Balancing Crank, Rods & Pistons Question ? ? ? ?

[ZammoTheCockroach]

so this isn't a hypothetical question? post up some pics, what engine is it?

yeah nah lol at the time my brain could not reach the correlation between the effects of slightly unbalanced reciprocating mass and engine harmonics

Its an old Toyota 18RG the place i brought it from is littered with 70s Toyos for rally purposes Celicas/Coronas/Hiluxes owner of current rally cars has gone holden v6

my theory is he picked up an old rally celica that he used all the panels off and the tweaked engine in it got chucked in the corner of the chicken coup as at the time the guy had a strong 2tg and wasnt interested in the RG or any of the others (i took 3 home).

head has been ported to suit 45s but it came with std 18RG mikunis


will grab a few pics next time i get the pallet down from storage and have a little play i really need to be concentrating on the current car not dreaming about the next one lol

[dat2kman]

so this isn't a hypothetical question? post up some pics, what engine is it?

In my case, an inline 6 Datsun (280Z Fuel Injection, no not a ZX! Car was built to Historic Group S rules, bore up 1.5 mm, stroke to stay stock.
Theory was use longest rods possible, shortest piston height, to inprove rod/stroke ratio.
Yes, the 120degree phading of the 6 cylinder Datsun crank, is badically a bent coat hanger, they break between 5 and 6, but will still run.
They have a second harmonic at around 7500, and if there is a flaw, or rpms are kept there, they let go.
By altering the crank wrights, and balancing crank with lighter but longer rods, lighter pistons with tapered gudgeons, and thinner rings, the crank guy shifted first harmonic upwards in rev range, second harmonipc is approx double the first.
They usually spin cranks ( due to centrifigal force on machine) only about 1800.
In mine, he reluctantly took it much higher. He was quite jappy with end result.
We also pulled a bit of weight out of periphery of the steel flywheel, big scallops, etc, and did a Jim Berry 200mm but 1350kg clamp clutch.