[DeTomaso] Techno Question: Quench Area Specs

[JDeRyke at aol.com]

In a message dated 5/22/08 7:42:09 PM, cengles at cox.net writes:

> Does anyone have the specs for the quench area clearance?  
> 0.035""---0.070"  ??    Is that right?     Is their an optimal clearance for a "street" 
> engine?
> 
Generally, 0.040" is about the 'safe' minimum; coincidentally also the 
compressed thickness of a good head gasket, so zero-decking a block/pistons works 
well (check compressed gasket thickness!) Less than .040 risks touching the head 
with the piston at high rpms & high oil temps (rod bearing clearance 
increases a bit w/high rpms & high oil temps) and the squish becomes so violent the 
mixture-stirring effect is somewhat diluted. I've used 0.032" and had valve 
marks left on piston crowns.... but luckily no breakage. Above .050, the squish 
action becomes milder so again, not as effective at stirring the mixture and 
concentrating it around the spark plug. Of course, theres always special cases -I 
used flat-top pistons & no more than a 280 at 050 cam; using pop-up pistons or a 
really radical cam might change the number a tiny bit one way or the other. 
Dyno runs are really needed to maximize the squish-effect vs power for a given 
parts combination.   FWIW- J DeRyke


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