Hiya guys,
I think I found the culprit of my out of balance/cracking flex plates issue - a lower end knock. I didn't hear it at first, but today I removed my inspection cover to be sure the shop put in a zero balance flex plate. They had. So, I put the cover back on and went under the hood to tighten a radiator hose that was leaking a little from when I had my water pump changed. When I started up the car to make sure the leak was gone I got under the hood and heard a noise that will haunt my dreams forever - a lower end knock.
Now that I know the problem, I'm going to try to work out a deal with the shop that built the motor. In your opinions, would it be cheaper for me to bring a block to this guy for a rebuild or to just buy one off him?
If I want to find a block to bring him, what should I look for to drop in? I have a brand spanking new tranny that I would really like to keep. Please help me out.
Sorry for the length of this post. Mods in the sig.

 

Id just get the crank turned, and put new rods and main bearings in. Unless its really knocking bad or has been for a long time. But I think I would just do the bottom end before I buy the new engine.

Digger

 

Even though this motor has already been rebuilt twice, you think I should do this?

 

When the motor was rebuilt did the crank get turned, and did it get align honed. What where the bearing clearences? And did you properly break it in. Because if I t has been rebuilt twice there should be no reason for it. I figure pull the engine put new bearings in it and sell it, buy a 350 and rebuild it. Maybe its not even a bearing, I had a 305 with a blown up piston that sounded like a low end knock. How much advance are you running? Because you could be running into detonation. Do you have the right balancer, because there are some with different timing marks, and you could be advancing it way to much. Anyway answering your question, you can use any small block they are all the same, they will all bolt up to your tranny. Just get a 350 and rebuild it. How competant of a machine shop are you taking it to, I mean its been rebuilt twice and you are still having problems. Take it some where else. just my 2 cents

Digger

 

you can rebuilt it again (mabey) or have to get a new engine, or sell it while you can, when a bearing starts to knock it just gets worse and wrose unless you really f' something up, i would not drive the car unless its in dire emergency for some reason.

 

Thanks for the input guys,
I believe this engine shop to be very competent. A few of my friends have had blocks done there with great results and they have an overall good rep. I got a lemon, it blew, I had it rebuilt, now this. They said the original reson for it blowing was a "Balooning torque converter." Can there be something inherently wrong in a block that would cause premature lower end failure repeatedly even with a good rebuild?
Anyway, the timing set perfectly, although I can't remember the advance (Maybe 12?).. it's definitely a lower end problem, because it keeps cracking my flex plate.

 

oh, yes the crank got turned and it was align honed/bored. Not sure about the bearing clearances - the shop knew all that stuff. I broke it in properly - no issues there. This is a daily driver, so I depend on this car.
It should be the right balancer. The shop should have shecked the balance. The pistons were replaced when the block blew. I think I have some Keith Black's in there right now.
And as much as I'd like to take it to a different shop, I can't afford to. This guy says that since it's been wrong twice, maybe we can work something out. I'm thinking, it blew once under warranty so they fixed it and now it's going again. Maybe they didn't do a good build job the second time? Couldn't that be a court case?

 

You could rebuild this motor 10 times and you still will have the same problem. The problem is balance the result is broken flex plate. Motors use to be inturnely balanced they quit that in the 1970's (balanced crankshaft) after that they drilled holes in the harmonic balancer and put a weight on the tork converter.I would gess that you took the shop a whole engin (motors are in electric fans) and it is all right. The problem is in the tranny. It doesn't balance the back half of your engin. So to fix the balance you need to put a weighted flex plate or properly weight your tork converter like whatever year motor was for the factory. as for the shop you took it to start with I would not give them any more money. they should have know this. If you git the balanced right your nock will probaly go away. if not check your crank and have it reground and replace your main bearings.

 

Was'nt the only small block chevy to be externally balanced the 400. All the rest are internal. That would explain why you would have to get a weighted flex plate and different balancer when you build a 383.
I dont think chevy weighted the converter but I know dodge did with the 360.

Where did you get that information?

 

350's are 0 balance.
No weight necessary on the plate or the converter.
400's and such need external balance.
Digger has got it right.
On bigger motors they can't sit big enough weights on the crank, so they mount them externally - on the flex plate or converter, depending on brand.

 

It still a balance problem. Go to this website http://www.paceparts.com./
and check out what they say about forged Crankshaftsfor 350's. I do not know what parts are in you engin and do not want to look up all the specks up if I did. Thats a job I do not want to do again.
I do Know this after Breaking some 8+ flex plates 20 +years ago.

Its a balance Problem that will not go away until you find it and change the parts to make it right.

 

It's a balance or alignment problem. Tear the engine down and inspect the thrust bearing, chances are, it's shot and that's what your knock is coming from. I know, it happend to me....TWICE!!

 

look at the following posts
https://www.thirdgen.org/oldarchives...ages/1017.html
they say some 350's are exturnaly balanced after 88 and how to tell the diff.
I just looked in the archives under balance there are outhers