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Discussion Starter · #1 ·
hello all

i am working on a project truck for many years now. A 1951 gmc 1/2 ton with newer chev running gear. Question is... the 305 in it has not been started in over 5 years. i am sure if i put a wrench to it and alot of muscle, i could turn it over by hand. have heard lots of opinions about how to "loosen" up the engine and try starting it. I would prefer to pull the motor, replace the main and rod bearings, put in a new cam/lifters, lube it up and button it up. is this a waste of effort? Would putting in a new cam with old bearings be a disaster? this is only a temp motor (maybe run for 2 years) until my budget can buy me a crate motor.

has anyone else tried to revive a near retired motor like this? any suggestions?

thanks
 

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for a temp motor, much less a 305 I wouldn't fuss over it too much. You're going to have smoke from valve seals that are more than likely gone, or cracked up pretty bad. Take all the plugs out and shoot some foging oil in each hole and let it soak in for a day or two. Then give it another small squirt before you go to start it up. You might consider putting some fresh oil in it and priming the oil back through the system. Bearings will likely be uneffected. Your biggest concern is rings that are sticky or wedged in a strange position.

After that, put the plugs back in and fire it off. Note, however, not to put too aweful much fogging oil in the bores right before you start it, you don't want to get hydro lock on the thing.

K
 

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agee with killer,

making sure the brittle (iron?) rings aren't rusted frozen to the iron block is the most important.

sounds like the motor is out of the car, tilt it so the cylinders are vertical, rig a hose on a can of PB Blaster, soak the cylinders, wait 24 hours. Pour about 3-4 oz of ATF in each, wait 20 minutes.

Just before you try to crank it for the first time with the plugs out, pour about 4-6 oz of ATF down the carb to lube the valves.

Next most important thing is PROTECT YOUR RADIATOR, there is going to be a ton of scale coming out of the block. rig a junk radiator or buy one of the screen filters ($40)

Starting a "junk yard dog" I use 5W20 and a can of Mystery oil. Gona smoke like a mosquito fogger but cleans and protects for start up.

Got a oil pressure guage, kill the ignition and repeatedly crank the starter till pressure builds 3 times with the plugs out.

Give it fresh gas out of your mower can to the pump, crank it up and laugh your butt off with all the smoke for 5 minutes...then change the oil again....

test the mains first: power brake to 2k, note oil pressure, 2k in neutral, compare pressure, close=good enough for now, 30psi at 3k=pump is good enough for now for street driving
 

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If it were mine, I would run some seafoam in each cylinder, let it soak a day or so then follow with oil. Next I`d reprime the system with fresh oil and filter. After starting, cycle the engine as if it were a new one, 1800 - 2200 rpms for about 20 minutes, this assures the cam will get plenty of lube, as I`ve seen many engines be restarted after years of sitting and it wipe the cam out, also be sure you watch the oil pressure and water tempature. As killer stated, the valve seals will likely be shot. The valve springs on whichever valves were open during the engines sleep will likely be tired and need replacing also, so you may want to keep a ear out for broken valve springs after start up.
 

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While you have the plugs out,look in each plug hole with a flash light to determine if it is even worth it.I f you have any cylinder walls covered with rust,you should be able to see the extent of it,then back away.If it is in the vehicle,get a mirror and get it to where you can see in there.You will not want all the scales in your rings or walls.Keep an eye for any leaks,fuel system,particularly the carb bowl gaskets can dry up in that amount of time.If there is fuel in it I would get rid of it,5 years can collect alot of condensation,making the engine run like poo.
 

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If I was going to replace it anyway I wouldnt waste too much time on a rebuild. The last time I broke a setting motor free here is what I did. It was a straight 6 in a old dodge van. Pulled the plugs and shot a large amount of liquid wrench into each cylinder. Left the plugs out and hooked 2 battery's in series giving 24 volts. Hit the starter. The motor turned maybe 1/4 inch. Used a wrench on the crank to turn it back and hit it again. Kept doing this until I finally got it to turn all the way around. Then Changed the oil reinstalled the plugs and hooked the battery back to origional configuration. Started it up. I was doing this with my father inlaw. It was his and he was doing the directing on what to do. He drove that van for 6 or 7 years before he junked it. I dont think it used much oil at all. I would have never thought it could be much good but he is real cheap and makes something from nothing. Most will say it wont work and might not in your case but it did here.
 

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personally I'd just buy a 305 off of someone thats in running condition. they are VERY common Chevy motors and aren't hard to get out of a junkyard or off of someone. I think it would save alot of time and work then playing around with this one and then finding out it's beyond help. and really any 305 would work..just make sure if it's computer controlled you find the computer. good luck to you!
~wes
 

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Discussion Starter · #9 ·
thank very much for all your advice! What is mystery oil and where can i find it?

the motor is still in the truck. There has been without water in it for the 5 years. the front end is off as i am doing all the body work as well. I need to pull it anyways as the seals on the tranny need replacing and it would be easier to get the tranny out that way. It makes sense i think to pull the heads at least and replace the valve seals. I just don't want to open up a can of worms - so to speak. The motor was ok before i started taking the truck apart, a little weak in the HP department though.

I was thinking it would be much easier to buy a running 350, but don't want to waste money if i can help it. I hear it actually costs more to rebuild an engine (as machining prices are getting higher) than buying a crate motor from Chev.

This forum is awesome. Nothing beats real experience from guys instead of theory.

Thanks
 

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Marvel makes it.It is actually called Mystery Oil. I get mine at a tool store here.But you can probably get it at a local owned hardware store.Do not know if the large chains carry it.
 

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fezz man

It's Marvel brand Mystery Oil, been around forever, most parts houses have it but any "frees sticking lifters" fix in a can will do. Basically they all just thin the oil more and disolve varnish.

"Ouch", no anti freeze in the block can be more scale because there was more exposed iron and "some" water in it. Do use a temporary junkyard radiator or the filter for ? 2,000 miles.

Motor is in the truck is ok, skip the adding ATF to the cylinders step, do pour some ATF down the carb. Reason for ATF is it is very thin oil, like a 2W (not sure) so it gets between tight corrosion spaces when you crank it first time.

I wouldn't pull the heads till I had run it awhile, and then tested the compression. Start it and drive it first.
 

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jimfulco, fezz- man

Jimfulco, thanks, I wrote, use your lawn mower (new) gas can to start it, forgot to tell him to buy 3' of gas hose when he buys the Marvel or Wynn's or store brand "frees sticking lifters" fix in a can

Fezz man, you have scale in the gas tank also. Add another $4 gas filter before the pump or at the tank when you hook up the gas line. Cheap insurance.

As you pour the Mystery oil into the crankcase, say a little prayer like your doing a batism, cause the main reason for using it with the thin oil is to free and clean the tight tolerances in the lifters....please lord, free all 16 and don't leave just one stuck......

(I've gotta look for "sea foam" never heard of that one, if it's marine grade, oughta be better)
 
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