are sigma valve assembly better then magna due to them being ajustable?

I realise that this question is over a year old, but hey, I have nothing better to do. All Sigma's up to early 85 have adjustable rocker gear......... 85 (leaded) GN Sigma's have basicly the same head as TM Magna's. They are an M1 with hydraulic lifters. The TR has a different cast #, but they are all the same as far as rocker placement goes. The only difference between the Sigma and Magna M1 head is the rear water port between cylinders 3 & 4. The Sigma has a small port to supply water to the heating system. But the Magna has a large port, because this is where the water pump and thermostat housing is located. If you compare the inlet side of a Sigma/Triton/Pajero head to a Magna head, you will see the difference. Back to the question....You can bolt up the early adjustable rocker gear from an early Sigma to a Magna. You just have to make sure to use the corresponding rocker posts and shafts. And if they are not adjusted periodicity, you get a sound like a noisy hydraulic lifter. Mind you I did use this setup on my GN Sigma for around 10 years with no issues. I just recently swamped it over for some TR roller rockers.

Hydraulic lifters are better due to low maintenance requirements........... You cannot adjust the earlier ones for better performance if thats what you were getting at. Vee