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Dont take too much notice of people who tell you they did the valves on a Rover V8 for unleaded as this is a total nonsense.
All Rover V8s of that era had alloy heads with valve seat inserts that were more than capable of dealing with unleaded and LPG
Camshafts wear out pretty quickly on these things but I would doubt if all 8 were completely absent of compression lets face it they were not a high compression engine right from the start.
One of my first thoughts when I witnessed the motor turning over freely on the starter was that it is normal due the low compression (8.13:1 ?) of the motor from factory.
If the lifters were gone that would stop valves opening.Quote:
Originally Posted by bee utey
That directly would have no effect on compression. Unless a valve was stuck open. Buggered lifters wont do that.
It would if the inlet valves weren't opening, in the same way as a closed throttle does.Quote:
Originally Posted by DAMINK
That sounds reasonable. My crappy old ute's 3.5 spins over like crazy on a fully charged N70Z with a late D1 Bosch starter fitted, despite it being a 9.35:1 car motor. Perhaps it's just something simple like a failed ignition module or a burnt out rotor button.Quote:
Originally Posted by pop058
Interesting. I would have thought compression would remain if valves stuck or no cam etc.Quote:
Originally Posted by bee utey
Each stroke comp going up and down. Perhaps pushing the comp past the rings out of force and perhaps even drawing air in past the rings from the crankcase.
My understanding is compression is a fixed number. No relationship to throttle position.
Theoretical Compression Ratio is a fixed number (unless you bend the con rods). Actual cylinder cranking pressure as measured by a compression tester is a variable depending on lots of factors, cam timing, wear, cranking speed, throttle opening, temperature, altitude etc. The spark doesn't fire anything unless conditions are right.Quote:
Originally Posted by DAMINK
Pulls the plugs and perform compression test.start with the basics.
Agree totally man. Not trying to argue the point. Just trying to give the best advice to the problem at hand.Quote:
Originally Posted by bee utey
Generally speaking compression is a fixed number. So if he has lost all cylinders (which i suspect he has not!) then its something other than cam, valves etc one can surmise.
Again i am taking the OP on face value here and trying to discuss the compression specific issues. The OP stated the previous owner just parked the car and that was it. No mention of bending rods or dramatic stuff like that.
Thats why i started with the obvious. Do a comp test. Wet and Dry. Might bring up some interesting numbers. Perhaps a couple cylinders are dead or none. But its paramount to start there.
Even before checking oil. As no oil pressure could dry out the rings and perhaps lower the comp? Unlikely but gotta be checked at this point.
The wet dry comp test will possibly identify valve/cam issues also or atleast give a direction to look in if a couple of cylinders show bad numbers.
If you believe it to be a compression issue there is no substitute foe a proper compression test. However, pull one plug and stick your thumb over the plug hole and give it a crank.. Disable the ignition first, of course... I'm with bee utey. My 3.5 always sounded like it had zip in the comp department, but it ran just fine.
Quote:
Originally Posted by pop058
Quote:
Originally Posted by bee utey
I am away for the weekend so I will do some basic checks next week. This may turn out simpler than expected. [thumbsupbig]Quote:
Originally Posted by johntins