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Help! Bent Frame or bad engine mounting? 1972 LS5

Bolisk

Well-known member
Joined
Nov 2, 2007
Messages
441
Location
Crystal Lake IL
Corvette
1972 LS5 Convertible PS, PB, A/C
I have a 1972 LS5, p/s, and a/c car. Needless to say, the v-belt routing is complex with the P/S pump, A/C compressor, and Alternator. . .all having their own belts. That said, I've noticed something on my car that I'm not sure is correct or ok.

In the top of the front cross member there is a large dimple where the crank/harmonic balancer pulley sits when the engine is in the car. Now in my configuration there are two belts that are driven directly off the lower crank/harmonic balancer pulley. One (the one closest to the back of the car) simply goes up and around the three channel water pump pulley with an idler helping to keep it tight. The next belt goes up and over the second channel on the water pump pulley, then it goes over to the PS pump and back down to the crank/harmonic balancer pulley.

Now when I want to remove these two belts. . .I have to remove the fan and the water pump after loosening the P/S pump and idler. I figured one I have done this, the belts would just fall off the lower pulley, and I could remove from from the lower pulley.

Turns out I cannot get the belts out of the car because there is not enough space between the front cross member and the bottom of the crank/harmonic balancer pulley. I actually have to remove the lower pulley as well in order to get the belts out!!! Is this normal? Anyone else have to do the same thing?

On closer inspection, the lower pulley is not in the middle of the dimple in the cross member. The pulley appears to be closer to the driver side of the dimple. . .and with the belts installed. . .the P/S belt is DAMN close to rubbing on the cross member. I can get a piece of paper to pass easily between the bottom of the belt and the cross member, but an index card rubs. . .when trying to get it to pass between the two.

It is possible that the engine is not mounted correct? Bad mounts? Missing spacers (if there are supposed to be some). . .

Regards!
 

Peer81

Well-known member
Joined
May 21, 2003
Messages
2,497
Location
Netherlands
Corvette
'81 Black
It never hurts to change the engine mounts but I don't think the rubber in the enginemount will compress over the years but I could be wrong on that one. You can also check the trans mount. As there is a large space between the trans and engine mounts and just a small space from enginemount to front crankpulley you just need to lift the trans mount a little to drop the crankpulley way more.

Greetings Peter
 
Joined
Jul 4, 2009
Messages
82
Location
orland park, illinois
Corvette
1966 black coupe - 454 w/5 speed
Are you sure that the lower pulley is a Corvette pulley? They are smaller that a full size or mid size pulley. I found this out when dropping a 454 in a '66 coupe.
 

gmjunkie

Well-known member
Joined
Nov 11, 2004
Messages
4,540
Location
Old Fort NC/Vero Beach FL
Corvette
03 Z-51,78 L82 Coupe
I'd bet both mounts are bad,I've ran into this a couple times on BB's and SB's! The rubber breaks or gets weak and lets the engine twist a little on the mounts,Left side torques up,Right side torques down. The engine will then set off to the left a little,Does the right valve cover look like it's lower in the car than the left?
 
Last edited:

Bolisk

Well-known member
Joined
Nov 2, 2007
Messages
441
Location
Crystal Lake IL
Corvette
1972 LS5 Convertible PS, PB, A/C
While this car has had lots of things messed with by "bubba" over it's life. . .thankfully the pulleys are all original to the car. I checked the part numbers.

The engine does have safety motor mounts with the correct spacers. . .so it's not that the spacers are missing. Did 1972 come with safety mounts?

After looking at it again last night. I need to do one of two things. . .

1) Raise the engine at least 1/8"
2) move the engine to the passenger side at least 1/8"

I'll be more than happy to replace the mounts. . .and see if that does it for me.
 

Bolisk

Well-known member
Joined
Nov 2, 2007
Messages
441
Location
Crystal Lake IL
Corvette
1972 LS5 Convertible PS, PB, A/C
Engine looks more or less level. BUT!!! The A/C compressor pully was chewing into the hood a bit. So maybe your on to something with regards to the engine being down on the left.
 

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