Register now to get rid of these ads!

Customs What is a reasonable compressor for a decent garage paint job?

Discussion in 'The Hokey Ass Message Board' started by airbrushguy, Mar 4, 2023.

  1. airbrushguy
    Joined: Jul 1, 2005
    Posts: 330

    from NJ

    I have painted many cars in diverse areas, but I have a 5hp 30 gallon compressor that I've only used for priming and finish painting if the car is in pieces. I have a '49 Hudson that I would like to put a nice base cote -clear cote paint job on and I would break it down to the top, the hood, the trunk and then the sides from the belt line break-off of the top, down.
    I'm afraid my old faithful 30 gallon will not be able to keep spraying without continually pumping to provide a good paint job.
    I have seen some 60 gallon ( 13.4 cam at 40psi, 11.5 at 90psi, 3.7 hp) stand-up compressors and am wondering if they could handle the job.
    Has anyone had any experience using a compressor like this to do a finished paint job on a car?
    Thanks in advance
    sidewayzz69 likes this.
  2. Bandit Billy
    Joined: Sep 16, 2014
    Posts: 10,332

    Bandit Billy

    The last thing you want to have is a compressor running all the time during a paint job. The heat caused condensation is the issue, besides the noise and dust if it is in the same environment. A 60 gallon tank with a 5hp compressor, 1700 RPMs or less and an air cooler of some sort combined with water traps will prevent one of those ahshit moments.
    alanp561 likes this.
  3. Mr48chev
    Joined: Dec 28, 2007
    Posts: 32,648


    Years ago one of my buddies in Texas had an extra tank off a compressor that died an early mechanical death (yard sale item) connected in line with his 5 hp but small tank compressor to get added volume.
    The Big question is are you running out of air before you run out of paint or primer in the cup? A bigger tank or more storage for air gives you longer before the compressor kicks on or before it can't keep up.
  4. Budget36
    Joined: Nov 29, 2014
    Posts: 11,588


    One thing that I noticed is the HP on the compressor you mentioned, 3.7 HP? That’s a new one on me. Can you provide a link to it?

  5. airbrushguy
    Joined: Jul 1, 2005
    Posts: 330

    from NJ

  6. Budget36
    Joined: Nov 29, 2014
    Posts: 11,588


    I’ll be darn.
  7. Probably an import motor...
    Truckdoctor Andy and Budget36 like this.
  8. lostone
    Joined: Oct 13, 2013
    Posts: 2,444

    from kansas

    A couple of points,

    1- realize that it's single stage which isn't a problem just be aware that the air out of the head into the tank will run around 315 to 325 degrees whereas a two stage runs about 100° cooler than that and I have infact checked this personally to be true. Where this matters is outside air temp and humidity and condensation which works its way into the tank and air lines. Of course air dryers take care of this.

    2. Depends too on whether your using a hvlp or old school type binks, the hvlp will use less air and pressure.

    Personally I believe that compressor would be fine for painting but as I said be sure to have air dryers in the line. I built a cooler/expansion chamber that goes between the head and tank on my compressor, air is 320° out of the head and 130° out of my chamber.

    alanp561 likes this.
  9. 1ton
    Joined: Dec 3, 2010
    Posts: 649


    I want to expand on what Bandit Billy said. The heat build up from the pump causes condensation.
    I seem to remember that all compressors kicked off at 125 psi. This worked fine.
    Then, in recent years it seems that everybody builds compressors to shut off at 175 psi. Even the little portable pancake ones.
    The last compressor that I picked up, 5 hp. 80 gal. verticle, went to 175. It happily brought the tank from 0 to 125 psi and then seemed to work it's ass off for the extra 50 psi. Pump ran reasonably cool until it was in the home stretch above 150. Then it got hot.
    I switched out the pressure switch to kick out at 125 psi. It runs cooler, less condensation and I firmly believe that the pump will last alot longer.
    After all, it's about volume, not pressure when it comes to compressed air. So any added storage capacity is a plus.
    plymouthgoat62 and alanp561 like this.
  10. 1952henry
    Joined: Jan 8, 2006
    Posts: 1,127


    As Bandit Billy said, get one with lower rpm motor. Good ones have a 1745 rpm motor. The 3450 rpm motors really spin the pump for the advertised cfm, but create a lot of heat.
    alanp561 likes this.
  11. caprockfabshop
    Joined: Dec 5, 2019
    Posts: 370


  12. dana barlow
    Joined: May 30, 2006
    Posts: 4,953

    dana barlow
    from Miami Fla.
    1. Y-blocks

    I never had a big shop size compressor. I have,being I paint my own stuff in the back yard now n then,added a extra 3 gal. airtank into/on too/ the small compressor I have. I don't need to do that,except if what I'm painting is bigger then just my open wheel 28A bobtailed roadster.< that works fine with just my 8 gal. tank.
    Others have talked about dryer an stuff,all good thing to do,
  13. 1971BB427
    Joined: Mar 6, 2010
    Posts: 8,218

    from Oregon

    About 25 years ago I was beginning a bunch of bodywork on a project, and wanted a compressor that could run my air tools, and later shoot primer and paint. Went to Coastal Farm & Ranch and picked up a 40 gallon upright, with a 4.5 hp motor, and it runs on 115 volts. Can't recall the brand, but it was made in Canada, and is metallic blue. I've used the heck out of it for air tools, and shooting paint, and it's worked out great. It was reasonable back then at around $420 on sale.
  14. I had a large compressor and never used to be concerned about this stuff until I sold my shop and reduced my tools down to what would fit in a 2 car garage.

    I have a Harbor Freight 75 gallon compressor on wheels now but I'm thinking of just adding an additional air tank in line next time I paint something. I'm thinking it's the volume more than anything that makes painting easier.

  15. indyjps
    Joined: Feb 21, 2007
    Posts: 5,349


    @1ton agree on pressure, I've adjusted all my small compressors down for years.

    Agree with dana barlow, I've painted with small compressors. Slow the reducer down and pause a bit before your passes. Not ideal, but it works.

    If you add a surge tank, figure out how to cool the tank ( surge tank in a tank of water ? ) pretty effective chiller. Water separator after.
  16. lostone
    Joined: Oct 13, 2013
    Posts: 2,444

    from kansas

    Here's the simple expansion tank I made out of pipe I had laying around.

    Like I stated earlier I get almost 200 degree drop. Have a drain on the bottom of the tubes.

    indyjps likes this.
  17. patterg2003
    Joined: Sep 21, 2014
    Posts: 817


    I would think the 5 hp compressor you have would be able to put out more cfm than a 3.7 hp. If it is good for 12 cfm at 90 psi then it will be more cfm at the 25 -40 psi used with an HLVP gun. You could put an auxiliary tank to add capacity. My son picked up a large compressor tank off the local Facebook man cave classifieds for $100. One thing is to use the quick disconnect fittings with the larger bore and 3/8" hose. The less flow restrictions will help deliver the air to the paint gun. We used the high flow couplings that was a house brand that are identical to the Milton high flow fittings shown in the link.
    If you are doing one car and the compressor can successfully paint it then why go to the added expense of a larger compressor? The compressor will need to put out the same total volume of air for the job irregardless of the tank size.
    metlmunchr, X-cpe and alanp561 like this.
  18. Fortunateson
    Joined: Apr 30, 2012
    Posts: 4,993


    A lot of times those “5 hp” compressors are actually 3.7 hp and they just run them at higher rpm. They are referred to as “cheater 5s”. I painted two cars with one of those and I’ve had it for around 25 years. I picked up an extra tank 60 gallon tank for extra capacity (at about 20% off retail) but before I had a chance to plumb it up I stumbled on a four year old DeVillbis 7.5 hp for next to nothing. The new compressor was blowing capacitors and the shop we’re buying cheap knock offs. Replaced with proper one and it runs perfectly. 80 gallon tank and more pressure than I'll ever need. The old one just sits in the corner though it’s in perfect shape. Shop around and check on Marketplace, etc if you’re not in a can be found!
    finn and indyjps like this.
  19. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 4,456

    from illinois

    Probably some bullshit rating like " Instant Peak Power" , 1 HP = 746 watts ÷ volts = amps . check the motor I D plate , I see home depot doesn't show that. The numbers they do show are mumbo jumbo ! I've painted many cars with a 4 HP / dual 30 gal tank , 2 water separators , condensate loops & final desiccant filter on gun , one was a 1ton crew dually with a cap on an 8' bed , that's a lot of surface !
    Are there any electric motors made in this country ?
  20. NoelC
    Joined: Mar 21, 2018
    Posts: 668


    Sounds to me like your good to go. Lots who will disagree however and rightly so. However, it's not like you couldn't cut and polish your way to a shiny clear if you did screw the pooch. Pro's do it all the time for the deep luster shine. Base is easy to spray and if ya take your time you'd have all day to spray that almost worry free. Clear, how much do you want to apply and how much do you want to lose in over spray?

    While I'm not known for holding a popular opinion very often, some might say I bring a fresh perspective, and the poor mans approach to getting it done.
    Contents 080.jpg

    This old compressor was a a gift from Dad back in the day and it managed to offer air to cover a few cars and plenty of air tools in it's service. You have my vote, go for it.
    indyjps, 2OLD2FAST and alanp561 like this.
  21. goldmountain
    Joined: Jun 12, 2016
    Posts: 4,092


    Since I am either poor or cheap, I too have a wimpy compressor. To paint my car, I purchased a cheap LVLP gun from China. That is low pressure, low volume. Surprised me as to how well it worked. I'm sure that more knowledgeable people here might scoff, but that's fine.
  22. indyjps
    Joined: Feb 21, 2007
    Posts: 5,349


    I shot paint with a compressor just like that. Never did full car, single stage enamel - hood, doors, decklid, plastic trim ( late model) were done separately. Roof / quarters were done together. Same color primer, same coats on each part.
    Put it all together and buffed it.
    NoelC likes this.
  23. hepme
    Joined: Feb 1, 2021
    Posts: 398


    I'm no pro but have done several. Was always told compressor size depended upon the gun you intend to use, say 13 scfm for the gun-compressor should be sized for that minimum at a certain pressure-can't remember that but its like 40-60 psi or so. Air volume in gallons needed is also in the equation. Suggest you research the pro painters info for that formula and advice. I didn't see what type guy you intend to use-siphon, hvlp, lvlp, etc. They all have different ratings of air usage. You might be o.k. if you can find the right gun that fits everything else.
  24. finn
    Joined: Jan 25, 2006
    Posts: 1,137


    Exactly. The 3.7 hp is probably relatively accurate. I don’t think anybody is using the old, inflated power numbers since there were a number of class action lawsuits, and, I think, some FTC actions related to that fraudulent practice.

    A 60 gallon tank and that pump should be ok for an occasional paint job. It won’t run a body shop, but if you take your time you’ll do fine.

    I painted cars with an old 240 v two hp Craftsman belt driven compressor, although I did some of it a panel at a time.
    2OLD2FAST likes this.
  25. NoelC
    Joined: Mar 21, 2018
    Posts: 668


    We all have different experiences that get brought out and laid on the table. I like that. A little conversation, some explanation, a bit of thinking.

    Most can agree painting a car doesn't require a shop set up but if you have the money and like spending it, skies the limit.
    That said, that out of the way, last summer I was looking into spraying some Elastomeric Paint. Discovered after reading the data sheet, "they" recommended a #26 tip size and a airless pump system that in reverse would probably pull oil from the ground. A very thick product indeed. Thin 10% max. I didn't.

    Needless to say it was a liquid latex, I end up brushing to cut, and rolling on 30 gals. The wash I ended up using as a primer. Point I'm getting to is, when you're rolling paint you have time to think. lol. I did a lot of thinking. Like I should have rented a gas powered airless sprayer.
    What was I thinking about... this stuff filling a 1/8" gap and those bullet holes that still needed fixing.
    Preserve it in latex? It crossed my mind.
    But that said, I thought about what would happen if I over thinned it, atomized a finer wetter droplet, could I spray it then like a water based paint in a conventional gun? Just not get the build up to bridge gaps maybe? Then could I shrink the tip size, reduce my need for pumping pressure?

    Anyhow, when I think of guns and needle size, volume of air, I think suck , blow and spitting the size of spray. That and if the drops flow together with out running down the surface, a guy did good.

    Yours is a big car to spray I'll give ya that. But at the end of the day, it's always the clear most struggle with spraying. 9 times out of 10 it isn't because of the size of compressor.
  26. Budget36
    Joined: Nov 29, 2014
    Posts: 11,588


    Noel, I guess you’re right about the size of compressor, I’ve never laid color on a whole vehicle, but have laid primer on many. I have put color on many tractors and implements, etc.
    That said, if you have to stop, wait for air to build up, then unless you have the “good eye” for it, it’s tough to start over with putting something that’s going to shine. Primer is very forgiving in that regard.
    I used my dads big 80 galling two stage compressor, it turned off at 185 and on at 135 as I recall. Never lacked for air pressure or volume of air. The only time I’d stop spraying was to mix, strain and fill up his Binks 19.
    Can liken it to a small plasma cutter I have, 10% duty cycle on the high side, 40/50% on the low side. Forget the make. Bit a PIA to run. If you stop, you have to sit there and wait till the machine lets you use it again.
  27. Automotive Stud
    Joined: Sep 26, 2004
    Posts: 4,236

    Automotive Stud

    The best compressor is the best one you can afford. I painted my model A two weeks ago with a $100 HVLP gun and a Harbor Freight 2.5 horse 20 gallon compressor in my single car garage and part in the driveway. It's single stage enamel, and a model A isn't a very big car, but it worked out okay. With a bigger compressor I probably wouldn't have had to wait between doing panels for the compressor to catch back up. 20230304_103749[1].jpg
    treb11 and Driver50x like this.
  28. Joe H
    Joined: Feb 10, 2008
    Posts: 1,377

    Joe H

    I've run my Craftsman 5HP - 30 gallon for many years, painting, wrenching, porting, and sand blasting. The rings finally gave out so I replaced the compressor with a higher cfm and pressure rating from an outfit in Texas. I then slowed it down and used the original pressure switch so the compressor doesn't work nearly as hard as the older one did. I have less condensation and it keeps up with the die grinder really easy.
    When adding an extra tank for capacity, doesn't the compressor now long twice as long to fill both tanks? What was gained?
    X-cpe likes this.
  29. stubbsrodandcustom
    Joined: Dec 28, 2010
    Posts: 2,017

    from Spring tx

    Ive painted a crap ton on a horizontal 20 gallon. Normally you could spray a complete panel and move and reposition and let the air catch back up, HVLP is low enough pressure as long as your able to provide the scfm it should be ok. I battle the condensation with 2 oversized decadent driers, this keeps the air clean and clear going to the gun. With larger driers even with warmer air you should be ok.

    I upgraded compressors after years to a 30 gallon Dewalt 2 stage and its been wonderful.

    Old sandborn worked many years for my grandfather and then myself. Still ran fine till I upgraded... If you have the room for a 40 and the electrical supply then I say do it, if you are 110v limited and budget limited I would say this dewalt is a good bang for the buck at tractor supply. If you want to go full tilt and get the best out there, Id go Quincy then.


    Here is the new garage layout and compressor.


    garage21.jpg garage23.jpg garage24.jpg

    Attached Files:

Share This Page

Register now to get rid of these ads!


Copyright © 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.