oh no a knock!!!!

[betonj97]

I have been away for a while now and finally made it back home.......started my truck up and I got a solid knock......damn......I will start removing the block within a couple days. I am not looking forward to this because the pocket is not deep enough to handle it at the moment. I thought about just dropping in a 2-300 dollar motor but its not worth it to me.....its gonna have to go to the shop. I am not sure what broke in it because if I accelarate it the knock goes away but yet I can reach down to the crank pulley and move it back and forth about an inch with no resistance....and that is no where near good! I will take pics as I move forward.
Its a 68 vette 327, so a nice bore will do the trick.....hopefully I can keep it under a thousand.

[chevy72blu]

An inch of play in the crank!? Wow. With the crank journals being worn that badly I cant imagine the block can be saved, at least with my somewhat limited knowledge.


Good luck and keep us updated.

[betonj97]

Its really not an up and down play its a turning motion...as if I was turning the motor...Man I hope and can salvage this thing......

[cdowns]

are you sure its not just a bad balancer that needs replaced??

[betonj97]

I pondered the same thought but when i turn the motor by hand i can hear it hit on the bottom end.....before i take it out i am gonna take the pan off just to make sure....but the play is what is making me nervous...its super free play.

[VetteVet]

I had the same thing in my 84 gmc s15 2.8 liter and it turned out to be the crank was broken. The darn thing still ran but made a lot of noise. That was pretty common with those small cranks but I haven't heard of any SBC engines doing it.
I would also pull the pan first and check. I think you should be able to repair it for under a grand if you don't need a lot of machining and if you do your own labor.

[betonj97]

OK so here is the curve ball....I started the truck again and knock knock at idle but when I accelerate it the loud knock goes away!...wtf...I don't get it!

[chevy72blu]

Ive been wondering that also, but it seems to make sense to me that with the increased piston speed and thus increased pressure from the rods on the crank would help to stabilize it centrificaly (sp?). Off the top of my head, but seems to make sense.

[70rs/ss]

I would stop running the motor!! If there is an issue, you are making worse!! Does it have oil pressure? Are there chunks of metal on your drainplug? There is a lot of stuff you can do to diagnose this, but continuing to start it a rev it up is just going to insure that it'll be junk when you do finally pull it apart.

[bhoeger70]

My guess would be main bearings. Knock at idle goes away when you rev it up.

[68C15]

higher engine speed = higher oil pressure and volume

just for sh1ts and grins pull the timing cover. I think you will find your slop is in the chain.

[webbes]

just drop the pan and find out for sure then we will all know the problem

oooooo and take pictures also good luck on the hunt

[truckdude239]

please stop running the motor you will just make it worse good luck witht he hunt

[into69z]

I had a simiular problem with a 350 I built. I had a deep knock and it was due to low oil to the bearings #1 &#2 rods plus the #1 main journel. Only had 300 miles on the motor-after teardown I found that the machine shop forgot to clean the oil passages after machine work( they were paid to do this) so maybe just a set of bearings if the crank checks ok-good luck

[betonj97]

Ok......Had a late night last night so I am starting a little late today but I will be dropping the pan to see where I stand...thanks to all for the input on what it might and might not be.....but for those who keep telling me to keep her shut down...man..I need to move the damn thing into my garage, its not as if I am starting it for fun! Because the fact is something is broken....we determined that with the knock....making it worse can only be interpreted by what your pocket has to offer. But enough about that...I just want to say thanks....pics will be posted by the end of the day

[fleetside]

Get that pan dropped and some pics up. My bet is a broken rod....but what do I know. I just wanna see.

[Jerry Jones]

Good luck.

[arkansas]

Someone else mentioned the harmonic balancer. I have a 400 in an ratty 49 coupe that had something similar going on with. The key in the crank had somehow gotten wallowed out and would let the balancer turn some like you mention. The knock I had wasn't too deep, but was the balancer turning back and forth hammering on the key which had lain over some in the keyway. It might save you from dropping the pan to check that first. On mine I pulled the balancer and timing cover, stood the key up and welded up the wallowed out area. Dressed it with a dremel tool and was up and running again. So far it has held.

[crazy longhorn]

Check the flywheel/flex plate, see if it came loose.....that will make one hell of a rattle crazyL

[DavesRide]

Originally Posted by crazy longhorn

Check the flywheel/flex plate, see if it came loose.....that will make one hell of a rattle crazyL

That would be the first thing I looked at myself. Then on from there.

[68C15]

you say the pan was leaking. it has a one piece gasket from fel-pro but it looks as if the pan flange is wavy between the bolts. I suggest getting the load spreaders to prevent this. they came on all small blocks in the late 80s. try the dealer.
I would also take a micrometer to the front snout of the crankshaft to see if it was damaged. I see the balancer ID is severely worn. also put some blue loc-tite on the balancer bolt and torque it to 85 ft.lbs.

[betonj97]

So here it is.....
http://www.flickr.com/photos/jagpics...7603725070778/
Today is a good day!
Let me just start by thanking you guys especially Cdowns and arkansas..... The least expected is what sometimes turns out to be what it is. I started by the pulling the balancer and sure enough the key was chewed up and so was the inside of the balancer. Thats what the play was that I had....as well as the knock at idle. I took the pan of just for fun....really it was leaking so I thought what they hey and just bring it down. As you can see in the pics the bottom end looks awesome. This is a fresh motor and after today it still remains fresh. What is dumb is that I never replaced the balancer so here it is taking a chunk out of my arse....yeah I said it...arse! LOL
Anyhow....I ran to the store and ordered a new balancer and gasket....I should have the gasket tomorrow and the balancer within two days.
Once again Thanks to all! I really appreciate the ideas

[betonj97]

Originally Posted by 68C15

you say the pan was leaking. it has a one piece gasket from fel-pro but it looks as if the pan flange is wavy between the bolts. I suggest getting the load spreaders to prevent this. they came on all small blocks in the late 80s. try the dealer.
I would also take a micrometer to the front snout of the crankshaft to see if it was damaged. I see the balancer ID is severely worn. also put some blue loc-tite on the balancer bolt and torque it to 85 ft.lbs.

I was just thinking about that.....thanks for the advice I got the gasket today but I am gonna wait to put it back on untill i have the load spreaders.

[betonj97]

So I ordered the balancer today for a 327.....now here is my question....I have a brand new balancer from my old 400 I never ran. I did lots of searching and of course it says not to run the 400 balancer...but this is the problem...It says you can run a 350 balancer...so I ran to AZ and pick up a 350 balancer....I put it on my digital ebay scale and it was almost 3lbs heavier then the 327 balancer....but yet my 400 balancer is only 2oz heaver which is nothing...Can I run the 400 balancer?????????

[PanelDeland]

I wouldn't IIRC some if not all 400 balancers were balance weighted.The weights were designed to hellp balance the crank.