318 engine vibrates

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cudajim

cudajim

cudajim
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My 69 Barracuda has a bone stock 318 2bbl engine/auto trans. I changed the engine a few years back using a short-block rebuilt from a engine company in Sacramento who "specializes" in rebuilds. Ever since, the engine has had a major vibration issue. I've swapped out the front damper, took all belts off (temporarily), even swapped the torque converter but it's still there. It noticeable at most speeds but some speeds are worse than others. In any case it's really annoying and cannot be good for the engine. What can I do to fix it?
 
Sounds like you may have an out of ballance engine. When you are using oversized pistons you have changed the ballance, sometimes you can get by with it but for smoothest tunning and longest life an engine reballance would be the prefered method. I have done it both ways and have been lucky so far.
 
You sure they didn't give you a 360 by mistake?? It has vibrated ever since it was brand new? Despite the vibes, how does it idle and accelerate? What did the company have to say about the problem?
 
Cast crank without the cast crank balancer and/or torque converter weight OR a cast crank balancer on a forged crank?
 
Have you done a leakdown or compression test? Maybe it's had a bad cylinder since it was built. Not to scare you or anything, btw. ;)
 
Some of these mass rebuilders...... I wouldn't be surprised if they bored one hole and stuck an oversized piston in it, honed the rest and called it good.
 
I got one of the "rebuild mill" 318s. The thing ALWAYS vibrated. everything checked out perfect (timing, compression, hardware) ....but nothing cured the vibration. After 2K, I pulled the friggin thing and put in a 60K mile 318. I did put the heads from the rebuilt motor onto the 60K 318. All the other hardware was the same....smooth as silk. Not a vibe in sight.

I got in touch with the company that did the rebuild, they told me screw off, even though it was in the mileage window, it was outside of the "time" window. I threw the long block into the scrap pile.

I had 1 experience with a "mass" rebuilder....never again. That being said. Pull the motor, return it for another before the warranty expires and you are stuck with it. Do it as many times as possible, until you get a smooth running one. The will not reimburse you for time spent swapping motors.

Thats my experience. I'm sure you'll find some people who bought 1 and it was perfect out of the box. just lucky I guess.
 
sounds like a cast crank motor 69 318s had steel cranks i'm pretty sure look and see if the converter has the two wts.if its the 69 converter probly not..just ad the wts.this can be dun without taking it out of the car..just trying to help...Artie
 
I had the same problem with my first Barracuda. Pulled and rebuilt a 318 from a van to replace a slant 6. I needed offset oil filter adapter, exhaust manifolds, pulleys, all the usual truck to A-body stuff. Donor was a locked up 273 in a parts yard.
The first problem I encountered was timing scale in the wrong location. Worked past that and went vibrating down the road.
Turns out a red paint balancer was wrong for a blue paint engine.
It's not carved in stone but as a general rule of thumb, red paint LA has a steel crank and blue paint engines have a cast crank.This doesn't hold true for early 340.
When I got the correct balancer the timing mark was right. the bolt holes in the bottom pulley had to be adjusted. There was my sign. :)
 
Hold on; I thought: all 318s are internally balanced. Steel crank 340s internally balanced. Cast crank 340s, eccentric harmonic balancer, neutral at the back end.
All 360s eccentric harmonic balancer AND eccentric balance on converter.
 
swing69 said:
Hold on; I thought: all 318s are internally balanced. Steel crank 340s internally balanced. Cast crank 340s, eccentric harmonic balancer, neutral at the back end.
All 360s eccentric harmonic balancer AND eccentric balance on converter.
Click to expand...
Thats right!!! But if they took a cast crank from a externally balanced 340 and stuck it in a 318 it would vibrate! The cast 340 has the same rod and main sizes as a 318. This might be his problem. I have never had this happen to any of the engines I rebuilt but I re-used the cranks and rods and harmonic balancers if they checked out.
 
All 318s are not internally balanced.
 
StrokerScamp said:
All 318s are not internally balanced.
Click to expand...

Oh, this is news to me, what years are externally balanced?? I've worked on my share and haven't seen one yet. Now they do share the same crank and rod journals with the externally balanced 340 and you might have a vibration problem with a 273 crank. It has a lighter rotating assembly but is internally balanced. I'm not sure about all of the polyspheres though. But we're talking the LA seriies 318's
 
StrokerScamp said:
All 318s are not internally balanced.
Click to expand...

Rob all 318 LA's are internally balanced. Even cast crank models. I have been told a 318 Magnum is externally balanced but I have yet to disassemble one to prove that.

Cudajim your probably not ever going to know until you take it apart and see what they screwed up. I've seen mass rebuilders do all kinds of stupid stuff. Bore out one hole and stick an oversize piston in it that's 50 grams heavier than the rest of the pistons. Use the wrong crank (340 and 273 will all bolt in but the bob weight was different for them so they require re-balancing). I had some heads once that a mass rebuilder replaced half the valves with stems that were .003 over because the guides were worn and they were too cheap to replace them. I wouldn't buy a rebuilder engine no matter what.
 
According to my Mopar engines book, the 273 and 318 cranks have the same bobweight, but the 273 uses a heavy wrist pin to bring the piston/pin weight equal to the 318.
 
65TerrorCuda said:
According to my Mopar engines book, the 273 and 318 cranks have the same bobweight, but the 273 uses a heavy wrist pin to bring the piston/pin weight equal to the 318.
Click to expand...

What book do you have? I dug all through the only Mopar engine book I have ("Small Block 'A' Engines" by Mopar perf.) and it doesn't mention much at all about piston pins. The only thing it mentions is there are 3 different weights for 273 pistons depending on what year the engine is.
 
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