IMO,
and I've never raced,
is that, if you are limited to a certain Static compression ratio, then to keep the Dynamic pressure up, you need to close the intake as soon as possible, working off the advertised numbers,( assuming they are in the .006/.008 tappet lift range).
This means a few things;
1) you need a cam with a fast rate of lift, and
2) it will need to be on a tight (small number) Lsa.
3) with as small a split pattern as possible
The cam in consideration is none of these..
However, I suppose that with a 4500 stall, this is not that big a deal.
To illustrate this,
Your selected cam; 289/297/109, installed at split overlap, will look like this; 289intake/108compression/101Power/297exh, with 75* o-lap, and 72* Ica
Most of that 75* overlap is gonna be sucked up in the ramps;
54 * of it is below .008, (Assuming the 050 spec is in fact .008) leaving just 21* as being useful.
The Wallace calculator predicts that the DCR will be 6.77, with pressure of 128.
On the street, these numbers would produce a very weak bottom end, and a markedly poor throttle response, compared to numbers over 185psi or even 165psi.
>Suppose we take the same 235 @050 intake spec, and combine it with a 239 exhaust lobe, but increase the intensity from 54* to 44*, and then tighten the LSA to 107*.. the new numbers, also at about split overlap, look like;
279 intake/114 compression/ 111Power/283exh, with 67 o-lap, and 66* Ica
Of the 67* overlap, now, only 44* goes to under .008, leaving 23* as useful. about same as before(21*).
Now, comparing the numbers, the new cam has;
plus 10* of Power extraction, and
Plus 6* of compression.
The Wallace calculator predicts that the DCR will rise from 6.77 to 7.0, and
the cranking cylinder pressure will rise from 128psi to 137psi
These are increases of 3.7%, and 7.0% respectively.............
From what is, essentially, the same 235*cam. and
>In other words, you could run a fast-rate cam, about 2 sizes bigger, than the current selection, to run the earlier pressure/lower Dcr numbers, For instance; lets add 14* (about 2 cam sizes) of fast-rate to 235 and 239.
equals 249 and 253 exhaust, then add back the 44* of clearance ramps, and lets tighten up the LSA another 1* to 106, and I get , again at split overlap;
293intake/108compression/105Power/297exh with 83* o-lap, and 72* Ica
NOW: Of the 83* overlap, 39 is now at over .008 tappet rise!
compare that to the selected cam at
289intake/108compression/101Power/297exh, with 75* o-lap, and 72* Ica
and still same 235*@.050
Compare the effective overlaps of 39* to 21*; that is 18*, which is, effectively, about 2.5 cam sizes. If you are running tuned headers, this is a very big deal.
The above is for illustration only. I know nothing about racing.
