Valve caps and double springs

[gs.davies]

I’m putting my 295 back together ready to fit in the next few days and as I’ve ‘mislaid’ some bits, I’ve had to dig into my stash of bits for the next engine build..

Does the way these springs sit in relation to the valve cap look ok?

Spec;

Large groove valves
Large groove collets
Caps from an 850, minus the shroud
Double valve springs from Minispares C-AEA525

Going through the parts it would seem that these should all work together but I’m not sure about the way the springs are sitting under the cap.

The caps have come directly from an 850 head and the part number is common to 850/997 and 998 cooper as well as anything small bore after the deletion of the shroud. This suggests it works with both single and double springs (hence being specified for 998 Cooper. I’ve just not had the pleasure of double valve springs before - the original set of single springs that came with this cam are lost until about three days after I get the engine running again, along with the caps and collets when Sod’s Law makes them visible again and spits them out of the nearest black hole (and they were also ex-850 standard head..)

I have some options;

- fit and forget
- AEA311 set of single springs
- some A-plus springs
- a Janspeed Cooper 998 head with guides that have more wear than the current 295 and a tiny bit more cc in the chamber. Already as a pitifully low CR of about 8.9/9:1 on a +10 1098

IMG_8772.jpeg

Thoughts anyone?

[CooperTune]

My approach is to have hard seats installed intake and exhaust for two reasons one to restore worn seats and to allow seats to be high raising compression. I also have given up on wide groove valves and keepers. In order for the valve seals to be effect the valve, spring and cap must be compressed and the o ring ( with great difficulty ) install in groove then the wide keepers also not easy. I spec new cast guides, new triple groove valves O/S both, lower valve spring collar, MSC std double springs, latest top hat seals and triple groove keepers and caps. I believe the triple groove keepers encourage valve rotation. Steve (CTR)
PS as per your pic I suspect they are fine.
Also Hemi Moly orange may clash with your blue.

[mowog]

Pics added for Steve

[Catmint]

We have had a bad experience with standard caps on double springs as the springs pushed the cap over the collet. This was on a Janspeed head fitted to a 998 cooper conversion. W spec caps sorted it out.

[gs.davies]

Ah yes I remember you saying.

At this points putting the Janspeed head on mine is the favourite option.

I’ve robbed a set of a plus springs from a 998 head, so could try that also.

I’ve established that the caps I’ve got aren’t suitable for the double springs as they’ve got a conical centre where the inner spring sits and that seems like it wouldn’t seat the spring correctly so it’s all got to come to bits again.

[tweedy998]

I was going to say to be wary using 850 top caps with double valve springs as they're the wrong shape, but you seem to have worked this out.

Last time I built up a 295 head I used the Minispares steel S-type Competition top caps - AEA653 with no problems at all.

[Exminiman]

Might be worth having a word with these guys, they might be able to offer advice and sell you what you need ?

http://www.gsvalves.co.uk/assets/race-e ... alogue.pdf

[Festus]

I'd be a little worried about coil bind at high RPMs. Have you tried mocking it up and checking the travel with a dial indicator? It might be worth swapping in those AEA311 single springs just for peace of mind.

[mab01uk]

Interesting short video which shows how valve springs behave at high rpm and why it's necessary to have a gap between coils at full lift to prevent breakage:-
https://www.youtube.com/watch?v=WtqDHJDN79w

[rnp68]

Couple of pics showing the different types.

[gs.davies]

Tonight I had another go and getting the head ready to fit, I don’t really want to hose a load of money at it as there’s a 1300 on the horizon and really this is just about getting going for a while.

I started fitting a set of A plus springs to the 295 head and ran into a problem when I noticed that some of the valves were being ‘gripped’ by the edges of the recess in the valve seat. That didn’t seem right to me, should there be a clearance? If so, how much?

The cam in question is a Minisport CA2 (basically a 997 cam) and the engine is a 1098. It’s a road car and so doesn’t really see extended high revs.

I have on hand a set of AEA311 springs brand new but these seem quite short and despite Somerfords quoting them as being suitable for a 997, they’re somewhat shorter than the quoted free length for 997 springs in the manuals. Alternatively I do have available a set of caps which will accept the C-AEA525 double valve spring set (though I suspect that set of springs is probably overkill for the cam..)

Is there anything particular about the 295 head that prevents is accepting an a plus valve?

What’s the best combination of bits to use?

[Catmint]

Something is rattling about in the back of my head about 1275 valves been longer than small bore - is this the same for A+ ? This is going back 30 years so could be getting confused. At the time it was fitting bigger valves to a 1100 head so we machined down 1275 valve heads and I think we put spacers under the springs - it put the rockers at a hell of an angle and used to eat guides. I am sure there are plenty of people here with better memories than me

[timmy201]

Yes 1275 and A+ are longer than A series small bore springs

https://www.minispares.com/12g1015-valv ... all-1300cc

[CooperTune]

Due to auto machine shops in my local area ( known as the seven cities ) closing forever finding a shop that can bore small bores has become an issue. I was informed a couple years back that one shop was selling their small boring bar out of the area, so I has three 998s bored for flat top press fit .060 pistons. At that time I also had three 295 heads machined as shown above. Zero decking the blocks and doing the math first two assembled required .065 removed from heads for 10.2 to 1 CR. One left with a SW5 and the other a Kent 266.

You indicated the cam was supplied with single springs ( currently misplaced ) for years the 997 cam was our autocross cam of choice. Not knowing if your seats have been cut/machined and if you are checking where the seat lands on freshly ground valves by lapping can't say why they stick for sure. I realize it's a budget job but if you can't afford to do it right how are you going to redo it? And it can get confusing as small bore heads and early Cooper S heads use a shorter valve length. If the seats are correctly machined and the valves ground the correct angle after lapping assuming guides are good the valve should bounce when dropped into position. Having 15,000 picture on file I should be able to find one of a valve that has been lapped correctly. Steve (CTR)

[mowog]

Pictures posted for Steve

[CooperTune]

While clearly not mini it's the first pics I came to. Steve (CTR)

[gs.davies]

You indicated the cam was supplied with single springs ( currently misplaced ) for years the 997 cam was our autocross cam of choice. Not knowing if your seats have been cut/machined and if you are checking where the seat lands on freshly ground valves by lapping can't say why they stick for sure. I realize it's a budget job but if you can't afford to do it right how are you going to redo it? And it can get confusing as small bore heads and early Cooper S heads use a shorter valve length. If the seats are correctly machined and the valves ground the correct angle after lapping assuming guides are good the valve should bounce when dropped into position. Having 15,000 picture on file I should be able to find one of a valve that has been lapped correctly. Steve (CTR)

The valves are seating nicely, no problem there. What I found was that in trying to fit a set of A plus springs from a CAM4810 head to the 12G295, the bottom of the springs were catching on the side of the recess cut for the spring seat. I've since learned that those springs are not really compatible with the 295, and so I'm left with a couple of options;

- Fit the AEA311 single valve springs with the top caps I have and call it good on the basis that those springs are specified in their own right for the 997 cars as well as other derivatives including the Mk3 Sprite, which I think ALSO used a 295 head, if not also a 997 cam.
- Fit the C-AEA525 double spring set with a set of suitable top caps that I've scavenged from another old head and accept that the poundage is almost certainly higher than the AEA311
- Obtain a replacement set of springs from MiniSport which is their own proprietary replacement for all 850/998/1098 single spring set ups and is the spring that was originally supplied. These are the ADL451458 springs, apparently 'stronger' than the standard. By how much, who knows?!

Hoping for another year or so from this set up, so reluctant to get involved in engineering costs and would just like the car back on the road earning it's keep ASAP.

Note to self, don't lose things