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I'm building a race 1293. I've had the block line bored with steel caps and a freshly cround crank. All sounds well, but there's a problem.
After torquing up the mains the crank spins freely for a while. If I stop it and leave it, it sticks. I need a lever to get it spinning again, but as long as I keep it rotating, it spins freely. I thought it was the lube used, but I've now removed the crank, and fitted it againg with regular motor oil. Same thing happens.

Has anyone else ever experienced this? The main clearance is 2thou as it should.

Have you got the thrusts in there?

if so they could be a bit springy,

It's not the thrusts. All four are "loose".
I've never had this happen before, that's what puzzles me. When that is said, I've never blocks line bored/honed before either.
Let's say that the housing diameter is a bit on the small side, let's say minimum size. Could I still end up with proper clearances while they're not? As I haven't plastugauged on all sides of the crank, this could be it although a bit strange as honing would make it round.

The cranks doesn't seem to be bent either, as it does feel the same all the way around.

some aston engines i build are like it! mainly 6 cylinder. ive allwase put it down to the blocks being slightly out. there not so tight you need a load of effort but they definitely grab. its like the oil is pinched out because its settled.ive never got to the bottom of it. its one of those situations you have to rely on youre gut feeling as an engine builder and aslong as youre confidant youre numbers are ok it should run fine and ware in.

a guy i used to work for used to run his formula ford cranks in with an electric motor and WD40.

i had a guy who INSISTED i built his race engine with .001" on the mains, it only started when you filled it with HOT water!

Is it tight on all 3 bearings ?

Can you slacken off one of the caps and it becomes free again ?

What make an age of bearings are you using ?

Is the crank freshly reground ?

Have you tried another crank in the block ?

I hvae struck this problem quite a few times over the years and other brands of engines. As soon as I've checked the clearances and satisfied myself all is OK, I've forgotten about it and carried on assembling. It's never caused me a problem.

Regards
Al

251 ENG wrote:Is it tight on all 3 bearings ?

Can you slacken off one of the caps and it becomes free again ?

What make an age of bearings are you using ?

Is the crank freshly reground ?

Have you tried another crank in the block ?

I've tried a different crank with different bearings. Same.
The bearings are Vandervell ones, the age I'm not certain of but they are from Minispares within the last five years.
None of the cranks are reground recently. They've both been run in engines before this.
If I slacken off the timing cover end it does loosen, but it seems as the protective coating has worn from the centre one. I've got a picture of this.

Taking the block to the machinist tomorrot to measure the hole.

I took the block to the machine shop, and it was indeed one housing that was on the small side. I had it ground "more" and now the cranks spins like it should. Let's hope it's OK.

This engine build doesn't seem to stop puzzling me.

I've timed the camshaft up and I early saw that the shis behind the small cam sprocket needed to go. After tightening everything up properly it seems that this particular engine needs shims between the camshaft and big sprocket. Has anyone ever experienced this? I could have the small sprocket milled down a couple of thou, but I've never come across this before, and I've not half built some engines

Anyone with similar experience?

What timing gear are you using? I had a similar issue with MS lightweight sprockets which Rich also later experienced and (I believe) an issue was found with the wrong crank sprocket being used in the kit in an effort to 'standardise' on the crank sprocket in the various different kits.

It is indeed a Minispares lightweight setup. Rich!

Vegard wrote:I took the block to the machine shop, and it was indeed one housing that was on the small side. I had it ground "more" and now the cranks spins like it should. Let's hope it's OK.

How come it never showed up when you checked the clearances? Good you found a problem anyway.

Al