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MG TD TF 1500 - Viton valve stem seals
|Found some viton valve seals. These are from " alexsparts.com " $10.49 for 16. Viton is said to have better wear resistance than most other seal materials , good flexibility so it can handle a bit of runnout as well.|
No personal interest in the company.
Interesting, Those seals seem to be a good find.
A couple of questions if you don't mind. It appears that the seating surface on your head for the valve springs has been re- machined deeper than stock. My heads don't have that ridge next to the guide. Is your head a late version with round water holes?
I don't see you using any seating washers #11 in your image? Or any shrouds(cut off for seal)#13?
It also appears your springs or retainers #12 are not stock MG TD? My spring edges are fully covered by the retainer.
I was studying your images to try and discover what might have caused your valve stem damage and I came up with these difference between your head and the ones I have worked on recently.
|So, these are a somewhat modern design, intended to fit over the valve guides? You can use those on the intake side and they should work nicely to help prevent oil burning later on. However, putting them on the exhaust side will cause the valves to seize up with the guides. I could be mistaken, but I don't think so.|
That was the stock machining on the head. It is a banana hole head.The springs are for the roller cam kit I have installed. No seating washers , they would not fit the larger springs ,no shrouds. After checking with Len Fanelli the designer/fabricator of the kit , he said it was fine to leave them off.
The car has run like this with Fel pro seals on intake and exhaust on iron and bronze valve guides with no issues for thousands of miles. ( three thou clearance on the bronze guides )
|Richard in the image you posted and in my Moss catalog also they both show only 4 rocker arms. If I remember there are 8. Where are the other 4? Forrest TDC/22679|
Forrest, Yes, you are right there are 8 ea. Rocker Arms. However, the Moss catalog only shows the minimum necessary information to order the required parts. If you look down at the listed parts, you will notice that there are only 4 different rocker part numbers--- 2 of each configuration are required to make a full set. For example, counting from the front, rockers at 2 and 6 position are the same part number and so on.
| This article mentions using 1275cc MG midget seal method in 3rd from last paragraph. The 1275 Midget only uses the seal on intake, and this article says to follow suit on the XPAG.|
This one specifically addresses the sort of guide seal you have found. It says what I said about those seals working too well on the exhaust side.
Oil spray going down the intake is what causes smoke out the exhaust pipe, perhaps also pinging and a loss in performance. It gets sucked down between the stem and guide if worn, and/or not sealed.
Oil spray getting on the exhaust valve stem does nothing to performance, except to lubricate it a bit. Oil will not get sucked down like the intake. If exhaust guide are worn, the opposite occurs, blowing away any oil that might try and drip down to the stem/guide. Oil that gets on the valve stem in the up position gives it some lubrication for the down and up stroke.
|Hello. IMO the parts# 11 12 and 13 are very|
importent centering the springs so they don't tuch the valve stem.
Thoralf. NORWAY TD4490 engine xpag td 2916.
|Thoralf Sorensen (TD4490)|
|A joke. Forrest TDC/22679|
|Interesting article .However ,since John Twist and Peter Edney are using positive valve seals on there rebuilds for everyday driving and racing on the XPAG ,I will choose to try them again. |
My purpose in posting was to give a possible better option to those who choose to use positive seals. There is no doubt though that the original o-ring design can work well when set up properly.
All the best
|I have used them rebuilding TR 6 and BMW heads. They work great. I would only do it if I was redoing a head. And then consider the cost. They only make sense with bronze guides and they need to be machined so they work.|
You can use them on both intake and exhaust valves.
When I rebuilt my spare TD head I went the traditional route. For $1.95 and as much as I drive it the cost benefit analysis was hard to beat. In my situation controlling costs for non essential, nice to do items was a concern. Others may have a different prospective.
Just to add balance to this issue, I found a couple of industry web sites that advocate use of the positive seal on exhausts as well as the intake. While some have certainly had problems with our engine type, one thing I notice is that there are numerous differences in valve guide, machine clearances, configuration of oil shrouds and types of seals used.
When things work well, people normally don't have much to say on these Forums, so we don't always get a complete assessment about what's in service and shown to be successful. What I'm saying is that for me, there doesn't seem to be enough practical experience yet with a common configuration for me to be sure about which way is absolutely correct, and preferable.
Any way here are the sites:
|If people have found a way for this to work in the XPAG without major changes, I would be interested in hearing about it.|
This thread was discussed between 13/02/2016 and 24/02/2016
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