Its really really bad though, so much so that I'm think of taking the heater tubes off and doing without even though its winter.

Is pouring something like redex into the carb and seeing where the smoke leaks out a good indication of whats leaking?

perfect!

sometimes just the bonnet up and watch what happens on a cold start

failing that Kens tip of using a piece of washer tubing as a sethescope and listening around the joints and the gasket area

Sean

Nice one Sean, thanks for that. I've read good and bad things about the copper seals that ECAS does, if it is a leaky head, is is worth fitting them anyway?

in order of probability
1 one of the ecxchange clamps

2 one of exhust gaskets on manifold

3 head to barrel

which is also the least expensive/simplest to most costly/PITA

if the exhaust is fine the head leaks smell diffrent to normal exhaust its a much sweeter almost marzipan smell

lapping and then assembly with a smear of coppergrease( which i always do anyway as copper grease is a hi temp sealant) has done it for me.

cant you stick your hand on the end of the exhaust and hear if its blowing?

if you have long arms

the exhaust will blow , where its blowing is more pertinent

I think he meant to build up a little back pressure and force the leak further up the system to leak more and thus reveal itself. You'd still need long arms tho'.

fair enough, maybe a dastedly assistent??

Aye I got that was just being silly

you need your head in the engine bay to find out where its leaking
sily putting your hand on the tail pipe simply tells you, and its a racing cert, that it does leak

Alkie,
if it does look as though it's eroded cylinder heads which are the source of the fumes entering the heating system, it's worth checking to see if it's both sides or only one.

To do that, disconnect only one heater tube at a time, capping the bare intake stub on the bulkhead with something like a plastic lid off a spray can and some duct tape.

ken