Interesting thread, I have a T4 engine 2.0ltr 1979 Bay. I suffered similar misfires and blowing back through the left Carb - NO3 & No4 cylinders It got worse and worse I ended up with compression from 1 - 4: 130, 130, 125 and zero!! The valve seat on No3 cylinder inlet had come loose, falling out loose when I took the valve out. Engine workshop, new valve seat £144 all in, including re-cutting all valve seats. The blowing back through the carb sounds like the very same symptoms I experienced including not getting any difference when trying to set the volume screws for idle. In my case No3 Inlet seat. FWIW I just drive mine up steel ramps to work underneath Or indeed to take the engine out, which I did for this job. Good luck with it.
Thanks for sharing your experiences Matt...it's all good information Do you have a link for who did your head work?
Its in Somerset, Auto Engineering, Yonder Hill, Chard tel; 01460 221223 . They come well recommended from a number of classic car owners I know I took the head and valves in, they did the rest.
So today, I took my time and went through everything again. All tappets set at .15 inlet and .2 exhaust. Noticed that the push rod tube retaining clip was missing - is this a vital bit? Checked and cleaned all plugs. Checked timing. Checked carb balance. Took it for a run...AND NO MORE MISFIRE/BACKFIRE. Drove smooth as anything.
Unless yo you have 1800 heads with sodium filled exhaust valves the clearance should be 0.015mm for inlet and exhaust valves. The pushrod tube retainer stops the tubes from working out of the crankcase and heads, friction of the 'o' rings will probably prevent any movement but it is something you should keep an eye on. Ideally replace the clip of course.
Was this after you filled up with the “full fat” stuff? I’ve been on a long run before, and it’s been perfect, then filled up with normal? fuel, and after 10 miles it drives like a pig, and it continues like this for 1/2 a tank, then I filled up somewhere else, and almost back to normal, and next 1/2 tank, perfect again. It is possible you have had some duff fuel.
Well, the problem has returned (not a suprise really) - no where as bad a before, but it's returned. Took rocker cover off and noticed that the #4 exhaust valve was heavily sooted (see below). Any thoughts from anyone?
Not on my camper but in my MGA- bad running , backfiring etc - turned out to be cracked exhaust valve seats.
So I've got the head of cylinders 1 & 2 (pics below). Cylinder 2 (it's down) has got damage on the bore. Will get the head off cylinders 3&4 tomorrow. I know the heads probably going to be stuffed as the valve guide has gone. Now I've got the head off, how do I work out what the actual capacity is (1700 fan shroud and 1800 block).
Measure the diameter of the cylinder and how far the piston goes up and down. 1700 bore 90mm, 1800 93mm and 2.0l 94mm. 1700 and 1800 66mm stroke, 2.0l 71mm.
