7 replies to this topic

[Trissy B]

Hi I have a new set of minispares 1.5:1 forged rockers. Everything runs fine but some of the rockers are offset.

 

2 & 7 aren't bad so I will leave.

 

4 and 5 can be shimmed to get central.

 

Put my problem is 3 and 6, they physically cant be moved because they are against the rocker post and,

 

1 and 8 - these again are defined by the end of the rocker shafts.

 

Any ideas? can i ditch the standard spring washers at the end of the shaft?

 

 

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[Dusky]

Switch 1 and 8 around?

[carbon]

I wouldn't worry too much about getting the rocker pads lined up with the valve tips. If you really want to you can, but check very carefully the running clearance between the pushrods and the edge of the pushrod holes going through the head as this is very close.

 

Some other pointers about these rockers, based on experience. Some of this may differ from set to set depending on when they were made:

- check the height of the rocker pillars compared to the standard height. They can be taller (mine were 3mm more) which causes a few issues.

- check the rocker adjuster ball ends for roundness. Mine were not so I replaced with other adjusters from old A+ set

- and most important check your valve lift and how much clearance you have before the valve springs go coil bound

 

Reason for emphasis on checking the valve lift is that the lift ratio on my set is about 1.65:1. Not a problem if your cam is 'old school' type running lobe lift of under 6.5mm, but if you have SW5, Piper 270, MD276 or hairier then you are running a lot of lift at the valve and you may well go coilbound. If you get this happening you will wreck the cam, and could also cause a lot more collateral damage.

[Trissy B]

Ok thanks and will do. I checked the valve springs didn't bottom out when I put the on but checking what full lift is won't hurt.

I looked just now and some push rods are not central, shimming those off centre rockers will help. So doing that will be a double bonus.

Thanks

[carbon]

Trissy,

 

There is a very useful information sheet supplied with the Minispares C-AHT436 1.5 ratio high-lift rocker set. Direct quotes:

 

ENSURE the valve springs cannot coil bind as it will place undue pressure on the rockers and shaft inevitably leading to failure

 

CHECK for coil binding. When fitting to anything other than a Mini Spares cylinder head assembly or a standard head with Mini Spares special valve springs which have a known specification (all in unmolested state) the valve geometry must be checked.

 

Simply looking for daylight between the coils, or slipping feeler blades through is insufficient and wholly inaccurate. Correct measurement of each valve/spring using a DTI and drill press, or some such, should be carried out.

 

An absolute minimum 0.085 inch (2.1mm) should exist between full valve lift and coil binding, with 0.100 inch (2.5mm) recommended.

[Trissy B]

Ok thanks for this. I had seen this but to be honest i ignored it as when fully open the springs are visually no where near binding. Maybe because they are double springs they have less coils (?) i don't know. I have an MG metro cam by the way.

 

There was also a article about this in the new mini world which pretty much said the same as this thread.

 

When I re-torque the head at adjust the tappets in a couple of weeks before London to Brighton I will check the total valve lift with the DTI gauge and swap the end washers around using the minispares solid type ones to give better alignment & push rod clearance (plus new split pins which weren't great when I reused them last time). Probably won't shim the more central ones.

 

Many thanks.

[carbon]

You're unlikely to get the valve springs going coil bound with the MG Metro cam profile, as this only has about 6.4mm lift at the lobe. With these rockers you should see about 10mm lift at the valve.

 

You should find a big difference in engine, much more responsive at med and high rpm?

 

But your ignition advance curve will probably need to be tweaked to get good response at lower rpm.

[Trissy B]

Well I put a decent head on at the same time so yes i can definitely feel the difference, but i cant tell what portion of that is the rockers. Its so much smother through the whole rev range, more grunt, revs up quicker and sounds more throaty!

 

I've just had the distributor re-curved by AC Dodd and its even better, especially at low revs. Would like to get it rolling roaded now to get the best out of it.