How to tell GM fenders from aftermarket

[Emo1956]

Hi everyone,I just started taking apart a 69 Z only to find out I believe are aftermarket fenders,inner panels and hood. The owner wants to do it right so I am hunting for NOS. I am no expert on body panels but I can remember something about marks on the fenders or something. What would be reasonable for a set of fenders with extensions or a ZL1 hood ? I found 1 set of fenders for 6k ! I almost fell out of my chair. As always thank you for all your help. If anyone knows who may have or can point me in the right direction I would appreciate it. Thank you Emo 

[x66 714]

If they are GM fenders (production line) they will have a number stamped on the inside edge near the header panel where the hood closes. Hood will have a number on the drivers side edge near the back of the hood. These numbers are very hard to see. When I'm looking for fender wells, I want to see original staple holes where all the rubber pieces are. See if that will help.
BTW if you want to go NOS, find the oldest NOS stuff you can. I've seen discussion about people preferring parts before the early 80's. There is still some used parts out there. I myself would rather use old original parts than anything new...Joe

[KevinW]

I think the hood hinge weld nuts are the easiest way to tell, just cannot remember what each looked like!

[ZLP955]

I think the hood hinge weld nuts are the easiest way to tell, just cannot remember what each looked like!

Square on originals, although some reproducers may have caught up with their latest offerings.

[Mike S]

 Looks like Tim and Kevin are correct about the nuts. I went into the shed to look at a spare NOS GM fender (for my 67 w/R/S) I bought around 1980 (I forget the year) and took pictures of the welded hinge nut, the date stamped into the metal and even the GM tag used at that time. Maybe the date is on the tag info?

Mike

[Emo1956]

So would nos have the same as line correct. How much does it really hurt the car ? Wouldn't NOS count for the same ? I found fenders @ 1900. ea extensions @ 180. cowl 395.  cowl hood @ 1300.  It's that bad of a looking car till you get close and know what your looking for.

[Emo1956]

 This is what somebody put for a motor in the car. It has GM aluminum heads on it 3946074 I think those came on a L78 if I am not mistaken.

[Emo1956]

Thank you mike for the pics and everyone else chiming in. I now know what to look for. Is it only the older NOS stuff that has the welded nut ?

[69Z28-RS]

Thank you mike for the pics and everyone else chiming in. I now know what to look for. Is it only the older NOS stuff that has the welded nut ?

Per NCRS guides, the '074' aluminum BB heads were used in 1969 Corvettes on the L88 and ZL1 engines, as well as the LS6 engines in 1971 (425 hp 454).     The L89 optional aluminum heads in '69 were 3919842, and I think would have been used on the L78 (were they opted for)...

[bcmiller]

Yep and the 074 heads were produced even into the 70s. I think one set I have has 1972 dates.

[Emo1956]

When the guy bought the car it was suppose to be a 427 but I ran the casting numbers on the block and I think it came back to a 454. I haven't look at the balancer or the flywheel yet. I know when I drove the car it was a dog ! I'll know today when I pull the motor out. Thank you for the infor.

[Emo1956]

Mike please look at this tag on a NOS fender compared to yours. There seems to be quite a bit of difference ! What do you think ? Thanks Emo

[Kelley W King]

I do not know what cam that motor has but with  those heads if you have highway gears it would be a dog.

[bcmiller]

When the guy bought the car it was suppose to be a 427 but I ran the casting numbers on the block and I think it came back to a 454. I haven't look at the balancer or the flywheel yet. I know when I drove the car it was a dog ! I'll know today when I pull the motor out. Thank you for the infor.

The 1969 427 casting number ends in 512 and that block casting was used for 454s in 70 and 71.

Cam swap will fix it being a dog. What rear gear?

[Emo1956]

It has a close ratio trans and I would say feels like a 3:73

[BULLITT65]

wow someone really liked HO enough to paint the firewall, heater box, booster, and brake lines. Thats dedication.
Have you located a DZ block?

[Emo1956]

LOL you notice that ha ! What a hack job. I took half the car apart  by just my hand so far. It took me about 5 months but I was lucky enough to have found the original block. The owner wants everything new in this car so I have been collecting parts for about 6 months. I am going to get rid of all the parts from this car for him so he can recoup some money.Look at the shim they used under the fender lol. This is the new dash I am building for the car.

[ZLP955]

Personally I would just hunt around for nice used GM fenders, they will be a fraction of the cost of NOS and you don't have to consider the fit and finish variances between early and late NOS stampings.

[Mike S]

Tim,

  How late were the NOS available from GM? I'm curious what the time frame distinction was between early and late. I heard the later NOS parts used a bar-code instead of a printed tag like the one I posted.

Mike

[69Z28-RS]

I'm with Tim on suggesting good southern/weatern ORIGINAL fenders/parts rather than NOS.   I suspect you'll have far less problems fitting them...

PS. for Bullitt...   EVERYONE loves the high output Hugger Orange Z's...     That's a HO HO for you Austin! 

[BULLITT65]

 
Well I am ok with Orange. But when it comes to painting the firewall, & heater box, I could deal with that on some rest mod I guess. The booster and brake lines though, come on...

I would rather see them in some aerosol overhaul fogged in black than the time it took them to do that.

Speaking of fenders though. I have two different markings on my white 69 fenders. Driver side has a half circle stamped out, just above where it bolts on the radiator support, but the passenger side fender does not have it. I am guessing one fender is reproduction?

[Emo1956]

OK here is what these fenders look like. They have the square nuts welded on. 1 inner panel says Twain and the other inner is a lot heavier.

[Emo1956]

More pics. The parts seem pretty heavy to me. Retros are liter and seem to bend easier.

[Emo1956]

Are these original ?

[69Z28-RS]

they appear to me to be GM parts (except for the TAiwain part).  Look on the flange as previously discussed to see if there's a 'week no' which indicates production line part; other wise probably an OTC part.  The black primered flanged makes me think that fender(s) were OTC parts.

[z28z11]

I've got a couple of '69 NOS fenders (R&L) if you need any particular views. I bought them in the mid 1980's from my local Chevy dealer, late '70's/early 80's vintage, long before they got discontinued. Extensions, too (were included with the fenders at that time). I can vouch for their age -

Regards,
Steve

[Emo1956]

Well I yanked the heads to find to my surprise 1 piston beat to hell lol. It looks like either someone dropped something down the carb or a plug broke off but that is a lot of damage for just a plug. I now think the engine is a 427 like the guy said when he bought the car. There is no counterweight on the balancer and it is a 4 bolt main engine. So maybe he got lucky and can recoup some money. I will know more when I pull the engine. Thanks to everyone for all the infor. You guys are the best. I hope the fenders are GM. Thanks Emo

[ZLP955]

Tim,
How late were the NOS available from GM? I'm curious what the time frame distinction was between early and late. I heard the later NOS parts used a bar-code instead of a printed tag like the one I posted.
Mike

Mike, can't answer that early/late timeframe with any authority, but as far as I'm aware, NOS fenders were available into the 90's but by that stage the tooling was worn, tolerances increased and panel stamping crispness and fitment reduced.
Most who have used NOS parts seem to recommend those with non-bar code part number labels as being better stampings than those with bar codes, or with 8-digit part numbers; but I'm not aware of when that transition happened.

[ssl78]

454 and 427 blocks are the same. If its a 427 it will have either a 7115 crank or a 6223 crank. If its a 454 it will have a 7416 crank.

[Sauron327]

   I have two pair of 69 fenders; one repro and one NOS. Both have square nuts as observed from the engine bay side. You cannot rely on the engine bay side view of square nuts in the photos posted. Look at the inside of the fenders. Repros may have conical and rounded tops on the backsides of the nuts, GM will not. There are no date stamps(run numbers) on the NOS fenders I have; however they are on assembly line take-offs. There are also no locator holes on the repro fender inner braces as on GM fenders.
    GM hood back sides are notched as in the photo B.A. provided but I've duplicated them with mild reworking. The front of a GM hood structure hem is well defined, not so in any repo hood. The spotwelds on the hood bumper contact discs are also different.

  Early stamping decals look like Mike's post, mid look like Bad Ass's for lack of a name, late had a bar code if at all. GM did not stamp these parts in the 90's. They were simply available at the dealerships as overstock. No factory stamps parts 20 years after production. They simply ended  up in warehouses as NOS.

 Made in Taiwan is self-explanatory.

  I like to use assembly line take offs even if they need work. I've had to throw a day of labor at some NOS bar coded '67 fenders to make them meet and exceed factory standards. Just installed a later 69 NOS doorskin that was double stamped at the bottom hem. Fixed it with a little extra H&D work but it proves that NOS panels are no guarantee. Common knowledge in the industry.

  All of this depends on the owner's goal and desires.

[Emo1956]

Well it's a 427 to my surprise.It has a cross drilled 6223 forged crank and it std-std. The rods in it seem huge to me with 11/16 nuts and it has Icon forged pistons. Someone put some money in this motor .