WILL A BLOWN HEAD GASKET KEEP MY 91 SATURN DOHC FROM STARTING?

Yes it sure will prevent start

If there's antifreeze in the cylinders there should be some sludge on the oil dip stick also, the sludge is a mixture of oil and antifreeze

NO SLUDGE ON DIP STICK.OILIS CLEAN.

Well your HG can still be screwed and not result in turning the oil into a chocolate milkshake. Sounds like its leaking exhaust gases into the coolant, obviously. But as long as there's not standing water in the cylinders, it should turn over and run. Sounds like you've got a different problem other than the blown HG preventing the car from running.

If compression is blowing into the cooling system, for sure there is a break between the 2 systems. most likely causes, either a blown head gasket or cracked head. THE SHORT ANSWER Get it out of your head that somehow you can milk a little more use out of a horse with a spear thru his side. It may be fixable now but every minute of just trying to see if it will run a little longer is just going to damage engine internals further and make the repair bill taller. Just driving it a little ways to the garage to save the tow bill just cost you $4000. THE LONG ANSWER If you must know for yourself WHY: You know you have a break in the coolant envelope because cylinder/combustion pressure is erupting into the coolant tank. Coolant is going to get into the oil thru that break. If you are lucky, not a lot has gotten into the oil. If you can get it started, don't start thinking you are lucky of clever, a smart me accomplishment. It means you are diluting your oil with WATER as the engine runs. aggggg!!! Engines require pressurized clean oil to keep from digesting themselves into a pile of scrap. If you dilute you oil with water, you lose the protective lubricating film. Now every minute you run you engine, you have metal on metal rubbing with great pressure. That is bad, bad, bad. Count UP by hundreds as the engine is running. In 20 seconds that is $2000, 30 seconds $3000. to repair the damage you are doing. Got the picture? Maybe you have a cracked head, maybe a blown head gasket. Pull the spark plugs and check for coolant blowing out of the plug holes. Do a compression check while the plugs are out see what cylinder is having a problem. But for sure, it will require a cylinder head removal. Cost you ask? Call around to at least 5 garages and get an estimate to replace a blown head gasket and option 2 to replace cracked head. Way over $1000, possibly $3000 or more depending on what your mechanic finds and how long you have been running it with coolant in the oil. No matter what your mechanic finds, have them drop the oil pan and check for coolant in the oil. Don't just drain the oil and hope for the best. Drop the pan. If there is no coolant in the pan, that is good, or the least of the bad. Maybe just a head gasket or cracked head. If you have water in the oil pan, you have been pumping water where oil should be going, your engine may already be scrap. Then you are going to price out a used engine from a wreck and cost to R&R the engine instead of just a new cylinder head or gasket.