The other post on distributor phasing got me thinking about spark plug indexing.

1) On a 340, which way should the gap opening face? Towards manifold?
2) I see both "flat" and "tapered" washers for this? What's the difference?

Thx

(1)I believe so (2) some plugs have tapered seats (for furd iirc), our plugs take flat washers

Stupid question but what is spark plug indexing?

From what I understand indexing uses different sized washers so all of the plugs face the same direction when installed.

Thank you for the explanation. Now back to the question.

I have done it on just on a stock rebuild a few times and got a noticable gain in performance

I will add that its not just facing all the plugs the same way,it is faceing the plug the correct way for the cyl only

as in the valves move around in the head depending on the cyl

e,i,i,e,e,i,i,e looking at the exhast manny this is the valve arangement so to speak,so the plug would face the corrosponding direction

I have not done it in a while but,seems I allways faced the open part of the gap towards the cold intake charge

not real sure wich way now I thinks on it

but it what RR said

in shade tree lingo the plug gaps dont all face the front of the engine

they would face the correct direction per cyl

I will stop now...

I just wish I had wrote it down be fore I forgot

oh and drilling the holes in the cap for ions to get out helps stop cross fire in the cap at high rpms

just not good for wet weather

and I only did that on chivy HEI dist on the BB mud truck

Ok, so I need to point the spark plug gap opening towards the intake valve, and away from the exhaust valve on each cylinder?

point the opening directly towards the center of the combustion area.

Which would be up, down,left or right?

IMO,its best to set a head up for indexing while its off the block and you can see the comb chamber

then # the plug acordingly to the cyl

its free performance and a smoother running engine for some easy labor when puting one together

I have faced the plug opening towards the itake valve and have lined them all up in line with the little rectangle indent in the cc at the plug hole

but as stated...putting them in so the plug gap faces the expanding "wedge" makes for a complete burn and more leverage pushing down on the piston

thats why its called a "wedge head"

Ok, which way should the spark plug gap opening point in this pic?

ok

I have lined them up in line with the recessed pad area off the plug hole

and I have lined them up with the open gap of plug facing the intake valve

need to know which way the shape of the of the cc on the heart shaped closed chamber heads swirl the intake charge around to to get it positioned in the right spot on the #302 heads, IMO

now I have also thought on putting the gap faceing into the cyl,so the gap faces the large side of the wedge to fire it from the small side and burn towards the big side maximizing the wedge effect of the wedge head

which IIRC is the right way for it to be facing

maybe someone else will correct me if I am wrong

Up. Directly towards the manifold. Remember that the intake is still open (slightly) when the the spark ignites the F/A mix so the fire is swirling from the intake (hence the term swirl port). Just point it directly towards the center of the combustion chamber. That makes the bulk of the incoming fuel charge pass by the spark.

I could have sworn on the slant site they said face the opening towards the exhaust valve.

I know I smooth out the pocket where the plug is for flame travel towards the exhaust when I grind the chambers.

From what I have read indexing is worthless on the street, and mild race applications.

Cutting the ground strap might do something.