• Having site issues? Contact Dub@southernPolyurethanes.com

Primer or filler?

I've got a few low spots on this part of the 1/4 I'm blocking. The last of the 3 clearly needs filler, but do the first 2? They are very close, but I'm not sure if some primer would fill them (Turbo?).
1st low spot is immediate
2nd is about 6 seconds in
3rd is at the end where the fender curves down

I personally use filler over any known defect... I feel it's a better repair plus it's quicker....if you can get to the backside of those spots, you might could remove them entirely with a slapper
There is already some filler behind this area so I don't want to use a slapper, and I can't get at some of the spots as well. I just shot another coat of primer over my filler work to see how close I am.

I'm trying to find a use for higher build primers, seems like super shallow spots would make sense to spray a quick coat. When I use filler I tend to over do it or over sand it. Some of these spots are shallow enough that the sand paper grit will lightly rub, so it has to be very close.

Any others have any opinions?
My opinion again....I've never used metal glaze but feel it's a little overkill for what your trying to do...any good skim filler would work tho...if you fill it and long block it, you can get it right. Only if primer is epoxy tho..I have used VERY thin coats of filler over high build with no problem tho...but I do scratch good with 80 grit. Make sure your epoxy is within the window of using filler if it's been a while. I believe SPI is 7 days before scratch and recoat is advised.


Trying to be the best me, I can be
Mitch is that a Z? Just curious. As for your question after looking at the video here is what I would do. First what grit are you using to block with? Looking at the vid I would start with somewhere from 120-180 grit. It looks a little rough so you want to block with a coarser grit to start. 150 would be a good choice. Block evenly across the panel from one end to the other. continue until you start to see metal peeking through in places. If you have lows remaining then depending on how deep you would want to either epoxy only, epoxy, wait then a urethane like SPI Turbo, or a high quality glaze (no cheap stuff please) to fill your low spots. When to do what is really a judgement on your part, based on how the panel feels in your hand. Hard to give advice on filler versus primer without laying hands on the vehicle. Suffice to say when in doubt glaze is better than too much primer. Stay with the coarse grits till you have the panels right, only then should you move up to 320-400 grit. It's a process that you may have to repeat multiple times until you have everything straight.
It's a Datsun 2000, 1970. I have been blocking in 80. What I did on the rockers (I'm slowly learning to do smaller sections instead of getting overwhelmed doing a whole half car) is blocked in 80 until my high spots were poking through, then used body filler on the lows, then another couple coats of epoxy. Once I get the whole rear half done, I'll go back over with finer paper, probably 220, then put one last coat of epoxy just to seal everything until I'm ready for final paint.
This is all after hours, so I don't spend tons and tons of time at once. Once I get things straight, I seal in epoxy. I have the fenders, doors, and hood all ready for their final blocking in finer grits. Once everything is ready, I'll block up to 400 grit, then paint all the panels at once.
I'm just having a hard time figuring out what needs filler, or glaze, or 2K. Maybe I should have sprayed a coat of epoxy, then a coat or 2 of 2k to store parts in, then block & seal, then color.


Trying to be the best me, I can be
I would first epoxy any bare metal (if there is any) then put 3-4 coats of SPI Turbo or 3 coats of SPI Hi-Build on it. Let if sit a couple of days and start blocking panel by panel with 150-180. I like 150 better for initial blocking of urethane as it cuts quicker. Obviously use a guide coat. If you still have lows after that, if there is any doubt use some glaze. Try to be as smooth as possible when applying the glaze, sand the areas, don't worry to much about cutting into the primer. After you have glazed all your lows and sanded go back with 3 more coats of either Turbo or Hi-Build and block it again with 220. when you finish if it looks good do a final wet with 400 grit. (depending on your color choice I sometimes work up to 320 dry then go 600 wet for final sand) If you still have lows you can glaze again and spot some Urethane over the area or do the entire process over again.
Chris, Curious why you suggest turbo or hi-build. Is there a place for standard 2k? I'm getting to a similar point in my project, so I'm curious.
Chris, Curious why you suggest turbo or hi-build. Is there a place for standard 2k? I'm getting to a similar point in my project, so I'm curious.
I use SPI "Regular 2K" 80-90% of the time. Turbo is a better product if you are in a hurry as most of it's shrinkage happens early, regular 2k seems to shrink about like every other 2k on the market. This is not in reference to the original post because I think it needs high build but to your question of is there a place for standard 2k? If you finish you body work well and do not rely on primer to do any of the filler work (which you shouldn't anyway) regular 2k is all you need. When you have other circumstances, that's when high-build or turbo come into play. We are all different and have different approaches. I don't think there is only one correct answer but I prefer to get my stuff really close before I prime (when I can, I'm not perfect either) and use SPI Regular 2k. It's always worked good for me, and I don't see any more shrinkage than the majors like PPG, S-W and I think it is better than BASF primer which I find shrinks for weeks not days.

Sorry I replied to this before I realized it was addressed to Chris...My apologies for my unsolicited opinion :)
I ended up filling and blocking. It's laser straight now.

I just trying to find the best times for each product. Obviously, 2k is used for it's filling properties or else there would be no use for it. I need to learn what something looks like that can be coated with 2k and end up level.
An experience thing for sure.

Next time I would definitely have used glaze instead of filler on 2 of the spots