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Underdrive Pulley Concern

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97gst_spyder

10+ Year Contributor
2,264
16
Sep 1, 2008
Lakeland, Florida
So I have a 4G63, I know the engine comes with a harmonic balancer. Now is it ok to install a full under drive pulley set since it doesn't have a harmonic balancer? The engine is completely stock. I've searched this before I posted this btw.
 
My aluminum pulley hasn't given me any engine issues for the 3 years or so I've had the car (it was on it when I bought the car) and I definitely beat on it and have passed 8000 rpms a few times and accidentally 9700 on a miss-shift once. If your harmonic damper is fine, I'd just leave it on though. Check it over once in a while though cause they tend to go shot and then the pulley slips and wiggles and can fly off. If these engines had a timing chain instead of belt the harmonic damper would be an absolute necessity.
 
You would need a balancer no matter what motor it is on as long it's a recprocating, piston drive motor.

Every time the cylinders fire, torque is imparted to the crankshaft. The crankshaft deflects under this torque, which sets up vibrations when the torque is released. At certain engine speeds the torques imparted by the cylinders are in synch with the vibrations in the crankshaft, which results in a phenomenon called resonance. This resonance causes stress beyond what the crankshaft can withstand, resulting in crankshaft failure.

As long as there is a vertical driving force to produce rotational motion, there will never be a continual smooth rotation produced from this operation.

Granted, the flywheel helps smooth out the rotation mass, and aids in maintaining the direction that the mass needs to rotate, but when an ignition pulse causing fuel ignition to push a piston down, there is this sudden torque that is created, a sudden twist is created and a sudden pull on the device that runs the cam assemblies.

This is where belt driven cam assemblies are much better than chain driven due to the fact that the belt can absorb these impulses of power from the vertical force than with chain driven assemblies.

Granted, the newer motors with silent, multilink chains -like the 4B11(T) that is in the new Lancers and the Sigma motors in the KIAS are just as good as a belt, but the older bicycle chain style of OHC drives couldn't handle these pulses, and after due time will cause chain breakage due to the sudden flexing and tugging of the chain.

So, play it safe - keep the balancer on the crankshaft. If the rubber looks kinda dry, it could be going. Get you a new balancer...

-DSM
 
Ok, thats the info I was looking for. So even though they have balance shafts it has to be balanced externally, complete opposite of Nissan's.
 
4cylinder in-line motors are actually the worst designed due there is no oppposite reaction to the downward force.

In as much there is downward force, there is also horizontal -front and back force due to the rods are actually being slung forward due to the downward force of the piston causing the front horizontal force..and the same on the back of the motor with the crank pushing up the piston, it slings the rod towards the back . The balancers cancel out this horizontal force on both sides of the motor.

Granted, some other maker's motors don't do 'silent shafts' like the Mitsu motors do. Either, they setup a balancing system within the block that runs directly off the crankshaft, or just heavier counterweights on the shaft itself..or just live with the vibrations that the motor produces at certain RPM's.

This is why Subaru's "flat-4" Boxer motors have it made when it comes to balancing since the pistons are opposite of one another - and both pushing and pulling at the same time - thus cancelling out their respective forces.
 
So I have a 4G63, I know the engine comes with a harmonic balancer. Now is it ok to install a full under drive pulley set since it doesn't have a harmonic balancer? The engine is completely stock. I've searched this before I posted this btw.

http://www.dsmtuners.com/forums/1513989-post386.html
http://www.dsmtuners.com/forums/cylinder-head-short-block/268533-broken-crankshaft.html
http://www.dsmtuners.com/forums/bolt-tech/300353-resolved-what-crank-pulley.html
 
In those posts that Defiant put up, I haven't seen cranks snap that bad as when I was working in a diesel truck shop as a clean-up boy many moons ago and seeing those huge diesel in-line 6 cylinder motors torn apart with their cranks laying on the shop floor snapped in half...and we're talking about journals good 6inches in diameter.

I asked mechanics on how those cranks snapped in half .. and it was the same story: harmonic resonance and bad harmonic balancers.
 
There is absolutely no benefit in ditching to stock harmonic pulleys. You won't make any more power, and will lose reliability. Especially if the engine is stock, there are 999,999 things you could do with that money you are obviously itching to spend.
 
This happened to a 5.0 mustang of mine a few years back, not only did the crank snap but the front 2 cylinders were seperated from the rest of block.

Anyone have a recommendation for a replacement ballancer, mine is starting to seperate.
 
This happened to a 5.0 mustang of mine a few years back, not only did the crank snap but the front 2 cylinders were seperated from the rest of block.

Anyone have a recommendation for a replacement ballancer, mine is starting to seperate.

I prefer getting OEM replacements for parts like this. Call JNZ tuning and they'll have it to your door in no time.
 
Thanks snowborder714 and lonewolf64.

Just ordered an oem ballancer from the local Mitsu dealer $138.07
 
I go out to yards and yank balancers pulleys off of any 4G63 motors that are out there. 5 to 10 bucks apiece in great condition-rubber still pliable and not cracked.

I have a few local salvage yards in the area I deal with but I didn't feel comfortable purchasing a moving part from them. I am sure it would be fine, just a personal prefrence.

OH BTW the Fluidampr is $291.50...sure is pretty though.
 
I would not recommend the Fluidampr, there have been quite a few crankshaft failures in V8 engines due to the way the Fluidampr suppresses harmonics, there was a wright up in Hot-Rod mag not to long ago about this issue.
 
I'm currently running a Fluidampr,and i have no complaints. Their dampers have silicone fluid and an inerta ring in a sealed housing,even though they look like a solid piece. Got sick of the OEM two piece units splitting.
 
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