While virtual window shopping for valve springs, the set from Moss has two sizes of springs, for a total of 16 pieces.
My existing head (Morris minor 948) only has the larger outer springs, as did my prior head (A+ 998).
Is adding the smaller inner springs to my setup recommended?
Thanks
Depends on your cam and intended RPMs. What are the details of your motor?
Edit: spring examples. Both of my fast road motors used roughly the same cam profile and lift with a 6k rpm rev limit/power band. A kent 266 cam with 1.4 rockers and a EVO1 cam with 1.27 measured S rockers. Far from a race setup but much more aggressive than stock, so they got dual springs. On a mini dual spring pressure for a basic setup like I'm using are in the ballpark of 200-220lbs of pressure at full lift, whatever that comes out to be when they measure mini springs. Dual springs are also beneficial in that they reduce spring harmonics. You want the sweet spot to keep your valves from floating but not so much pressure your wearing valve train parts. I took a lot more time setting up type 1 motors for VWs with regards to springs as the spring rates are either soft as hell or crazy amounts of pressure. I'm talking 400+ pounds at an inch of lift. I went so far as to buy a scale for my press and measured the pressure at intended lift, as well as installed height pressure from various springs. Valve weight, push rod weight, end keeper weight, lift, and cam ramps went into the calculation process. In the end I went with an outter spring only, but from a dual spring kit that are race springs. It gave me the desired pressure needed for the intended parts and rpms. It's also a shorter spring which given the lift I'll have starts getting close to the springs coil bind. I'll have enough clearance so it's preferable because it reduces harmonics the closer it is to coil bind.
Quote from: 94touring on July 31, 2025, 05:20:31 AMWhat are the details of your motor?
Nothing special, just an A+ 998 with a Morris Minor 948 head. I'm interested in adding them mostly based on what I've read about dual springs being better valve alignment.
Also confirming that I'm not missing the inner set. I wasn't the last one to do the job, and based on other things I've seen it wouldn't surprise me if they were overlooked / omitted.
You don't have to use inners, provided the outters have enough spring pressure for a stock setup. Which they probably do I'm going to guess. Dual springs are really just for added spring pressure with a benefit of harmonics.
Edit: bare in mind your valve alignment is achieved with the guides and associated machine work when installing and cutting the seats. There's the topic of rocker arm geometry to reduce valve guide wear, but that's not really something that applies to minis.
Like Dan says, the real question is what kind of motor are you building? If you're like almost all Mini owners, you rarely get close to redline......so if your driving is in the 3-4,500 rpm range, singles will work just fine, just like the factory built it.
thanks everyone. I'm glad I'm not missing any parts after all.
And related, this old head has the old style valves with oring seals and clips for the collets. I've read different info and opinions regarding these clips and apparently they are no longer necessary. I'm curious what people here think. According to Mini Spares:
I don't think they're needed, again you aren't heading for 7K RPMs....but if you like them for the originality, why not?
Quote from: MiniDave on July 31, 2025, 05:10:38 PMif you like them for the originality, why not?
I actually had one break and would need to order more... haven't found any domestically yet.