Hi all
I have a situation with SRM head bolts (SR alloy head)
The bolts are longer than the old ones so I contacted SRM who were very helpful as always and went through the sequence of fitment and the fact that I needed to use a 3/8 bsf threading tap to clear the lower threads which I am in the process of doing just thought I would ask if anyone on the forum has encountered this themselves all comments gratefully received
Thanks
Mitch
Hi Mitch,
Used bolts for iron from SRM but did not notice if they were slightly longer. As I always clean the threads right to the bottom with a tap it would not have been a problem. It is interesting how much deeper the threaded holes are than the original bolts and how much crud accumulates at the bottom. Torquing the head down against any resistance can mean poor sealing on the head gasket. It is always a good idea to make sure that all threaded holes are clean to the bottom especially on aluminium cases. Trying to tighten the screws against a plug of old gasket and gasket goo can lead to stripped threads, leaking joints and cracks in the thread bosses especially in primary side.
Dave.
Hi Mitch,
As Dave said, plus ensure the bolts have the minimum high temperature grease applied and the threaded holes are free of oil. This ensures the bolt does not 'hydraulic' which will give false torque readings.
Best wishes...
Thank you Dave & Bess much appreciated
The BSA Service sheets states the bolt Lenghs, if your old bolts came out the new ones should go in
SRM gave me the tip about checking bolt lengths years ago. Logical really as the head may have been skimmed a number of times plus the amount of Red Hermetite stuck in the bottom of the hole is astounding! As such, I always clean the holes out every time. Also, they recommend a light smear of ordinary clear bath silicone sealant on either side of the head gasket. I have done this for many years and it works well. (Keep it away from the oil drain holes though).