Honing marks V12

[doffo25]

Im trying to assess the condition of my engine without removing the head.

The car was driven into a Michigan garage in 1982 with 56K on the clock and not driven much since.

Are these boroscope pics what you would expect for 56K or has block been remachined?

What do you make of the brown splodges on cylinder wall?

Finally Im still trying to establish what compression test pressure expected on 7.8:1 engine? (Im getting around 105psi)

thanks

David

[angelw]

Hello David,
105 psi is low, it should be up around 160 psi for a low miles, low compression engine.

A compression test doesn't tell you much as to what is causing the low compression. You should carry out a Leak Back test, which will show whether it's the rings, valves, or blown head gasket that is the issue. Further, you can conduct this test without having to turn, I suspect is, a relatively poorly lubricated engine over a copious number of times.

Regards,

Bill

[abowie]

Caveat: I have no hands on experience with the V12 engine and Bill knows a lot more than me.

But. Assuming that compression pressure is relative and not absolute, then pressures should be 7.8 x 14.9 psi = 116psi. Now it will be higher with heat, and adiabatic heating will happen with compression, but I'd have thought that the figure would be less than 160psi.

And if you redid the compression with the engine hot and everything lubricated I reckon you'll get higher compression numbers.

Otherwise, the brown splodges might be surface corrosion, and I would have thought that you'd still see honing marks at 56K.

[doffo25]

Thank you both for your replies.

Bill why do you suspect the engine is poorly lubricated....because it appears so from the pic?

David

[angelw]

David Wrote:

Bill why do you suspect the engine is poorly lubricated....because it appears so from the pic?

Hello David,
Because its been sitting for 42 years, and just about every trace of oil will have drained away.

For any new engine builds I do and for any cars we have in the shop where the engines have sat for a considerable time, I have a pre start lubricating system that pumps oil around and up to normal oil pressure before the crank is rotated.

Given the orientation of your picture, the cross hatching of the cylinders look OK.

Regards,

Bill

[abowie]

What Bill's saying is that you need to make sure everything's oiled before you start it.

I'm familiar with pressurising the oil galleries on 6 cylinder engines prior to starting, but I don't know how to do this with the V12.

Additionally you'd squirt some of your favorite lubricant into the plug holes and hand rotate the engine so that the rings aren't dry.

Probably the critical area is lubrication of the cam lobes; you could take off the rocker covers and slather it all with start up lube, or you could just rely on your pressurising.

Once you've got it all lubed to your satisfaction, then you start it up.

[doffo25]

Thank you for your advice Bill and Andrew. noted andvery much appreciated.

Ive bought a leak down tester and will perform that over the weekend.....

kind regards

David