Those of you who have been following my posts may be aware that I have not long 'done' an engine for my 7. Basically I had a big end let go in a very worn engine some time ago, but had a 'spare' engine in stock.

This engine came with a 1930 chummy my father bought sometime ago without telling his then wife. The engine was a little rough, broken studs etc, but with the head off it was clear that it had at least just been decoak'd, though I suspect it had been honed from looking at the bores. I did most of the studs in the block and fitted it, even though the crancase studs and sump blts were decidedly iffy.

The engine started up beatifully, ran ok if a little hot. on a trip down the road it developed an intermittent knock. Long and short of it was the crankcase lip had come off (it looked ok when I had taken the sump off typically)

I bought a new crankcase, helicoiled all the iffy threads, had a steel lip fitted, measured the crank and rods to find that they were likely very recently metalled, and fitted this to the crankcase with a full set of crank bearings (ball and roller on the front). As the 'top end' was all nice and shiny I left it well alone. Refitted and there you go.

Now then, Ive done nearly 2500 miles since I put it in. trouble free in terms of the engine itself, oil pressure of about 3lbs when nice and warm, and none at tickover.

On Monday having been at an event in mid wales, I had the car parked with a little choke at a fast idle, while I sorted the modern and tin tent ready for going home, when it started to run rough, a bit like when there is much in the jet, I strolled over, proded the throttle, and got a loud metallic bang and a small puff of smoke. The engine continued to run but with a god awfull rattle. I noticed about 20 lbs on the pressure guage, and she had been running about 5 mins.

Having had it RAC'd home, I finally got the enthusiasm to have a look. Took head off to find nothing other than a fair bit of soot, I half expected a broken valve, so then took the sump off, again nothing obvious. The engine is a lot looser than when it went together, there is a fair bit of endfloat (along the crank) in the big ends (there was when it went together), the crank doesnt move longditudonally but
so obvious cause of the bang or rattle. I took the cap of no2 which had most end float, nothing untoward, still taking the high spots of the metal by the looks of it. Also all the bolts were still in the little ends, and the gudgeon pin moved with the rods.

Any ideas engine will be coming out at somepoint, but the obvious suspects look ok.

Anyone want to buy a RL

Hedd

Presumably nothing wrong with dizzy or dynamo?
Or flywheel /clutch?

Steve.

p.s Keep smiling , mine was taken apart twice even before I got on the road, since then it has come apart once for a broken piston, head gasket and valve grind.

Hi Hedd
The clue might be in the sudden rise in oil pressure!
A sure sign of a blocked jet. A little end float in the B/E caps is not uncommon.Did you look at all the big ends? I fear the worst!!

As the car had only been running 5 minuites and I had left it running at fast idle to warm up, the carb spindle need sorting and it is a bit of a nuicance when not warm. I think the oil pressure was on its way down, not up. As I said I have taken off the loosest (in terms of end float) big end cap (no 2), and saw nothing wrong.

No progress today, rivetting the tubeplate and firehold door ring on my Steam roller's boiler.

I think the next step is to remove said engine, and have a look at the timing gears and clutch.

Hi,

Have a good look at the crankshaft webs, when my crank broke many years ago it broke about 80% across the web and it wasn't until I removed the bearings that the crack opened up to show the damage.

Hopefully I am wrong but it is worth checking!

Spent an hour or so under the in situ engine last night still scratching my head. Crank is not broken, nor can I find a mechanical source of the knocking.

Going back to the soot I found in the combustion chamber, I know I have an air leak on my carb spindle (not got round to sorting it yet), the engine has used a fair bit of oil since it was put together, and runs noticably hotter than the 'old' engine.

Could the trouble be pre-ignition and/or detonation? Im not sure if this is possible at fast idle, any ideas.

Long shot Hedd but it could be carbon which has come from the head getting caught between the piston and the head, makes a terrible racket which dissapears fairly quickly....


Good luck

Ruairidh