Technical > Spud Miller's Cave

Nitro and engine size

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msundstrom:
Hi Spud,
Does nitro have a preference in bore/stroke combinations? 4" stroke vs. 4.25" , shorter stroke/bigger bore, longer stroke/smaller bore, does size matter?

Thanks
Mark S

Spud Miller:

 Hmmmm. It just makes every combination better! :)

 Thinking in terms of theory, the same rules for bore, stroke and torque and all that should hold true...just be amplified.

 However, nitro burns pretty slow and at some point a huge bore size would be a detriment I'd think. Getting it all to burn without using tons of timing would seem easier in a smaller bore. The parasitic losses that come with using an extreme amount of timing are something that would get you eventually if you just kept getting bigger and bigger on the bore I think.

 Spud

captndiet:
It seems most A/fuel cars running a Hemi have a 4.375" bore and 3.50" stroke with a longggg rod.

Jeff

Nitrobaron:
The small bore 291 Desoto Hemi's loved nitro, some of the fastest Jr. Fuel cars had little Desoto's in the frame rails.
The 331 Chryslers (3.8125 bore) and the 354 Chryslers (3.975 bore) ran right with the 392"s in the early days on nitro.
This seems to support the small bore theory.
We are putting together a small Chrysler, 3.90 bore x 3.625 stroke (347 cu in+/-) injected on nitro.
At least that is the plan.

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