Rubbing/Thumping/Dragging From Engine When Cranking?

Hey Guys,

I tried using the search to find previous threads that dealt with this but came up empty, so here goes:

I've got a 62' Biscayne 2-door I have just about got running again. I got it as a roller, and I've put an O/T 79' 350 in it with a BW Super T-10. The 350 was acquired off craigslist as a complete, fresh rebuild. After getting all the electric hooked up, I tried turning her over to see if everything was on the right track. It turns over just like it should, but I noticed that when it cranks, there is a rubbing sound/vibration I can feel in the cab. It's about 1/2 speed of the sound of the starter cranking. Needless to say, this has me quite concerned. It's my first attempt at something like this, so I'm turning to you guys for some ideas/help. I promise to be way calmer than 56PontiacPiano was. Here are some specifics on the situation:

-1979 350ci. 4 bolt main. It was assembled except for oil pan/intake, which were removed at time of purchase so I could turn over by hand and check out all the inner components. Turned free as a bird.
-Put the oil pan back on, filled it up with oil, then pre-oiled it
-Shortly after pre-oiling, I accidentally dumped it off a make-shift stand I had it on while installing the flywheel. It cracked the valve covers but otherwise it seemed ok. Turned over by hand just fine after that, no rubbing, no interferences. It was upside down for about 5 minutes before i got it righted. 2 of those minutes were me just staring at it, in shock. Fast forward about 6 months, I am now experiencing that rubbing/thumping when cranking.
-Engine has 5 quarts of oil in it, plus whatever is in the filter.
-Car is always in neutral when cranking
-I noted that after a handful of times cranking, I saw no oil in the tube that leads to my mechanical oil pressure gauge. Tube enters engine just above oil filter on drivers side (removed pipe plug).
-At the moment, car has open headers


That's about all I can think of. I am leery of trying to fire it up for real at this point (I have everything connected and fuel in the tank, just none in the carb). Any ideas? I will provide as much info as necessary. If something needs to be checked out on the car, I'll investigate when I get home from work.


Thanks everyone,

Mark

 

Check the accessories hooked up to it (alternator, etc) see if that's the source of your noise.

 

I'll investigate that for sure. I have not turned it over by hand since putting on the alternator (new) and fuel pump (new), so possibly one of those is the culprit. Also, I had to shim the water pump and crank pulleys because the water pump pulley was hitting the pump housing. I will check that with someone else cranking. It's hard to pinpoint while sitting in the driver's seat.

 

You mentioned the new fuel pump... is it installed correctly? On SBC's, you can use too long of a bolt on the alternator mount boss and potentially bind the fuel pump pushrod. Check that too!

 

Bell housing inspection plate?

 

check the timing

 

Cracked a valve cover. Did you replace it and put it on upside down?

Maybe dipstick is hitting crank?

 

You using a long shaft pulley set on a short water pump?

 

Flywheel hitting something???

 

check for metal filings in the inspection hole for the clutch . flywheel can be rubbing on the bellhouse . it will grind a slot with just the starter motor . when you dumped it did you check to make sure the flywheel was still straight with the back of the block ?? you can also bend the crank flange if the flywheel hit the ground

 

Make sure the right size bolts are in the front motor mount holes. These are the holes below the water pump, on either side of the balancer pully. On the fuel pump side as stated above you can use a long one to hold the rod up. If one too long os in there it will rub the fuel pump rod and give you odd noises like that. Drives off cam, half speed of crank.

 

Yes that's what I was trying to say.

 

Thanks for all the suggestions, guys. I have several items to investigate. I'm running a scattershield and blockplate instead of a standard bellhousing and inspection cover, but there is another starter hole on the driver's side I can peer into and check the teeth of the flywheel for marks. I am hoping this isn't it. I'll back out the plugs and have someone turn the motor by hand so I can listen in there too. I turned the motor over myself by hand several times after I had the flywheel/clutch/trans bolted up and never heard or felt any drag. I have not turned it over by hand since I installed the fuel pump, so that brings me to the second area of inspection. I am using the hole at the fuel pump rod in the front of the block for my neg bat cable, and I believe I put a 1" bolt in. I'll double check it. Also, I can't remember but I MAY have used a wrench to tighten a bolt against the fuel pump push rod during installation. I understand this could have bent it. I'll check this too. Oh, and the water pump pulley is stamped "SWP" on the inside. Since I'm in Chicago, I may not get out into my unheated, uninsulated garage tonight. I will update as soon as I have some more info. Thanks again, guys.

 

See if there are any dents in the oil pan, especially up towards the front of the engine. The crank runs pretty close the pan in that area and it doesn't take much a dent for the crank to hit it.

 

Pull the plugs and use a long breaker bar on the crank and turn the motor over. Listen for the area the noise is coming from then and maybe you'll even fell some resistance turning the motor.

 

I would also suggest putting some mufflers on the car before starting. Its hard to hear noises from a fresh engine when the exhaust is loud. You also said you had no oil travelling up your oil pressure line. I think it would be a good idea to preoil the engine before starting. You'll have to pull the distributor back out but its well worth the effort. Good luck.

 

While on the topic of prelubing, use one of these:

http://www.summitracing.com/parts/sum-901010/overview/

I like to use the ones with a bushing, so it'll pressurize the oil galleys.

 

Loose starter?

 

Well guys, here is an update. I bared the cold tonight and got some more info:

Oil pan is dent free. I peered into the 2nd starter hole on the drivers side and the flywheel looks just fine. I ran my finger over the teeth, felt no issues. No metal filings on my finger either. Ran a magnet along the flywheel teeth and again, no metal filings. I took a photo:


After that, I pulled all the plugs and turned the engine over by hand several times. Couldn't feel or hear anything other than the typical wet "whoosh" sound (if that makes sense). I pulled the inlet hose from the fuel pump and it was dry. Pulled off the fuel pump and inspected the push rod. It didn't appear damaged and moved freely. I have a 3/4" bolt in the access hole on the front of the block with a few washers stacked to make it even shorter. Push rod moved fine with bolt installed.

Oh, some good news. When I put the light by the flywheel, I noticed oil in the tube that leads to my mech oil pressure gauge. I had pre-oiled the engine about 6 months ago.

So now I'm really stumped.


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did you feed the little gremlin in the oil pan ??? maybe hes wants a burger ... LOl

for the oil line loosen the nut on the gauge end( not all the way off ) and pull the hose back a little to pop it off the seat then wrap it in a rag and crank the motor over with the coil unplugged and bleed the air out of it then tighten it back up it will give you a truer reading on the gauge , oil cannot compress but air does . and the gauge will read low .

when you inspected the flywheel did you rotate it one full rotation to make sure its not wobbling ???
also when cranking is the clutch pedal in or out ?? if its pushed in , try it with it out , also is the trans filled ?

 

have you looked at the oil pump drive shaft to dist, if the motor overturned it could have fell off oil pump.

 

Did all your accessories check out ok?

 

I had some simular sounding noises and it turned out to be the sheet metal flexplate cover rubbing on the crank flange. one of the sides of the 'U' shaped area was distorted.

 

mentioned you used spacers on the WP pulley...
could the bolts be too long and rubbing on the pump housing?

 

remove the fan belt, remove the fuel pump, remove the scattershield and the blockplate, reinstall the flywheel. Crank it over, still have noise? it's internal. no noise? start replacing parts, (i'd start with the fan belt), 'till you hear the noise again. If it's internal, all the cranking in the world ain't gonna hurt it any more than it allready is.......

 

Accessories checked out. Pulled the fuel pump, plate, and rod and removed the belt. Now after doing all this, I jumped back in the car and hit the ignition to test....without putting the spark plugs back in. No noise. Forgive this totally asinine question, but the motor still spins as normal, just no compression.... Right? If this were an internal parts issue or an issue with the flywheel, wouldn't I hear it ANY time the engine spins?! I put the plugs back in tried again. It's back. So now I'm down to timing or it's just a normal sound of an engine with compression turning over through open headers that I'm blowing out of proportion. Feeling slightly dumb at the moment!

So tomorrow I'll pull the distributor again, reset engine at TDC and reinstall to verify timing.


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Also, I tried taking a video to capture the sound and it's inaudible. So low you can't hear it over the starter.




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plugs back in, noise returns = rocker arm/s clearance too tight or intake manifold gasket leak or wrong sparkplugs and compression leaking past the plug.
Next thing I'd do? A compression check. Pull ALL the plugs and check each cylinder one at a time. If all PSI numbers are even, then it's a leak in the intake manifold or you worry too much. That's all I've got.......
timing should not make a noise, especially if the motor ain't running.

 

^ If your compression test checks out ok, maybe go ahead and fire it up after checking the rocker/lash adjustment. If it runs, set the static timing and hook up a vacuum gauge to see what it tells you.

Compression test and vacuum gauge readings will tell you so much about an engine.