Technical Spark Plug Torque Setting for 1978 Fiat 124 Spider

[stevenk9958]

Can anyone tell me what the correct torque setting should be for the spark plugs for a 1978 Fiat 124 Spider in both newton-meters and pounds? I've seen lots of "opinions" and am hoping someone that has a reliable service manual can tell me for sure for the 1978 model year?

 

[bugsymike]

Can anyone tell me what the correct torque setting should be for the spark plugs for a 1978 Fiat 124 Spider in both newton-meters and pounds? I've seen lots of "opinions" and am hoping someone that has a reliable service manual can tell me for sure for the 1978 model year?

Best I can do is this from similar age / engine types of Fiats. 25-30 Nm. If you are using a decent Torque wrench it will have the scale in NM and in foot pounds of measurement.
One small point, I have worked full time since 1969 repairing all makes including Fiats and I have never needed to torque a spark plug and never had one come out or be over tightened, it is just feel and experience.
Where they have a sealing washer you nip them up and then a little more to compress the sealing washer.

 

[s130]

Best I can do is this from similar age / engine types of Fiats. 25-30 Nm. If you are using a decent Torque wrench it will have the scale in NM and in foot pounds of measurement.
One small point, I have worked full time since 1969 repairing all makes including Fiats and I have never needed to torque a spark plug and never had one come out or be over tightened, it is just feel and experience.
Where they have a sealing washer you nip them up and then a little more to compress the sealing washer.

Plugs with washers as opposed to angled seats the "hand tight" PLUS 1/4 turn / 90 degrees is common practice.

The objective is a gas tight seal without over doing it. If you are not sure your "softly softly" approach has done the job then a water / fairly liquid soap mix can be sprayed/applied to the plug sealing surfaces. Any leaks no matter how small will soon show.

 

[Slotman]

Just thought I would add to prevent galling from dissimilar metals it wouldn't hurt to add some anti sieze to the plug threads

 

[124BC1]

Tightening torques figures in an official Fiat Workshop Manual for the 124 twin cam - 4.1 kgm or 29.7 ft.lbs
Or in a Haynes Workshop Manual (usually quite reliable, accurate) - 30 ft.lbs

Conversion factors - To convert Nm to ft/lbs multiply by 0.738
To convert ft/lbs to Nm multiply by 1.356

(nowadays, ft/lbs is more correctly referred to as lbf ft or lb ft)

So, 'bugsymike' is correct (as usual ), as indeed are others who recommended to seat the plug then tighten by 1/4 turn (when a crush washer is used), and it's what I do on *most* 'classic' cars.

It's interesting that the original Fiat supplied trunk toolkit included a basic tube type spark plug wrench and an approx. 6 inch punch/ T-bar to use to turn it.. ( it would be difficult to over-tighten the s. plugs using these tools.)

A little word of caution, be very careful when installing the no.4 spark plug, this is close to the engine firewall (bulkhead)(so a little tight on space) and because it goes in at an angle to the vertical, is easy to cross-thread. (most cylinder heads I've seen needing a thread repair/insert , needed it on the no. 4 plug hole). So. if the plug won't screw in by hand until seated, don't force it, remove it and check out what is wrong. Most of these cylinder heads I've seen that needed a thread repair/insert, needed it on no. 4 plug hole.
A little *anti-seize or even some graphite grease is also a good idea, as already suggested by 'Slotman'.

* However, be careful when changing spark plugs on more modern vehicles especially those fitted with long-life plugs or plugs of smaller size than the old 14mm thread, 21mm hex. Very often there are fitting instructions on the spark plug packaging (print can be a little small though ) but there's lots of information on the spark plug manufacturer's websites. E.g. on the Denso website, they recommend that no lubricant/anti-seize is used on the threads and that the correct torque figure be used, the only exception is spark plugs designed to be used used in forklift engines running on e.g. LPG which are supplied with thread lubricant already applied. Lubricating the plug threads can result in over-tightening when the correct torque figure is used, possibly causing distortion of the plug body (remember I mentioned smaller s. plugs), affecting the heat range/transfer of heat etc.etc.

 

[bugsymike]

Good point re LPG engine spark plugs that I was unaware of @124BC1.
I have only seen close up LPG on plant stationary engines at auctions, where the majority were there due to low compression from valve failure. I put that down to a lack of lubrication in the fuel. In fact I had a discussion with an advocate of LPG in cars, we agreed to disagree.
On reading a little about it, where a good installation has been done, additives and even petrol is introduced to help regarding the lubrication side.
Like you, I always manually screw in spark plugs and most nuts and bolts, so it is easy to feel if there is a problem. The time saved by using power tools etc. is soon lost when having to repair the damage caused by cross threads etc.
As an apprentice in the old days we had no power tools, a speed brace in our socket sets was about the limit.
Just found this spark plug thread chasser from the 1970s (British Made) it was handy to clean any carbon from the thread hole and clean up on earlier Renaults which had the very short reach spark plugs and as you mentioned it was usually if damage found the back spark plug almost under the bulkhead.
I recall a guy coming in with a "top hat " dent in his bonnet and engine making a blowing noise where a damaged plug had blown out hitting the bonnet.

 

[124BC1]

'bugsymike' Ah, the good ol' days (that I often mention, probably goes 'over the heads' of many members here). I served an apprenticeship on motorcycles from 1973 and then a car apprenticeship from 1976, so I remember the days of no power tools. When we eventually got an air gun, the boss didn't buy any impact sockets, so everyone used their regular sockets which is not a good idea (wrecks the socket and is potentially dangerous to the user). Also, I remember that, back then, everyone had sets of Whitworth, A/F and if needed, metric open-end and ring (box) spanners (wrenches), before combination spanners became commonplace.

Often used speedbraces and still do! I do have cheap air tools (thanks to Lidl, Aldi etc.) but rarely use them - I would have to fire up the compressor ....(noisy ), wait for pressure to build up, use the air tool and then remember to drain the tank to (hopefully?) prevent internal corrosion. I do use the air compressor however, if I'm topping up multiple tyre air pressures. And while I have an air impact wrench, I also have an electric impact wrench that works just as well (similar no. of joules, beats/minute, and Nm), is available to use immediately and use it to loosen wheel nuts/bolts or very tight hub nuts etc. I prefer to fit and tighten nuts/bolts manually - I'm retired so no need to rush and actually enjoy taking my time and doing things the old, manual way.

I remember those spark plug thread chasers. I used to use a thread tap of the correct size and found it could actually start removing some material on some alloy cyl. heads so the thread chaser is safer/better. In my early days working on motorcycles at home, I used an old spark plug with a couple of hacksaw cuts down the length of thread and the crush washer removed to clean carbon out of threads - worked quite well and was very cheap (i.e free!) - if you angled the cuts slightly it worked better, essentially I reckon? you were adding a little rake angle to the 'cutting' teeth of the old spark plug.

Incidentally, while working at that motorcycle workshop, I also learned how to fit Helicoil thread repair inserts. We had a (usually) safe method of fitting a Helicoil insert with the cyl. head in situ - but if the job went wrong, we would do the full repair (i.e. remove the cyl. head etc.) at no extra cost to the customer.
We also had a Gunson's BeadBlaster, could overhaul built-up motorcycle crankshafts, could straighten accident-damaged frames and fork stanchions and had a m/cycle 'Rolling-Road', so we gained a lot of work from other M/cycle workshops that were not so well-equipped. I learned a lot from the great people at this 'shop, we even had our own part-time Wheelwright who kindly showed me the basics of spoked-wheel building and trueing ....
Fun times, a great learning experience and great memories

And as regards stories of customers getting it wrong when working on their car, we once had a car towed in, customer had stripped a plug thread on a Fiat twincam engine, decided to remove the cylinder to have the thread repaired, removed all the cylinder head bolts, couldn't figure out how to disconnect the timing belt (maybe realised he was 'in over his head'). We had to remove the cylinder head to fit a new head gasket (oil and coolant had seeped between the gasket and head/block with the bolts removed). Customer was kicking himself that he had messed up a simple job (changing spark plugs), he was even more upset when we told him we probably could have fitted a Helicoil insert with the head in situ, maybe even got one of the Mechanics to call to his house afterhours to fit an insert (to avoid a tow-in charge and keep the cost down i.e. maybe just pay the Mechanic as a private job/favour). I reckon careful use of one the thread chasers you mentioned would likely have rescued the situation - only the 1st few threads had been mangled - at least well enough to get him mobile again and sort out the fitting of an insert at a later, more convenient time.

 

[bugsymike]

'bugsymike' Ah, the good ol' days (that I often mention, probably goes 'over the heads' of many members here). I served an apprenticeship on motorcycles from 1973 and then a car apprenticeship from 1976, so I remember the days of no power tools. When we eventually got an air gun, the boss didn't buy any impact sockets, so everyone used their regular sockets which is not a good idea (wrecks the socket and is potentially dangerous to the user). Also, I remember that, back then, everyone had sets of Whitworth, A/F and if needed, metric open-end and ring (box) spanners (wrenches), before combination spanners became commonplace.

Often used speedbraces and still do! I do have cheap air tools (thanks to Lidl, Aldi etc.) but rarely use them - I would have to fire up the compressor ....(noisy ), wait for pressure to build up, use the air tool and then remember to drain the tank to (hopefully?) prevent internal corrosion. I do use the air compressor however, if I'm topping up multiple tyre air pressures. And while I have an air impact wrench, I also have an electric impact wrench that works just as well (similar no. of joules, beats/minute, and Nm), is available to use immediately and use it to loosen wheel nuts/bolts or very tight hub nuts etc. I prefer to fit and tighten nuts/bolts manually - I'm retired so no need to rush and actually enjoy taking my time and doing things the old, manual way.

I remember those spark plug thread chasers. I used to use a thread tap of the correct size and found it could actually start removing some material on some alloy cyl. heads so the thread chaser is safer/better. In my early days working on motorcycles at home, I used an old spark plug with a couple of hacksaw cuts down the length of thread and the crush washer removed to clean carbon out of threads - worked quite well and was very cheap (i.e free!) - if you angled the cuts slightly it worked better, essentially I reckon? you were adding a little rake angle to the 'cutting' teeth of the old spark plug.

Incidentally, while working at that motorcycle workshop, I also learned how to fit Helicoil thread repair inserts. We had a (usually) safe method of fitting a Helicoil insert with the cyl. head in situ - but if the job went wrong, we would do the full repair (i.e. remove the cyl. head etc.) at no extra cost to the customer.
We also had a Gunson's BeadBlaster, could overhaul built-up motorcycle crankshafts, could straighten accident-damaged frames and fork stanchions and had a m/cycle 'Rolling-Road', so we gained a lot of work from other M/cycle workshops that were not so well-equipped. I learned a lot from the great people at this 'shop, we even had our own part-time Wheelwright who kindly showed me the basics of spoked-wheel building and trueing ....
Fun times, a great learning experience and great memories

And as regards stories of customers getting it wrong when working on their car, we once had a car towed in, customer had stripped a plug thread on a Fiat twincam engine, decided to remove the cylinder to have the thread repaired, removed all the cylinder head bolts, couldn't figure out how to disconnect the timing belt (maybe realised he was 'in over his head'). We had to remove the cylinder head to fit a new head gasket (oil and coolant had seeped between the gasket and head/block with the bolts removed). Customer was kicking himself that he had messed up a simple job (changing spark plugs), he was even more upset when we told him we probably could have fitted a Helicoil insert with the head in situ, maybe even got one of the Mechanics to call to his house afterhours to fit an insert (to avoid a tow-in charge and keep the cost down i.e. maybe just pay the Mechanic as a private job/favour). I reckon careful use of one the thread chasers you mentioned would likely have rescued the situation - only the 1st few threads had been mangled - at least well enough to get him mobile again and sort out the fitting of an insert at a later, more convenient time.

Brings back many happy memories.
Mine was a car apprenticeship, but I had a good mate who was foreman of the local Honda Motorcycle Dealers, so I used to buy any cheap British bikes that came in part exchange as no one wanted them. One of their mechanics could respoke wheels on an old dustbin from memory before truing them.
I never stripped built up cranks , but when later I worked at a Wartburg Dealers the three cylinder two stroke cranks that needed attention we sent to Alpha Bearings in Dudley, the same place we used to buy racing conrods etc for our Villiers 9E 197cc Class four karts we raced when at college.
I too had Whitworth , A/F and Metric combination spanners, I was fortunate at College to win an award for being the best practical student of my year (I used to say it didn't say much for the other students) apart from my name in the local paper and a presentation evening, it included a £5 worth award of a full set of Whitworth, A/F and Metric combination spanners by Brittool, my choice to include the Whitworth as many of my old bikes used them, but also any 50s cars . I still have most of those spanners 53 years later, though you couldn't even buy the smallest single spanner for £5 these days.
The home made thread tap/chasser idea I often use on rebuilding engines when cleaning cylinder blocks using the old head bolts as I always clean out to the bottom of the threads so when torquing new bolts I know the head is being pulled down tight and not a bolt jamming in the threads, then blowing the dirt out and running the new lightly oiled bolts all the way down to check. Things like that take extra time and wouldn't be viable in a modern dealership, but well worth while and added to the satisfaction of knowing when you turned the key everything would be right.
I was fortunate to never have to work to a time clock, although as a youngster the boss often used to come up to to you after 30 minutes into a job and ask silly questions like"what was the old clutch like?" knowing full well the job had only just started, just as a wind up. They were good people to work for, but I had to move on to progress, as starting as the boy, seven years later I was still making the coffee as they took on no more apprentices. Leaving there was my choice, so that two weeks was the only time since 1969 that I have ever been out of work until retiring, so my mum was dead right about getting that apprenticeship, also the two places I worked before going on my own, in both cases they asked me to work for them, so not bad.

 

[124BC1]

I think everyone who worked in a workshop in those days likely has fond memories and funny stories - I remember once being asked by a stingy motorist why I had fitted new 'points', could I not have sharpened the old ones?... or residents local to the dealership (who might not even spend any money with us) coming in with bag-fulls of old worn out, often oiled-up spark plugs wanting them cleaned for free - management wanted to stay on the right side of the locals in a mainly residential area, so patiently indulged them - guess who always got to clean the plugs - an apprentice, of course. As regards time taken on jobs - the foreman used to ask e.g. if I had gotten enough sleep the night before? and then say, given how long it's taking you, I was sure you must have fallen asleep on the job!
Yes, Alpha Bearing were one of our sources of crank bearing parts (most of our parts were ordered as large stock orders from Japan, where the boss had developed contacts, but delivery took much time in those days). The guys at Alpha Bearings certainly knew their stuff, real old-school engineers who could even devise modifications to overcome inherent crank problems.
By the time I started working on motorcycles professionally, new British bikes were not selling at all over here and second-hand machines were v. difficult to shift, so I didn't have much to do with them, workshop never had any in, dealership we were connected to (business arrangement between 2 separate business owners) had ceased taking in any as trade-ins and were running down their stock of spares.

I wish I had bought more of the 'proper' Britool tools (I do have a reasonable collection) when I could have done so, the later tools after Britool changed hands? were nowhere near as good. Unwisely, I got swept along by the hype surrounding Snap-On tools - 'free' credit, slim design, lovely shiny finish and life-time guarantee (of no use if the previous agent went bust and his replacement didn't want to know) - ended up with having run-up significant credit (debt) that I struggled to pay off for years while on an apprentice's low wages. At that time, Snap On tools cost about twice what Britool cost and about 3 times what Snap-On cost in the USA (Snap-On tools in Ireland were imported from Scotland? so were subject to 2 currency exchange rates, 2 shipping charges and 2 sales taxes ), our sales tax (vat) alone on hand-tools was 35% in those times... . Also wish I had bought more Hazet tools, I thought they were nice also, afaik, they were used in M-B dealerships.

I think we're of the same approach as regards cleaning and checking everything as we go along doing a job to the very best of our ability.

 

[bugsymike]

I love the "sharpen the points" bit.
Monday mornings we used to get breakdown jobs from occasional customers who after washing their cars on Sunday morning then felt it was a good time to service them as how hard can it be when the monkeys at the garage can do it? Husband had gone off to work by by then by bus as car wouldn't start, so we had to deal with wife. Quick check to find no spark and new points badly assembled in distributor going straight to earth. Soon fixed and on querying the new points it was often denied that anyone had even opened the bonnet. Oh yeah!
I expect you are the same as me, when a car comes in that you have regularly worked on , you immediately can see if someone else has been in there, the same as if someone has been in your tool box.
Re the British part exchange bikes I recall buying two Francis Barnetts £7 and £9 and a Triumph 21 (350cc bathtub model) predecessor to the Tiger 90 for £25, considering they were being replaced by 250 Honda Dreams and Super Dreams I wonder if any buyers remorse later on?
I had most of my tools before Snap On arrived on the scene, so paid outright when I had the money, I did buy an American pair of "molegrips" by Proto for 30 bob (£1.50) as an apprentice and the other mechanics said I was silly as a genuine pair of Molegrips was 19/6p at the time, however I still have the Proto ones around 54 years later all be it modified but still gripping well.
I am glad I escaped the Snap On revolution, paying on the drip for a toolbox alone that was more than most of the cars I bought. French Facom tools are another good brand I found.