The Jack's Small Engines Forum - Join Our Online Community
Reply to post

Exhaust valve seal

Author
Mrcalm
Master of None
  • Total Posts : 14
  • Scores: 0
  • Reward points: 0
  • Joined: 2016/06/26 02:10:11
  • Location: Flint, Michigan
  • Status: offline
2018/09/27 20:47:03 (permalink)
0

Exhaust valve seal

Hello; I have been rebuilding a B&S 5 hp engine and I was under the impression the exhaust valve had a valve seal. The intake has one but there isn't anywhere to install the exhaust valve seal. Does the exhaust valve have a seal? This engine wasn't even machined for one. Please enlighten me so I can finish assembling it. This engine I have had apart for 4 years. I am thinking I am remembering the valve seal was just floating up and down on the valve stem but I can't remember which valve. Waiting patiently.

3 Replies Related Threads

    Roy
    Moderator
    • Total Posts : 505
    • Scores: 13
    • Reward points: 1
    • Joined: 2016/07/27 22:51:23
    • Location: British Columbia
    • Status: offline
    Re: Exhaust valve seal 2018/09/27 21:39:53 (permalink)
    0
    Normally an exhaust valve seal isn't required. The intake seal prevents oil from being drawn past the guide under vacuum but there is pressure in the combustion area when the exhaust is open.
    Mrcalm
    Master of None
    • Total Posts : 14
    • Scores: 0
    • Reward points: 0
    • Joined: 2016/06/26 02:10:11
    • Location: Flint, Michigan
    • Status: offline
    Re: Exhaust valve seal 2018/09/28 17:06:38 (permalink)
    0
    Roy
    Normally an exhaust valve seal isn't required. The intake seal prevents oil from being drawn past the guide under vacuum but there is pressure in the combustion area when the exhaust is open.


    Thank you very much Roy now I can continue to put it together. That is the first time I remember having this dalema in all the years I have been working on them, in my spare time. Thanks again.
    AVB
    Super Member
    • Total Posts : 642
    • Scores: 27
    • Reward points: 0
    • Joined: 2017/06/21 16:35:48
    • Location: Elora, TN
    • Status: offline
    Re: Exhaust valve seal 2018/09/28 17:24:06 (permalink)
    0
    Even though the exhaust is under pressure on exhaust a badly worn valve guide on L-head engines will still allow cylinder blowby and crankcase pressure to enter the exhaust system causing smoking. But with good a valve guide the oil surface tension is enough to prevent this.
    Jump to:
    Copyright © 1994 - 2016 Jacks Small Engine & Generator Service, LLC