Mark V Backfiring on over run

I have purchased heat insulating blocks for mine, same as used on MGTC, Moss Motors part 372-030, but have no running experience yet.

BTW piston return springs were first used in XK120 and Mark VII which have aluminum pistons.

Would they be the same spacers? MGTCs had 1 1/4"carbies. Not only a different main hole but different spacing of the mounting holes.

Yep, same SU H4 carbs, same holes, also used on TR2 incidentally.

Sorry about the bad focus.
I got the idea from the fact that they did the same thing on XK120 and Mark VII when they were getting vapor lock, i.e. fuel vaporizing in the jets from too much heat transferring to the carb bodies. They added a 1/4" spacer and extra gasket in about 1952. All subsequent carburetor Jag engines had them.

They help…sorta. Fuel loops work better.