1.5 Rockers

Post by **Longdog** » Fri Oct 24, 2008 6:01 pm

Hi has anyone had problems with valve spring bind/breakage with 1.5 ratio rockers on 1275's?
Cam used is Swiftune sw5 so high lift.
I broke 2 springs on the way to the National but with a different head/engine so am keen not to repeat performance!!!

Post by **bmcecosse** » Sat Oct 25, 2008 11:40 am

You should throw the high lift rockers away! Many Mini lads have had seriously worn cam/cam followers/valve guides/broken springs - and even dropped valves. The power increase was measured a while back by one of the mags - 1 bhp!! The SW5 is bad enough with it's sharp ramps and high lift (but still very 'soft' timing) - don't make it any worse. For moderate poer increase on a 1275 the MG Metro cam is good -used with the big valve head and carb from the same car - it works very well indeed. For more power - a 544 cam is the best choice - but it does need revving!

Post by **Longdog** » Sun Oct 26, 2008 5:30 am

Hi thanks very much for advice will stick with standard 1.3's.It was just that they need to be replaced anyhow, and I had an idea that they may cause undue stress.
I guess I shall just have to be content with 88bhp which does make for a satisfying power to weight ratio in the mog.
I also currently get 40mpg so I should leave well alone.
Cheers and happy minoring

Post by **grumpygrandad** » Sun Oct 26, 2008 8:04 am

if it aint broke dont fix it,,grandad

Post by **bmcecosse** » Sun Oct 26, 2008 11:37 am

88 bhp - hmmmm.

Post by **Longdog** » Sun Oct 26, 2008 5:50 pm

Cam isn't only mod so whilst I can understand your disbelief at 88 horses the car has been tuned by a guy who used to race minis on his rolling road so has been confirmed.Engine also ties with 90bhp spec in Des Hammils 1275 Bible.

Post by **bmcecosse** » Sun Oct 26, 2008 5:55 pm

Hmmm - Des Hammil indeed!! I would take these figures with a large pinch of salt. But it's how it GOES that matters, not some arbitrary figure from an optimistic rolling road.
For a genuine 88 bhp I would say you need an S head (or a 12G940 brought up to S valve sizes) and then thoroughly 'worked over' with CR at ~ 10:1, probably with a 544 cam and a single 1.75 SU on a good alloy inlet (or twin 1.5" SUs on a GOOD (ie not BMC) inlet manifold) and of course an LCB exhaust. Suitably lightened and balanced etc and able to rev to 7000/7500 should be ~ 90 bhp.

Post by **Longdog** » Mon Oct 27, 2008 5:09 pm

Yeah its got all that bar the cam.The same rolling road was used to test my tuned 1098 which gave 51 bhp so I think I can trust the figures.The guy who did the work used to work on works minis for Downton.Incidentally that is where the advice on head gaskets came from along with keith calver who wrote the piece on the Mini Spares website, but don't take my word for it

Post by **bmcecosse** » Mon Oct 27, 2008 11:39 pm

KC !!!!!!!!!!! Not the most respected 'expert' there either!

Post by **Longdog** » Tue Oct 28, 2008 8:23 pm

zzzzzzzzzzzz..............zzzzz...........................zzzzzzzzzzzzzzzzzzzzzzz

Post by **Peetee** » Tue Oct 28, 2008 10:10 pm

There is a certain engine tuner with a rolling road in his garage in the middle of Hampshire who made a complete dogs breakfast of tuning one car of mine. he spent nearly a hour fiddling and fettling, took it out on the road twice and then just gave up and lost interest. I ended up with a noisy, thirsty snail.

Post by **bmcecosse** » Tue Oct 28, 2008 10:23 pm

Wasn't KC - was it ???????????