ZR1991

Here is my opinion about the C4 clamshell hood:

It is a very desirable feature, for all the reasons we already know, but it is nuisance, and is responsible single handedly for most of the rap C4’s get about rattles and squeaks.

For example, rattles and other noises that you swear are coming from the dash, the A/C vent system, the dash panels, wiring harness, and especially the front hinge areas of the doors are actually the hood, and the noise it creates is transmitted into the car in such a way that it fools you.

Obviously some rattles you can never get out, but most are surprisingly easy.

And as a plus, the other problem that is always associated with the C4 is that the hood “moves around” when the car is driven. This complaint is so common that I have seen it referred to in magazine articles.

The great news is that my three-step plan solves both problems.

1) May seem obvious, but have you studied the underside of your hood? The black painted side? Notice that there might be some “damaged” areas, where the black paint has been scuffed off. Look in the engine compartment where each white spot would be when the hood is closed, and you will find something that is touching the hood. Common places are the radiator shroud, and upper parts of the plenum, and the contact areas with the body around the edges, especially in front of the wheels. For each one, fix it. Either move the item, adjust the hood fit, adjust the panel fit, or simply put a small rubber pad with a sticky side on the item. Then paint the white spots black and observe every few months for new ones. This makes a big difference, trust me. If you have a ZR1, it is so crowded that you may find 8 or 10 spots.
2) Next, take a look at the latch-down pin. That is the big pin with the spring on it that latches when the hood is closed. It and the latch will have obvious shiny and worn areas on them. No matter how much you lubricate them, they make noise. The noise is almost a scrubbing, or groaning sound, as if two large items were rubbing. It is NOT a rattle. If the hood is otherwise adjusted OK (if it isn’t do that first), then cut out of thin (1/4 inch) rubber a couple of “doughnuts”. The rubber should be fairly tough, like neoprene, and the hole in the donut should be a bit smaller than the big part of the pin. The outer part of the donut should be a bit larger than the receptacle. Grease this part, and the associated pin and receptacle, and that noise will disappear, probably for about a year, before you need to re lubricate it. See the picture:
3) Now this is the neatest trick of all. Look again at the area of the hood near the latch pins. Right near those pins you will see another pin (one each side) that is about as big as a pencil, and pointing down. It is a guide pin, responsible for keeping the hood from moving. Guess what…. It doesn’t work. (before you start make sure these pins are TIGHT. They have a nut at their base.) Lay the hood down if you have to and fine the small, square receptacle that it goes into. You will see one of two things. One is that there is a stupid, loose piece of hard plastic in the receptacle that is supposed to hold the pin. If it’s there, take it out and throw it away. The second, and very likely possibility is that it is already gone, in which case you are saved the trouble of throwing it away. Now comes the tricky part. Tricky only because it is hard to describe, not because it is hard to do. Find some more neoprene rubber, this time much thicker than the one you made the doughnuts out of. This has to be really tough rubber, and about as thick as HALF the opening left after the plastic is thrown away. Note the size of the rectangular opening, and imagine a piece of rubber folded in half and stuffed into the opening (see the pic). Cut a piece of rubber about 1 ˝ inches long (about twice the long dimension of the opening), by about 1 inch wide. Then in each end of the rubber, you should cut two small notches like this: The purpose of these notches is to hold the rubber in place when you stuff it into the receptacle (see picture). Note that the notches are nearer the bottom. This is so when they “hook up”, they will tilt the folded rubber back (see pic). What you will then have is the receptacle lined with a wrapping of this rubber, with the folded part to the rear. (See the pic). Lubricate this piece, and lower the hood slowly to make sure the pin starts to force its way through. Once it is right, raise the hood and close it normally.

You will notice one thing instantly. The entire sound of the hood closing has changed. It is now a soft, heavy “clunk” instead of the hollow rattle-like sound it was.

Then drive the car and you will be stunned at all the noises that have disappeared. Step three really does a lot here.

Then the last thing you will notice is that in normal driving, the hood is steady, and doesn’t shimmy around. This is provided you used heavy, stiff, and thick rubber, like in the pic. The pin must actually force its way through when the hood is closed.

That’s it!

Check every now and then that nothing has moved, and that there is adequate lubricant, and enjoy your new, tight, and quiet C4!

PS for those doubters. The pieces you see in the pics have been on my car for a year now, and there has never been an experienced Corvette person riding in it that hasn’t noticed that something was “different”. The difference? Assuming the wheels are still on the pavement, the car is quiet, and the hood doesn’t move about.

Try it, you’ll be amazed! By the way, if you can’t find quality neoprene, it is usually available by the square foot in any thickness at commercial outlets. All towns have places like this, where air conditioner guys and plumbers by stuff like that. In the meantime, any relatively tough rubber will work for a 30-minute try out experiment. Though not as effective and not as permanent, it will prove the point until you can find a source of the good stuff.

Have fun, and remember I am still working on my C4 chassis stiffener that really, really, really works to make the car as tight with the top off as it is with it on. Hopefully in another month or so, I’ll have that ready. I know I wrote about it a couple months ago, but the legal and medical stuff has slowed me down… but not stopped me.

By the way, for those that asked for this information because they saw the “for sale” posts I had put up, the Cobra sold in about 8 hours (as I hoped), and I am going to try to keep the ZR1. After all, I need it for the experiment to stiffen the chassis… Don’t I?

Regards, and have fun.

Post how these tricks work for you. It truly makes the C4 what we always wanted it to be.

[Modified by ZR1991, 8:05 PM 8/27/2002]


[Modified by ZR1991, 8:08 PM 8/27/2002]

BiZ

Thanks for posting this

Looks like I have some examining to do tomorrow :cheers:

mikeg826

:yesnod: :cheers:

bogus

I know what my after dinner project is gonna be....

Thanks!!!!! :cheers:

Caboboy

groan..... another one on the list :D

very nice post, thanks! :cheers:

fsr402

YUP and if guys keep posting thing like this My girl friend wont let me play with you any more

Tx07BlackZ51

Thanks so much for posting this, I'll print it and work on it soon. Congratulations on selling the Cobra, and I really hope you can keep the ZR1. Good luck with your other project too :cheers:

CowboyNVette

Thanks Art :yesnod: I am also awaiting your C4 chassis stiffener. If you need any assistance, I am only a couple hours away from you.

Hammer

Thank you very much!

Oly

Very :cool: ...... looks like I will be rounding up some rubber pieces for a worthwhile project.

Thanks...... :cheers:

Aggravated4life

Where were YOU when GM needed HELP for these problems during the C4 run???
:D
Thanks for the detailed post on what to check and do.Im sure it will help many.
:)

BrianCunningham

:cool: idea

ZR1991

to the top once.

And, Cowboy, I will definately call you. We gotta get football season started first, then I'll be glad to call you.

Regards,


[Modified by ZR1991, 10:44 PM 8/29/2002]

CowboyNVette

I'll be waiting.....Besides when LSU gets playing its hard to distract me.... :lol:

BrianS

Thanks for the post... Always looking for a way to keep the vette tighter/quieter. :D

_Brian

jimmyd

Thanks, glad you kept the Z.

bigdan

thank you! :cheers:

KyleBst264

Thank you for posting that. That was some pretty useful information.

2HIP4U

Great post! I've also taken to periodically
lubricating the adjusting bumpers and locating pins
with silicon grease (the type used on the
weather seals).

Thanks.


:seeya

John Row

This is excellent, you should post it as a TECH TIP. That way it won't get lost.

Thanks,