Tecumseh HS40 HS50 connecting rod improvement thoughts
- Thread starter cfh
- Start date
On the LH195 having 5.5 hp instead of 5 hp.... I was just speculating that was the cam. I think I made that clear in the document that it wasn’t like I put it on the Dyno or anything. I find it hard to believe that you could get an extra half horsepower running it at 3800 RPM instead of 3600 RPM. But again it’s just speculation. I don’t know what the thinking was at Tecumseh. Heck they might’ve been fudging numbers...
on the Dynocam RPMs those are the numbers They gave me over the phone. I have no reason to contest what they say. I’m sure you can always find ways to make things spin faster!
I try and be as accurate as I can in the document. But you’re right there’s a lot of others that are smarter than me and can probably pick it apart. I’m doing the best I can, given my experience and the tools and knowledge that I have.
on the Dynocam RPMs those are the numbers They gave me over the phone. I have no reason to contest what they say. I’m sure you can always find ways to make things spin faster!
I try and be as accurate as I can in the document. But you’re right there’s a lot of others that are smarter than me and can probably pick it apart. I’m doing the best I can, given my experience and the tools and knowledge that I have.
part number for the retainers/kit ohh stuff is 37259K and the springs are 37281K
here is what i found kind of strange. the H50 has a different spring number 36805K both use the same retainer/kit. this is only base on looking up park numbers for the motorsports stuff.
here is how the tecumseh retainer fits on the briggs animal spring(center valve) fit good on the spring,but note the slight off set it has. this could be good or real bad in some cases. bad case would be to much valve spring pressure and valve spring bind could also happen or it could be only enough off set to create little more valve spring pressure on the cam and wouldn't hurt it at all. this would really need to be look at with correct measuring devices.
left side is a briggs animal retainer /kit..............way to much off-set.
here is a better picture of way to much off-set when installed in a small block tecumseh.
here is what i found kind of strange. the H50 has a different spring number 36805K both use the same retainer/kit. this is only base on looking up park numbers for the motorsports stuff.
here is how the tecumseh retainer fits on the briggs animal spring(center valve) fit good on the spring,but note the slight off set it has. this could be good or real bad in some cases. bad case would be to much valve spring pressure and valve spring bind could also happen or it could be only enough off set to create little more valve spring pressure on the cam and wouldn't hurt it at all. this would really need to be look at with correct measuring devices.
left side is a briggs animal retainer /kit..............way to much off-set.
here is a better picture of way to much off-set when installed in a small block tecumseh.
i see you mention about my discovery on using animal springs and dyno retainers from a briggs flathead and modifying them to work with the single springs(animal) and using the newer compression release cams in your pinrepair right up and me not getting any credit for it....lol. there is one more retainer that might work and that would be the tecumseh motorsports parts. maybe on my next small block build i will look into this and if it works you can add it to you pin right up.
also in your right up i feel your little misleading on the 245 cam and it's power band(rpm range) you say it's only is good to 5000 rpm's?
i guarantee with my 245 in my hs-40 it pulls easy 7000 rpm's. if i am correct that cam was rated for 6500+ in a ohh-motor and 255 was 7000 and the 356 was 9500. here is also something you cam mention in your right up. dyno will grind other profiles. i know of one other member here pm and told me they had a 308 profile ground. just may try that out in a ohh motor some day.
running a 18 pound springs is not alot of spring pressure for a stock or even a 245 cam. when you start to get into the 20+ pounds and above you can start to wear on the cam if it's not harden correct. i just tore apart my hs-40 a while ago and did not see any damage at all on the cam lobes and that was using 18 pounds animal springs and we all know that engine went to hell and back more then once...lol..
also looking back when you installed the newer compression release cam in a old hs block with the hs lifters you where getting about .030 higher lift. thats because the newer cams with the release have a different base circle then the older cams did and you where picking up the extra .030+/- height. not the reason why tecumseh was getting 5.5 horse power out of there engines. 5.5hp is more then likely coming from jetting,rpm settings...etc.....
if your going to have this info out there for everybody to see need to try to get some of this more accurate....
also in your right up i feel your little misleading on the 245 cam and it's power band(rpm range) you say it's only is good to 5000 rpm's?
i guarantee with my 245 in my hs-40 it pulls easy 7000 rpm's. if i am correct that cam was rated for 6500+ in a ohh-motor and 255 was 7000 and the 356 was 9500. here is also something you cam mention in your right up. dyno will grind other profiles. i know of one other member here pm and told me they had a 308 profile ground. just may try that out in a ohh motor some day.
running a 18 pound springs is not alot of spring pressure for a stock or even a 245 cam. when you start to get into the 20+ pounds and above you can start to wear on the cam if it's not harden correct. i just tore apart my hs-40 a while ago and did not see any damage at all on the cam lobes and that was using 18 pounds animal springs and we all know that engine went to hell and back more then once...lol..
also looking back when you installed the newer compression release cam in a old hs block with the hs lifters you where getting about .030 higher lift. thats because the newer cams with the release have a different base circle then the older cams did and you where picking up the extra .030+/- height. not the reason why tecumseh was getting 5.5 horse power out of there engines. 5.5hp is more then likely coming from jetting,rpm settings...etc.....
if your going to have this info out there for everybody to see need to try to get some of this more accurate....
Interesting thoughts on the extra 1/2 a pony, I'm going to dive in to an early HS and later LH195SP/HSSK55 (have both) and measure everything for myself but my teardown bench is blocked up until after the holidays.
The larger base circle, was that across the (small frame) cam production or just the 37040 cam? I can't remember if I heard that cam was an OHV part that made it's way into later production HS(SK) or designed originally for the flatheads.
Wouldn't surprise me if the 5.5hp was just a sticker or an actual hp increase from a combination of other tweaks but 10% is a big gain for production engines.
you could say the newer style compression release is little overrated...lol. for me it's really easy to pull little hs motor over without the release unit once you do get the motor setup correct.
there are some good points of having it too. good examples when it comes to the newer stock steel unit, they make a good mild hot rod cam with the hot coil(36605K ) or playing around with advancing the old mag on a points engine and all correct other mod's done to it and to the bike. does make it easy to pull over the times when you do forget to turn the motor correct to pull on it....lol. they do like to pull strong up to 4700+ rpms. not bad for a stock steel cam with just mod's done to it. also better cam then the older hs-motors that use the bump built into the back lobe. allowing the valve to bounce open all the time. sure thats not the best thing to do for the valve train on a hot rod motor.
there are some good points of having it too. good examples when it comes to the newer stock steel unit, they make a good mild hot rod cam with the hot coil(36605K ) or playing around with advancing the old mag on a points engine and all correct other mod's done to it and to the bike. does make it easy to pull over the times when you do forget to turn the motor correct to pull on it....lol. they do like to pull strong up to 4700+ rpms. not bad for a stock steel cam with just mod's done to it. also better cam then the older hs-motors that use the bump built into the back lobe. allowing the valve to bounce open all the time. sure thats not the best thing to do for the valve train on a hot rod motor.
I got one of those hot cdi coils 36606k from you Del, but i've never seen another for sale. where did you find those?? been meaning to play around with advancing points timing to see what changes can easily be incorporated... but haven't got there yet. also milling a head too. like you, i don't like compression releases. i don't need that stuff. it's easy enough to pull the engine to the right spot before i tug it!
when i started to get into mod's on my ohh stuff the hot coil was like putting on a light switch. day and night difference. i stumble on a bunch few years ago at a swapmeet with some very hard to find ohh motorsports performance parts.
you haven't tried it yet? save it until you get all the mod's done. i think you will be happy with it. i still have not tried it out on a flathead build yet. my flathead build was points engine and the rest of my tecumseh builds have been ohh motors.
have not done the research yet,but with the right coil off a clone,briggs..etc..? and brackets a guy could advance the motor that way too.
here is a example adjustable bracket for a coil set up. just need to find the right stuff. not saying any of this will work. just trying to give you a ideal what i am talking about.
you haven't tried it yet? save it until you get all the mod's done. i think you will be happy with it. i still have not tried it out on a flathead build yet. my flathead build was points engine and the rest of my tecumseh builds have been ohh motors.
have not done the research yet,but with the right coil off a clone,briggs..etc..? and brackets a guy could advance the motor that way too.
here is a example adjustable bracket for a coil set up. just need to find the right stuff. not saying any of this will work. just trying to give you a ideal what i am talking about.
Hi CFH,
I have the late Tecumseh manuals set and many of the Factory Training Tecumseh Updates 200X that
were published each year up to about 2008, when Tecumseh went out business. Here is my understanding:
The original HS50 was renamed LH195SA
Then about 2006 or so, Tecumseh manufactured the LH195SP. ( The "P" stands for "Powered-up".)
Tecumseh changed the design slightly and revamped the forging and manufacturing process to produce
better, smoother fitting head, porting, and intake manifold. The Tecumseh Updates state that the SP
engines have a little better air flow. The result is that the LH195SP does put out
about 1/2 HP more at 3,600 RPM. I think this is an honest figure.
Same story with the OH195SA 6.0 HP
and OH195SP 6.5 HP.
The SP engines can be found on some of the Ariens 932 series snowblowers from about model year 2006 to 2008.
Had Tecumseh remained in business longer, the SP engines would have also showed-up in OH318SP and OH358SP
at about 1 HP higher
as the new manufacturing improvements were phased in over the engine model lines.
My favorite Christmas Wish would be that some investor group would resurrect the Tecumseh engine line.
Last edited:
to orsen yancey. something to note, from some research I did on an engine that looked eerily like an ohh55 but different, I think a group did buy the rights to the tecumseh engines and re engineered they're designs and currently makes and sells engines. so getting the rights would be hard. cant remember the company name though. they are different enough from tecumseh engines that I doubt any parts would interchange but unless I took one apart I couldn't be sure.