Phenolic spacer

[fordman302]

Hi all, I'm just after some advice to help me with a problem I am having. I recently pulled my xr8 apart to give it some much needed love, stem seals, lifters and fix some oil leaks, all seemed to go well until I got to the upper manifold.

I have a phenolic spacer that was fitted by the previous owner, the first time I pulled the manifold down in sequence from middle out to 20nm I managed to crack off the lower back corner of the upper manifold, I then got that welded and had another go, didn't even get it to 20 this time and crack it went again through the welded repair.

After this I thought I wouldn't persist with that upper manifold so I purchased another one, made sure everything was right, started pulling down the bolts and this time the front lower part cracked, so now it's off getting welded again and I am going to order another spacer just incase this one is getting sad, I can't take it out because of my higher after market rocker covers which are there for my higher after market roller rockers.

Has anybody had this sort of experience before and can point me to what I am doing wrong and how to rectify the situation, I am at a stage of growing frustration, thanks