hi everyone, this is my first ever forum post so please forgive any mistakes lol.
I have a 1968 MGB GT which ive spent the past few years rebuilding. Ive had it on the road since last september, its running with a +0.030 overbore, a 714 camshaft, AAA needles, K&N filters and a freeflow stainless exhaust.
My problem is that until the weekend my car was running great, i was traveling along the motorway at around 4-4500 rpm in top gear with overdrive. i looked in my rear view mirror and saw a lot (and i mean a lot) of white/grey smoke coming from the back of the car. I went to pull over on the hard shoulder but as i lifted off the pedal i noticed the smoke vanished. All my gauges seemed to read correctly, good pressure and temperature. I drove rather slowly back home constantly looking in my rear view mirror but didnt see any more smoke. I got home, and got a friend to rev the car up as i looked at the exhaust, there were small puffs of white/grey smoke when high revs were reached.
I then let the engine cool, i checked the water level, it was exactly as it was when i left earlier in the day. The oil had no watery deposits or sludge, and i even checked the brake fluid as it is servo assisted. I then started the engine, let it warm up and revved the absolute nuts off it, and there was no smoke at all. i then drove hard down the road with my dad watching and he said there was a barely anything, only a tiny puff at max revs. Any ideas as to what this could be? At first i thought head gasket but all my fluids are present and correct and under the bonnet it looks fine with no leaks. I do have several oil leaks and i wonder if this could have caused it. Also I did notice the smoke on the motorway was coming from the whole of the rear, not just the side where the exhaust is but then maybe the turbulance the car creates could cause this.