well i have an 85' berlinetta 2.8 mpfi (digi-dash). VERY VERY nice 3rd gen... at least it is compared to my other 3rd gens. it has 49,320 original miles. its 100% factory and original. it was garaged its whole life and owned by an extremely old granny since new. she died, so her grandson inherited it when he turned 16, and he blew it up in a couple days....(stupid ***)

anyway i baught it from them and i dont have a garage and i unfortunatly let it sit for 2 years in my yard and let the blistering cold winter snow eat it up, and scortching hot summers bake it...i still hate myself for it too, so take it easy on me lol.

but i live in indiana and you locals know how bad the weather gets. but im going a differant route with this car than i did with my 4 other ones, im going FACTORY FREAK on this one. the underbody got 2years worth of flash rust on the raw parts.

so winter is creaping up again, and unfortunatly with my funds, the engine build will not be done soon (more internal damage than i thaught). so will undercoating the underbody of the car de-value it? it came factory with a grayish color paint underneath. would it be smarter to clean up the flash rust and undercoat it,(so no more damage happens this winter) OR should i pay a body shop to repaint the under body the original color?

or is the 49,xxx miles beyond the desirable factory freak value to where i should go ahead and do undercoating, paint engine, replace or upgrade factory parts, ect...and just make it a "clean" 3rdgen?

 

car isnt worth much anyways, so go ahead an spray it

 

That would be primer, the underbody never really got painted( unless you count overspray).

While value is what it is to each individual, the above makes the car greatly less desirable than other models.
That being said, I'd say that most people would probably suggest something such as POR-15 on the underside. Do a search, it has been covered a few times.
Here's one search result to get you started - link

 

Under-coating won't de-value it as much as rust and rot will. Get it undercoated, IMO.

 

Well, you really need to get the rust off first if you can. some can be done with wire brushes on a hand held grinder. and some is hard to do without sand blasting. If it was me, and i went through the trouble of cleaning up all the rust first, i would take pictures of it, then use the under coating. Reason is, if anyone asks, you have proof the undercoating wasn't done to hide problems.
If i had a place to put it in a protected environment, like a garage, I would want to paint the under body. If it's got to remain outdoors, then the under coating will give better protection.

 

the 2.8s are worthless, You'd probably get more money when selling if you said it was a rolling chassis, no drivetrain... ... the ones that are a bit more desirable I would say are the 1LE models... ...

 

yea yea yea i know the 2.8 was very very undesirable, but hey if i tossed something else in there, numbers wouldnt match. i know the real money is in the 1le's, mint iroc's, pacecars, iron dukes (?) ect.. but my iroc is already customized, so it aint worth jack unless its the right buyer. my other 3 are rs's all with 3.1's....

i just cant explain how nice this berlinetta is!! it blows my freakin mind. i have to get interior pics to show you. the exterior has one dent (no biggy). has original and flawless weather stripping too.. but in indiana, a 3rd gen this rust free is crazy lol. the only rust is flash on the rear end, trailing arms, exhaust, ect. even the pinch welds arnt even TOUCHED. all my other ones have smashed ones or rotted ones.

yeah i wish it was atleast the 305 version, but you end up with whatever you come across.

and keldrin, thats what makes the most sense to me. because thats what i meant by de-value with undercoating because it can hide stuff.