Toothed Belt Drives

[chimpvalet]

I'm building up an engine with added drive for a dry sump pump and find the 8m cog wheels purchased differ in pitch from the OEM cam cogs. I'm curious what pitch would have been standard for '70's era belt driven cams? Also, does anyone have a link to any catalog listing OEM cam belts by either length or tooth count?

Thanks
Steve

[dannobee]

Probably 3/8" pitch. Square tooth belts are generally SAE. Rounded tooth belts generally have metric pitch.

Do you know the number of teeth on the old belt?

https://aviaid.com/shopsite_sc/store/ht ... belts.html

[chimpvalet]

Believe the tooth count is 188. Yeah, I am thinking the HTD tooth profile was adopted while keeping the original Gilmer pitch of 3/8. Wonder whether the manufacturers in general went with 3/8 throughout or moved over to metric 8mm along the way?

[BCjohnny]

It's a world domination thing ..... battle of the metrology doctrines ......

More seriously, I think it's just an historic fact, to some extent ...... countries using the medieval system mostly held the design sway until the 'johnny come lately' foreigners started to catch up and invent their own stuff, using a more understandable metric

Or something like that

[jacksoni]

Are you asking/looking for cam belts or what amounts to Gilmer and similar in variety of pitches for a dry sump. Not same thing at all really. There are the usual suppliers of pulleys/belts for that specific application ( like:http://petersonfluidsys.com/pump_drysump.html) but sites like this cover all normal bases: https://www.bbman.com/

[jacksoni]

And if you have something really unusual Gates (Design IQ3) has a program that will let you design the entire drive system, pulley sizes, belts exact size with idlers and adjusters and let you, if you can calculate or figure some how, the load needed will tell you how big the belt needs to be. Speeds included. I used this to build a totally custom belt drive for the cams on a special build. I use a Gates Carbon belt 21mm wide (they have 36's I think) and so far has worked well. 10200 rpm shift points.

[chimpvalet]

Thanks chaps! I believe my oil pump drive project will be resolved with Moroso round tooth cogs and 8M belt available from Gates, etc. Pieces are coming along steadily on that. The engine cam drive remains a point of interest as it did include the OEM oil pump and distributor, both becoming redundant in this build. That opens an option to delete the associated pulley and related belt run, then switch to a shorter cam belt running a much less tortuous path. Pretty much have the industrial/aftermarket drive components fully researched in terms of the oil pump, just trying to complete the exercise in learning on cam drives.

Cheers