Lancia Motor Club Forum
Model Technical and Interest => Fulvia => Topic started by: MLA on 13 September, 2025, 09:43:28 PM
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I would like to change the spark plugs in our '72 Fulvia Sport 1.6 (818.750). The manual recommends Champion R-61. The vehicle currently has Denso W24EPR-U plugs. On other older vehicles I have used NGKs to good effect. I am having a difficult time cross referencing the Champion & the Denso to an NGK equivalent. Any thoughts on what plug would best suit the 1.6?
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I use NGK D7EA (7912) on my 1.6 HF
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Unfortunately, the NGK D7EA plugs are 12mm. Our Sport 1.6 takes 14mm plugs.
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Unfortunately, the NGK D7EA plugs are 12mm. Our Sport 1.6 takes 14mm plugs.
Are you sure? You must have a 1300 head modified if thats the case. What is the casting numbe on the front of the head?
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NGK's own info: https://www.ngkpartfinder.co.uk/catalogues/classic-vehicles/search/plugs/LANCIA/FULVIA/1972/ (https://www.ngkpartfinder.co.uk/catalogues/classic-vehicles/search/plugs/LANCIA/FULVIA/1972/)
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I originally purchased NGK D8EA plugs. When I took out the old Denso plugs and noticed that the NGK 12mm plugs didn't fit, that is when I became confused. The car was sold to us as being a '72 Sport 1.6.
The car's chassis number is: 818.750 00649.
Number stamped on the front of the head is: 818.540 2286651 (see attached photo)
Number stamped on the bell housing: 818.540. 009053
Number plate on the transmission: 818.750 (can't make out the other numbers)
While new to the Lancia world, the above numbers suggest the car is a Sport 1.6. Given that, why don't the 12mm plugs fit? Any thoughts?
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Those numbers point to genuine LHD 1600 Sport. Some 12mm plugs had larger hex. Photo of the denso plug would be interesting. There really isnt room for the 14mm as the 1600 head has larger valves. Cracking across the aluminium from the plug thread to the seat is quite common on 1600s.
Out of interest are all denso plugs the same size??
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Denso do make a plug that is the same size as the NGK D7/D8EA (i.e.M12x1.25 with a 19mm thread length). It is theX24ESU. Is it possible that this is the Denso plug fitted?
If not, then the head must have been modified to accept M14 plugs...
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Cracking across the aluminium from the plug thread to the seat is quite common on 1600s.
If cracking was an issue, could the head have been rescued by fitting hardened valve seats and M14 plugs?
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Cracking across the aluminium from the plug thread to the seat is quite common on 1600s.
If cracking was an issue, could the head have been rescued by fitting hardened valve seats and M14 plugs?
The seats arent the problem (Lancia seats are already hard and 1600 seats are very hard). Its the alloy that cracks from plug thread to the valve seat. (the seat could drop out....).
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The removed Denso plugs are W24EPR-U. (see attachment) They are all the same specification. They cross reference to NGK BPR8ES.
A detailed list (in Italian) of work done on the car around 2016 notes, among other items, "head reboring". Talking to Andrew at Omicron yesterday, he speculated at some point the head needed work and for whatever reason the plug thread hole was enlarged from 12mm to 14mm. I asked if this was a normal practice, he said no. Why our Fulvia 1600 head takes a 14mm spark plug remains a mystery. At this point my curiosity isn't enough to take the head off for more information. Our Lancia Fulvia adventure continues.
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The removed Denso plugs are W24EPR-U. (see attachment) They are all the same specification. They cross reference to NGK BPR8ES.
Talking to Andrew at Omicron yesterday, he speculated at some point the head needed work and for whatever reason the plug thread hole was enlarged from 12mm to 14mm. I asked if this was a normal practice, he said no.
I have not come across this before (& I have owned a 1600 coupe for 39 years) but it could simply be that a previous owner had over-tightened a 12mm plug and stripped the thread.
Although written for Coupes not Sports, the mechanical and electrical sections of these Owners Notes may help you to figure out if any other modifications have been made.
See https://tinyurl.com/Owners-Notes-Electrical-2ndEd and https://tinyurl.com/Owners-Notes-Restoration-v22
PDF copies of the original Lancia Fulvia Instruction books and Dati Tecnici are also available online from Omicron (UK) and Pieces Fulvia (France). Enjoy your Fulvia journey!
Glyn
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On the 1600 engine enlarging the sparkplug holes may render the wall between the cylinders and the waterways very thin indeed. This was the reason to fit narrower plugs originally.
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On the 1600 engine enlarging the sparkplug holes may render the wall between the cylinders and the waterways very thin indeed. This was the reason to fit narrower plugs originally.
I tend to disagree. The smaller diameter plug hole was to retain sufficient alloy head material around the "enlarged" valve seats fitted to 1600HF heads - hence my comment about a greater possibility the a valve seat coming loose.
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Yes, Tim but the wall is very thin.