The Dodge Challenger Message Board

Why does the text on the hood say 429 c.i.? A misprint due to an upside-down "6"? Overbore making in 426+3=429?

Quite a few Hemis back in the day stated 429 C I on their hoods. I suspect they were mildly bored.

fal308 wrote:Quite a few Hemis back in the day stated 429 C I on their hoods. I suspect they were mildly bored.

Thanks! I did not now that.

It feels like it would have been smarter to write 426c.i. from an advertising perspective. Well, this engine managed to become quite famous anyway, right?

To 'overbore' a 426 hemi's stock 4.250 bore to 429 cubes would require a bore/hone of only .010. Which would only leave .005 on each side to machine with a cutter than hone the metal for the correct plateau finish on the walls,(doubtful they did this) I think the 429 was the maximum displacement allowed by the rules. I'm sure they just used a shorter piston/larger chamber/smaller stroke, ect there are many ways to accomplish this, instead of trying to remove precious cylinder wall material. It's interesting because I've never seen a '429' used by Mopar, the only 2 Hemi sizes in nascar grand national racing I ever saw where the 400 cube,(1965) and 426 cube plants.(after 1966's homolagation requirement), maybe the engine was used in USAC where there are all kinds of permutations to the rules and engine sizes? Not saying I'm right, just some other theories.

Eddie, quite a few NASCAR cars had 429 on their hoods. I'm thinkig they were just cleaning and straightening up the bore with a very mild overbore.

NASCAR did have a 7.0 liter rule in effect at the time.
You'll also see a wing car with 305 on the hood. That's because Bill Fr4ance instituted a 5.0 liter rule effectively banning the 426 Hemi ( except for the 305 Hemi that Keith Black built)

fal308 wrote:NASCAR did have a 7.0 liter rule in effect at the time.
You'll also see a wing car with 305 on the hood. That's because Bill Fr4ance instituted a 5.0 liter rule effectively banning the 426 Hemi ( except for the 305 Hemi that Keith Black built)

That was in 1971.Ramo Stott's car I believe, he crashed while leading the race, and unfortunately didnt finish well enough to return with the 305 Hemi and Aero Package. I bet France would have 'shit a brick' had that "Cheeky Chrysler" won huh!! I think in 1970 with the Hemi and Wingcar program they won 67% of their races for that year and Bobby Isaac won the Championship in Nord Krauskaps Charger Daytona, the K&K Insurance car.

fal308 wrote:NASCAR did have a 7.0 liter rule in effect at the time.

That does not make sence to me. From the back of my head, I know that 7,0 litre=427c.i.
I managed to find a convertion table, and the calculation gave the same answer (See below).
429 c.i. is above the volume limit!?

1 ml = 0.061024 cubic inches (from: http://www.infolinx-no.com/ssi/tjeneste/konvert.htm )

7000 ml (=7,0 litre) = 427.168 c.i

fal308 wrote:Eddie, quite a few NASCAR cars had 429 on their hoods. I'm thinkig they were just cleaning and straightening up the bore with a very mild overbore.

I am having the idea that they might have done this overbore (honing?) just because they wanted more piston to cylinder clearence. At full throttle during longer periods of time (creating a lot of heat and due to that more than normal heat expansion of the piston), the standard piston/cylinder gap maybe was too small? Another theory is that they wanted a "race-gap" with loose-fit and minimal friction. Well, just my own theories...

7.0 litre is 427.1662 cubic inches.

BUT.
429 cubic inches works out as 7.03005 Litres. Which might have been just inside the rules.

Also 429 inches is only a 20 thou overbore on a hemi block. That may have been in the rules as well. You may have been allowed a slight overbore.

dave-r wrote:7.0 litre is 427.1662 cubic inch

What conversion factor are you using?

christer wrote:1 ml = 0.061024 cubic inches (from: http://www.infolinx-no.com/ssi/tjeneste/konvert.htm )

7000 ml (=7,0 litre) = 427.168 c.i

My old school teacher once told me that you can not have more "value-digits" in the answer compared to the number of value digits you are using in the calculation (due to round off faults.)

Giving it another thought, my answer above is not prefectly OK. Value digits in calculation=5 (61024), value digits in answer=6 (427168). I will have to round off the answer to 427.17 instead. That will give the same answer as yours, Dave. The difference was only due to round off faults, if you ask me.

The only answer I can give you is two words. Bill France
He ruled NASCAR as if it was his own fiefdom. He abhorred relinquishing any control to anyone. If he said a square was round, in the NASCAR world a square was round.
Also I would imagine the 429 was allowed originally in the 7 liter rule due to Ford's 429 NASCAR engine (before France outlawed it)

dave-r wrote:Also 429 inches is only a 20 thou overbore on a hemi block. That may have been in the rules as well. You may have been allowed a slight overbore.

From the NHRA Drag Rules 1972 I get: Maximum .035 overbore on any 1963 and later model year engine (Stock eliminator class).

I do not find it unlikely that the same applies to the 1969 NASCAR season. Or?