Hi,

I went round this for Ballard and the DTB F15 Polsten; years ago.

Now the plug spec hides in the "Instruction book" - Driving - Maintenance - Repairs, not in the workshop manual.

It gives Champion H9, H10 and J10, only the H10 cross refers in the excellent NGK catalogue to B6L.

Our local wholesaler keeps a fair range on the shelf but not the B6L (or indeed BKUR6ET-10 for my 16V Golf until recently), however we're alright for Morris-Commercials as they always keep the NGK A6 (18mm), probably as Ballard Jr. has bought two boxes for his M-Cs and thus truly foxed the re-order computer.

Anyway, B defines 14mm, 6 is the heat range and L defines a 11.2mm reach. Modern plugs are very tolerant and it is obvious reading the cross-reference tables that handfuls of old types are replaced by one modern one.

We met the NGK tech rep by chance whilst grimbling about the shelves and he confirmed the position and suggested that either we order and wait for the B6L or use the common B4LM already there. The change in heat range is minimal (4) and the important mechanical configuration is identical (B & L). The M gives a shortened 18.5mm outer insulator as this is a lawn mower plug but the short insulator doesn't look out of place in the dark recesses of the Ford engine bay.

Looking at the applications its also obvious that in power/cc the average Briggs & Stratton is very nearly identical to the Ford V8.

Ballard's DTB F15 has done thousands of miles now on the NGK B4LM and always goes hot or cold with minimal difficulty, so much so that I had to call in a moment ago and pull the engine cover to ascertain what we had actually used since they've been a fit and forget.

It more than can be said of the aftermarket "Classic" plug suppliers, their Polish made "equivalents" were troublesome and grossly over-rich hot starts with the typical Ford fuel percolation hassle was nearly a non goer.

I did try to "back" refer the B6L to Bosch in the NGK conversion tables by scanning the listings but there seems to be none.

R.