Dem valves keep on bouncin'

[erictharg]

There's a song there somewhere...
Dutifully turned up at Northampton Motorsport for another rolling road session. Having in my mind that I've not really pushed the car revs wise for the first couple of races of the season. We get it all strapped down and do the inital baseline runs. And valve bounce again at 6300 'ish. This is getting tiresome. Abandon the session, zip over to GPR to collect my HANS seat kit whilst in the N/Hampton area and call MED. We agree I'll take the head over to them in the afternoon.
Get home and pull the head (got it down to 30 mins now) and head over to Leicester with it. Steve at MED is as puzzled as I am. He strips the head, and measures all the usual spring related dimensions. Nothing untoward. The only option is to assume it's duff springs (rare) and add another 0.5mm shim for good measure. So now he's built the head up (instead of me - potentially dumb customer). Head is re-fitted and I'll do a run Saturday to check it out. But given that these springs usually go to over 8000 on MED engines I'm thinking there's something else amiss. But I can't work out what it could be. Valve bounce is basically a function of valve train mass (nothing radical there), valve lift (also mild - MED XT cam) and springs. Spring height is right so....
The hastily replaced front bearing seems fine. Need to replace the rear bearings before Brands, along with fitting my "Growlerised" halfshafts. Also fit the uprated shoes from Pete May or I'll be suffering a very long brake pedal towards the end of the Spa race.
I have to keep reminding myself I enjoy this!
On the plus side the big new gazebo (3 x 4.5mt) has arrived. Big enough to accomodate both me and the car.
Adam - we're now travelling on Thursday. Probably there late Thursday night but will hold a place for you if I can.

[adamwilkinson]

Thats very strange, 6300 isnt really a great deal of revs - ok it is for an engine designed decades ago but even so it sounds like the springs arent strong enough to seat the valves properly.

Hopefully we'll be arriving at Spa around lunchtime on the Friday.

[erictharg]

Sorted. Was out on the road yesterday and happily pulling to over 7000. Must have been the springs. New rear shoes and bearings fitted, along with modified driveshafts. Got my moulded seat kit but it really needs to be over 20 degC to be sure of it curing. Might have to rig up a heater for the garage. In June?
New gazebo less of a success. Put it up last night as a test, and the overnight rain has already defeated it. £165 for a 3 x 4.5mt is on the low side but I was hoping for a little more from Quictent. Looks as if I'll have to bite the bullet and go for one of the £300 heaver duty products from one of the more reputable suppliers. As ever, you get what you pay for....