360 engine vibration

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If he's getting vibration in neutral, hasn't that eliminated converter/flexplate vibration?

I agree with others. Must fix that chewed mount first.
 
uber cool said:
Hi, new to the Dodge dart and have an issue with engine vibration over about 1500 rpm. Now a little background first , its a 360 engine mated to a 727 transmission , im based in the uk and bought the car last year from Texas. Now it wasn't an original 360 ( I wish) or even a v8, car was originally a slant 6 904 box and 7 1/2 rear axle. someone has spent a bit of money uprating the back axle to 8 3/4 fitting a 727 trans and rebuilt 360 engine, most of it looks new is recently rebuilt, i think it was a stalled restoration, i got it from a texas classic car dealer.

now back to the vibration, the car is not not UK legal, so i cant take it for a run. I've read loads of threads on here re harmonic balancers and internal and external balanced cranks. ive tried the obvious and removed drive belts, checked firing order, plugs firing, exhausts not rubbing on body etc. I now started to look around the crank balance, the front pulley looks to have an external balance and ive rotated and looked all around the converter and cant see an balance weights, so i'm thinking I will need the B&M balanced flex plate, as it look to be a stock flex plate. any ideas or suggestions?
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Hi guys,this might be a little late but I'll share anyway.I was a auto tech for forty years,I saw alot of 360's right out of the showroom that had a bad vibration in neutral and driving too,most obvious in park at about 1500rpm.The problem was the new 360 engine had a cast crankshaft,they just started using them on the 360 unlike the 340 and 318 which had steel cranks.Cast cranks were externally balanced using the torque converter to accomplish this now the converter weighs maybe 40 pounds if it is out of balance it's gonna shake tremendously.I had some cars that I thought the dash was going to shake loose.This whole deal was a design flaw.See if you can find a converter for a cast crank.Oh by the way I'm a big block guy,and I race a 64 Fury.Been a mopar nut since 1970. Good Luck.
 
I vote to put the B&M externally balanced flex plate in there...I had factory flex plate completely rip apart with a stock 340.
 
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Hi Guys, back from our USA holiday 1500 miles around California and Nevada. Awesome country I must say! Anyway whilst there picked up a B&M flex plate and a new transmission mount. However I also have a diff oil leak so stripped that out thinking it was a 8 3/4 dodge item,( bought gasket ready) turns out to be a 9" ford unit???WTF!! and not sure if the prop is also too tight as there was zero movement to slide the yoke into the 727 trans? So starting at the rear I will sort this first, check prop length, yoke play and then move back the the vibration issue.
 
I'm also a U.K. MOparvowner and had a home built Dart with a 360 & 727. The converter had weights on it and I used a TCI flex plate with the cut away in it. Didn't vibrate.
 
I was thinking when I read the above..... you don't use both the TC weight AND the imbalanced flexplate. But in looking closer, the flex plate linked above does not have cutouts for imbalance, just for removing mass; it is balanced and says so on the description: "Internal balance".
 
ok i have the diff out now and struggling to get the sliding yoke out, so that's tonight's job. its either jammed in the transmission or the prop is too long as there is no movement to slide the prop forwards. I had to dismantle the rear UJ to get the prop clear of the diff. So still not getting closer to the the engine vibrations. But need to sort all these things out before i can go for a run in it. I'm in the stage of the more I remove the more I think the PO was on LSD when he fitted the 360. It has has top quality new bits just poorly assembled! However with the prop off the exhausts off and the car nice and high on stands i might as well take the trans out and change the flex plate. Oh did I mentions the trans sump is so distorted and over tightened and covered in red sealant that it leaks from every seam. So there's another job.
 
well this was the wiring by the PO, 3 crimped inline connections, what the hell for?
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All the work was done in the USA, I imported it from Texas last year, but I bought it from a dealer who had no history. It was originally a 6 pot with a 904 trans and 7 1/2 diff. Now 360 engine, 727 trans, ford 9 1/2 diff, larger disc brakes and re cambered rear leaf springs. I think it was either a stalled conversions or completed and the did very little miles since conversions. Maybe due to the trans vibrations and propshaft issues the PO may have lost interest?? who knows, but would sure love to get some insight into its history. if you live in the Texas katy area maybe you saw it around as the plates tags are dates Sep 2013
 
Ok back to the top with this one, oh yes you may have spotted I first raised the issue in Dec 2016! The car is still not on the road, more to do with other projects and helping others rebuild there engines and cars. Anyhow Im back on it now and determined to bottom this issue out.

When I say vibration its like the engine is shaking around as if it has dropped a couple of plugs. If a pull a lead off on eat a time you can here it drop a cylinder but no noticeable difference to the shake.

The compression is good on all cylinders at 150 PSI, the carb has been stripped and rebuilt, its an Elberbrock 1406, the ignition stripped and rebuilt, new plugs,cap rotor arm, leads, pickup, coil converted to GM HEI. I've checked the valve gear, thought I had found the issue one side had the valve rockers LH and RH reversed and push rods rubbing against the head.

the converter appears to have no balance weights and I've fitted the B&M 360 flex plate, strange it has made no difference to the vibration at all before or after.

I haven't driven it on the road as yet but its clear if you hold part throttle at say 1500 to 2000 rpm the engine shakes and you can feel it throughout the body.

If you read back from the start I've also replaced the ripped transmission mount.
Any ideas?
 
Also to add it starts straight away , initial timing is 16 deg and 32 at full advance, vac gauges reads a nice steady 20 at idle. Took the rocker covers off today and thought this was the issue, with the rockers crossed over, however made no difference.

I have a slight leak on No1 header at the manifold gasket but that's it. When I first got the car nearly every cylinder leaked, once again no improvement to this shake. Open headers or full exhaust no difference.

As Ive been fault finding this car and engine its amazing how many things I have found incorrect, put right and made no difference to its running!

could incorrect cam timing cause this symptom?

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well that was funny googled 360 LA engine harmonic balancer and got a picture of my engine. which reminds me the balancer (red arrow) is running true, but the pulley wheels (blue arrow) have quite a wobble, maybe 1/16 to 1/8". are there bolted to the harmonic balancer or welded in place?

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The pully bolts to the balancer. I had the same issue once with a 360, and the balancer had slipped and caused it to vibrate. My balancer had wobble to it though.
 
Here you go my friend, this is what you need.

This one came out of a 1976 Dodge W200 Pickup with a 360 2bbl engine and a 727 transmission. Factory Weighted torque converter for External Balanced 360.

I like, it has the factory drain plug too.


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From what I can tell that engine looks Like a carbureted LA 360 with Stock cast iron heads, mopar stamped rockers on one main shaft, with basic early mopar electronic ignition with the small brain box, and ballast resistor setup and early 12 volt ignition coil that bolts to the intake manifold.

And the front vibration damper is the little bit later style damper or a replacement damper and is the correct one for the external balance 360 engines. I like that style damper better than some that came on the 76 360 engines with the lopsided weight hanging out on them just behind the pulleys.

Although the placement of used AC brackets at the alternator could suggest a later style 360 just before the magnums, or suggesting that the brackets came off a magnum short block to begin with. The front balancer looks later 360 or magnum too when considering this.

Hot rodding cars anything is possible, It could be a magnum short block (black in color) and the silver unpainted water pump makes me wonder the year too. Possible they took a magnum short block and put early style mopar cast heads on it, like the J heads. This way they can go Old School Carburetion and Intake and heads, on the newer generation Magnum style short block.

(If it were a magnum 360 with magnum heads, the heads would have rocker studs coming out of the head for each rocker.) Hope this helps lead you in the right direction
 
Obviously whoever put this thing together didn't have any idea what he was doing. Maybe , getting a new short block or crate motor, you'd be $$$$ ahead, know what you have and keep your sanity. No telling what is inside for crank , rods and pistons . Could be a mixed batch of parts The car looks worth it !
 
JDMopar said:
The pully bolts to the balancer. I had the same issue once with a 360, and the balancer had slipped and caused it to vibrate. My balancer had wobble to it though.
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thanks Im going to remove the balancer and pulleys and have a look why it is not aligned correctly.
 
George Jets, your pretty much on the money with your comments. The block casting number reads 360LA dated 1978. The rockers look used and have that used dirt to them, they are on a shaft so assume this confirms they are LA heads. Heads look recon with new clean valve springs. The engine oil has been changed and remains clean, this lead me to think its recently rebuilt.
The new speedo that was fitted showed 7 miles and there is zero wear on brake pads and shoes. The block has new core plugs and all gaskets look recent, suspect the unpainted water pump is a new one. I suspect its a fresh rebuilt motor with little miles as its the same throughout the build.
Someone spent some serious money on this. Its has a fresh rebuilt 727 trans, ford 9" back axle, all new brakes and suspension front and rear.
The converter is new with no weights and i have fitted a B&M externally balanced flex plate (see photo below).
The ignition is stock expect me upgrading to GM HEI. Is there a difference between magnum and LA front dampers? Could it have a magnum crank in an LA block? The crank has a notch out at the rear where the flex plate bolts on does this suggest LA crank? ( see photo below)
My thoughts at present are a balancing issue or cam timing out of whack. Or cam not broke in correct and worn lobes. I need to check all valves are fully opening with rocker covers off.

But this is my first V8 and mopar, so steep learning curve. I'm more familiar with straight sixes or flat fours, so all help appreciated.
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Checked the invoice and it says BM 10236, also a stroke of luck since it is fitted now is that I took a photo of the plate and fitting instructions before fitting and these confirm 10236. Strange thing is I noticed no difference before and after fitting the BVM flexplate, maybe the vibration this is meant to eliminate happens at higher rpm or frequency? Mine is still at about 1000rpm plus.

I need to take the front pulley off and check this is the correct balance for a 360 LA engine. is there a difference between magnum and LA front harmonic balancers?
 
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