Valve adjustment and compression. Would like opinion or comments

Barry when I check compression I always have the throttle at full wide open. Try squirting some oil in the cylinder that reads low and check the compression again and see if the compression increases, if it does then the rings is probably just stuck in a collapse position and usually loosens up after driving it for a while or other possibility is that the valves are not seating properly, just a thought. 70k miles is really not high, ive seen 308 with double that mileage and ran like a top.

 

Mike, no way that a cast iron slider or an original Borgo piston can last 140 K miles with still a good compression ratio: carburated cars had them as OEM equipment and so at that mileage they are gone since a lot of time. It depends about the usage, of course, but the average cast iron slider with OEM Borgo pistons durability is around 70-80 K miles. I mean when the play between the slider and the piston will go over the maximum play allowed: the engine still works, of course, but the compression ratio starts going down quickly and the oil consumption starts going up quickly too.

But you are 100% correct if you are talking about QV and 328 only, as they have OEM Nickasil coated sliders and Mahle pistons: they can last 140-150K miles, not as new, but without losing too much compression.

So, in my opinion: if you have a carbed car with 70+K miles and you have some compression ratio issue, very likely a lot of the loss comes from valve seats and guides, but some comes from the sliders and pistons too.

ciao

 

Just reset the clearances as they have only decreased by .05 to . 1 in 45 k miles. That is 2 to 4 thou. Valve clearance can drop as the valve impacts into the seat. In regard to the one compression being a little down, give the car an oil change and a few hundred miles of speed running and see if it evens out. You may just have gummed rings and the new oil can help to free them up.
I have seen a ferry engine get sea water in the sump oil and jam the rings, after changing the water pump to stop the water ingress we changed the sump oil and ran the engine at low power for a few hours, did this for a few days changing oil every day and increasing power until we had it back at 5000 horsepower. The new oil every day cleaned out the gunge from the ring packs

 

Hold a very high-powered pocket magnet next to the socket/fastener while turning the tool; do it slowly and the magnet will catch them.

 

Ok, I give, what are "sliders?"

Lester

 

He means (cylinder) "liners".

 

Got it. I kinda figured cylinders just couldn't navigate my brain to sliders.
Thanks,

Lester

 

The exhaust valve will expand its length due to the exhaust temp, hence it has a bigger clearance. The inlet valve runs a lot cooler due to the inlet charge keeping it cooled.
First time i have heard a liner called a slider

 

Are you running 5/40oil ? Re the noise when hot

 

Depends on the adhesive material. If it's silicone, it's just a lot of manual cleaning. Personally, I'm a fan of plastic scrapers.

 

Is it the first time you've read an Italian writing in English and not getting the translation perfect? How's your Italian? Perhaps we should be cutting Alberto a bit of slack.

 

Liners, sorry: the cylinder walls where the piston goes up and down.
My fault.

Ciao

 

Some calls it sleeve cylinder

 

I had a go learning Italian but have to admit it got the better of me.

 

Ferrari calls them "barrels" in the 308 QV spare parts catalogue and "liners" in the 308 GTB spare part catalogue. In Italian they are called "camicie" (shirts) by mechanics and "canne" by technicians

 

I guess different countries and different mechanics have different terms but here in the US it’s know as cylinder sleeves but I guess they are all the same thing.
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Yea I think in the States “sliders” are little hamburgers. It could get confusing lol.