XPAG spring bouncing!

[Chris Blood esq.]

Has anyone experienced this phenomena? and how do you know if you have it? At about 3.5k I am sure I can detect bounce. I only have 1 large spring on each tappet although I have seen other engines with smaller springs including. Whats the concensus? Chris TC 2686 Notts England

[Skip Kelsey]

Chris: If you are experiencing valve bounce at 3500 RPM, then the single spring is too soft. Not a good thing. If you use a stock spring, be sure that they are the 120 lb. rated springs. The springs that Moss and Abingdon spares sell are too high a rating, and this will exacerbate the wear of the tappets, and cam. Skip Kelsey......................... At 12:20 PM 4/16/01, Chris Blood esq. wrote:

>Has anyone experienced this phenomena? and how do you know if you have it? > >At about 3.5k I am sure I can detect bounce. I only have 1 large spring on >each tappet although I have seen other engines with smaller springs including. > >Whats the concensus? > >Chris TC 2686 Notts England > >Your use of Yahoo! Groups is subject to the >http://docs.yahoo.com/info/terms/>Yahoo! Terms of Service.

[Chip Old]

On Mon, 16 Apr 2001, Chris Blood esq. wrote to mg-tabc@yahoogroups.com:

> Has anyone experienced this phenomena? and how do you know if you have > it? > > At about 3.5k I am sure I can detect bounce. I only have 1 large > spring on each tappet although I have seen other engines with smaller > springs including.

The standard XPAG valve spring setup uses two springs per valve. Is the single spring you're using the large spring from a standard two-spring set, or is it a spring actually designed to work without the inner spring?? If it's the large spring from a standard two-spring set, then bounce at 3500 RPM shouldn't come as a surprise. The two-spring setup counts on the combined spring rate of the two springs to prevent bounce up to 5000+ RPM. If you remove the smaller inner spring, you reduce the spring rate considerably so the engine speed at which bounce occurs is correspondingly lower. Also, in a standard two-spring set the difference in spring rate between the inner and outer spring helps to dampen out harmonics that can also contribute to bounce. It's entirely possible to design a single spring to provide the same spring rate and dampening characteristics as the standard two-spring set. If your single spring setup is from a specialist supplier and is actually intended to be used on the XPAG without an inner spring, then it's reasonable to expect that it was designed accordingly. You'll need to discuss the bouncing problem with the supplier. On the other hand if the single spring is just the outer spring from a standard two-spring set, you need to install the inner springs. -- Chip Old 1948 M.G. TC TC6710 XPAG7430 NEMGTR #2271 Cub Hill, MD, USA 1962 Triumph TR4 CT3154LO CT3479E fold@bcpl.net