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Discussion Starter #1
The time has come, i will be priming my '74 GTV in PPG high-build primer.

The car was taken back to bare metal and has already been primed in epoxy (filler work is also done).

I need to prime all the outside, the engine bay, inside of doors, hood, trunk etc.

I have heard around 4L should do it but i think i will need more than that.

Because of the amount of metalwork completed i want to put on as much high-build as reasonably possibly because most will be sanded off anyways...i just want to avoid sanding through to the epoxy as much as possible.

Anyone have suggestions from experience? 6 litres perhaps?

I will use an HVLP gun to try and minimise overspray. :D
 

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*subscribed*

My PPG guy reckons 4L should be heaps - that said i've not got to that stage and have no idea. I thought the idea was to build up a as thin a base as possible?

Your experience actually inspired me to have a go at my Duetto myself - i'm still bare-metalling and welding (okay cutting). So lots of pictures please :)

Craig
 

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I've used these primers in two colors: grey and black. Spray one color on, let dry, overcoat with the other color. Then sand (esp outer body panels) with a long sander - body shops will have them, and the low-clog paper you need; I got one that is 24 inches long (slightly flexible). You will quickly see where the high and low spots are. Bad lows need expert hammer work or a thin bondo coat. Modest ones (most common) just sand as flat as possible and spray the next color HBP again. Just a little patience and you end up with show-car flat panels!

Robert
 

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Discussion Starter #5
Craig_m67 - Good to hear you decided to DIY, it is satisfying stuff, a steep learning curve no doubt, but not as hard as one might think, the financial savings are well worth it.

Typhoon90 - I'll probably just get the 4L tin for now, can always buy more if i need to!

60sRacer – That’s an interesting method you described... i was reading an old hot rod magazine article on painting cars and one guy would put on a couple thick coats of HBP then block it back dry with 80 grit on a speed file as you described. Then after he was happy with it being as straight a possible he would do another coat of HBP and wet sand as per normal.

I think this would be a good way of achieving very straight panels. I really want this car to be very straight… !
 

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Don't need 80 grit on HBP. I'd use that if I needed some plastic filler, but for those I'm partial to a hammer and dolly and a torch, and a lot of patience.
]
I use 120/150/180 grit with a long body file on the primer. Alfa's are pretty good as they don't have a lot of compound curves. To keep from sanding thru the primer at the body lines, put a strip of masking tape over the peak lines.

I'm at my best, and most patient if I only work for a few hours at a time, then quit for something else.

Robert
 

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I once used high build on a car, knocked it back with 180 grit on an orbital sander, then two more coats of regular primer, then wet rubbed that back.
Reason was lots of small imperfections in the metal (some animal stripped the car to bare metal just before I bought it with a disc sander). It worked very well and saved a ton of time. I also did it when I painted the quarter panels and roof on the 90 (except I didn't use high build), just used the orbital sander to knock down the high spots then one nice wet coat of primer.
The big advantage of dry sanding primers is you can use aluminium oxide paper, which is very resistant to clogging.
 

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4 ltrs should be enough.
If you block down and them reprime you'll prob need more but outer skin only on the 2nd shoot.
Most hi-fills mix at 4:1.
For the outer shell, from bare metal and in this order I..
wet on wet acid etch, 2k prime 1 coat, polyester 4 coats then block down 120g.
Then hi-fill prime 4 coats, block down 240g then 360.
Reprime as necessary, block 360, 500, 800.
Shoot colour.
 

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Discussion Starter #9
Thanks Blue_Flame, i have no reason to doubt your techniques.... your restorations are jaw-dropping stuff!

Can't wait to get the car in colour, not long to go now :)

Will PM you abut another car i have that needs some specialist chassis attention...
 

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The are many ways to go about and I'll vary it depending on what the car requires but the general principle stated by Graig_m67 is correct, keep it as thin as possible without breaking through the layers.
This is to maintain the flexibility and stability of the painted surface and underlying substrates.
To do this on an old car then the metal has to be as straight as can be, hence 60'sRacer's hammer, dolly and torch principle makes for a good foundation.
Thanks GoldCloverLeaf, other car sounds interesting...
 

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On some of the older cars ( I had an MGTD for example), the flat sides would become wrinkled simply with age. The original stamped sheet metal was nicely work hardened when new, but at 40++ years old, it has self-anealed. That is, its metal grain structure grows larger, and the metal becomes softer. But this happens in spots, so you get that wavy look common to old cars - and especially to old aircraft (aluminum - just look at a pic of an old B-52).

fF you really want it to be straight again, you have to re-establish the surface work hardening by hammering the entire panel. Broad hammer, broad nearly flat dolly, not too much force - you are not trying to move any metal.

Wet the surface and look at a low angle with a light behind the surface, and you can see the problem, and the effect of your work. Fortunately, our 105's are pretty good and have enough curves that they don't have too much waviness. The GTV doors have a little trouble, and the hood and trunk lid sometimes suffer.

All it takes is a little patience. Minimize the torch as this softens the metal again. Actually a LOT of patience.

Robert
 
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