1275 valve springs

[Hairyone]

I'm re-building a 1275 for my frogeye. Only mildly tuned, Titan 1.5:1 rockers & a Swiftune sw5 cam. So only a little higher lift. About 9:1 compression. It's not going to be a screamer, just a road car.
The head I have is from a later Ausin Metro which has hardened valve seats, but only single valve springs.
Question is: What are the benifts of double valve springs?

Thanks
Adrian

 

[BlueMax]

Contact cam manufacture for spring seat pressure and install height. Cam manufacture should provide a spring set for your cam. If not check with David Anton @ APT, inform David of what you need and he should have a spring that will fit your application.

 

[Glen_B]

The benefit is avoidance of floating a valve at a particular RPM due to the harmonic frequency of the spring. A second spring has different dimensions and a different harmonic unlikely to match the first. Thus one or the other is able to close the valve across the range of RPM.

Glen Byrns

 

[Falkon]

That's really cool and kinda crazy at the same time. But if they knew that then why didn't they do it on the other engines.

 

[Glen_B]

Depending on the spring properties and the engine RPM, the harmonic of the spring may never be reached. Low RPM with a nice hearty spring should be fine, higher RPM engines are more demanding.

Glen

 

[smaceng]

I second the suggestion to call David, he was very helpful to me in my 1275 engine build.
Scott in CA

 

[Hap Waldrop]

David uses Isky valve springs I not a big fan of them, I prefer the Mini Spares .520" and .570" lift valve springs, Mini Mania sells them as well as GB car parts, you use 1275 dual spring retainers and 1275 single groove collets with that set up. I used this set up a bunch of times on both street and race 1275, it's proven package. Also with your Titanc 1.5" roller rocker arms you need about 1/8" of pedestal shim to correct the geomentry and that will also help restore some of the lost lift from the bad geomentry, it net you about .030" of lost lift back. You don't want to use stock springs with this set up, due to the SW5 and 1.5 rocker lift, you could experiecne valve spring coil bind.

After re-reading you post, I see you are in the mother land, just call Stevie at Mini Spares in Potters Bar, she can fix you up with the .520 lift valve springs and the dual spring retianers/valve top cups and collets, your current head should have the dual groove collets, if so you need a set of late single groove collets. You may also have to change valve type to use this set up, but MS will have everything you need to do it, your head probably has the larger 1.4" intake valve.

Hope this helps.

 

[dklawson]

Or... he could call Nick at Switftune and see what he recommends. I have probably got the same 12G940 head with big valves and single springs on my Mini. But I only have standard forged rocker arms. Having single springs instead of dual and never been a problem for my car... but it is a street engine. Regardless, if you are set on double springs, Nick will know what works with the 12G940 casting, the SW5 cam, and your 1.5:1 rockers.

BTW, I think you'll like the SW5.

 

[Hairyone]

Cheers Hap & Doug, & Glen ahha spring harmonics yes I see.
I don't think spring binding will be a problem on the standard single spring. I looked at the Swiftune spring kit, but was put off by the price. DOH! DOH! Knumbskull !!
I've just looked again (and at Mini spares) I presumed the springs were £35.50 per pair so x8 that's a lot of bucks, it's for the whole set. So that's now the answer. A new dual spring kit. :banana:
Thanks Hap I've already read your postings about the Titan rocker pillars.
I know the owner & his step daughter (who is in their sales department). I'll try & find out why they dont offer different pillar heights, or the shims.

Adrian

 

[Hap Waldrop]

The deal on the roller roacker arm, bascily all of them, they are designed at stock shaft height, but the body of the roller rocker arm takes up space, so this askews the geomentry, it's been a issue forever, MS probably does offer the 1/8" pedesal shim, but no choice in pedestal heights, here in the US APT offers the shim, and you can always make same as well.

FWIW, I'm not real impressed with what I saw on the inside of "ST" engines, somewhat overpriced sloppy work if you ask me. Trust me "ST" does not want me exposing to the world what I found wrong with one of their top of the line street engines. If I not found this issue on bascily a dyno time only engine, it would have destroyed the engine in short period of time. Oh and don't even get me started on their head porting, not a clue is the thought that comes to mind.