My old 1972 /6 uses Autolite 66 plugs, but when I bought plugs for my new '79 head engine, it takes 5/8" reduced hex plugs. It needed Autolite 26 plugs. In the 66/26 numbers, is the first number the type of plug, and the second number the heat range?

Tim,

You are correct. Depending on your ignition, you may want to run a slightly cooler plug, like a 25. I guess you'll only have 9:1 comp, so it's probably fine with 26's.

Later,

Lou

madsenl@caltech.edu

Yes, my new /6 has 9.04 compression. I now have the tools, so everything has been cc'd and calculated. I have regular electronic ignition that I put on in place of the old points system. A junkyard control box and distributor. Nothing fancy. It will have an Offenhauser intake, Holley 450 mechanical secondary, and Clifford headers also, if that matters. And a Purple Shaft 268 cam. And a 175K MP converter.

You have a pretty good combo of parts Tim, when do you get to "light this thing-off"??

Be sure to leave the valve lash loose on start-up. I think that .268 MP cam calls-out .030 for both Intake and Exhaust. It will take some "trial & error" to find a setting that idles OK with-out a bunch of tappit noise.
DD

The MP engines book says to use 28/32 lash, but a paper included with the cam said 16/20. I'll probably end up around 16/22-25. The engine is in the car now, just need to finish assembling everything. It's only 2 or 3 days away from fire-up! I'll set the lash more towards 25/30 for initial startup. I imagine the cam gets plastered with oil from the crank pretty good, so I'm not too worried about the break in, as long as the engine starts quickly! New motor, converter, cam, and carburetor all at once! Way to get the nerves and blood pressure up!

One "trick" when starting a SL6 for the first time is to fill the filter with oil and keep a quart out untill you know the engine is going to run.
When you are ready to run the engine "sustained" for a while, pour the last quart over all the valve gear. That last quart will run down and help keep the cam "lubed" during break-in. You do not have to run a SL6 at real high rpms to get plenty of oil onto the cam. (the cam is much lower and more exposed then in a V8, it gets lots of oil "splash")
DD

It is also a good idea to watch the lifters to see if they are "spinning" in the bores. They may not all spin at the same speed, but if they aren't spinning at all, it will wipe out a cam lobe.


slantzilla@excite.com

Good tip Dennis, I go as far as putting a dab of white paint on the top of each pushrod (just under the cup) so it is super easy to see them spin. ( I really use "junkyard yellow", from my paint marker. Just make sure the area you mark is clean so the paint sticks)
As Dennis said, if a pushrod is not spinning, shut the engine down ASAP and pull-out that pushrod & lifter for a look-see. 90% of the time I have fixed a "no spinner" by honing-out the lifter bore and / or replacing the lifter with another. (not a good "crown" ground onto the lifter)
The other 10% is a bitch, a cam that does not have enough taper ground onto the lobe(s). But think about it, changing a cam before it "chews-off" a lobe is better then changing one after all that lobe metal has gone through your new engine. Besides, I have better luck getting a replacement cam from the manufacturer when it's still "measureable", he can't hid behind that " you did not break it in correctly" lip service.
DD