Rolling Road Unproductive!

[erictharg]

Flew back in from two weeks in the US this morning. Got home in time and got the car out to Northampton Motorsport for 15:00 as planned. Even managed to find some super unleaded (at the third attempt). Strapped the car down but on the first run up we were getting valve bounce at 6600. Seems the current springs can't cope with the high lift rockers. Disappointing as MED supplied both. So didn't do any tweaking - bit of a waste of time. For the race I'll put the old 1.3's back on. Grrrr. Good job it's not a big job to swap them.

[adamwilkinson]

Really?
Thats strange, I take it they are double springs. Not sure who we got our springs from, possibly minispares, all I know is they are happy to go to 8k (not that we go there nowadays).

Good luck for Sunday, I'll be out on the 300 circuit at Snett giving the car a shake down, just need to get 40ltrs of v-power...

[erictharg]

They are doubles, as supplied on the MED head. I know they're marginal as I had to replace them mid year after about 5 hours racing for the same reason. I guess that with the extra lift and acceleration needed with the high ratio rockers it's just beyond their limit. The old 1.3's are back on for now. I managed to find 20 ltrs of premium today so that should cover me for tomorrow but I expect the fuelling station at Silverstone will have some more if needed. Good luck at the testing.

[Westfield 129]

When fitting high lift rockers, it is important to check the geometry if the cylinder head has been milled. Often the edges of the retainers can touch and bind the rockers and springs, causing a problem not unlike valve float.

The fix is an easy one. Simply install shims beneath the rocker shaft towers. MED probably has what you need on the shelf. I had to install shims on my last engine as the cylinder head had been cut for a 21cc chamber.

I use Iskendarian springs, and have never had a problem with valve float, all the way to 7200 RPM. That said, the springs that came with my last Longman head were equal to Isky quality, and I have had no problems with that setup as well.

[adamwilkinson]

Fairly sucessful trackday, i say fairly due to us finding out a few issues now rather than at Spa.
Car was very quick, so happy on that front although the day was almost a non-starter due to failing the noise test, 108db!! Its never been that high, realised that we'd (we me) had over packed the silencer when repacking it so it was having no muffling affect on the car. Whats stranger is that with an empty can the car ran at 105db, well we fished out as much of the wadding as possible and then repacked it leaving out a carrier bags work of wadding, 103db final outcome - trackday was back on.
Problem 1 out the way, problem 2 was about to appear...
Oil pressure, after only a few laps the light would flick on going into hairpins - back to the pits, turned out a top up of oil was all that was needed. or so we thought... back to that later
Problem 3 then decided to come knocking in the form of a leaky carb, not too much of an issue as the drips fell between the exhaust plus our exhaust is lagged so its hot to touch but wont burn you.
So anyay, back out on track everything going very well, car is handling well (the Snetterton 300 circuit is a very different animal to the original, a lot more involving). Then after about 15mins the oil light starts to flicker again (oil temp around 110degrees which isnt an issue for the oil we use), this time coming on more and more during the braking zones (i must add that our light comes on around 10psi and only under braking, touch the throttle and normal pressure is resumed). I venture back to the pits and sitting in the garage on idle the pressure gauge is reading ~8psi. After some head scratching we come to the conclusion that we think we ran a bearing at Spa 2010 (not used since then).
So before Spa its engine out to inspect and replace all the bearings, thankfully thats an easy and fair cheap option, hey ho...

How was your race Charles?

[erictharg]

Jan - already running 1.3mm pedestal spacers to stop the top of the pushrod fouling the somewhat chunky MED rockers. Engine happily running to 7000 today on the 1.3's....call needed to MED.

[jonclancy]

adamwilkinson wrote:

> After some head scratching we come to the conclusion that we think we ran
> a bearing at Spa 2010 (not used since then).
> So before Spa its engine out to inspect and replace all the bearings,
> thankfully thats an easy and fair cheap option, hey ho...

Just out of interest, how long would that operation take you, Adam?

[adamwilkinson]

From removing to reinstalling the engine - 1 day IF everything goes to plan, more likely to be a couple of days though to be honest.

We shouldnt need to touch the head although it goes make things easier when working on the bottom end. As said the engine pulls well so we have no real need to remove the pistons etc, just lift out the crank and replace all shells. I dont think there will be any damage to the crank, steel crank that even the machine shop guys said was a git to machine!

You can leave the engine in place to replace all the shells as you dont need to drop the crank to replace the shells - I've done this before and although it makes things trickier its ideal if you dont have a crane or another way to remove the engine, plus you cant thoroughly inspect parts.

[erictharg]

I hope you are right about the crank, but suspect that if you've spun a bearing it is likely to have at least marked up the journal, even if not scored.
Spoke with MED today on the rockers and we came to the conclusion that as I didn't check the installed spring height when re-assembling the head, I need some more pre-load on the springs to get that correct height. Makes sense. The perception that the 1.3's don't get valve bounce is likely just that - I didn't rev much, if any above 6500 yesterday being mindful that there maybe a problem.

[Westfield 129]

Removing and replacing the engine is pretty easy. You can leave the transmission in place. I've got it down to about an hour in/out as there is not much to remove other than the alternator, carb/exhaust and hoses. Plenty of room to work. Best if you use two people. If you have a running car to start (so you are not fabricating parts during the engine install), you can easily put the engine back in within 2 hours if you are familiar.

I think that the last time I did mine alone, with a few breaks for phone calls, it took three hours from engine on the floor to drive off. It's a pretty simple car.

Installed valve spring height and shimming makes sense as far as your problem valve float problem goes. I always have a specialist set up my cylinder heads and inspect the valve springs for height. Oh, and most roller rockers are "clunky" as they are alloy, and require much more material to maintain strength. My Swiftune rockers are also pretty stout.