deck height:

Jeff Lee · 11-13-2010, 09:40 PM

Quote:

Originally Posted by art leong

Jeff how confidant would you be with a zero deck height spec? Can you be sure the bearing didn't wear a bit, or the rod didn't stretch a touch? And as far as piston to head problems won't a thicker head gasket achieve the same thing?
If you can't build in a little safety margin you are going to get tossed for stuff that won't help performance one bit.

Then pull the deck height spec out of the books. Just list a tolerance for gasket and deck height combined.

I'm at a loss to figure out how all those zero deck engines made it through tech for 35+ years before NHRA changed this rule. Guess those old engines did not have bearing wear or rod stretch?
Still trying to figure out why a rocker ratio is so important when using this issue as a comparison.

art leong · 11-14-2010, 11:10 AM

Quote:

Originally Posted by Jeff Lee

Then pull the deck height spec out of the books. Just list a tolerance for gasket and deck height combined.

I'm at a loss to figure out how all those zero deck engines made it through tech for 35+ years before NHRA changed this rule. Guess those old engines did not have bearing wear or rod stretch?
Still trying to figure out why a rocker ratio is so important when using this issue as a comparison.

It was a stupid no common sense rule if the piston was specified to be .001 down the bore if you were 1 inch down it would be fine. If the specification were .001 out of the bore 1 inch out would be legal. What purpose did the old rule serve?
It wasn't a problem as long as there was more clearance than less. Till I drove my car to Maple Grove, set the record with a motor that had never had a head removed. And had .034 to little deck height. Then curt leshure had a problem, and I had a bigger problem.
As far as tolerance goes my motor had 134,000 miles on it was never out of the car (or had the head off) and it was .034 from the stock (listed) specs.
And on some motors adjusting the rod length is not possible.

Adger Smith · 11-16-2010, 10:30 AM

This is the exact quote of the rule about deck height out of the 2006 NHRA Technical Policies & Procedures
I don't think it has changed any since 2006. .

1.2 ENGINE BLOCK
1.2a STOCK AND SUPER STOCK
The deck dimension of the engine block can be either in or out of the block, provided that the
difference in the compression is made up with the cylinder head gasket. Example: if the spec is for
.002-inch deck and .020-inch gasket, and the actual measurement for the engine is .005-inch positive
deck, then a gasket must be at least .027 inches. The opposite is true if the deck is below the block on
an above the block spec, then the gasket may be thinner to the allowable total dimension.

11-16-2010, 10:30 AM	#3
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: deck height: This is the exact quote of the rule about deck height out of the 2006 NHRA Technical Policies & Procedures I don't think it has changed any since 2006. . 1.2 ENGINE BLOCK 1.2a STOCK AND SUPER STOCK The deck dimension of the engine block can be either in or out of the block, provided that the difference in the compression is made up with the cylinder head gasket. Example: if the spec is for .002-inch deck and .020-inch gasket, and the actual measurement for the engine is .005-inch positive deck, then a gasket must be at least .027 inches. The opposite is true if the deck is below the block on an above the block spec, then the gasket may be thinner to the allowable total dimension. __________________ Adger Smith (Former SS)