new sbh engine build.

#1
new build. just got a new old stock sbh 7276-a . i don't know what year it is but it has the big exhaust valve, both points and electronic ignition bosses. nice thin ring piston with 2.795 bore. i have lots of goodies for this one. i will post pics when i get started. Anthony. IMG_1158.JPG
 
#3
markus. i tried to find your model. imposable. this in the only big valve i could come up with. it has a large taper crank with no ballbearing. i have a ballbearing crank and cover , but did not want to wast them on the ruff casting block. i found a brand new in the box small taper ballbearing crank. and to go with it a brand new bearing side cover without the big ugly snow blower oil fill. the guy took my offer on the short block. $125.00 shipped. im happy with it with the exception of a loose and wobbly exhaust guide. what is it with tecumseh exhaust guides. anthony.
 
#4
markus. i read your link. thats funny. i do remember you telling me about a brand new small bore motor. at the time i did not know how small of a difference there was in the bore size. and this is a small taper crank. i got the new crank bscouse i have no way to cut the grove for the retaining clip for the bearing. i have a 20 over fat ring piston but no need to bore a brand new block plus i like the thin ring piston. looks lighter and less friction.
 

markus

Well-Known Member
#5
markus. i tried to find your model. imposable. this in the only big valve i could come up with. it has a large taper crank with no ballbearing. i have a ballbearing crank and cover , but did not want to wast them on the ruff casting block. i found a brand new in the box small taper ballbearing crank. and to go with it a brand new bearing side cover without the big ugly snow blower oil fill. the guy took my offer on the short block. $125.00 shipped. im happy with it with the exception of a loose and wobbly exhaust guide. what is it with tecumseh exhaust guides. anthony.
yea I got that Ball bearing one from them for $150 shipped, I was pretty happy with that price considering the layout of it. I almost bought that one, but I have enough good HS50 blocks big and small bore to work with.

Exhaust valves have a smaller od than intake valves.....by about .004" but the guides are drilled the same. I will take a wild guess and say that is done to compensate for heat expansion/valve sticking issues.
 
#6
yea I got that Ball bearing one from them for $150 shipped, I was pretty happy with that price considering the layout of it. I almost bought that one, but I have enough good HS50 blocks big and small bore to work with.

Exhaust valves have a smaller od than intake valves.....by about .004" but the guides are drilled the same. I will take a wild guess and say that is done to compensate for heat expansion/valve sticking issues.
yes i miked them out when i found a ton of movement in the exhaust valve. my exhaust is 0.005 smaller than the intake i have ben trying to post a video showing the exhaust valve movement but it won't go thru. imon the phone waiting for a mac tech to do a screen share to fix it. hopefully i can send that video. anthony.
 

markus

Well-Known Member
#7
yes i miked them out when i found a ton of movement in the exhaust valve. my exhaust is 0.005 smaller than the intake i have ben trying to post a video showing the exhaust valve movement but it won't go thru. imon the phone waiting for a mac tech to do a screen share to fix it. hopefully i can send that video. anthony.
yea it equals what looks like A LOT of slop when its up off the seat. I had a few NOS short blocks around here in HS size and they all were the same when I have given them "the wiggle test"....I always felt uneasy with the slop in the past thinking I really needed to upsize or replace the guide on some of the engines I was redoing when I first got into them. I Cracked an NOS HS40 open one day that I picked up and and I was like "wait, what???" They actually don't seem to wear to terribly bad in the small frames and the seats even hold up fairly well. the medium frames (H50 size) is another story though, I usually find those to be pretty worn out on the older ones I have messed with, seats and guides!
 
#8
i just got off the phone with mac ten support. wast of time. i can't send videos out and they can't tel me wye. i wish i could show you just how sloppy this to valve is. i spent o fortune on four reams and pilots and seat cutters and the dam exhaust valves are supposed to be loose. i can't post a video. maybe someone will read this and put up a video of a good exhaust valve wiggle test. then maybe i will feel a little better. anthony.
 

markus

Well-Known Member
#9
Take your valve seat cutter pilot and stick in the holes, you may be surprised what you see. I have a an HS40 block sitting on the bench right now from an engine with only a few minutes run time on it, They ran it once, then it sat....for 35 years......in a damp environment. There isn't even carbon in the exhaust port/valve, but something like that has to come apart and be cleaned and gone through or your asking for trouble as it was exposed to moisture and who knows what over the years (a new gasket set and seals is cheap insurance) Anyway that one actually locks the tapered pilot in place higher up on exhaust side than the intake side...between 1/2-3/4 up the shaft. Its a minuscule amount and even running my Briggs and Stratton 1/4" guide finish reamer in (upisde down/smooth end), there is no noticeable difference in the slop between the guides, its all in the valve stem and .004/.005" difference., You gotta watch that on the h25-35's as the seats are the same size on those, Gotta make sure your putting the right valves in those if the valves you got aren't marked....keep a magnet handy to double check;)
 
#10
i just went out side and measured my pilot. i bought 1/4 plus 0.0001 to make sure it would be tight. mine also stops short of the bottom of the guide. just barely. exhaust valve stem mikes at 0.244 that gives me 0.007 i just posted a video on youtube. please try to watch it and give me your opinion. type in tecumseh exhaust valve excessive play youtube. anthony
 

delray

Well-Known Member
#11
that does not look good. if i'm correct a vintage valve is around .248 at the stem and the newer stuff went a .244
 
#14
yep,that did not look good at all. if that motor is new and all? I wonder if they installed the wrong valve?
the valve is dead on speck. 0.244 the guide is 0.051 markus thinks this mite be normal for this engine. iv read there should be 0.004 to 0.005 clearance. iv got 0.007 when i wobble that valve it makes me cringe. that motor is not going together until several top guys on hear watch that video. i have all the tools to take the slop out. the hs50 valve has the exact same dimensions the only difference being the valve stem diameter. its a couple of thousandths bigger. i guess thats wye they hav diffrent part numbers. i could put a 1/32 oversized hs50 valve in and it will be nice and snug. maybe to snug. i don't like all that slop but maybe thats correct. gonna loose sleep over this. by the way markus has not ben wrong once. so far i got two out of five opinions from guys i trust. probably get to the bottom of this in a day or two. if not im going with 0.005 thanks to all who chimed in today on both the valve guide slop. and the animal springs and keepers. anthony
 
#15
I used cut down briggs ex valves as they had larger diameter. It was either .247 or .248. I think I posted pics in a build thread on her but it was a few years ago.
 

delray

Well-Known Member
#17
the valve is dead on speck. 0.244 the guide is 0.051 markus thinks this mite be normal for this engine. iv read there should be 0.004 to 0.005 clearance. iv got 0.007 when i wobble that valve it makes me cringe. that motor is not going together until several top guys on hear watch that video. i have all the tools to take the slop out. the hs50 valve has the exact same dimensions the only difference being the valve stem diameter. its a couple of thousandths bigger. i guess thats wye they hav diffrent part numbers. i could put a 1/32 oversized hs50 valve in and it will be nice and snug. maybe to snug. i don't like all that slop but maybe thats correct. gonna loose sleep over this. by the way markus has not ben wrong once. so far i got two out of five opinions from guys i trust. probably get to the bottom of this in a day or two. if not im going with 0.005 thanks to all who chimed in today on both the valve guide slop. and the animal springs and keepers. anthony
.007 is way to much clearance. try to get it closer to .002-.003.
personally I would be putting .248 valve stem in it.
 
#18
the valve is dead on speck. 0.244 the guide is 0.051 markus thinks this mite be normal for this engine. iv read there should be 0.004 to 0.005 clearance. iv got 0.007 when i wobble that valve it makes me cringe. that motor is not going together until several top guys on hear watch that video. i have all the tools to take the slop out. the hs50 valve has the exact same dimensions the only difference being the valve stem diameter. its a couple of thousandths bigger. i guess thats wye they hav diffrent part numbers. i could put a 1/32 oversized hs50 valve in and it will be nice and snug. maybe to snug. i don't like all that slop but maybe thats correct. gonna loose sleep over this. by the way markus has not ben wrong once. so far i got two out of five opinions from guys i trust. probably get to the bottom of this in a day or two. if not im going with 0.005 thanks to all who chimed in today on both the valve guide slop. and the animal springs and keepers. anthony
made a mistake in my post. the valve stem is 0.244 the guide is 0.251 thats were i got the 0.007 clearance. i should have proof read that. ben frustrated all day with this. anthony
 
#19
the valve is dead on speck. 0.244 the guide is 0.051 markus thinks this mite be normal for this engine. iv read there should be 0.004 to 0.005 clearance. iv got 0.007 when i wobble that valve it makes me cringe. that motor is not going together until several top guys on hear watch that video. i have all the tools to take the slop out. the hs50 valve has the exact same dimensions the only difference being the valve stem diameter. its a couple of thousandths bigger. i guess thats wye they hav diffrent part numbers. i could put a 1/32 oversized hs50 valve in and it will be nice and snug. maybe to snug. i don't like all that slop but maybe thats correct. gonna loose sleep over this. by the way markus has not ben wrong once. so far i got two out of five opinions from guys i trust. probably get to the bottom of this in a day or two. if not im going with 0.005 thanks to all who chimed in today on both the valve guide slop. and the animal springs and keepers. anthony
I just went through this exact same issue with an early H30 I just completed a rebuild on. When I re-assembled it, I found my guides were good, but the I had the same issue. All the exhaust valves I ordered were .2435 which was real sloppy. I finally found a .245 stem valve which helped but seemed too loose yet. after speaking with Markus, I went with it and have had no issue with the motor. Starts on fist pull and runs good. No issues. I'd run it. Consider how hot that valve gets while running, it needs room to grow...
 
#20
I just went through this exact same issue with an early H30 I just completed a rebuild on. When I re-assembled it, I found my guides were good, but the I had the same issue. All the exhaust valves I ordered were .2435 which was real sloppy. I finally found a .245 stem valve which helped but seemed too loose yet. after speaking with Markus, I went with it and have had no issue with the motor. Starts on fist pull and runs good. No issues. I'd run it. Consider how hot that valve gets while running, it needs room to grow...
i don't know if you watched to video on youtube. but if so i think you would agree that valve is crazy sloppy. iv ordered the 1/32 oversized valve .two more reamers and another seat cutter guide. when im done il have 0.003 to 0.004 il run and tune before i paint it. if the valve hangs up i will tear it down and give it a bit more clearance.
 
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