BarryK

hi all

this is a strange one and it has me baffled.

2 years ago when I got my '78 it only had an original 9700 miles but it had been neglected and the last owner left it out in the driveway for the previous 2-3 years under a plastic tarp.
To clean it up properly and make it presentable again required pulling the motor out to repaint the block and all parts and to clean up the surface rust from the front of the frame and repaint the frame.
Part of the job also required removing the core support to clean that up and repaint it. The car sat approx 4 weeks on jackstands with the core support removed. I noticed no droop from the front end while the core support was out based on the panel gaps at the cowl and front of the doors from this though.
When reassembling the motor I put on brand new motor mounts since the rubber on the original mounts was beyond reusing.

After reinstalling the motor, core support, radiator, etc the fan shroud was not fitting correctly. Once bolted into place it was sitting so low it was causing the fanblade to hit on the top of the shroud, and yet the bottom of the shroud wouldn't reach down far enough to go into the clips designed to hold it at the lower portion of the core support.
Assuming the issue was it hitting the fan was caused by the nose drooping from not being supported for a month I corrected the issue by loosening all 6 of the core support side bolts, placing a jack under the core support and jacking it up to raise it to gain clearance for the fan than tightened the bolts back up before lowering the jack down. This gave me some working clearance for the fan although there is suppose to be about 1/2" of clearance or so and the best I could get was between 1/16" - 1/8". Enough to allow the fan to operate without hitting the shroud but not as much as it's suppose to have.
Compounding the problem is that the air intake duct for the aircleaner goes over the shroud and radiator and it's so tight that when the hood is closed it pushes down on the air duct causing that to push down on the shroud reducing the very little clearance I have to the fan. It's enough that just power braking the car or if I hit a dip certain ways and the frame flexes at all you can hear the fan start to rub the shroud.

I've tried everything I can think of to get the fan/shroud clearance that i'm suppose to have but nothing works. I've tried re-jacking up the core support more but there is no more of the very little adjustment there was, i've tried loosning the bolts and readjusting just the shroud but there is no play in the mounting bolts to allow adjustment there, I've confirmed that the radiator is fully seated in the rubber seats in the core support, etc.
The big issue here is that I need to raise the shroud to gain clearance for the fan but any amount of lift on that simply gets lost when the hood is closed and pushes down on the air duct which pushes back down on the shroud.......

The only other thing I can think of is the way the motor is sitting rather than the way the core support / radiator / shroud sits. Is it at all possible that the new motor mounts would cause the motor to sit any higher than before?? Even though the old mounts had the rubber all deteriorated which is why i replaced them, there obviously was enough proper clearance for the fan when the car was brand new with brand new motor mounts back than so how could new motor mounts now cause an issue?

sorry for the very long post but didn't know any other way to describe the problem so it would make sense.

any ideas or suggestions are greatly appreciated

DC3

I am far from experienced on this issue but my first thought after reading your post was that maybe the new motor mounts are somehow the wrong ones.

DC

BarryK

thought of that also. As I recall (but it's been 2 years now) they seemed correct. If they were very different, at least visually looking at them I most likely would have questioned it at the time since that's my nature but after having gone through everything else I can think of my thinking is definitely on those new mounts so I do have to consider that as a possibility.

What makes it more difficult now is that for some strange reason I can't find the reciept in my file on the car for the new motor mounts to double check the part number. I have every reciept for every penny I spent on the car down to the most misc item but I can't find the one for the motor mounts! go figure

AimHigh

Something is out of line or installed wrong or wrong part.
Your frame and structural support don't just go away like that, especially with no travel or trips and only sitting up on jacks.

dannyman

Sounds as if the ride height should be confirmed. Do you have the AIM for this car? My '77 has pages of measurements just for the ride height.

Where did you locate the jacks for this long term storage?

I suppose it's possible the mounts are incorrect, but highly unlikely. I'm leaning toward raising the complete front clip to adjust; if it has sagged during your storage stage.

BarryK

yep, I have the AIM for my car.

jacks were placed at the rear just infront of the rear kick-up areas of the frame and in the front were placed just where the frame starts to curve inwards towards the front cross member. It's the same stand placement recommended in the AIM and shop manuals.

Based on the panel gaps before and after R&R'ing the core support there didn't seem to be any actual front end droop though. all the panel gaps stayed the same. If the front end drooped the top of the gaps at the front of the doors and cowl area would have increased. Besides, when jacking up the front under the core support should have corrected that even if there was some droop

70 LS1

So let me see if I get this right. You pulled the motor, radiator, core support, shroud and reinstalled all the same pieces. The only parts that are new are the motor mounts? And your indications of a problem are fan hitting shroud, not body gap?

I don't see how the body would have sagged in the front with no engine, radiator or core support in there. The frame is what provides the support for the body, not the engine or core support. Plus if the body sagged, the hood probably would not line up or the fender to door gaps would be different than before.

I had mine up on jackstands for a year with no motor, radiator or core support and nothing sagged.

I would guess the motor mounts are too thick. I remember being at the parts store and seeing a few different thicknesses.

BarryK

Jeff
if you remove the core support in a C3 and do NOT support the nose it CAN droop, especially with the weight of those heavy headlight buckets. But regardless, as mentioned, I really don't think it drooped in my case based on the panel gaps and I agree that at this point i'm leaning towards the motor mounts as the issue.

Somehow I think the mounts were too think. I probably didn't notice because the rubber on the old ones was so deteriorated that I couldn't see the difference to compare.

I wonder if the correct mounts are still available from the Chevy parts counter and if they would work any better.

AimHigh

C'mon guys this has to be parts or install mistake....

if there was a panel drop, then common sense would say our guy can not open a door now or a hood without really messing up the cars front clip to door or hood to front clip!

(I'm assuming he can still open the doors?)

...Roger...

Adjust the 2 core support mounts on the bottom of the core support.Thats what holds the nose up.

...Roger...

If the nose droops the fenders will pucker above the wheels.The opening between the door and the fender cant change unless the bonding is broken.Do you remember putting the bolts back in under the radiator?Sometimes there are shims there also.

ratflinger

Well you could dump the shroud & fan and go with electric fans, but this answer doesn't address any cause.

Raphiki

Is the car on the ground now or still on jack stands? I had the same problem with mine (fan hitting the shroud) while it was up. Problem went away with all 4 wheels on the ground.

chevymans 77

You said you loosened the 6 bolts that hold the core support, there are two more on the bottom of the vacuum canister, the pipe welded between the frame rails.

This has happened two a few members here, on my car one fender was higher than the other when measuring from the ground or from the tire, I loosened the 6 core support bolts and used a jack but could not get it to move enough to get the fenders to even out. One day I was working on something I don't remember what now but had loosened the two bolts on the bottom of the core support. When walking around the car I noticed that the fenders looked even so I measured them and they were even. I got to looking and the holes in the two brackets are over-sized and the bolts have large washers on them. I supported the front-end were it needed to be and tightened the 6 core support bolts and the two on the bottom and it stayed in place.

Neal

noonie

Only you know about the motor mounts so can't help with that, but they are usually not a problem.

What you did with the 6 core support bolts made it reversed.
You want to loosen the bolts and also the 4 big bolts below from the core to the vacuum tube. Then you want to lower the core support as much as you can. There isn't a lot of adjustment anyway.
Then tighten the 6 core bolts. That will properly clearance the core to the hood.

Then with protection, jack up the core support with the front body, and tighten the bolts to the vacuum tube. They are on slotted angle brackets. 1/2" bolts I think.

If that isn't enough, then you will have to loosen the frame horn brackets that mount the vacuum tube and core support. That whole assembly with the nose can be raised with a jack too and retightened.

Don't worry about the bonds at the firewall. The glass will flex all the way along and especially at the bonds at the firewall enough for this without breaking. You won't be moving it enough anyway.

Have the front of the car either jacked up directly behind the stabilizer mounts on the horns as close to the arm as possible or raised with front blocks under the front wheels. I prefer the stands and that way when raising the body the suspension won't be moving on you.

When reinstalling and regluing a front end, etc the first alignment that must be made is the fan/shroud/core. Everyhting fits to that.
Be glad your left to right is good in the shroud, that's a real pain.

70 LS1

Its been a while since I have looked under the front of my car. I must have been mistaken.

BarryK

of course I put the blts back in at the bottom of the core support.

There were no shims when I removed it.........

BarryK

it's been on the ground for 2 years now. it was only up on jacks for about 4-6 weeks back 2 years when I was getting it to run

BarryK

i only loosened and re-tighten the 6 side bolts, I left the 2 large bolts at the bottom alone figuring when I jacked up the core support from the bottom that would have allowed the entire nose to lift up also.
Perhaps my figuring was wrong.

BarryK

that's the truth!

ok, I'm following you so far.... I can understand this, lowring the core support without moving the nose gives me the hood clearance. So far so good.

ok, this is making sense. the first step only lowered the core support to give the hood room, but now we are jacking up the core support to gain the clearance for the fan but also raising the entire nose with it, including the hood, that that won't affect the adjustment from step one. I got ya.

Isn't this basically accomplishing the same as shimming the bottom of the core support as many cars had from the factory (but mine didn't)?

Oh wait, one thing I don't get though as i'm playing this thru my mind. Without adding shims under the core support, I don't see how the nose is going to stay up and not droop down again once the jack is removed. How are the bolts on the bottom of the core support going to keep the nose up?