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Full Auto head


Evenin All, I bit the bullet & bought 1 of the 850 heads from AN.

I can't say I'm over the moon with it! 1st problem was not being able to screw in fully ex tappet cover top studs, after speaking to AN & them getting in touch with FA, I had to run a tap down them. 

I now have another problem, when fitting inlet valve spring bottom cup, it won't sit directly on the head as there's a little collar on the guide that stops it going down fully, ex were ok, cups are new from AN. Still awaiting result from AN.

Ashleigh(AN) looked at another head in stock & that is the same.

Anybody else bought these heads & had problems or is it my luck!



Is it an Australian or USA built head? I got an Aussie 850 from the second to last batch. Everything fitted perfectly including new AN valve spring cups and insulating washers. Valve spring heights were set to 1.20” giving around 100lb seat pressure on the Kibblewhite valves according to a Jim Schmidt chart. I used stainless socket cap screws on the exhaust rocker covers rather than studs.  No problems in the 20,000+ miles since fitting the head in 2018 and still running strong.

Very nice piece of engineering to replace my tired original RH4 which gradually died everywhere.


Have you fitted the tufnol valve spring insulator? What cam have or intend to use with this engine? Taking out the insulating spacers to allow more valve movement to avoid coil binding can lead to problems like this. Higher lift cams cause all sorts of grief and in my opinion are not needed. They take a few horsepower from the bottom end to put a couple on up the top end. 


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