BBC engine hitting snag while rotating by hand?
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Joined: Mar 2014
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From: bumpy roads NJ
BBC engine hitting snag while rotating by hand?
Hey guys. About 5 mths ago I did a full disassembly and reassembly of my 396 BBC. I put everything back together, adjusted the valves/rockers and bolted everything up. Today I primed the oil pump to get ready to hopefully start the car next week. I put the distributor back in and realized I wanted to check that I was at TDC. I was about 1/8 turn from getting there and the crank won't rotate anymore. Feels like something is hitting. I rotated back the other way and it's good until it gets to about the same point. It comes to a dead stop. What am I missing that could be causing this? Is there a bolt somewhere I could have put in that's too long and causing something to hit? I can't find any, and not sure where else to look. Everything spun fine before so I'm assuming I did something along the way to jam up the rotation.
Any hints would be appreciated!!
Any hints would be appreciated!!
Thread Starter
Pro
Joined: Mar 2014
Posts: 518
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From: bumpy roads NJ
I was trying to see if there may be a place where a bolt has the opportunity to be too long and hit the crank or a lobe or something. It was literally fine during assembly so I'm stumped!
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Pro
Joined: Mar 2014
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From: bumpy roads NJ
Update:: got both side off, it looks like #7 spring is compressed more than the others, and when I turn the engine and it stops, the valve moves up very very slightly, so it looks like that may be the issue -- all of the caps are loose, any advice on how to loosen it all the way (short of removing the whole valve assembly)?
Last edited by Muuhaha; Jul 16, 2022 at 01:35 PM.
Team Owner
Joined: Mar 2002
Posts: 44,603
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From: Huntsville AL
Anyway to listen to where a thunk sound might be coming from when it stops? If no issues when you adjusted the valves, I would focus on everything you did after that step. Too long of a bolt in the pulley installs???????
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Thread Starter
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Joined: Mar 2014
Posts: 518
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From: bumpy roads NJ
Took off the pass side yesterday, didn't see anything crazy. I'll pull the other in a few. Working on putting the rear chrome bumpers on now
Update:: got both side off, it looks like #7 spring is compressed more than the others, and when I turn the engine and it stops, the valve moves up very very slightly, so it looks like that may be the issue -- all of the caps are loose, any advice on how to loosen it all the way (short of removing the whole valve assembly)?
Update:: got both side off, it looks like #7 spring is compressed more than the others, and when I turn the engine and it stops, the valve moves up very very slightly, so it looks like that may be the issue -- all of the caps are loose, any advice on how to loosen it all the way (short of removing the whole valve assembly)?
Derek was right, the valve was stuck. I sprayed a ton of wd40 on it and tapped it lightly with a socket/extension/hammer and it loosened up. I can now rotate everything again !!!
Any advice on what to do next? If I start the car next week or so, should it loosen itself up naturally? I probably should have primed it sooner, sitting for so long probably (obviously) locked everything up. Put everything back together and prime the engine for a few minutes?
Tech Contributor
Joined: Jun 2004
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Derek was right, the valve was stuck. I sprayed a ton of wd40 on it and tapped it lightly with a socket/extension/hammer and it loosened up. I can now rotate everything again !!!
Any advice on what to do next? If I start the car next week or so, should it loosen itself up naturally? I probably should have primed it sooner, sitting for so long probably (obviously) locked everything up. Put everything back together and prime the engine for a few minutes?
Any advice on what to do next? If I start the car next week or so, should it loosen itself up naturally? I probably should have primed it sooner, sitting for so long probably (obviously) locked everything up. Put everything back together and prime the engine for a few minutes?
Looks like Derek's next beer is on you.
Thread Starter
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Joined: Mar 2014
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From: bumpy roads NJ
Definitely haha. After I let it sit for 30min the problem came back, so I'm going to remove the spring/retainers and pray I don't drop the valve into the cylinder!! 😩
Race Director
Joined: Jul 2015
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From: SW Florida.
do this with #7 piston close to but not up against the valve. or lower piston and put a couple feet of 1/4 inch clothesline in the plug hole and jam the rope against the valve. now. smack the valve retainer at about a 45 degree angle. this will unstick the keepers. now compress the spring and remove the keepers and valve spring.take the valve spring off. drop piston down a bit. chuck a drill on the valve stem. spray it with wd or any oil. spin it and work it up and down to sort of ream-polish the stuff off the guide and valve stem to get it good and free. the corrosion crap that stuck the valve is still there. best would be pull both heads and check all 16. but as soon as you do that it snowballs until a sticky valve cost 5k...
Thread Starter
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Joined: Mar 2014
Posts: 518
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From: bumpy roads NJ
do this with #7 piston close to but not up against the valve. or lower piston and put a couple feet of 1/4 inch clothesline in the plug hole and jam the rope against the valve. now. smack the valve retainer at about a 45 degree angle. this will unstick the keepers. now compress the spring and remove the keepers and valve spring.take the valve spring off. drop piston down a bit. chuck a drill on the valve stem. spray it with wd or any oil. spin it and work it up and down to sort of ream-polish the stuff off the guide and valve stem to get it good and free. the corrosion crap that stuck the valve is still there. best would be pull both heads and check all 16. but as soon as you do that it snowballs until a sticky valve cost 5k...
I have a spring compressor, and a spark plug air chuck so hopefully that helps. It may not if the valve isn't seated properly. I bought some clothesline (Amazon) so I'll try that method 1st. If I find TDC on #7 how much should I back it off? 1 whole rotation? Half?
Appreciate the thought!
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
7 is 2 cyls before 1. so it should be as timing mark is 180 degrees from the timing mark. feed in clothesline and turn engine until you feel the rope hit the head. softer, squishier hit than metal to metal. now you know where piston is. just back it off enough to move valve about 1/4 or 3/8 inch.. full lift is around 1/2 inch. maybe a little less than 45 degrees crank rotation.
Burning Brakes
Joined: Aug 2007
Posts: 892
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From: Green Valley Ca
If I didn't do the full rebuild and tried to take a shortcut then I would have been ok pulling the heads, but I literally spent 2-3 mths doing a rebuild and don't want to pull everything haha. It will def lead to a stripped head bolt thread or something 😅.
I have a spring compressor, and a spark plug air chuck so hopefully that helps. It may not if the valve isn't seated properly. I bought some clothesline (Amazon) so I'll try that method 1st. If I find TDC on #7 how much should I back it off? 1 whole rotation? Half?
Appreciate the thought!
I have a spring compressor, and a spark plug air chuck so hopefully that helps. It may not if the valve isn't seated properly. I bought some clothesline (Amazon) so I'll try that method 1st. If I find TDC on #7 how much should I back it off? 1 whole rotation? Half?
Appreciate the thought!
Thread Starter
Pro
Joined: Mar 2014
Posts: 518
Likes: 38
From: bumpy roads NJ
7 is 2 cyls before 1. so it should be as timing mark is 180 degrees from the timing mark. feed in clothesline and turn engine until you feel the rope hit the head. softer, squishier hit than metal to metal. now you know where piston is. just back it off enough to move valve about 1/4 or 3/8 inch.. full lift is around 1/2 inch. maybe a little less than 45 degrees crank rotation.
When I change out the springs on my 350, I had the cord and the air adapt, so I started with #1 I brought it up on tdc and I figured out that the valve wouldn’t fall done into the cylinder. The valve moved down into the cylinder about a half inch before it touched the piston.
You guys are the best! Stuff doesn't get here until Monday so I'll update this on maybe Tuesday. Appreciate it!
Thread Starter
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Joined: Mar 2014
Posts: 518
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From: bumpy roads NJ
Was able to use the rope+drill method to free things up last night... Seems like it's good to go! Highly possible I can actually turn this thing over this weekend for the 1st time!
Appreciate all the help fellas!
Appreciate all the help fellas!