Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

Question 1:

    The block manifold intake mount has a machined section cut out.  What is the purpose of the cutout section?  I've seen this on three heads and possibly it's on more but I've just started noticing cutout sections.  It would seem it's for airflow in some way but I'm not sure.  What is the purpose of the cutout area?

Question 2:

    I was taking out the valves and the piece shown was on top of the valve spring on the intake valve.  There's usually a metal cover there - the exhaust valve had the expected cover.  This is the first time I've seen such a top cover.  

   The engine is a 155032 Tecumseh and the drawings call out standard upper valve spring caps and not this part.   Is this something that was inserted on an earlier valve job?  It's plastic so seems odd that it would be a guide.  What is it's purpose?

Thanks, trouts2

 

Regarding question no. 1.

It looks like the manifold is manufactured using a cast method.  Is there a chance that the sprue left from the casting process was ground off?  I've seen a lot of manifolds and from the picture you've posted, can't see how that machine work would enhance flow characteristics. 

Can't help you at all on question no. 2. 

I have seen on some engines a "rotator" for  valves on generators and other units that run at one governed speed to reduce carbon build up..    I have seen neoprene tappet covers on odd equipment to limit valve lash noise, but never on  a Tec. engine..

Friiy

Sorry - I screwed up.  The engine I referenced was the wrong engine.  The correction is the engine is an 8hp, 155316M:

The first picture is the is of a block looking into where the manifold attaches.  So it is a cast block looking into where the mainfold attaches to the block. 

I looked at the intake area where the gouge is and noticed that the inset part has tool marks where most of the inset area is but also to the right of the tool marks is an inset area which is part of the casting.  It seems like the original cast had an inset area build into the block but did not go far enough.  The designers probably realized that and called for the block to be machined to get the full proper inset.   I've got a second engine, 10hp  159468X which has the same thing - part of inset area on the right is a case inset and the part on the left is machined out.   The 10hp is from the early 2000's and the 8hp from the late 90's.  I think the blocks are the same and probably made from the same master with the same design flaw.  Well, I'm guessing it was a flaw.

Now that I realized I had the number of the wrong engine I got the right drawing for the 8hp (155316M).  It calls out two parts for the intake valve cap.

149A    27882    Cap, Upper valve spring,    and              149A 35862  Seal Assy., Intake valve.   What came out of the machine is in the picture. 

So it's a seal and a new one on me.  I'm rebuilding the engine.  Do you think this part needs to be replaced?  Obviously, I don't have any spec on wear limits. 

trouts2