Quote:
Originally Posted by dci
I have a question for the ones here that say a shorter deck is needed. If our lifter bores are all in line, and we run offset rocker arms of up to .850" with only a .180" offset in the lifter. Won't the shorter decks create more stress and side load on the pushrods? I'm not saying that i do not agree with a shorter deck, but it's a little more involved than just shortening the deck. The other part of this equation is the actual need for shorter decks. Until we can spread the bore spacing out to get bigger bores. I think we have the ideal deck height right now. The only way for us to get more cubes is to go with longer strokes and we need deck height to do that.
Don Johnston
DCI MOTORSPORTS INC.
330-850-5050 shop
330-628-3354 cell
Designer of the DCI Tiger Heads and the NEW DCI Ram Air 5 Heads !!!!!
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Yes and no...for big cubes a longer wider deck opens things up quite a bit and allows us to have same (or greater) bore advantage. Beside head flow, bore size(spacing) is pretty much a large factor in why Pontiacs arent making NHRA pro-stock power at 500 ci now. Bore size dictates valve size ultimately dictating HP! In the VE picture stroke wont get you there.
However the short deck at current bore space(even with std lifter bore placement) offers us some different opportunities... 400-454 ci LS and SBC, SBF, SBM, combos are rather popular with combos from mild to wild... and some stout 327- 370 inch packages are out there as well...
I strongly feel we should focus on the 400-460 inch segment until we have the stretched blocks(heads too) to go toe to toe with the bad boys 500 ci up. We are doing good there to a point, but the bore advantage they have does show up in the upper levels though. So... its about time we go LS hunting instead!
We have bore space advantage in the 400-460 inch range if we use our 301 deck height(or close), the 10.2 deck doesnt allow the lighter recip etc... that a shorter deck allows.
Shorter deck also eases packaging in tight places like 82-up small light cars... the 301 deck height still allows over 460 ci combos but then it competing against bigger bore motors. The 301 deck would allow us to do ok in the 300-400 ci range but an even shorter deck might do better...
As far as offset lifter cups and rockers... its not the best way to go about it. Crower prefers no offset and up to .150 on the lifter cup can work ok but beyond that the side loading on roller axles becomes a new issue to deal with. Big angle offsets in the pushrod affects side loading of rocker pivots.
If you are trying for high rpm, using offset lifter cups and rockers, makes the task harder. Dealing with one arc of travel is far easier to control than a compounded arc. (Think valvetrain control and spring life/roller axle and rocker maintenance).
A change in the lifter bank would be better... revise all our block castings to allow simplified changes that can easier accomodate standard lifter placement with the option to deliver block with no lifter bores drilled for placement wherever, however, whatever, any particular head design needs them to be.
The lifter bank just needs to be a continuous rectangle the length of the valley... revising the cam tunnel while your at it to allow bigger journals and options in height would be a good thing as well. Such a revision allows for an easier way to control the valvetrain allowing more time and resources channled to making power. One other block revision could have options on main bearing bore size but 3" will work ok for many apps.
RPM is a very important element in making power... High rpm was never a Pontiac's strongest attribute, as Pontiac had neither the heads or the block to support it... We have plenty of killer head choices for the "smaller" ci combos we could build with a short deck. The block revisions I'm suggesting opens the door to new head designs.
IMO the short deck sells better than a longer stretched block does, as it allows quite a few existing components... Other than intake manifold, any other obstacles like existing headers or lack of stock replacement valley covers are very minor.
Until there is consencus on a stretched block and how much it gets stretched... 301TTF makes more sense.