Big block serpentine alignment problems

[skinnan]

Long story short hopefully. I have a 72 GMC 20 series 2WD with 402 BB. Original PS and Alt brackets were bent so I decided to install a serpentine system I pulled from the junk yard from a mid 90's chevy truck. I bought the Kwik performance kit to retrofit the SBC brackets to the BB engine. Also bought the spacer Kwik sells that sits between the balancer and the crank pulley. After originally installing it seemed like the alignment was just fine. I started working on other items.

Decided to replace the mechanical fuel pump. As I was doing so, the fuel pump push rod was in a place that made it tough to install the new pump. I turned the motor using the front crank bolt to get the fuel pump push rod in a better position. In doing so, the balancer bolt tightened some. I reinstalled everything and reinstalled the belt. Now the crank pulley is about a 1/4" further in then it was and the belt tries to run off one side and tears. Any ideas why this happened and how I can fix it? Thanks for your help in advance.

[Sheepdip]

Originally Posted by skinnan

Long story short hopefully. I have a 72 GMC 20 series 2WD with 402 BB. Original PS and Alt brackets were bent so I decided to install a serpentine system I pulled from the junk yard from a mid 90's chevy truck. I bought the Kwik performance kit to retrofit the SBC brackets to the BB engine. Also bought the spacer Kwik sells that sits between the balancer and the crank pulley. After originally installing it seemed like the alignment was just fine. I started working on other items.

Decided to replace the mechanical fuel pump. As I was doing so, the fuel pump push rod was in a place that made it tough to install the new pump. I turned the motor using the front crank bolt to get the fuel pump push rod in a better position. In doing so, the balancer bolt tightened some. I reinstalled everything and reinstalled the belt. Now the crank pulley is about a 1/4" further in then it was and the belt tries to run off one side and tears. Any ideas why this happened and how I can fix it? Thanks for your help in advance.

Sounds like your balancer was never properly torqued, I would torque it then put spacers between the balancer and pully to get the desired position. Might have to have a machine shop turn them out if it's a non-standard length.

[Accelo]

GM actually used a spacer between the crank face and the balancer on some Corvettes.
This spacer could be made by turning and parting an old balancer? It slips onto the crankshaft snout before the balancer is installed. Of course it lacks the interference fit the balancer has.
I am assuming the crankshaft is larger diameter on the BBC so 2 of the 1/8" thick SBC part will not fit. If you can install the spacer with the key-way removed it's a simple washer I will even build one to fit and mail it to you at no cost.

Could the BBC be like SBC and have several h/balancers with different thickness.

Does the spacer manufacture make more than one spacer width?

The cheap way out is to stack washers behind the bolts. Can't believe I said that?
Not recommended, It would leave you with no good way to center the pulley.
Cheers.

[skinnan]

Originally Posted by Accelo

GM actually used a spacer between the crank face and the balancer on some Corvettes.
This spacer could be made by turning and parting an old balancer? It slips onto the crankshaft snout before the balancer is installed. Of course it lacks the interference fit the balancer has.
I am assuming the crankshaft is larger diameter on the BBC so 2 of the 1/8" thick SBC part will not fit. If you can install the spacer with the key-way removed it's a simple washer I will even build one to fit and mail it to you at no cost.

Could the BBC be like SBC and have several h/balancers with different thickness.

Does the spacer manufacture make more than one spacer width?

The cheap way out is to stack washers behind the bolts. Can't believe I said that?
Not recommended, It would leave you with no good way to center the pulley.
Cheers.

Thanks to both of you for the replies. I was wondering about some sort of additional spacer as well. Really doesn't need to be too much and washers may do the trick. Literally one of the ribs on the belt is trying to sneak over the edge of the pulley. I ordered a new pulley just in case I ended up with the wrong one.

[skinnan]

Originally Posted by Sheepdip

Sounds like your balancer was never properly torqued, I would torque it then put spacers between the balancer and pully to get the desired position. Might have to have a machine shop turn them out if it's a non-standard length.

Thank you, I'm considering the spacers or washers. Appreciate the reply.

[j_cst_10]

Make sure the tensioner is new. Common probem on the 454 factory serpentine set ups. They go bad and push the belt towards the front grill and it rides on the lip of the pulley and eventually shreds itself. Ask me how I know....