Spark plugs

[administrator]

UMB 386 was originally fitted to L431, a 1936 2 seater DHC.  It suggests your engine is a pre-war block with a post-war cylinder head.

[mmouss]

Here it is Robin, so, post war isn't it?

[administrator]

That is a post-war block with the front engine mounts at the side, so it shouldn't be stamped 386.  Perhaps 1386 - probably from a 2 Litre saloon?

[Robin A Woolmer]

As has been said by the Administrator, it is a Post War engine, the water jacket looks fairly good but the picture does not give enough definition, if you are going to remove the head studs be very careful as they can be weakened at the junction of the head & block due to corrosion of the steel stud , effectively making a notch where they often shear!
Unfortunately the studs become tight due to them corroding down the stud drilling!
As you have a 16/80 it should have a Cats Paw block. Unfortunately these are very difficult to find & often very corroded!     

[mmouss]

Yes Robin, the water jacket is in very good condition and I do not think I will have to remove the head studs as the top face seems correct.
Even if it is not original, I will keep this block and fit it with new liners & pistons.

I checked and cleaned the cylinder head and noticed the ports castings were very rough from new, so I spent some time smoothing and adjusting them with the manifolds.
Also noticed the gas holes in the intake gaskets between manifolds and head were protruding 2 or 3 mm all round into the ports, which seems far from optimum in terms of efficiency!!!

[Robin A Woolmer]

You will clearly have improved performance when it is reassembled, hope all will go well.

Robin

[mmouss]

Hope so Robin, but still a lot of work to do in rebuilding it!

[mmouss]

So, after a lot of work done, the engine is now ready to be dropped again in the chassis.
The crank has been reground, rods & mains have been re-white metaled, small end bushes are new as well as liners & pistons.

[SpqrEddie]

Thank you for your answer AC Ace Bristol, but my engine is an AC, not a Bristol...

mmouss.

I appreciate   your engine is AC whereas mine is Bristol, I posted links as your  original post referred to plug  temperature  ratings, so I thought the links
would be of interest and helpful.

According to NGK catalogue NGK's  equivalent to Champion L85 /  L86/ L86C/ L86CC & L87  is their B6HS not B5HS, Which is a hotter /  softer plug .

Regards your latest question, reference 14mm & 18mm plugs,    Brian is right ,  14mm /18mm adaptors were ( are ? ) available so 14 mm plugs can be screwed into 18mm heads,  Just be cautious regards over length thread reach  into your cylinder head. / Combustion chamber.

B =14mm Thread pitch 1.25mm
6 = heat rating
H = thread pitch 12.7mm
S = Firing end construction ( Std  super copper core centre electrode.)

A = 18mm thread pitch 1.50mm

NGK  tel number  01442 281000 ( Hemel Hempstead, Hertfordshire. HP2 4SD


Keith
.

Hello,
I see many differet option for the Champion. What people are using? 82, 85, or 86?
I found a lot of Lodge HN as per manual, but some of them already burned... they seems not to like rich carburation, and i am still dealing with carb tuning so not ideal.
I am using NGK B6HS but they dont seems to run as nice as the Lodge, and i would like to try some altrnatives.
What are you using for a CLB engine?

As well, are you using the reccomended gap as per manual (0.015 to 0.018 inch, 0.38 to 0.46mm), or wider?
Thanks!
Eddie

[SpqrEddie]

in the end i set for the NGK B6HS given that i am using a lot of them! and they are readly avilable at the local autoparts store.

But today i seems to finally got the carb tuning right witht the help of somebody more experienced than me.

I left the spark gap as per manual at 0.018 in. (0.45mm) , but he was suggesting to go for a wider gap. 0.0236 (.60mm).

Wich gap are you using?

Thanks!

[Big col]

I gap them at about 0.025" and it seems to run OK with the plug colour being a light biscuit/grey colour. I use 14mm plugs with adapters to suit. I have also disabled the manual advance retard and use a distributor with bob weights and triple 1 1/8 " carbs. The voltage regulator has also been updated to a solid state unit, but I still run with point and condenser set up.
It has taken a while for me to get everything settled down and the motor to run smoothly after a complete engine and carburettor rebuild. I can't say if that is just as it is after a rebuild and running in or if it was me that was crap at tuning.

[Big col]

Good fun, this old car stuff. Out and about today and the car ran great. Better than it has since the rebuild.
But for one small hick up. I don't know why but there was a slight hesitation on a straight bit of road when the motor seemed to struggle to pull. I was travelling at about 60 to 65, around 3000 rpm or just over, and it wouldn't give any more. I eased off for a roundabout and geared down, then opened up to pull away up to about 3800rpm and it picked up fine. I haven't got a clue what it was but it cleared just as quick as it appeared so I am not going to worry about it for now.

[SpqrEddie]

I gap them at about 0.025" and it seems to run OK with the plug colour being a light biscuit/grey colour. I use 14mm plugs with adapters to suit. I have also disabled the manual advance retard and use a distributor with bob weights and triple 1 1/8 " carbs. The voltage regulator has also been updated to a solid state unit, but I still run with point and condenser set up.
It has taken a while for me to get everything settled down and the motor to run smoothly after a complete engine and carburettor rebuild. I can't say if that is just as it is after a rebuild and running in or if it was me that was crap at tuning.

thank you very much Big Col for your contribution!
0.25 seems in line with what i am beeing suggested.

What the other are doing?

Thanks!!