local Ferrari mechanic that is going to help me with this engine. I'm hoping he may have someone from his home country of Italy find me a head. We will see...
the hobbler
Distinguished member
- Joined
- Jul 25, 2012
- Messages
- 4,405
- Points
- 1,107
Steven;
Whilst I will continue to look for a new head for you, you comment regarding your Italian mechanic looking for 1 in Italy might be your most logical route. When I was in Italy last year (in the Senegallia region) there were still lots of 500s running around, and there were over 60 at a mixed (i.e not 500 only) Raduno---there MUST be new 500F heads floating around over there!
Whilst I will continue to look for a new head for you, you comment regarding your Italian mechanic looking for 1 in Italy might be your most logical route. When I was in Italy last year (in the Senegallia region) there were still lots of 500s running around, and there were over 60 at a mixed (i.e not 500 only) Raduno---there MUST be new 500F heads floating around over there!
Labman,
PM me. I have a buddy in San Diego that has two or three around the shop.
PM me. I have a buddy in San Diego that has two or three around the shop.
- Joined
- Apr 1, 2017
- Messages
- 361
- Points
- 137
I’m with Al on this one, strip the head and give it a good clean first it may only be superficial damage and the head may not be a failed component here. Don’t write it off at this stage.
The piston is deffo beyond repair and whilst I agree with Al’s comments about checking the cylinder for damage I would be tempted to just replace both barrels and pistons.
We’ve all been where you are now where you look at worst case scenario and feel utterly off, deep breath, get some cleaner and start to have a look at what’s really happened.
For what it’s worth my thoughts are that the head was fine but you’ve thrown a ring, it’s how much damage the failed part has caused. Be optimistic as it may not be as bad as it appears.
The piston is deffo beyond repair and whilst I agree with Al’s comments about checking the cylinder for damage I would be tempted to just replace both barrels and pistons.
We’ve all been where you are now where you look at worst case scenario and feel utterly off, deep breath, get some cleaner and start to have a look at what’s really happened.
For what it’s worth my thoughts are that the head was fine but you’ve thrown a ring, it’s how much damage the failed part has caused. Be optimistic as it may not be as bad as it appears.
OP
OP
OP
OP
The head has a huge gash in it and a pulverized valve seat ring which is embedded in the top oh head next to the spark plug hole. I can’t see how this can be fixed nor would I trust it again if it could be.
I can't quite work out where the seat has gone missing (obviously it must have done!) as both valves appear to be sitting reasonably correctly. When mine did that it looked like this.
OP
OP
Hard to see but it’s sitting a bit higher in the head than it should be. It has to be that because it was repaired (you can see the little guide holes) and had zero compression. Did the oil test too to make sure it wasn’t the rings. Head gasket was fine.
That head could be repaired, it's not that bad.
To see what can be done by a professional you might check out - www.brodix.com
or simply enter 'BRODIX Cylinder Head Repair Video' on YouTube
(there's lots of others)
Obviously, this kind of work costs, so I'd have to agree that a good s/hand head might be the most cost/time effective solution in your case.
Me? I just don't like scrapping parts that can be repaired and prefer to work with what I have.
I've had bad luck with s/hand parts - a cheap head won't look so cheap if you have to fit new guides, seat inserts, valves, skim it and possibly fit spark plug thread inserts! So unless you can strip and inspect the s/hand before purchase..... Ymmv.
Have you dropped the valves out of the head yet? If you don't have a valve spring compressor, just place a socket over the spring cap and give it a firm tap with a hammer (mallet if you're squeamish), this'll pop the spring cap off the valve and the valve collets will be constrained by the socket.
I'd be interested to see if indeed the valve seat insert has broken. Your pic in post #26 'seems' to show at least part of the seat insert (left of pic) still in situ - I've never seen this.
In your post #23 , you mention compression pressure figures of 0 on cyl. no.1 and 90 psi on cyl. no.2..... 90 psi is too low, so as The Whitakers suggest, it would be a good idea to pull both cyl. barrels and pistons for inspection.
Al.
I've seen this on a couple of occasions. When this happens, the engine looses a cylinder (due to zero compression) but the seat insert is retained by the valve head (as in your pic) preventing it from entering the cylinder and doing a lot of damage. If part of the seat broke away, then surely the remainder would do so also, resulting in no valve seat so the valve would sink into the seat insert recess in the head - yet it looks to be sitting normally?
Al.
Those 'little guide holes' look to me to be centre (dot) punch marks.
2 reasons for these marks.
1. To try to tighten a loose seat insert (either the original or a new one). Bad idea, won't last. The seat insert is supposed to be an interference (i.e. v. tight) fit in the recess in the head to ensure it never comes loose/falls out and also for heat transfer (v. important for exhaust valves). If the recess is too large to achieve this interference fit, there are oversize seat inserts available or the recess has to be reclaimed by welding and machining.
2. As extra insurance having fitted a new seat insert. Not needed + looks amateurish. If the seat insert has been correctly fitted it won't come loose/fall out. If you don't believe me, just try removing a valve seat insert at home.....
It's not a good idea to leave any sharp edges/points in a combustion chamber (using a centre punch can do this) - such points can glow red hot and cause pre-ignition (not good).
I don't mean any disrespect to your older mechanic who reconditioned this cyl. head - anyone who has worked on VW engines for years obviously has great experience on air-cooled engines - maybe using a centre punch as 'extra insurance' was just a habit he developed over the years - most mechanics develop their own way of doing things over many years, including adopting certain little habits without actually stopping to evaluate if these habits are indeed necessary or might be potentially harmful to either the car or themselves.
Al.
Last edited:
