SS snowblower engines tecumseh

[jgflawn]

AH600 1640M 6156
Th139SA 8337G
hmsk100 159280T
hs50 67175D

Hello there. Hoping someone can help with info. Looking for the connecting rod length - center to center (not total length) - for the above 4 machines.

I must say after lurking around this forum for a few days, it is well worth signing up. Hopefully I'll have something to contribute over time.

edit (added)
I am also looking for the Performance curves for these models. I have the small ones (2" x 2") from the 2000 engine and accessories brochure, however does anyone have access to the mircofiche 1 and 1A? with possibly better resolution - as I think that is where they are located. Would love to have normal paper size for better resolution....
thanks!!

[jgflawn]

I should explain too ... as upon reading the question again, well seems like just a request for info...

I have the performance curves for these engines (although as mentioned, I'd like to have bigger and better resolution). The problem I'm facing is that the performance curves are incomplete. They give me max. torque curve; max BHP curve and recommended operating max BHP pbut they aren't complete. They don't provide the minimum output curve, so I'm going to just assume everything below the recommended is above the minimum and that everything on the graph below the recommended is allowable as continuous rated output. Also, I'm going to assume that rpm on the graph as the recommended operating speed range..

"Potential" on an engine is WOT. and the curves are all based on that. if you keep extending max bhp it eventually just stops at a certain rpm. the engine can't physically move faster or will come apart. Limits are scavenging, carb. delivery etc. etc.

So, to properly adjust a governor - when outside factory rpm - requires that it be set so that the engine can still maintain power at a stable engine speed. So, if factory rated power has the governor set to 50% open at governed maximum to allow for stable rpm. Anything putting more load will draw more fuel, less load, less fuel, but rpm will remain (relatively) constant - some speed drop expected. Honda limits drop to 5% for high speed applications such as my HS621 SS snowblower, but also ships at 90% of maximum BHP and after run-in 95% of maximum BHP. After run-in, Honda will run at max BHP under heavy load, dropping to 95% under normal load. So that's one machine I don't have to adjust.....

B&S on the other hand uses 85% leaving room for improvement, and I'm assuming my TEC are the same as B&S at only 85%.

So (wow, I'm long-winded), I need the rod lengths in order to calculate piston acceleration, and thereby arrive at the theoretical max. rpm before ring flutter occurs. That in conjunction with piston speed , BMEP etc. will allow me to tune these engines for my specific need rather than relying on factory settings. This will allow me to 'complete the curves' by providing the vertical drop off point for the maximum BHP curve, beyond which WOT is approached and things go badly.

Trying to be safe - using governor etc., but wanting to get full potential out of the engines for a specific application - increase rpm, sacrifice some torque etc. while also taking into consideration that I'm running these engines at -ve. temperatures, gaining 1% power output for every 6 deg (actually 5.6) below 15.6. ie. I gain 3% just by using below freezing temperatures.

Of course, I can do it myself if I pull all four engines apart and measure myself...but I was hoping someone might have the measurements, or have a rod in a parts bin, or scrap bin....and save me the work. thanks

[bobodu]

Whew.....you could just read some of the racing forums instead of reinventing the wheel....
You should understand the we tend to keep engines in running condition instead of making grenades.
Also...con-rods aren't usually something we have laying around because they are most likely just pieces when we get em...

[jgflawn]

Yeah, I agree. Although, I'm not looking to make a grenade. Far from it. My TH139SA is currently 'set' to 4.5HP. But the exact same engine on other machines is 'set' to deliver 5 and even 7 HP. So the engine itself can and has been used already at higher settings in other applications - sometimes just through the use of different governor springs, occasionally a different muffler too. This is really what the performance curves are all about. higher rpm, higher HP, lower torque or vice versa.

For example the TH139 will deliver 6 ft. lbs at BOTH 2000 and 3500 rpm based on the torque curve. and both are within the operating range. I think you'd agree that if this engine was on a lawnmower 2000 would be the right choice (regulations aside) versus 3500 rpm based on the application. neither would create engine damage. it is the application that makes the choice (blade tip speed) while the SS snowblower would be set at 3500 rpm for max. torque. However, 4 different SS brands using the same engine use 3700, 3800, 3850 and 4000 rpm with the same engine

For another engine I have, it is a 4HP at 5500 RPM. Those 'other' sites you mention have shown repeatedly that the engine can survive 11000 rpm - albeit with probably weekly top end rebuilds (the grenade). But the 'math' says I can bump by 1000 or even 2000 rpm with no engine risk, only loss of torque with a max. just above 8000 before damage starts. - although I can't say I want my SS snowblower to throw snow over the house - but with the engine at 11000 rpm it would...

I must admit to being a little bit analytical as well, hence all the math I'm doing. But I like to understand how stuff works, and why it works the way it does.

thank you for the help thus far. this site is great. and I really appreciate the fact that you caution the average reader by your response here not to even think about what I'm doing without knowing what your doing...i agree.

[jgflawn]

In the middle of vacuuming, I thought of a good way to illustrate.

Lets assume the same B&S engine with an operating range of 1200 to 4000 rpm is used on three different snowblowers
1. 24" dual stage, with friction wheel - 5 speeds
2. 30" dual stage, with friction wheel - 5 speeds
3. 30" dual stage, with hydrostatic transmission, infinite user control of ground speed.

The factory set rpm for these 3 machines should be different - resulting in different recommended maximum BHP for each for efficient governor control. Lower potential load in 24" than 30" because of width, so higher rpm allowed on the 24" for any given ground speed. However, on the hydrostatic, given the user has infinite control of ground speed, and can control the load on the machine, slowing it down to a snail pace if necessary, allowing the governor a closer tolerance to maximum BHP. However, user education required to slow the machine, otherwise the machine will bog down, start puffing black smoke as the throttle opens full, until it finally stalls under load. You only need to think what would happen if you went on forward speed 5 into 30" of end of drive... If I purchase a B&S engine to bolt onto one of these machines, do I just go with the factory set rpm even though end use isn't know when it is set? nope. That engine can be used on a rototiller, log splitter, chipper, snowblower. Lets face it, that's where small engine shops are the expert and use a tach to set rpm. sometimes only 100 or 200 rpm here or there.. but that makes a difference.

The following from Honda:
"The engine speed setting must be chosen so that even if maximum load is suddenly applied, the engine speed may not drop below the point where maximum torque is developed; this speed setting assures good performance and fuel economy."

But if the user has control of maximum load via ground speed....

Given load for a snowblower is determined by snow condition (fluffy versus wet), width of machine, depth of snow, AND ground speed, there is considerable room for adjustment. To just set at 3600 rpm and be done with it, when 3800 rpm (which is within engine specs) will throw the snow 10' further, and at a faster ground speed under less than full load conditions without any engine harm..allows me to clear my 17 properties faster...

So my 3 hp 30 year old HSK600 (98cc) at the factory set 4300 rpm (at minimum available torque -according to the performance curve) throws snow way better than my brand new B&S at the factory set 3060 (for max. torque). But I can't use the HSK600 for EOD as it immediately stalls. The B&S I can and do use for EOD because it is set for max. torque, but it won't throw 1" of light fluffy snow out of the chute until about 10' of ground travel and enough snow accumulates inside the auger housing.

I know most of you know the above, but for those that don't...

[jgflawn]

oh, and on the original post for con rod length given the responses so far, I'd settle for an 'educated' guess within 1/2" +/- from anyone that has worked on the specific model?

[Deere2me]

About all I can say ( other than seconding Bobo) is W.T.F.???

[bobodu]

I tried to explain that unless it has pictures of something shiny ...most of won't read more than two sentences.

[jgflawn]

I guess I was hoping that someone like Tman; trouts2 or borat might have migrated over from PERR and taken an interest ...

[KE4AVB]

Torque is not the same as speed. The speed of the auger determine the distance thrown. But to get that distance you give up overall torque at the auger. The differences between the engine to auger drive. Different pulley ratios will affect overall performance. It like having vehicle gets great fuel economy but doesn't the get up and go or big rig that is geared for high torque but has lousy fuel economy.

If you're swapping engines determine your auger speed and then you may only need change out one or both of pulleys and belt to achieve the current auger speed.
This way you can be comparing apples to apples as performance will then be more about overall torque developed at the auger