Lowering the rear of your hood or front of trunk: alignment - Chevelle Tech
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post #1 of 54 (permalink) Old Jul 22nd, 12, 8:52 PM Thread Starter
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Lowering the rear of your hood or front of trunk: alignment

How to lower the back of your hood or front of your trunk.

I have seen this come up on forums for so long and lately there seems to be a run on it so I felt the need to explain this a little different.

There are a number of different hood hinge designs, but they all follow in basically the same general geometry.

Be it this 1965 GM A body.



This 1959 Rambler.



Or this 2003 Dodge Caravan which has only one part and one pivot.



They all follow the same basic geometry in that the pivot point is moved back behind and below the hoods top surface line.



As you can see by my crude drawings I too am in the dark about the exact geometry that is at play in these old hinges but I have the basic idea. Where the exact intersection (pivot point) I donít know but it is something like this.

On my wifeís family truckster (the Caravan) it is very simple, here is the hinge with the hood lowered.




If you were to add a shim between the hinge and the hood on the front bolt like this. It effectively forces the hinge to go down lower right?



When you add a shim between the hood and front of the hinge the hinge is then forced to go down further because the front of the hood will only go so far right?
You can see by this drawing with my paper hinge how when it lowers further like if it is pushed by a shim, it lowers the rear too. You can clearly see that in this model, it IS lower at the rear.



Which results in the hood going down at the rear!



In both of these photos the hood is fully latched at the front and no other adjustments were made.

Now, I understand this is a last resort, you donít want shims showing under your hood. I donít think it is that big of a deal being there are a whole stack of them at your fender bolts not ten inches away, but they didnít have them there from the factory so many of us donít want one there now.
The solution is to rotate your hinge back. Lifting the front higher and lowering the rear. If you wanted to go as far as you could as an example you would loosen all the bolts on the hinge and with the hood open simply push it up in the front opening it as far as it will go while someone tightens the bolts to the fender. At that point the rear of the hood is going to be as low as you can get it without hogging holes in the hinge or shims. Notice how this will make the hinge go further down just as it did on the wifeís truckster hinge.


Brian Martin
1965 Buick Gran Sport Convertible
1959 Rambler American. Yeah, I said RAMBLER, you want to make something of it punk?
"Fan of most anything that moves human beings"
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post #2 of 54 (permalink) Old Jul 22nd, 12, 8:53 PM Thread Starter
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Re: Lowering the rear of your hood or front of trunk: alignment

If you want to go further without a shim you would need to enlarge the lower portion of the front hole and the upper portion of the rear holes in your hinge where it bolts to the fender. Then you can repeat the pushing up on the front of the hood to lower the back.



Just part of the dance you often need to do to fit body panels. This information is more about understanding the geometry than anything else. Sure you could open up holes you can add shims but if you understand the geometry you can also understand that bending the hood or trunk structure or hinge if itís designed like the wifeís truckster or the trunk hinge on your Mustang or Chevelle you can also lower it that way. But Iíll tell you what, if you understand the geometry and stick a shim in there to see and it fits, you are way ahead of the game, now you may choose to bend something or open a hole for more movement.

Brian Martin
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post #3 of 54 (permalink) Old Jul 23rd, 12, 9:14 AM
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Re: Lowering the rear of your hood or front of trunk: alignment

So your saying if you want the rear of the hood up and the front down you need to do the opposite and rotate the hinge counterclockwise?
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post #4 of 54 (permalink) Old Jul 23rd, 12, 9:49 AM Thread Starter
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Re: Lowering the rear of your hood or front of trunk: alignment

The one thing I didn't make clear is when you rotate that hinge UP it lowers the pivot point LOWERING the rear of the hood!.


Brian


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post #5 of 54 (permalink) Old Jul 23rd, 12, 9:51 AM Thread Starter
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Re: Lowering the rear of your hood or front of trunk: alignment

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Originally Posted by Dsmith411 View Post
So your saying if you want the rear of the hood up and the front down you need to do the opposite and rotate the hinge counterclockwise?
Yep, it's that simple. By rotating the hinge like this it takes only one person too. And you aren't loosening all the bolts leaving one tight, you have much more control. You can move it a 1/16th of an inch if you like, it is very easy to control how much. No moving forward or back, just up and down as much or as little as you would like.

Brian

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post #6 of 54 (permalink) Old Jul 23rd, 12, 10:22 AM
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Re: Lowering the rear of your hood or front of trunk: alignment

So can you just lower the front of the hinge and get so much adjustment and if that is not enough raise the back of the hinge and get more or do you need to move both at one time? (lower the front and raise the back)
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post #7 of 54 (permalink) Old Jul 23rd, 12, 10:31 AM Thread Starter
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Re: Lowering the rear of your hood or front of trunk: alignment

Some hinges have slotted holes only on one end or the other. So on some hinges it will rotate just not at both ends, same results, a rotated hinge. But yes, you can raise or lower each end and get the hood to go up or down in the back at ease. It's one of those things that you just go and try. I will often when aligning have an idea, move it and find that I was wrong and do something else after moving it back to where it was. This is common and not a big deal. That's the cool thing, simply loosen a bolt and move it, no welding, no drilling, no sanding, no repainting, just loosen the bolt and move it a little.

Brian

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post #8 of 54 (permalink) Old Jul 25th, 12, 7:47 PM
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Re: Lowering the rear of your hood or front of trunk: alignment

brian,,,,,man them pics you made to explaine are awsome!! that makes it so easy to explaine to people how it all works. good job man.
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post #9 of 54 (permalink) Old Jul 25th, 12, 10:44 PM Thread Starter
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Re: Lowering the rear of your hood or front of trunk: alignment

Thanks for the kind words. It's the kinda thing that REALLY needed some photos, and proof. Shimming down the wife's truckser hood shows exactly how it works. I have explained it many times over the years and it always is left a little gray, I wanted to make it perfectly clear. Hope it helps out someone!

Brian

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post #10 of 54 (permalink) Old Jul 26th, 12, 12:33 AM
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Re: Lowering the rear of your hood or front of trunk: alignment

You know I cant beleive it, I read this last night. I thought "It cant be this simple". So I tried it today. It works! The trunk and hood on my Chevelle were up at the rear edge, I added one 1/16 shim to trunk and 1/8 shim to hood and it fits much better! THANKS!
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post #11 of 54 (permalink) Old Jul 26th, 12, 11:35 AM Thread Starter
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Re: Lowering the rear of your hood or front of trunk: alignment

Quote:
Originally Posted by poloaa008 View Post
Some hinges have slotted holes only on one end or the other.
Yes, but the same principles are still at play.

Brian

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post #12 of 54 (permalink) Old Jul 26th, 12, 11:37 AM Thread Starter
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Re: Lowering the rear of your hood or front of trunk: alignment

Quote:
Originally Posted by 1967 chevelle malibu View Post
You know I cant beleive it, I read this last night. I thought "It cant be this simple". So I tried it today. It works! The trunk and hood on my Chevelle were up at the rear edge, I added one 1/16 shim to trunk and 1/8 shim to hood and it fits much better! THANKS!
An Ahhhh Haaa moment. I love those. Ok, now that you see how the principle works maybe you can roll the hinge back (one at a time is fine) on the hood and maybe tweek the trunk hinge to get it where you want without the shim.

Brian

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post #13 of 54 (permalink) Old Jul 26th, 12, 2:06 PM
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Re: Lowering the rear of your hood or front of trunk: alignment

Thank you greatly Brian. I know what I'll be working on this weekend.
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post #14 of 54 (permalink) Old Jul 27th, 12, 11:01 AM
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Re: Lowering the rear of your hood or front of trunk: alignment

So why does the front of my hood go sideways when I try rotating the hinge to lower the left rear corner?

The front of the hood goes toward the left side so bad that the pin misses the latch hole.
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post #15 of 54 (permalink) Old Jul 27th, 12, 1:15 PM Thread Starter
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Re: Lowering the rear of your hood or front of trunk: alignment

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Originally Posted by Dean View Post
So why does the front of my hood go sideways when I try rotating the hinge to lower the left rear corner?

The front of the hood goes toward the left side so bad that the pin misses the latch hole.
LOL, I love it when I think something out so well that it is perfectly clear and then someone asks a question to show a glaring omission in my original post.

What is happening is because you are rotating the hinge BACK, it is bringing the hood back as well and you need to simply move the hood forward on that hinge after it's rotated.

Sorry for not adding that little tidbit to the original explanation.

Brian

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1965 Buick Gran Sport Convertible
1959 Rambler American. Yeah, I said RAMBLER, you want to make something of it punk?
"Fan of most anything that moves human beings"
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