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Triumph TR6 - valve stem seals
|I have seen listed valve stem seals on ebay recently, they claim to be usable on the Tr6 engine with steel guides and dual springs. Does anyone have an opinion or history with this product? Thanks.|
|Does the original engine have the valve stem seals? And why double springs? I am new to this so be patient.|
|The original steel valve stems do not have stem seals, however, this product claims to fit in any case. The springs on the TR6 have an inner and outer spring on both intake and exhaust.|
|Do you have the ebay URL? I am somewhat curious, it would be nice information to tuck away.|
I am not aware of a specific valve stem seal that will fit a dual spring set up on a TR6 unless the guides have been fly cut. The ID of the inner spring is relatively small and there is not that much clearance between it and the OD of the guides. With a fly cut of the guides and a smaller OD valve stem seal it does work.
There is a Perfect Circle part number that will work with the single spring set up such as that fitted on the TR250 and the early TR6 with the narrow spaced inlet port configuration. Obviously if the springs have been changed to the dual spring set up, then those won't work on an narrow port head either.
|I know that Richard Good makes a set of stem seals for the TR6 - I think they only fit if the guide has been set up to take them - I bought his kit with guides and seals and the machine shop didn't mention having a problem with them. Whether they are needed/helpful is not really clear to me, but everything I see from Goodparts impresses me so I am prepared to take his word that they are a Good thing (Good, geddit?)|
|The item number on ebay is 2001107723803. They sell for $35. and are made or Vitol. They are also on the Austn site.|
|Found the listing and the casual "eyeball on screen look" says that fitting on a dual spring set up is iffy. But then again that is eyeball on screen, not caliper on seal OD and inner spring ID. As far as the materials go, it appears to be a bonded elastomer to bronze sleeve. Viton is a pretty decent high temp elastomer, I have used it many a time as a sealing mechanism for instrumentation ports on some of the funny little test vessels I used to design and make from my days as a lab rat. Now I'm chained to a desk and never get to have any fun.....|
Regarding the guides and seals from Richard Good, the guides have clearly been machined away to fit the seals. Since they are loose, they can be turned down in a lathe, you only get put in the position of having to fly cut the guides if they are already installed. Richard in turn lists two valve stem seals. One is for machined guides and will work with either single or dual springs, while the other seal is specifically stated as being for use with single spring set ups only on stock size guides. Here is the URL:
Bottom line is that you pay your money and take your chances. Hopefully they would fit a dual spring set up on standard size (.501") guides as indicated. When you go to do the install, just be real careful and don't drop a valve down in to the cylinder. If you do, then it's off with the head to retreive it.
I have tried the ebay seals and they will not fit factory dual valve springs. The inner spring will not clear the OD of the seal. The seals are of a very good quality...shame they didn't fit. The seller is a good guy who knows cars and is giving a full refund and changing his ebay info.
|Mike. Thanks for the information on the ebay seals and valve spring clearance. Do you know if the early single springs will fit in place of the later dual springs and would that give the required clearance ? Thanks.|
D.Smolko 75 TR6
|D., I assume dual springs give quicker, tighter closure of the valve to prevent valve float at high RPM's and to help prevent "burnt" valves...others on this board know this mechanical stuff a whole lot better than me. And it appears that most "upgrades" go to dual springs versus the single springs. The single spring would give adequate clearance for the seals, but I don't know how you get the right spring constant. Guys?|
|As a general rule, the valve springs are matched to the camshaft requirements. The camshaft producer will typically specify a seat pressure and springs are selected accordingly taking into account things such as where a cam would produce peak power, what engine speeds are expected, the type of cam follower used and the relative hardness of the camshaft and cam follower.|
First, I would like to make clear that I have never done any actual spring constant determinations on the stock springs for the single or dual set ups. This means that what I have to offer is a subjective based on a general experience take on the situation. Second, when this has needed to be done, I have contacted the folks at Crane Cams, told them the basic spring dimensions needed, what the nominal installed spring height happens to be and the lift at the valve. From there we have worked within their catalog to determine spring sets to be used. We then take all of the bits to a guy we know that specializes in setting race engines to get the springs installed and properly shimmed to get the appropriate seat pressure. So here goes....
There are three production camshaft grinds used from the factory in the TR6. There is the early carb cam, the early PI cam and the late carb/late PI cam. Of the three the most aggressive profile is on the early PI cam and the least aggressive is on the early carb cam. Only the early carb cam used a single spring set up from the factory. Both the early PI and the late carb/late PI cam used the same dual spring set up.
From the engine modeling we have done on the TR6 motors with a variety of camshafts, the difference in peak power RPM for the early carb and the early PI cam is approximately 1000 RPM with the early carb cam making its max power at the lower RPM. The late carb/late PI cam is in between the two, biased toward the early PI cam side of things.
What this means is that as long as you stayed within the range of engine speed associated with the early carb cam, you should be safe using the early single spring set up. You would also likely be safe using the single spring set up if you were to take it above that to the other cam ranges, but would not have as much margin of safety and if done on a routine basis, would not be a good idea. The saving grace is that due to its long stroke, these are not high revving engines.
As far as fitting valve stem seals on single spring set ups, I have done it. I am curious though as to your motivation in adding valve stem seals. If it is to resolve an oil consumption issue due to guide wear, I don't see much benefit. As the valve is pushed sideways in the guide, the seal will be distorted and the sealing surface is compromised. While I like to run valve stem seals, others do not, it really boils down to preference. I have typically done them as either replacements for existing seals or when building up a head using new seats, valves and guides that are cut to accept seals compatible with a dual spring set up.
|Steve's covered most of the points. A few additions though:|
Dual springs will generally raise the redline by a few hundred RPM since each spring (inner vs. outer) has a different harmonic frequency.
An easy way to raise redline is by lightening valve train components - alloy valve spring caps, tubular pushrods, and lightened lifters. This has the added benefit of decreased wear on the cam and lifters.
|Like Alistair, I went to Goodparts and bought the uprated double springs and bronze valve guides machined to take the teflon valve stem seals. I had a good machine shop do the work and will be installing the new engine in early Spring. No particular reason for the extra expense except trying for a mild upgrade. Also added new hardened valves and had hardened exhaust valve seats installed by the shop. Goodparts GP2 cam and milling the head completes that part of the project. The engine is together but we are waiting for the big chill to ease before pulling out the old one and detailing the engine bay and dropping in the new engine.|
1976 - TR6
|DPO added valve stem seals and removed inner spring in attempt to (cheaply) reduce spark plug fouling likely caused by excessive oil migration down worn valve stem guides. I have been told that the original design included a slight oil seepage to lubricate the guides. Makes sense to me as the valve stem seals minimized this lubrication and eventually may have contributed to the bent rocker arm shaft. Total rebuild fixed all this. Just another opinion. Good luck.|
This thread was discussed between 06/02/2008 and 27/02/2008
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