creia wrote:bgsengine wrote:Yeah from those photos now, I would tend to say it is your *exhaust* cam lobe that is worn out, oddly enough - it looks almost re-ground - I cant recall seeing them with such a size disparity - looks like intake cam lobe is much larger - but as you have discovered - it's gonna be expensive in any case, and with luck you may be able to find "NOS" (New Old Stock) parts on ebay or elsewhere - should be able to look up part numbers and then run a number search in google.
Brian,
You are correct (no surprise) about the size disparity of the cam lobes! I've never seen anything like that in any Briggs or Tecumseh engine we have ever worked on. Our research has revealed that this particular cam was a bit of an odd-ball (The lifters are also different lengths). From 1971-on Tecumseh went to a cam with lobes and lifters identical in size in the HS40. A OEM replacement for our 1970 HS40 cam is NLA, however, we have been informed from a reliable source that the 1971-on cam and lifters are a direct fit in our block and THEY are available for not too bad of a price.
If it turns out we definitely need a new cam, that is the route we would likely go.
Michael
AH-HA! That rings a bell now - I do recall those different sized cam lobes - I only wish I happened to have the memory to recall the dimensions - I only vaguely recall (this was back in the mid-1980's ... `85 if i remember right.) rebuilding one of those engines and having to question the camshaft lobe sizes, several measurements trying to figure out how to explain it to tech support (at tecumseh factory - even THEY did not know anything about it until they went (I think) to their engineering dept. - All done over the phone by my boss at the time as we were trying to find replacement lifters for one that broke after being hit by something after throwing the rod.. I seem to recall the lifter options were not shown in parts books..) - It was the one and only of those weird cams I have ever seen .. and your comment about the different lifter sizes was what triggered the memory - but after 30 odd years it's difficult to even remember even roughly the dimensions or much other detail..
I can't recall if we had ever gotten the right parts or if we had replaced cam and lifters as a set (back to "standard" configuration) - but I have a theory that those engines were a very limited production and intended for performance applications - seems to me having a shorter lift, longer duration on the intake would perhaps allow for a different "turbulence" and intake port opening (I cant remember - do they have different sized valves?). theoretically helping improve combustion and air flow (especially if they are built for higher RPM applications)
(We probably are!) 
My son is committed to seeing this project to completion, which includes rebuilding the worn out OEM Tec HS40 engine. $$$ Also, as you stated - "Learning experience"- Look what THAT is worth and how do you place a price cap on THAT?
As some of you may remember from my previous posts (I know that Brian does), my son loves working on the old Briggs and Tecumseh flatheads. Almost ever engine he has ever owned or built is over 40 years old.
It looks like this model HS40 was a very limited production run, just as Brian (and I) suspected.
I remember him very well. He helped my son and I a few years ago on some of our other 40 year old Tecumsehs. Has anybody heard anything about him?
