Inliners International Forums General Discussion MOPAR Power tips/tricks...vintage NASCAR build Questions

Hello all,

After some exhaustive reading/research on the subject I was amazed to find that Mopars were incredibly competitive in the early years of NASCAR 'strictly stock' (aka Grand National) racing...leading me to consider an early 'stock car' build for my '50 Plymouth fastback.

For the year 1950, some 52 Plymouths were registered with NASCAR, and together, they compiled an impressive resume;

4 wins
28 top 5's
49 top 10's

All this in only 19 races! In fact, a 1950 Plymouth fastback driven by Johnny Mantz won the first 500 mile race in NASCAR history at the then-new Darlington Raceway, at an average speed of just over 75 mph (Mantz's margin of victory over Fireball Roberts' big V8 Olds was 9 laps...or about 11 miles)

I've had a chance to read up on NASCAR's early rules, and it seems like the cars really were 'stock' cars back in the day...the 1950 rules required the following;

Cars - 1946-1950 models, complete bodies, fenders, hood etc. Headlights removed or taped. Muffler and rear seat cushions removed. Front seat intact. Doors strapped shut. Wheels, hubs and some steering and parts could be reinforced, most other items had to be stock and unchanged.

I've read a lot about how these little flattys don't like lots of revs...assuming Mantz's car was using a stock 3.73 rear end (he was also using Firestone truck tires...probably oversize) 75 mph would be right in the ballpark of 3300-3500 rpms.

I'm curious about what internal modifications might have been made to allow for such high revs at long intervals (the 1950 Southern 500 lasted 6 1/2 hours).

Also, what tuning 'tricks' were these NASCAR guys using to make these cars competitive with the big OHV V8's from the likes of Olds, Buick, and Caddilac?

All help is greatly appreciated!

Thanks,

Gary

Aside from the normal porting and relieving that was done to similar engines like the Flathead Ford, lightening the rotating assembly(turning the counterweights down), was a trick the Ford guys did, so I would suspect that crossed over to other Flathead guys, regardless of the brand. Its also possible that a weight break was given to Flathead engines over the OHV engines, it was done in other racing arenas later in the fifties, in an attempt the help the Flatty's compete against the 265 Chevy's....perhaps!

They must have had some advantage under the rules or the simple displacement (Olds = 303") and efficiency differences (OHV vs. SV) would have killed them.
I agree - lightening the crank is probably on the list.

At this point I'm unaware of any official rules created to give less competitive makes an advantage.

The Olds 88 Club Coupe weighed in at 3600+ lbs.

The little Plymouth weighed 2800-2900 lbs.

Olds produced 135 hp stock (27 lbs per hp)
Plymouth produced 97 (around 29 lb per hp)

Old produced 263 ft-lbs stock (14 lb per ft-lb)
Plymouth 175 ft-lbs (16 lb per ft-lb)

So all-in-all, the Plymouth's weren't that far off...I think the real competitive advantage came due to the fact the cars were lighter, therefore easier on tires (this was back in the day of street-stock bias plys rather than hi-tech slicks).

MoPars seemed to do well on tougher handling tracks, where the big Olds, Caddilacs, and Mercurys chewed up tires. Johnny Mantz's Southern 500 winning Plymouth used truck tires that lasted the entire race...3rd place finisher Red Byron's Cadillac went thru no less than 24 tires during the race.

On the longer courses...especially Daytona's high-speed course, the Plymouths could finish no better than mid-pack.

Could be - I had no idea the Plymouth was that light.

Tyres and brakes would have been the answer...

The weight of the car doesn't matter much when you are in high speed stuff. Then it's wind resistance and power that count. But come to a corner, the brakes have to slow the weight and the tyres have to take the corner.

Coming off the corners it's traction and torque. The others had the torque, maybe they were lacking in traction?