markus . did you watch the youtube video? 0.007 is what its at now with the crazy slop. if you look at the video i think you might agree. i have a choice between .003 .004 .005 i think i will go with .004 if the dam valve sticks i will know better on the next one. new old stock flywheel came today.
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Yea its normal slop, I will say however that if you are really getting and honest .251 out of the guide, it is measuring larger than normal by .001-.002. An no I am not just throwing mythical numbers out there, I actually pulled some blocks out and did some measuring:
Far left engine is an NOS HS50 from 1994 (with the small taper BB crank though, built to replace 1972-1980 engines0. The three HS40s next to it are extremely low run time blocks, I think 2 of them may have been training engines from Belsaw. the far right one is the one I mentioned earlier that had been stored in a wet environment, I did some hone work as it had some spotting on the cylinder wall from it. I also did check a whipped HS50 block (needs bored oversize) not shown
with that said, all those exhaust valves, and there are 3 different versions form mid 70's-mid 90's all came in at .244 even the batch of NOS ones at the bottom left measured out the same. Tecumseh DID NOT MAKE a .248 sized exhaust valve with that style keeper. The real early pinned valves I think may have been thicker, but that's not gonna help. there are some .246 but I'll get to those at the end.
The guides measure in on the new/next to new blocks at .249-.2495 range, there is a used but clean HS40 (top right in photo) that comes in at an honest .250 and the whipped HS50 block (not seen) came in at .250.5/.251. I used the standard Neway 1/4 pilot and a briggs .250 finish reamer as guides as well as 2 different dial calipers. the briggs reamer comes in at .250 exact on the cutter end so it would not go into the any of the 4 blocks in the front measuring under the .250, that HS40 top right It would go but have to twist to get it through and the whipped HS50 would go with light twist (no force though and could feel very slight movement. when it was all the way through.
with all that said, common spec is .004/.05 for the Tecumseh EX side, this is also the same on the small frame H engines as they shared the same exhaust valve.
Regarding the .246 size, I found a used one here; Its fresh out of a 1967 H35 I started to rebuild and its the original. It is a 29313 (the same part number used through 1996/97. The only time I can remember finding that sized valve was in the late 60's engines. I think they shrunk them down to the .244 size into the 70's, that kinda goes along with them going to aluminum bore only for the most part on the small frames and the introduction of the HS50 but I don't know if size reduction is connected to that or not. That part number did get revised a few times (29313b/ 29313c) Best chance to maybe find one new would be to look for the old style scripted box and probably the 29313 number only on it, I put an early box (its an intake valve actually in that one) on the table just to the right of the loose valves so you can get an idea of the style, the boxes for the loose valves on the left are the 1970's into 80's era parts boxes-those are 29313c. And I am taking a stab that you will get a .246 valve as I do not know for sure so don't blame me if its not that size
I think one of the revisions or alphabet letters just indicates it comes with the keepers for both H/HS40 and HS50 as they are different (so those are post 1972 made)
Oh yea, that crusty valve on the burnt block of wood on the table was my "Heat test" valve
In my late teens me and my buddies bought a bunch of yard/fun karts, we would do midnight runs during full moons on paved golf course trails and dirt roads out in the boonies. I just followed the glowing red dot that was the exhaust coming out of the pipe of my buddies 5hp B&S when we would hit the straights and he would start to walk away with his big tire kart......they do get pretty warm, made for a good tail light!