I'm in the planning phase (still) for the motor in my era-correct stock car project (1950 Plymouth), and, after some discussion with Cory (Moparsled on the HAMB) I decided to take a good look at how to optimize my little flatty.
I'm basically stuck with having to run a stock bore x stroke (max 0.030" overbore), cam, valves, valve springs, manifolds, head, and carb (per the 1950/51 NASCAR rulebook). The rules specify that the word "stock" is to be understood as factory cataloged parts appropriate for the year/model/type of car. Rules further specify that the flywheel and camshaft cannot be altered in any way...this provides a hair of 'wiggle room' to modify some of the internals, as long as they are appropriate factory cataloged parts for the year/model/type, so I'll be looking into port work, head milling, decking, carb tuning/jetting &c.
Preliminary measurements of my bone-stock 1950 block show a deck clearance of 0.016" (piston is in the hole 0.016"). I am under the impression that all head gaskets for these motors measure in at around 1/16 (0.0625) compressed height, giving a quench distance in stock configuration of about 0.0785" (0.016 + 0.0625). Which seems rather excessive. Please forgive me if my terminology is not up to snuff...the learning curve is steep
I estimate that my deck thickness is somewhere in the vicinity of 0.3125", so I'm not quite sure how much I could safely deck the block to improve the quench distance. George Asche seems to think 0.020 should be safe although he remembers a conversation with NASCAR legend Cotton Owens in which Mr. Owens revealed that they had gone as far as 0.040.
Can anyone give some insight into how far I could go on the deck and still expect a high degree of reliability? I believe the tappets will adjust to a deck at least 0.040" lower, but am unsure how to handle the valve seat area after making such a cut...(I'd like to go 0.020-0.030 if possible).
On the subject of head milling, I'm looking at going somewhere around 0.060", which should yield a combustion chamber size of 72cc (give or take). My stock chambers measure right at 85cc. This, of course, depends on where I set my quench distance and how that affects the static compression ratio...I'd like to be able to run on premium fuel (92-93 octane in my area) at an elevation of less than 1,000 ft.
Mr. Asche also stated that an old circle track trick with these motors was to retard the cam by 2-3* to bump up mid-high RPM power...I hope to be able to run this motor reliably at upwards of 4000-4200 RPM for fairly long periods (20-30 min at a time), although that may be a pipe dream...does anyone have a suggestion on retarding the cam & how I might consider going about this?
Thanks in advance...I'm looking forward to your insights!
Gary
