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Valve adjust fun

FM Former Member
So today was the day to check & adjust (as needed) my valve lash.

Sure glad I did!

It seems as if the last "tech" adjusted them in reverse. The intakes were set at .006 and the exhaust were set at 004. Seems a little dyslexic. Well let me take that back... One cylinder (#4) was set at 004 & 004... But the others were exactly reversed.

Also my rocker adjuster nuts are HUGE (yeah, I said my nuts are huge). They were found to be 15mm Vs the regular 13mm nuts. Cool I guess.

Then I looked at the spark plugs. It had NGK BP5ES-A. These are pretty long reach and have a long center electrode. The Bosch WR8 supers I replaced them with are short reach with a tiny center electrode. If this would have gone the other way around I may not have installed that long plug in fear of making piston contact (lots longer). But the shorter plug is of course a non-event.

BTW.. The NGK plug burn looked perfect.

Anyone have opinions on that NGK?

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FM Former Member
So today was the day to check & adjust (as needed) my valve lash.

Sure glad I did!

It seems as if the last "tech" adjusted them in reverse. The intakes were set at .006 and the exhaust were set at 004. Seems a little dyslexic. Well let me take that back... One cylinder (#4) was set at 004 & 004... But the others were exactly reversed.

Also my rocker adjuster nuts are HUGE (yeah, I said my nuts are huge). They were found to be 15mm Vs the regular 13mm nuts. Cool I guess.

Then I looked at the spark plugs. It had NGK BP5ES-A. These are pretty long reach and have a long center electrode. The Bosch WR8 supers I replaced them with are short reach with a tiny center electrode. If this would have gone the other way around I may not have installed that long plug in fear of making piston contact (lots longer). But the shorter plug is of course a non-event.

BTW.. The NGK plug burn looked perfect.

Anyone have opinions on that NGK?

LeonChuppLeonChupp
Check your cylinder head type......Some (such as C.B.Perf. 044's ) use long reach plugs....Installing a short reach plug in one of these heads will leave the plug shrouded (possible misfiring and short life) and the bottom threads in the head will collect carbon and possibly act as a glow plug.....Also the carbon can cause big head aches when the proper plug is re installed...Thread seizure.... Just my .02
Stan GalatStan Galat
Michael-

A BP5ES-A breaks down as follows:

BP means it's got a 14mm thread, 3/4 reach, 13/16" hex, non-resistor, gasket seat, and a projected insulator.

5 is the heat range. In NGK, the smaller the number, the hotter the plug.

ES is a 3/4" reach, with a 2.5 mm center electrode.

A indicates "something special".

It's a pretty hot plug, but if you have a low compression engine, and it reads OK, you'll be fine.

http://www.ngksparkplugs.com/docs/tech/partnumberkey.pdf
Gordon NicholsGordon NicholsMassachusetts 1993 CMC Supporting Member
Mike:

Easy way to find the thickness of your heads:

Get a 12" piece of electrical wire (like romex for your house) and remove and strip one of the individual wires (hint: The ground wire is already stripped).

Using needle nose pliers, put a small (1/4") hook on one end, then remove a plug and gently insert the hooked end into the plug hole until you can feel it catch on the inside when you pull it back out. Either mark the outside edge of the head on the wire with a magic marker, or hold the wire with your fingers where the outer edge of the head is and then remove the wire and measure the distance from that place or mark to the top of the hook point and THAT is the depth/thickness of your head where the plug is. Proper plug shank depth is even (or plus 1/8") with the inside surface of the head.

gn
FM Former Member
Barry,
The coeffecient of thermal expansion is vastly larger for aluminum than for chrome-moly. So aluminum will expand (lengthen) more than chrome-moly when elevated from room temperature to operating temperature. It may only be a few thousands, but it can make a BIG difference when the valve, on the other end of the push rod, is getting that close to a piston at 5000+ RPM.

Believe it or not, the whole damn engine expands and gets wider when it is up to operating temperature. The valve train just happens to be a lot more critical of this change in length than, say the oil return tubes housing the pushrods.

Hope this helps.
Stan GalatStan Galat
Barry-

It's a 2332 right now, so the bore is 94 mm. Oil temps never go above 210 or so, but I've got a DTM with a Type 4 cooler, a 96 plate cooler, and nickasil cylinders. There's a lot more than the coatings at work.

FWIW, it's my belief that the coatings primarily assist in head cooling, as opposed to oil cooling (although the two are somewhat related, they are surprisingly independent of one another).

Last thing- I believe in cro-moly push-rods because they expand less than AL, and as a result can be set up to "loose zero". The valve clearance will never be less than at stone cold because the cylinders and heads will expand away from the center-line of the engine more than the steel push-rods. I know they weigh more, are louder (and all that) than AL- but to me, the trade-off is worth it.
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