My engine saga - part 5 I want to cry......

One thing I've just learned the hard way. Never look a gift horse in the mouth......check it's teeth, tonsils, temperature, vetinary history etc!

I was so close to starting the engine today I could taste it only I hadn't got any spark plugs. No problem, quick check of NGK site confirmed 14mm so off I went and got some.

Strange, when attempting to fit them they just rattled around in the plug holes - OK I thought they must be the same as the ones from my old 289 heads which were 18mm. Quick rummage, find a plug and.......no they're too big.

Hmmm...14mm too small, 18mmm too big - WTF! Now admittedly when I was offered to swap my old '65 289 heads for these Ford GT heads I was a little carried away by the bigger valve sizes but I did go get a spring compressor and check out the valves, seats and guides and they were all good to go. It never occured to me to check the plug holes.....

Perhaps they've been helicoiled and the inserts came out with the plugs but all 8 are the same - surely no one would helicoil all 8! One thing's for sure - they ain't a standard thread and faced with the prospect of tearing the engine down to get the heads off to resolve this which after all the agro and time I've spent rebuilding the thing makes me want to beat it about with a very large hammer!

Moral of story: Check, double check and check again!!

[simon]

Post the head specs on clubcobra.com, you'll get some info there.

Simon

Good idea but I can't find any trace of plugs, racing or street, in between 14 and 18mm.

Only way I can sort this properly is to take the heads off which means additional cost of a new gasket set as well

[Grease Monkey]

Found this, looks like you might be a bit stuffed. Out of the hundreds here I can't see any listed between 14 and 18mm ?!

http://www.mopar1.us/sparkplug.html

[Grease Monkey]

Found these as well (Nothing else to do you see?)

Champion and NKG Plug codes, no 16mm

[simon]

Time to have a word with the seller of the heads?

And here's the offending hole!


7mm of thread depth then 11mm smooth....argh!

[Happy Jim]

Is the threaded portion of the plug getting down to the thread in the head? Short/Long reach plugs?


Straw/Clutch/Grasp etc

[Grease Monkey]

I guess you could invest in a few bolts and see what screws into the plug threads. At least you'd know what you were looking for then.

[Purple AK]

Smash.

Looking at the picture it looks like the plug hole was made like that Is the thread at the bottom 14mm or more? If it's 14mm, then MAYBE it's designed for a 17.5mm (.705") reach, taper seat plug. BCPR6EFS should do it