'51 8N question

[boler76]

the oil pump pick up came loose and sucked air causing the crankshaft and bearings to be damaged hence got crank redone at an engine machine shop, installed repaired crank with new bearings that engine shop supplied, engine runs well but as it warms up it starts to make a noise, not a hard noise but sharp noise that increases with temp increase engine does not overheat.... also this engine does not have sleeves and the bore is now 6 thou larger than the pistons, could this be piston slap or connecting rod bearing noise, when cold noise isnt there? I am puzzled thanks for all input..

 

[Jim L WA]

If I remember correctly, a piston slap is heard when reving up. Not sure about rod bearing knocks. I'd have to go get out my old Motors Manuals. But you never mentioned oil pressure. Does the gauge work?

 

[boler76]

If I remember correctly, a piston slap is heard when reving up. Not sure about rod bearing knocks. I'd have to go get out my old Motors Manuals. But you never mentioned oil pressure. Does the gauge work?

oil pressure is 40 psi and drops very little with increase in temp but does flutter slightly when warm at idle . thanks for rep[ly

 

[Duner Wi]

Cylinder head gasket installed same thickness as old removed gasket?

 

[TheOldHokie]

oil pressure is 40 psi and drops very little with increase in temp but does flutter slightly when warm at idle . thanks for rep[ly

Oil pessure is great indicating tight bearings all around

Piston to bore clearance is 2X the spec.

TOH

 

[Eman85]

The no noise when cold is the opposite of what piston slap does usually. Usually it's heard more cold and as the pistons warm and expand the noise diminishes.

 

[boler76]

Cylinder head gasket installed same thickness as old removed Yes same gasket thickness . thanks I am in need of more advice please

 

[TheOldHokie]

MY advice. You have two options.

1. Live with it.
2. Tear the engine down, inspect and correct all worn parts and clearances starting with new sleeves and pistons.

Yes, I know, there are no sleeves currently in the block.

TOH

 

[soaked]

Hi boler76,
Was the 51 side dist engine swapped for 9n front mount? Adjustable valve tappets?
Have you put a hand at different places to attempt to feel the sharp noise?
A loose grill can make unusual sounds...

 

[HarryVanderpool]

Loose exhaust clamp?

 

[Duner Wi]

Use stethoscope and narrow it down.

 

[MeanGene1]

oil pressure is 40 psi and drops very little with increase in temp but does flutter slightly when warm at idle . thanks for rep[ly

A lot of folks do not know that most modern pressure guages are "dampened" because of that, to smooth out the spikes. Many N guages will normally dance like Tina Turner at idle. The guage on my '50 with 1100 original hours will pulse regularly at idle, and smooth out with RPM increase

 

[boler76]

How much of a gap will loctite take up if putting sleeves in an oversized bore? also is there a tool that can be used with an electric drill to hone a bore to accept sleeves? Thanks

 

[TheOldHokie]

How much of a gap will loctite take up if putting sleeves in an oversized bore? also is there a tool that can be used with an electric drill to hone a bore to accept sleeves? Thanks

Dont even try. Have it bored for standard .090 sleeves. It will be back to stock and good to go for the future.

TOH

 

[boler76]

Without remeasuring I think I recall that the bore ID is worn bigger than the 90 sleeve OD, but why not a piston slap when cold , but as temp rises noise increases, could expansion cause wrist pin to tighten up causing more slap?

 

[TheOldHokie]

Without remeasuring I think I recall that the bore ID is worn bigger than the 90 sleeve OD, but why not a piston slap when cold , but as temp rises noise increases, could expansion cause wrist pin to tighten up causing more slap?

That would be huge. There is barely enough meat for a stock .090 sleeve = 3.367. The piston in bore bodge was typically 3.267.

TOH

 

[DanielW]

I'd be following Duner's advice and narrowing it down with a stethoscope before diving into anything. Does it make the noise regardless of the clutch being engaged/disengaged? Possibly coming from the starter area? There are a lot of ways an N can make some similar noises that won't require you to tear into it.

 

[boler76]

Cylinder head gasket installed same thickness as old removed gasket?

well that appears to maybe the problem as when I took head off again just now, there is very small shiny spot on top of one piston, should I remove material from piston or from the head is my next question. thanks for all the advice

 

[Duner Wi]

If you use same brand and thickness of head gasket I would take .032 thousands from head. in and around the bright spot. Leave piston alone is my advice.

 

[DanielW]

I'd be very curious to see a picture of that. Not sure what you have for oversized pistons - a few options were used when the liners were pulled. Is the domed top crowned that much?