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leegrady · 03-09-2010, 05:51 PM

Compression

Spark at the right time

Fuel

With these you are well on your way.

My two cents is: the base timing is off, and possibly no or low compression in one or more cylinders.

Set #1 at tdc of the compression stroke. Crank the engine over with #1 spark plug out, and your finger over the hole, and stop cranking when you feel air being push out. Now your in the ball park turn the crank manually until the mark on the harmonic balancer points right at zero ("0") degrees on the scale. (Remember that the crankshaft to camshaft ratio is: 2:1, so that mark will also point at the scale 180 opposite the compression stroke.) So, again, #1 at tdc compression stroke, both intake and exhaust valves closed, and next be sure the rotor in the distributor is pointed at #1 spark plug wire. If I'm not mistaken that distributor shaft will only go two ways: correct, and 180 degrees off. You don't need to remove the timing cover to know the sprockets are installed correctly.

If I found a no, or low compression cylinder I'd perform a cylinder leak down test to determine if the lack of compression is caused by an intake valve not seating properly, or an exhaust valve not seating, or if the rings are not holding. You simply pump (low psi) compressed air into the cylinder by way of the spark plug hole, and listen for the tall tale hiss of air. Listen down the carb for intake, yep, the exhaust pipe for, you guess it, an exhaust valve that is not closed when it should be, and finally remove the oil filler cap on the valve cover and hear what you've been missing. A hiss here says: rings. Oh, yeah, this must be done with all the valves on the cylinder you're testing be on the flat of the cam, (closed) compression stroke of that cylinder.

I hope compression is not your problem. I want to write too not to be confused by ole wife's tales. Your problem will be obvious once you find it. On a personal note: that ole big block will at least run rough even if there is oil, wd-40, low octane gas, moose piss and beer contamination in the cylinders. Cold weather be damned. I get in my truck 81 GMC K2500 on some mornings up here in 25 degrees below zero, not wind chill factor, and it fires right up no problem. Sep' my coffee turns to slush before I open the door.
No, your problem is there, and you'll probably go, "of course!".

03-09-2010, 05:51 PM	#83
leegrady Registered User Join Date: Mar 2010 Location: Lyle, MN Posts: 60	Re: New engine, won't run! Compression Spark at the right time Fuel With these you are well on your way. My two cents is: the base timing is off, and possibly no or low compression in one or more cylinders. Set #1 at tdc of the compression stroke. Crank the engine over with #1 spark plug out, and your finger over the hole, and stop cranking when you feel air being push out. Now your in the ball park turn the crank manually until the mark on the harmonic balancer points right at zero ("0") degrees on the scale. (Remember that the crankshaft to camshaft ratio is: 2:1, so that mark will also point at the scale 180 opposite the compression stroke.) So, again, #1 at tdc compression stroke, both intake and exhaust valves closed, and next be sure the rotor in the distributor is pointed at #1 spark plug wire. If I'm not mistaken that distributor shaft will only go two ways: correct, and 180 degrees off. You don't need to remove the timing cover to know the sprockets are installed correctly. If I found a no, or low compression cylinder I'd perform a cylinder leak down test to determine if the lack of compression is caused by an intake valve not seating properly, or an exhaust valve not seating, or if the rings are not holding. You simply pump (low psi) compressed air into the cylinder by way of the spark plug hole, and listen for the tall tale hiss of air. Listen down the carb for intake, yep, the exhaust pipe for, you guess it, an exhaust valve that is not closed when it should be, and finally remove the oil filler cap on the valve cover and hear what you've been missing. A hiss here says: rings. Oh, yeah, this must be done with all the valves on the cylinder you're testing be on the flat of the cam, (closed) compression stroke of that cylinder. I hope compression is not your problem. I want to write too not to be confused by ole wife's tales. Your problem will be obvious once you find it. On a personal note: that ole big block will at least run rough even if there is oil, wd-40, low octane gas, moose piss and beer contamination in the cylinders. Cold weather be damned. I get in my truck 81 GMC K2500 on some mornings up here in 25 degrees below zero, not wind chill factor, and it fires right up no problem. Sep' my coffee turns to slush before I open the door. No, your problem is there, and you'll probably go, "of course!". Last edited by leegrady; 03-09-2010 at 08:26 PM.