Hi Stuart
The block is wider at the exhaust side motor mount
elan-f15/crossflow-tall-block-measurement-t18272.htmlTHe Exhaust side looking from the flywheel end. The inset photo is that of a 711 (wide width) and the main picture is that of a 681 (narrow block)
Seeing you have been here I would have thought that this would have been taken care of, did you narrow the block or reduce the exhaust side spacers by 11 mm. They should be 11/16 inch long or 17.5 mm now.
I'm not sure what or how the fuel pumps access plate bodge you are going on about, it should be in the same place as before?
All in all it sounds like there are some teething problems to fix. Did some one replace the valve seats on this head? Somehow I wouldn't think that an Exhaust seat should be dropping out at idle, I would have a qualified person inspect all of the work done previously.
Do you know the expression "when you pay peanuts, you get monkeys", sometimes that is the kind of info you get for free on the Internet. Lots of info on this site is the same, you need to read it, look at it, look elsewhere, compare, weigh all the information gathered. Then take you best guess as to what it all really means. Even then the guarantee is null and void. None of us are seeing what you are looking at so the help you get is coming from images that are conjured out of our imaginations from the info we receive from you the people that are posting these problems. Most times folk that have had the same issues before can help, other times you are on your own.
Gary
P.S. I guess that with the engine out, the next step is the gearbox out and the drive shaft too, so access to the Fuel line should be ok. I used a 3/8 inch i.d.line, thats a bit of an over kill but one of those safe than sorry approaches that I sometimes use. I think the stock is maybe 1/4 inch (Max), something like 5/16 or 8mm would be ok. That said, I am not sure what the 26r used in the day, could have been stock and they were pulling 145hp or there abouts. anyway its up to you what you fit and where it goes.