HSSK50 small block mods

delray

Well-Known Member
#42
now that i got my new tooling in i can start to work on my build. i still needed to finish up my exhaust first. valve that i had for it was way over size and needed to be shorten and the valve it self needed to be much smaller also.
chuck it up and took a ton material off of it.
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next i wanted to take some material off the back side and the stem area and then start to polish the area by starting with a small roll sander on a dremel tool while the lathe spinning slow...
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next i hit with this polish brush. (help take out the sand marks)
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then polish it up with some polishing compound.
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more to come........:scooter:
 

delray

Well-Known Member
#43
here is the exhaust valve before cutting the angles into them.
69.jpg

cut a 45 and blend the 30 cut into the polish narrow stem. for me i thought this would be a better improvement for air flow then enlarging the valve itself. especially for a engine that won't spin more then 5000 rpm's.
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seat's clean up real nice. just few turn's with my seat cutter and done.
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lapping the valves was very easy and quick. theses valves fit spot on.
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cfh

Well-Known Member
#45
I am doing an HSSK50/LH195 now. I got the engine for $25 from a snowblower guy. the problem is, the motor was stored on it's side in water. The head had to be cut off because the bolts refused to let go! got that sorted out and checked the bore... nearly new with factory hatch marks in tack.

the problem with the motor is the 7/8" pto. i turned it down to 3/4". but i'm not doing what Delray did... i'm not a ball bearing side cover type of guy, i view that as overkill, and the side covers are hard to find and expensive. instead just turning the pto to 3/4" and re-cuting the keyway.

i will use a Precision 30/30 cam (basically a dyno245 copy) and keep the CDI ignition cast flywheel.

http://www.pinrepair.com/minibikes/p/hssk50crank1.jpg
 

delray

Well-Known Member
#46
I am doing an HSSK50/LH195 now. I got the engine for $25 from a snowblower guy. the problem is, the motor was stored on it's side in water. The head had to be cut off because the bolts refused to let go! got that sorted out and checked the bore... nearly new with factory hatch marks in tack.

the problem with the motor is the 7/8" pto. i turned it down to 3/4". but i'm not doing what Delray did... i'm not a ball bearing side cover type of guy, i view that as overkill, and the side covers are hard to find and expensive. instead just turning the pto to 3/4" and re-cuting the keyway.

i will use a Precision 30/30 cam (basically a dyno245 copy) and keep the CDI ignition cast flywheel.

http://www.pinrepair.com/minibikes/p/hssk50crank1.jpg
nice,are going to try out the hot coil. that will make a difference with a aftermarket cam....:scooter:
 

delray

Well-Known Member
#48
Del i am *scared* to try that hot tecumseh coil! you know why? because i'm afraid i will like it. and then what do i do??? i can't get any more of them!!

I put the mill attachment on the lathe and cut the 3/16" keyway into the crank. I've always used a mill to do this, but no longer have access to one. So this was my best alternative...

http://www.pinrepair.com/minibikes/p/hssk50crank2.jpg
like that old fixture. i like to find one for my lathe someday even though i got a mill to do that. i like to do a lot stuff on the lathe.
how did you get that crank centered with only a three jaw. hopefully it's not to out of round. maybe with a cast steel flywheel your crank won't know the difference.
another option maybe to look into would be to see if some of the aftermarket coil brackets and coils for a flathead briggs/racing would work for advancing the timing. someday when i get some time going to look into that.
 
#49
like that old fixture. i like to find one for my lathe someday even though i got a mill to do that. i like to do a lot stuff on the lathe.
how did you get that crank centered with only a three jaw. hopefully it's not to out of round. maybe with a cast steel flywheel your crank won't know the difference.
another option maybe to look into would be to see if some of the aftermarket coil brackets and coils for a flathead briggs/racing would work for advancing the timing. someday when i get some time going to look into that.
I own mostly points tecumsehs, but my Blockzilla has one of those coil brackets that you are talking about.
I bet something similar could be made for a Tec if the Briggs one doesn’t work
 

cfh

Well-Known Member
#50
Did some measuring of valve lift with the engine buttoned up, and the Precision 30/30 cam installed. I would say the Precision 30/30 cam is basically a Dynocam245 clone. Precision didn't provide a cam card unfortunately, but the valve lift is idential to the dynocam 245.

I had a scrap head so I made a cutaway head today. It's really interesting... The Precision 30/30 (dynocam245) provides about all the valve lift you could get on a stock head Tecumseh. Check out the picture below, and you'll see the exhaust valve hitting the head. Now note the head gasket (about .060" thick) is not installed. But that's not a lot of clearance... even less if you're using a Dynocam 255 (another .010" of valve lift.) But don't mill a Tecumseh head more than about .010" or you will be in trouble!

http://www.pinrepair.com/minibikes/p/grindcam21.jpg
 

cfh

Well-Known Member
#52
that head was the original head to that motor. but to get it off, i had to cut it. so i figured i would cut it some more to make it a learning tool. it's pretty cool to see how close the valves get to the head. also would be useful in determining timing.
 
#54
I did my first HS50 years ago and am a little fuzzy on the head but I did mill it and add a usless fireslot, this is the only pic I have but I did what you did try it without the head gasket and it did hit the head so I had to raise the pocket above the valves a bit till it stopped hitting and the valve to head clearance became the gasket thickness. The isky is a black mamba jr grind but with a 108 LC.
 

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delray

Well-Known Member
#55
Getting little off on my engine build. I had a friend that built a hs50 ran just over 300 lift with a copper gasket(.042) and had no problems. I need to ask him if he had to cut out pocket reliefs for the valves.
 

delray

Well-Known Member
#56
I did my first HS50 years ago and am a little fuzzy on the head but I did mill it and add a usless fireslot, this is the only pic I have but I did what you did try it without the head gasket and it did hit the head so I had to raise the pocket above the valves a bit till it stopped hitting and the valve to head clearance became the gasket thickness. The isky is a black mamba jr grind but with a 108 LC.
Ole4 what does the fire slot really do......lower the compression....lol
 
#59
pretty sure it did nothing but lower compression but the marketing BS said it forced the quench area charge thru the slot into the chamber. Pretty sure it killed off some of the high velocity charge sqeezed out from the squish into the chamber.
 

cfh

Well-Known Member
#60
so is there *any* mod that can be made to the hs50 head? i've heard some guys mill the head .010", but that hardly seems worth the trouble.
 
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