Jump to content

Nominations for Tractor of the Month
Garden Tractors and Parts on eBay



Photo
- - - - -

Problem Child


  • Please log in to reply
12 replies to this topic

#1 637Yeoman OFFLINE  

637Yeoman

    The Simplicity collector

  • Senior Member
  • GTt Junior
  • Member No: 77049
  • 465 Thanks
  • 467 posts
  • Location: SW Michigan

Posted January 10, 2016 - 09:35 PM

 This is my littleJohn Deere 70 gt puller.It has a 7hp cast iron techumseh. With some modifications its pushing 10 or 11hp. We havent bored it yet but we will soon. The biggest things we did was add a "Sonic tube" , ported the engine, and changed the electrical to a car coil,milled the head and added an aluminum piston from a mini bike.. The sonic tube has to be a certain length and diameter for your engine. It does something with the pulses of the engine. The car coil is for hotter spark and so we can run racing gas. The hotter spark makes it burn all the fuel and getter more power out of each stroke. The racing gas makes it burn slower.

The Mini bike piston makes it torque up faster.

 

We also cut the tires which gives it wicked traction. Beats any cut ag-tire around.So after we did that and added a front and back weight bracket and wheelie bar it is a pretty wicked machine. 

post-77049-0-62299600-1452218062_thumb.ppost-77049-0-00833500-1452218104_thumb.ppost-77049-0-59483800-1452218084_thumb.p


Edited by 637Yeoman, January 11, 2016 - 03:00 PM.

  • rustyoldjunk, Alc, Traill95 and 3 others have said thanks

#2 dodge trucker ONLINE  

dodge trucker
  • Senior Member
  • Member No: 19314
  • 1,440 Thanks
  • 1,897 posts
  • Location: kankakee

Posted January 10, 2016 - 10:40 PM

I can agree with all but one thing in your build, probably increasing power as you claim; the "minibike piston"; if its out of another 7HP Tecumseh it won't do anything different than the original,  you say it's an aluminum piston/ ok;  yes it probably is, but so was the original one. even though you have a cast iron block and the minibike engine would most likely have been an aluminum block; some aluminum block Tecumsehs still had cast iron cylinder liners.   

and to bore it out enough to make any difference (other than to maybe correct a well-worn cylinder) you'd be into the fins... a 0.010/0.020/0.030 overbore won't amount to much if any, of a measurable HP increase.  Saying that it will, is a long held myth.

If you do bore it, you may play with piston to wall clearance a bit but really not much being an air cooled engine. again any gains there would be minimal. 

If you actually dyno'd it, any gains with piston and cylinder  would come from a freshen up and restoring original clearance tolerances.

Not at all saying that you haven't improved the output of that engine, just questioning where the gains may be coming from. 

That 7HP was the largest HP in that block "family"  stock from the factory. Unlike the Kohlers where for example you could put a 16- 18HP cam into a lower HP version of that engine and get some gains, you're at the top of that engine family already.

Short of knowing someone that raced tec powered engines years ago or maybe getting to know an old tec engineer that may have some "experimental" parts stashed away that you could talk him out of, you'd have to have your cam lobes reground.

It's definitely cool though, seeing someone playing with what most would claim a "less popular" engine.

kind of like the Chevy guys vs the Ford guys vs us Dodge guys....


  • LilysDad, Dieselcubmike, Chopperhed and 1 other said thanks

#3 MH81 ONLINE  

MH81

    Proud to be Deplorable

  • Staff Admin
  • Staff
  • -GTt Supporter-
  • Contributor
  • Member No: 802
  • 27,306 Thanks
  • 28,628 posts
  • Location: N. W. PA

Posted January 11, 2016 - 03:46 AM

That's a very nice looking machine.
Glad you're having fun with it.

One thing to keep in mind was the failure point of many of these engines. The connecting rod.
I have seen several of these engines with the dreaded "sight hole" issue. Often these engines have been exposed to less than frequent oil changes and/or tweaking of the governor to get a few more RPM's out of them

Super happy you're having fun and learning all you have. You have a great little machine there and I only mention it to help keep it fun for you and your machine happy too.
  • 637Yeoman and Bolens QT-17 have said thanks

#4 rustyoldjunk ONLINE  

rustyoldjunk

    Has anybody seen my coffee ?

  • Senior Member
  • Member No: 325
  • 2,368 Thanks
  • 1,212 posts
  • Location: Indiana

Posted January 11, 2016 - 06:12 AM

Looks great Luke and I'm glad you have it running good. I will just add to MH's post that the rod issue is one shared with Kohlers. I have seen more Kohlers than any other with a "disfigured" rod. The cast iron Briggs and Wisconsin seem to be the two brands that have withstood the test of time the best from what I have seen over the last 15-20 years.


  • 637Yeoman and Bolens QT-17 have said thanks

#5 Dieselcubmike OFFLINE  

Dieselcubmike
  • Senior Member
  • Member No: 11127
  • 1,327 Thanks
  • 1,511 posts
  • Location: Southwestern,Pa

Posted January 11, 2016 - 02:00 PM

I definitely agree with dodge trucker. Its a little more than just using a car coil to get hotter spark to run race gas. You need a good bit of compression to help it. Have you milled the head? That's a start to it. You might want to also get your cam done. More lift and duration would help. If you plan on really turning the engine up I would have it professionally done. Not sure how far your wanting to get into it but a good start would be a billet head, stainless steel valves, billet crank, performance piston like an aries or JE piston. And a billet flywheel to help keep your rpms up and also to keep the old flywheel from turning into a grenade. Also a good gas carb as well. I know this seems way off course but with what I just said you could make a double digit engine very easily. Thats my opinion but dodge trucker explained it better than I did lol. 


  • 637Yeoman and Bolens QT-17 have said thanks

#6 637Yeoman OFFLINE  

637Yeoman

    The Simplicity collector

  • Senior Member
  • GTt Junior
  • Member No: 77049
  • 465 Thanks
  • 467 posts
  • Location: SW Michigan

Posted January 11, 2016 - 02:28 PM

I definitely agree with dodge trucker. Its a little more than just using a car coil to get hotter spark to run race gas. You need a good bit of compression to help it. Have you milled the head? That's a start to it. You might want to also get your cam done. More lift and duration would help. If you plan on really turning the engine up I would have it professionally done. Not sure how far your wanting to get into it but a good start would be a billet head, stainless steel valves, billet crank, performance piston like an aries or JE piston. And a billet flywheel to help keep your rpms up and also to keep the old flywheel from turning into a grenade. Also a good gas carb as well. I know this seems way off course but with what I just said you could make a double digit engine very easily. Thats my opinion but dodge trucker explained it better than I did lol. 

We milled the head. It has more compression. 

I dont know if we will build it anymore.



#7 637Yeoman OFFLINE  

637Yeoman

    The Simplicity collector

  • Senior Member
  • GTt Junior
  • Member No: 77049
  • 465 Thanks
  • 467 posts
  • Location: SW Michigan

Posted January 11, 2016 - 03:02 PM

I can agree with all but one thing in your build, probably increasing power as you claim; the "minibike piston"; if its out of another 7HP Tecumseh it won't do anything different than the original,  you say it's an aluminum piston/ ok;  yes it probably is, but so was the original one. even though you have a cast iron block and the minibike engine would most likely have been an aluminum block; some aluminum block Tecumsehs still had cast iron cylinder liners.   

and to bore it out enough to make any difference (other than to maybe correct a well-worn cylinder) you'd be into the fins... a 0.010/0.020/0.030 overbore won't amount to much if any, of a measurable HP increase.  Saying that it will, is a long held myth.

If you do bore it, you may play with piston to wall clearance a bit but really not much being an air cooled engine. again any gains there would be minimal. 

If you actually dyno'd it, any gains with piston and cylinder  would come from a freshen up and restoring original clearance tolerances.

Not at all saying that you haven't improved the output of that engine, just questioning where the gains may be coming from. 

That 7HP was the largest HP in that block "family"  stock from the factory. Unlike the Kohlers where for example you could put a 16- 18HP cam into a lower HP version of that engine and get some gains, you're at the top of that engine family already.

Short of knowing someone that raced tec powered engines years ago or maybe getting to know an old tec engineer that may have some "experimental" parts stashed away that you could talk him out of, you'd have to have your cam lobes reground.

It's definitely cool though, seeing someone playing with what most would claim a "less popular" engine.

kind of like the Chevy guys vs the Ford guys vs us Dodge guys....

Ididn't mean the new piston gave it more power, it makes it torque up faster. The original piston was aluminum. The mini bike pistons are lighter so they would torque up faster.

We would only bore it to correct the cylinder like you said.


Edited by 637Yeoman, January 11, 2016 - 09:20 PM.


#8 637Yeoman OFFLINE  

637Yeoman

    The Simplicity collector

  • Senior Member
  • GTt Junior
  • Member No: 77049
  • 465 Thanks
  • 467 posts
  • Location: SW Michigan

Posted January 11, 2016 - 03:05 PM

That's a very nice looking machine.
Glad you're having fun with it.

One thing to keep in mind was the failure point of many of these engines. The connecting rod.
I have seen several of these engines with the dreaded "sight hole" issue. Often these engines have been exposed to less than frequent oil changes and/or tweaking of the governor to get a few more RPM's out of them

Super happy you're having fun and learning all you have. You have a great little machine there and I only mention it to help keep it fun for you and your machine happy too.

We have already blew it up. Problem? the rod. :(


  • rustyoldjunk, MH81 and KennyP have said thanks

#9 MH81 ONLINE  

MH81

    Proud to be Deplorable

  • Staff Admin
  • Staff
  • -GTt Supporter-
  • Contributor
  • Member No: 802
  • 27,306 Thanks
  • 28,628 posts
  • Location: N. W. PA

Posted January 11, 2016 - 03:09 PM

Yeah, sorry to hear it.
Did it puncture the block?
  • 637Yeoman said thank you

#10 637Yeoman OFFLINE  

637Yeoman

    The Simplicity collector

  • Senior Member
  • GTt Junior
  • Member No: 77049
  • 465 Thanks
  • 467 posts
  • Location: SW Michigan

Posted January 11, 2016 - 03:11 PM

Yeah, sorry to hear it.
Did it puncture the block?

yup.

My dad is a welder so he fixed that up quick.


  • MH81 said thank you

#11 DaveBb OFFLINE  

DaveBb
  • Senior Member
  • Member No: 62819
  • 375 Thanks
  • 157 posts
  • Location: Quebec

Posted February 02, 2016 - 05:33 PM

Once upon a time worked in a small engine repair shop. A normal winters work would include at least 10 techumseh short blocks. Snowblowers with rpm slightly turned up almost always resulted in a rod failure and hole in the block. If you plan to continue I would look for a kohler. Parts are all over the place and plenty of info around


Edited by Saxist, February 02, 2016 - 05:35 PM.

  • MH81 and 637Yeoman have said thanks

#12 LilysDad ONLINE  

LilysDad

    Cat Lover

  • Senior Member
  • -GTt Supporter-
  • Contributor
  • Member No: 10443
  • 9,661 Thanks
  • 7,682 posts
  • Location: N. Illinois, DeKalb County

Posted February 02, 2016 - 07:28 PM

Once upon a time worked in a small engine repair shop. A normal winters work would include at least 10 techumseh short blocks. Snowblowers with rpm slightly turned up almost always resulted in a rod failure and hole in the block. If you plan to continue I would look for a kohler. Parts are all over the place and plenty of info around

 

. . . . . or a 4cyl Ford!


  • 637Yeoman said thank you

#13 637Yeoman OFFLINE  

637Yeoman

    The Simplicity collector

  • Senior Member
  • GTt Junior
  • Member No: 77049
  • 465 Thanks
  • 467 posts
  • Location: SW Michigan

Posted February 18, 2016 - 01:30 PM

Once upon a time worked in a small engine repair shop. A normal winters work would include at least 10 techumseh short blocks. Snowblowers with rpm slightly turned up almost always resulted in a rod failure and hole in the block. If you plan to continue I would look for a kohler. Parts are all over the place and plenty of info around

Im going to keep it that built. i think we already pushed the limits. Might build a cub. simplicities cant stand up to that power.






Top