1968 Tecumseh H50 "Hot Rod" Build

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ubernoob51

Active Member
#1
#1
So guys, here's what I'm planning. I have a '68 Tecumseh H50, aluminum block with iron cylinder liner, and I already have a Motorsports billet rod, HH60 bearing crank, chrome-plated 0.010 over piston/rings, and a few other bits.

My question is, what would you guys do for valvetrain? What valves, guides, and cam?

I have an H70 ACR cam I plan to run, so I can actually pull start it but no compression release bump.

But base circle and peak lift are nearly identical to my stock H50 cam.

Does any place regrind medium-frame cams?
 

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ole4

ole4

#2
#2
Try emailing Tim isky. If you just regrind without welding your base circle will be smaller and you will need longer valves or tappets to make up the difference if it is much smaller than stock.
 
delray

delray

Well-Known Member
#3
#3
another option would to look into a newer hh block that came with a compression release(thats if you really want to pull it over with a rope) and send it to dyno cams attn: randy (call randy first)he can weld up any cam profile you want with in reason($100). for valves you might have the option to use aftermarket stainless steel valves from a briggs flathead or maybe a animal. need to do some research first on that...length long enough? if so can you machine new valve locks and cut to correct length or get lucky and find some nos tecumseh motorsport valves.
 
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ubernoob51

Active Member
#4
#4
delray said:
another option would to look into a newer hh block that came with a compression release(thats if you really want to pull it over with a rope) and send it to dyno cams attn: randy (call randy first)he can weld up any cam profile you want with in reason($100). for valves you might have the option to use aftermarket stainless steel valves from a briggs flathead or maybe a animal. need to do some research first on that...length long enough? if so can you machine new valve locks and cut to correct length or get lucky and find some nos tecumseh motorsport valves.
Click to expand...
Rope start is a must. The cam I bought for this build has a mechanical compression release.
 

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markus

markus

Well-Known Member
#5
#5
Uber, did you catch that statement that Jeff Clements mentioned recently on FB about the extended (PTO) version camshafts Being the ductile iron rather than just the gray iron and that they were better to regrind? I thought that was a neat bit of info, although I don't know if that applied through the years or only on later version engines (I am guessing later ones). The ductile was used on the Motorsports cams and cranks as well.

VKE did an engine for another member on here a few years back called a super 7 or something like that based off an H70. They machined in a push button comp release on the head for him as it was built pretty wild inside. I got to see it, it was pretty trick and started pretty easy. Chris offered to let me ride it.........but I wreck stuff so I graciously passed :D I have the MCR camshaft like what you got probably from his Donor H70 he sent to them stuffed in a box somewhere, Figured I would use it on an H50 rebuild at some point over the stock BCR they came with normally.
 
delray

delray

Well-Known Member
#6
#6
if your good at fabricating things. a air bleed compression button like marcus was talking about would be a another good option.. in the pass had fab up one on a overhead valve engine that did not have a factory compression release cam. work pretty slick once i figure out how to control the air bleed. with 12:1 compression and a 255 cam with 1.3 ratio rocker it helps on the arm....lol
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joshua. c.

joshua. c.

Well-Known Member
#17
#17
so a rupp with a hot-rodded engine, it looks mostly stock and dellortos are common on rupps so I guess that's a sleeper then. nice build!

so did you port the block? stock ports have allot of sharp edges and can be improved allot, and considering you can do it at home with a Dremel its a free power gain. also did you advance the timing? seems like Tecumseh's really like that.
 
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ubernoob51

Active Member
#18
#18
joshua. c. said:
so a rupp with a hot-rodded engine, it looks mostly stock and dellortos are common on rupps so I guess that's a sleeper then. nice build!

so did you port the block? stock ports have allot of sharp edges and can be improved allot, and considering you can do it at home with a Dremel its a free power gain. also did you advance the timing? seems like Tecumseh's really like that.
Click to expand...
I did shave the brows, timing I advanced a little bit, I set it o 0.085" BTDC (0.080 is stock). Didn't port the block though, maybe I'll save that for when I install slimmer valves.

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ubernoob51

Active Member
#19
#19
So I put fresh rings into the electric start HH60 that's on my go-kart. It already has a Motorsports billet rod and a Dell'Orto, but it burned oil and I've never looked at the rings.

Haven't ridden it yet, but it seems to smoke less on the bench already.

I have a 0.010 over piston/ring set if the need arises.
 

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Dipstik82

New Member
#20
#20
ubernoob51 said:
So I put fresh rings into the electric start HH60 that's on my go-kart. It already has a Motorsports billet rod and a Dell'Orto, but it burned oil and I've never looked at the rings.

Haven't ridden it yet, but it seems to smoke less on the bench already.

I have a 0.010 over piston/ring set if the need arises.
Click to expand...
Did you deglaze the cylinder before you installed the new rings?
 
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