Lotus Europa Forums > The Paddock

807/TS DD, Auto-X, Hill-Climb build.

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Richard48Y:
It occurs to me that since the cam followers are inclined in relation to the cam thinning the head moves them a fraction from the original factory geometry.
Probably not enough to be a major issue but does it affect their "Spin"?

Bumpy pistons, yep.
Wossner's.

GavinT:
I guess what happens is the lifters are effective lowered into the cam well.
Hmmm . . can't see it affecting the spin significantly because the lowering still retains the same axial relationship between lifter and cam lobe – happy to be educated.

One thing that comes to mind is whether the lifters run out of 'upwards' travel when the head is shaved. Probably not difficult to relieve the lower entrance to the lifter bores.
Perhaps other thing might be a need to either shorten the pushrods or look at shorter rocker adjustment screws.
I've never seen comment on either of the above so presumably it's OK, but still worth checking.

Richard48Y:
For myself I am happy to find my head is uncut.  :)
I do intend to grab a set of the Ti. valve spring keepers that are available unless the cost is just crazy.
Looked into Ti. valves from Ferrea and found they are not interested in small volume sales.
My current intakes are 42mm but the faces are worn to concave.
I may have found a less expensive Ti. valve maker but am still unsure of their use in a street engine.
Discussions of coatings and special valve seats come up regards them, more $$$.

I am still looking at getting my cam Cryo treated, my lifter faces and rocker tips plated with ?
Also still trying to find a set of beehive springs with the lowest working spring pressure. For that I need to know my cam specs and valve weights.
I spoke to one engine builder who tried beehive springs in his TS race engine.
He said they were too stiff so wiped the cam.
That was several years ago and since I know beehive springs are now used in everything from Chevy LS to sport-bikes suitable springs should be available.
My hope is that significant reduction in valve train mass will increase component life.
I am surprised the racers have not already found answers to these questions.

Mecky:

--- Quote from: GavinT on Tuesday,December 06, 2022, 07:00:56 PM ---
--- Quote from: Mecky on Tuesday,December 06, 2022, 03:22:11 AM ---
Do you know, why the minimum repair height is set to 93 mm? My racing head is already well below that and supplies good power. Of course, the combustion chamber is machined in order to fit the high compression pistons. But if the crimp endge in the cylinder head chamber is adjusted to the piston height, it should be no problem to go below 93 mm or is there a danger of cutting into oil or water channels, when doing more plane milling? I have now four cylinder heads and want to modify a second one to full race spec. Maybe even further than the first one, which was a bit more towards safety with compression ratio of 11,5:1.

--- End quote ---

Hi Stefan,

The minimum head thickness is set by the factory and is intended as a reference point within a retail Renault service environment.  It more relates to customer cars & warranties etc. I expect all manufacturers would have something similar.
Once you go beyond that, understandably, you're on your own as far as the factory is concerned – it's a statement as to the limitation of their liability.

On the other hand, I expect we've all seen some seriously shaved & modified heads. Motor engineers may find this acceptable but with some caveats, conditions and agreement from the customer.
For instance, there's the cam and lifter relationship. Also, it's possible the dizzy base may need to be shimmed as it gets closer to they drive gear. We know that removing material from the combustion chamber comes close to the water jacket - lots of things like this.

I once bought a Renault crossflow F2 engine and the owner said he'd blown it up more times than I'd had hot dinners. I laughed and thought that was a pretty funny anecdote but he wasn't looking to make some sort of warranty claim.
Incidentally, that head measures at 92.8mm.

That JL Engineering head is very pretty.

Interesting . . your Formula Renault Europe pistons are a very similar style to the Renault Sport pistons used in the 1800cc Alpine rally cars (pic below). We often see Gordini style pistons with a different pronounced bulbous hump in the middle.
Do yours also have the "FTV' marking? I'm not familiar with the brand so perhaps it is no more.

--- End quote ---
Hi Gavin, the pistons I used to have didn't have any inscription, just the diameter figure, which is 77,8 in my case, and an arrow pointing towards the exhaust side of the piston. The pistons were not forged, but cast, I think.

@Richard, I love the look of the fresh Wössner pistons. Going to purchase them soon, too. I will go for the Ø42/35,35 mm valves. This is the famous Mignotet configuration. Marc Mignotet was the engine guru, who developed and tested the Alpine rallye and racing engines. I heard that this guy had the engine dyno next to his house and fine-tuned all the works Alpine engines there. I was thinking about using bigger valves, but if the guy from Alpines engine department, who slept next to the dyno, found this as the most effective way to make horsepower and torque, I go for it, too.

My dream would be to achieve around 172 HP from the engine, which I read on some occasions should be possible from that engine in a best-case scenario at 7200 or 7500 RPM. The torque figure of 192 Nm (of course a bit lower in the rev range) was also something that I read should be possible, if everything works out perfectly. There's a lot of wishful thinking involved, but as long as I reach 160 HP, I'll be happy.

GavinT:
What I know about beehive springs could be scratched on the back of an aspirin with a crowbar – or even conventional springs for that matter.

And I thought they were supposed to allow lower seat pressure?
Still interesting and I reckon you're right in that there should be something suitable around – same for Ti retainers. Worth pursuing methinks.

Around these parts, most folk default to using the set up recommended by Collier's in Sydney. Collier's were part of the Oz R12G rally effort back in the day. The R12G springs were prone to breaking so they developed longer springs which meant machining the valve spring seats deeper to accomodate. I put Paul Z on the old Yahoo list onto them and I believe he's happy.

The French vendors now seem to offer 43mm valves instead of the older 42.1mm ones.
Some 'enthusiasts' offer 44mm valves but with offset valve guides.
Some time ago I did a quick experiment with a Nissan 45mm valve (pic below) . . and they're problematic, though the length is OK and could likely be reshaped to a suitable size.

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