Taller gearing and its negative impact on FE
 

All:

With the discussion of Metro gearing, I remembered this and did some digging, and found some of it online:

https://www.studebakerdriversclub.com/tech_gearing.asp

Re-affirms the discussions from 1960-1 in the car mags of the time on the Studebaker Lark FE problems when Stude allowed customers to order specific rear ends and OD on the 6 cyl cars. Cars with 4.10 rear ends were doing better with FE than 3.54. Also, higher top speeds could be had (with much higher engine RPM) in 3rd Vs. 3rd/OD, R&T's January 1960 Lark 6 cyl (flat-head!) test showed 82 mph in 3rd Vs. 78 mph in 3rd/OD (99 in theory) with finaldrive ratios of 4.10 and 2.87.

Why is this? Weight to HP and air/wind resistance.

They were getting in the mid 20s out of the Larks by the way, with 5.90 15 bias tires. I wonder what imrpovement you would see to day with 165 R15 radials alone?

Funny how this car with a 2.7l flat head all castiron six that Stude developed in 1939 with a TINY Carter single throat carb does as well as some of to day!

well, where was the power band? creap out of that, and of course mileage is going to suffer.

In 39 most manufacturers probably were not too interested in fuel economy - gas was cheap.
Cheap fuel and no EPA to worry about allowed manufacturers to run poor designs.

But the flathead could be made to do well in FE , its just no one ever realy wanted to. , especially as hot rodding was much more fun.
https://www.motorcityspeedequipment.c...ges/block7.jpg

Tall gearing has done wonders for my FE. Ryland is right...it's all about staying in the power band.

:thumbup: Honda

carbed engines are tuned to run best at some rpm. change the gearing w/o futzing with the carb can muss some stuff up.

I'me not sure I understand what you wrote there omgwtfbyobbq., but a well tuned carb can supply good mixtures across a wide range of rev's.

On some primitive carbs you may not have the full range of fuel jets , air jets , emulsion tubes power valves and jets and venturies.
In fact on old Holley carbs that have the metering body between the main body and float chamber there are no adjustments.
So if it doesnt work rite , you will not get it to work rite.

On carbs that these parts are available they can work very well.

from what i've heard, if you just change gearing on a car w/o adjusting the carb jet/s/float level/etc you can hurt mileage at some speed, since a carb is set so that max vacuum occurs at some rpm. not that you couldn't set it properly in most cases (although that holley sounds like it might be a problem) just that after a significant change in gearing it might need to be adjusted. but then again, i haven't had nearly as much exposure to carbs compared to mech/electronic fi, so this is just what i've heard.

"Futzing with the carb" is always the "way out" of an engine problem...be it poor(er) MPG or low(er) power ( ye ol' butt dyno!). There is , however , something very basic going on inside the engine...it's known as valve timing! Valve timing affects carb (FI) air flow, mixture ratio, engine vacuum curves, mechanical (dis?)advantage, to name a few parameters. What changes valve timing? Nothing (unless you have some pretty expensive hardware in your engine). What determines valve timing? The profile of the camshaft lobes. This is fixed! Some very up-to-date auto mfgrs advance / retard their camshafts , some aftermarket people supply cam followers (lifters) which "pump up" with RPM (Rhodes lifters); most, however, don't address this issue! Progress and profit margin don't get along very well!