So I rebuilt a 305 myself, replaced all the internals with new including a new comp cams camshaft, put it in the car and started it up. First off the distributor was 180 off, and after that it fired up. However getting the RPMs up to 2500 for the new cam was a struggle. It fought with me getting up there and didn't want to stay there, it was running very rough. So I shut it down, played with timing and stuff, and tried again. It fired up and still fought me. So I shut it down again and after the engine wound down a bit it suddenly stopped. Now it won’t even crank. So I was able to back it off manually at the flywheel, and was very smooth. So I backed it up a complete rotation and went to crank it again. It stopped at the exact same place as before. So I pulled all the pushrods and they were all straight. So tried cranking with the rockers off to relieve any pressure from the pushrods. It still stopped. So I am at a loss as to what it could be. Any help would be much appreciated.

 

so wait, you cranked without pushrods so the valves wouldnt open and spark plugs in?

 

Can you turn it over through full rotations by hand? You had the preload on the lifters set correctly?

 

Just from reading the first post, I wouldn't even recommend a simple fix. It sounds like you have an internal problem. If you pull all the pushrods, you should remove all the spark plugs also then bar the engine over by hand. You shouldn't crank the engine over with the pushrods out. The cam will push the lifters out of the lifter bores if it cranks fast enough.

Exactly what did you do when you say "replaced all the internals with new"?

How big is the camshaft?

 

Ok, so I had the spark plugs out, took the rocker arms off to see if pressure on the pushrods would release the bind inside the engine. It didn’t so I figure it is something internal. No I cannot get a full rotation either direction no matter what I do. I originally thought the preload was too tight, which would explain the rough running and a bent pushrod as a result of that might explain the seized single location. But all the pushrods came out and were straight.

I replaced all crankshaft bearings, ground the crank, and had the cylinders bored with new pistons, rings, and original connecting rods. The heads were cleaned and inspected, as well as the intake manifold. The camshaft is a comp cams 08-500-8 which is just above the stock cam.

I really don’t know what would cause the engine to stop like that, unless I am making contact with a piston and valve or something. Like I said it ran, and all the clearances checked out.

 

ive seen this happen and the problem was the main bearings were installed wrong. locking it up tight.

 

The safest thing to do it strip her back down and find the root cause of the problem. You want to visually verify that the engine is fit to run or risk more damage. When you said that you fought to get it to 2500 RPM do you mean you held it WOT to get it there? Fuel injection or carb? Hopefully you were not running excessively lean as the heat generated could of wrecked havoc to your new parts. Did you prime oil system and check for pressure and flow before initial start up? Try removing pan and taking a peek from the bottom?

 

Did the machine shop check that the mains were all perfectly straight? Did you crank the motor over seveal times by hand before putting it in? When I built mine I would turn the motor over a few times after putting any new part in. Also with the rockers off make sure that all the valves are all the way up and perfectly even. Check for broken valve springs that may have let a valve drop down.

 

When I was fighting it, it seemed like I had to almost do WOT, injection is throttle body. I primed the oil system right before I put it in, and with the drill I had I got adequate oil pressure, around 30 to 40 psi.

I installed everything myself except cam journals and water plugs. Main bearings were all installed correctly, with break-in lube. Everything was torqued properly and double checked

The entire valve train is new, new guides, springs, the works.

One of these days I’m going to tear into the intake manifold, then the heads, then to the oil pan if necessary. Just start from ground zero.

 

The last run
http://www.youtube.com/watch?v=fhSwHW-qp0s

Before reversing the crank
http://www.youtube.com/watch?v=b1vBNKX85OY

After reversing the crank
http://www.youtube.com/watch?v=TvCJmhqJCEI

 

sounds to me shes locked up tight! pull her back and and tear it down. That is the easiest thing to do, doesnt sound easy now, but by the time you play around checking this and that, and taking stuff apart adn back together, it will be easier to pull it out and check everything over. just my

 

Pully the dizzy and try to turn... take off the timing chain and try to turn when then doesn't work... and when that doesn't work.. pull the pan if you would like and have a buddy give it a turn. Won't do any good though cause the motor will still need to come out unless you just want to do it half-@$$ed.

 

Also, bear in mind that some kind of serious internal transmission failure could also perhaps limit movement ....? not as likely though. BTW what happens if you reverse it GENTLY more than 180 or 360 degrees?

 

I dont have the transmission connected, as i need to replace the synchros. i can reverse the engine almost 360 degrees, but it stops right before the same spot as the other side. I am not looking to take any shortcuts, just looking at ideas on what could be wrong or if anyone else has run into this problem before.

 

I'd guess an object in one of the chambers.

Doesn't really matter though, anything that could cause a problem like that will require the engine to be pulled and torn down.

 

yeah it could be but, if it were an object in the chamber it would probably have an issue at the 180 degree mark aswell (unless it's interacting with the valves)

I dunno, if you want the least hassle and most direct way to solve the mystery.. take off the timing chain and turn the crank (still keep the pushrods disconnected!!!). If it still stops... get the engine hoist... if it turns free, sweet! (kinda)

 

Doesnt matter what it is, the motors coming apart. The only thing that may cause this would be a broken valve spring letting a valve touch the piston. Bottom line though, start taking stuff apart. Time spent here is time you could use finding the problem. I dont think there is anything more anyone here can do till you find out more about the problem.

 

No, it'll have an issue at the same point in the rotation, forwards and backwards.

 

you're correct - sorry it's a bit late here I was thinking in cam degrees... d'oh! someone can smack me now

I'd also have to agree that you should just pull the engine. it really is the only smart option, there is no "easy" fix. or at least no proper/safe one.

 

Pulling the engine is what im doing. Thanks, y'all, appreciate your input.

And the posibility of a valve spring is possible, it sounds like it might be a piston clearance issue. we will see once i tear it apart again.

 

I had a Dodge 545RFE lock-up at 6,000 rpm behind a 4.7 in Ram pickup. SCREECHED to a halt with a heavy bang. Even the dealer diagnosed it as a seized engine. So it CAN and DOES happen.

BUT...He doesn't even have it connected.

That being said I would say if its at a certain point in rotation its an object in the chamber or some other interference.

 

Take off the oil filter and cut it open. If you toasted a bearing, the filter will be full of metal.

 

I didn't read through it all, but did you try cranking with the spark plugs removed? it may have a cracked cylinder and is hydrolocking on that one. Coolant will come out the spark plug if that's your issue.

 

After reviewing my post from over a year ago I realized I left the post open ended. What I later found out to be wrong was a long term series of different problems. The new engine had a lot of stress on it due to the MAP sensor going out (another long story) and caused one of the connecting rod caps to break in half. The connecting rod went through the side of the oil pan and that was what seized it. So I got a cheap running 350 and threw it in. I didn't discover the MAP issue until this last November after replacing all sorts of things. But she is up and running strong and cannot wait till spring to finally get her licensed for the first time.