Quote:
Originally Posted by davidvizard-gfn
polyquad in practice.
the first type of head that polyquad was applied to was the arao 4 valve pushrod chevy head conversion for small block chevy’s. This was a good candidate as we could reference the results directly against a two valve head design. Essentially here is what was done. Russ arao had already done a series of tests along these lines but with all the heads using the same 112 degree lca camshaft. The heads tested included a pair of vortec heads. These heads are considered to be one of the best designs for producing strong low speed output. Anyone who has run back to back tests with a good aftermarket head will attest to the fact that at low speed they are almost unbeatable and are certainly far from shabby at high speed. The vortec heads then seemed like the best to use for our low speed benchmark. To represent an aftermarket head situation i ported a set of a well known brand of heads that ended up at about 185 cc port volume and 280 cfm at 0.600 lift with the flow curve flattening out from there on up. The vortec heads, the ported heads and the polyquaded arao four valve heads were all run on the same short block. In each case the cam events were optimized for the heads concerned. The two valve heads both produced the best power curve on a 108 lca cam. The polyquad heads were best at 112 to 114 lca. The intent here is to see how much better the polyquad heads were at low speed compared to a two valve setup. With the wider lca the intake would close later on the compression stroke. So that there was a total match on the intake closure point the duration of the intake was shortened for the four valve heads so that in all tests the dynamic compression was the same (as was the static compression). The exhaust was also shortened to match the new shorter intake. The tests then were done with each pair of heads having the same intake closure point and an appropriate lca. The results are as per the following chart.
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Dave,
I'm really curious about results of a "standard" Arao head (if there is such a thing) compared to the PQ'd one. Did it lose? Did it gain? Where in the powerband did each happen?
Thanks for your hard work. I may end of trying to get the PQ mods done to a set of Olds Aurora heads for my Northstar.