Author Topic: Harmonic balancer snapped  (Read 300 times)

Offline docsuess84

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Harmonic balancer snapped
« on: March 07, 2019, 05:26:31 PM »
So my wife was driving our 86 5.7 K20 Suburban and the harmonic balancer snapped off taking a bit of the crank with it. Now weíre in the market for a new (used) motor. Iím curious what models of truck we can borrow from as far as direct replacement goes without any modification. We love the rig and donít want to see it go to the scrap yard yet. Itís in really good shape overall.

Offline MIKE S

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Re: Harmonic balancer snapped
« Reply #1 on: March 07, 2019, 06:15:13 PM »
I think that is a 1 piece rear main seal engine. If that is the case 86 is the only year for that seal type with carbureted heads. You can use a TBI block with your heads only if the fuel pump boss is drilled. You can use a pre 86 engine but you have to change flywheel for use with 2 piece rear main.

Offline docsuess84

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Re: Harmonic balancer snapped
« Reply #2 on: March 08, 2019, 02:06:31 PM »
Thanks for the info. My friend found a used TBI one out of a 94 GMC. I live in California and my understanding for smog requirements here is that when an engine replacement happens, the emissions controls need to be in place and functional. Will that be an issue? Iím not sure what emissions controls were in place on a 94 TBI vs an 86 carbureted version.

Offline MIKE S

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Re: Harmonic balancer snapped
« Reply #3 on: March 08, 2019, 06:03:47 PM »
If you are thinking about changing to a compete TBI engine with the TBI setup it is not a straight forward task. You will need the entire electrical system with computer. Fuel system from tank to TBI. Exhaust system with cat conv and evap system. Calif is very strict. Only attempt if you have a complete doner vehicle to take your parts out of. Know if your just going to replace the engine that shouldn't be much of a problem. I don't think you can use the TBI heads without a special manifold which would raise a re flag with the Calif bar. You can use your original heads but just make sure that the engine has a functional fuel pump mount. In other word a lot of TBI engines had a fuel pump boss in the casting but was not drilled for the push rod which would force you to use an electric pump which not only would not be emissions legal, in my experience most aftermarket electric fuel pumps are not reliable.

Offline Wyomingite

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Re: Harmonic balancer snapped
« Reply #4 on: March 10, 2019, 08:59:41 PM »
Might be easiest just to have your engine rebuilt by a decent machine shop. If just building a stock engine it can be done pretty cheap.


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