How to tell when headers TOO close to paint?

It's HOT to the touch, but how can you tell BEFORE you fuck the paint when it's too hot?

 

Groucho.You know what I am visioning, that heat wrap cloth that I see on the Harley exhuast wrapped around your headers. I think that would be a nice touch to your car and would help in the heat-paint question. KNUX!

 

Easy fix. Any opinions on how it'd look on my car? I know, better than blisters in the flake. Besides that, seriously

 

get you a infa-red therometer to tell you exactly how hot it's getting. as long as your moving the air should keep transfering the heat out of the area. seems like if it was going to blister it would have already done it.

 

hmmm. . . if the paint surface itself is too hot to touch, chances are its going to eventually blister and burn the paint off as well.

maybe think about a semi tubular stainless or polished aluminum shroud attached to the top and bottom header cap bolts, and maybe drill/tap or braze another mount point up forward of the collectors?

 

header tape is good, but i think for as clean as this car is, a guard or shroud would be a more appealing solution

 

I think you should be fine. The painted steering box on my 56 has only about 1/8th" clearence to the tube header and no burnt paint until now. As it looks in the pic you have at least 1" of clearence, that should be plenty..

 

Is that paint on the headers? If so, a ceramic coating will reduce surface temps significantly. There's a type even available in white now. It's exact name escapes me but I could find out.

 

Mine was closer than yours with Jet Hot coating. After 6 years, paint was still fine. Oh, by the way, Jet Hot coating radiates a LOT of heat......just cools down faster.

 

Well, here in Socal, it's not uncommon for paint to be HOT to the touch just sitting outside on a hot day. I sure'd like to know how hot is too hot? Also the paint on the grill shell's HOT as hell too. Everyone gets that. 200 plus degrees radiating to the painted shell an inch away. VERY hot to the touch

WOW, 1/8"? I've got about 2 inches. But, it feels pretty HOT. I've got an infrared gun, but i don't know what temps to look for.

 

And more of it stays inside the header where it belongs. The readings I've taken with a non-contact thermometer on coated mild steel headers showed a nearly 200 degree reduction in external surface temperatures measured on the primary pipes a few inches from the head, compared to uncoated mild steel headers. At the collectors the difference was less but still over 125 degrees cooler. This was on a 350 Chevy making about 370 RWHP.

 

Paint goes flat.
A little later and a touch more heat, the paint bubbles.
Eventually the paint will come off, but the primer stays.
After a while the primer leaves as well.

The pic taken several months before it got down to bare metal.

Funny part about this paint blistered area is that the headers aren't real close.
One primary, about 10" - 12" forward is about 1/8" off the hood side panel on the inside.
The air from the fan pushes the heat off the header to the rear and the blistered area is hotter than the area right over the header primary.
The paint in the pic is acrylic lacquer.

On the other side, the inside of the frame boxing plate is about 3/8" - 1/2" from the header.
Paint in that area went flat, but did not blister.

The frame paint is a catalized urethane.

 

take a reading from several different places on the car, then compare?

far as temp borderline before it'll do damage, i'd say over 200 for sure. . . i had painted a set of heads with regular rattle bomb a few years ago and it got up around 200 plenty around the exhaust ports and only blistered and peeled within an inch of the ports/manifolds so you MIGHT be OK as is. . . c'mon paint gurus... lets hear the difinitive word

 

Here's another pic that may be of interest.

Posche red acrylic enamel on my 32's engine.

Take note of how far up the head the exhaust port paint has burned off.
Once you get close to a water jacketed area the burning stops.

 

Your situation clearly involves trapped heat inside the hood. I'd like to know what kind of surface temps were involed in doing that kind of damage

 

If I knew I'd tell you.

Just thought it might be interesting to see how it goes when the paint starts going.

I might be able to tell you next week . . . I'm on the verge of getting an infrared gun once I make up my mind which one....

 

I personally like the idea of using a heat shield. You know how side exhausts (Corvettes) have a slotted shield around them? I'm thinking a similar vented shield, yet is conical to match the exhaust between the flange and the first upward pipe. This shield would consist of two halves that are screwed together (one side could be hinged). Could then be painted to match the rest of the exhaust pipe. I'd probably also have the inside header pipes ceramic coated.
Paint jobs are just too expensive these days to take a chance on ruining. My 2 sense.

P

 

The secret is to coat them inside and out.... yeah they'll still be hot, but not near what they would be uncoated...

 

Groucho,
You've got a good amount of space between the tube, end plate, and the cowl. A backside aluminum shield would protect it even more, but I only saw blistering, when the header tubes were 3/8" above the fenders on my A. (I am estimating here, as when I built the headers, they were even closer! 1/4" or so off of the fender. Used acrylic laquer, painted in 1984 or so.

 

This is my old car, drove it for a few years and never had a problem with the paint, and the headers were pretty close to the body. I ran turn-outs on it when the headers were un-capped though. Gary

 

Beautiful car Gary!! There just aren't enough car shows in Houston to see these kinds of rods!

Patrick

 

Groucho, I painted my engine block with auto paint and it never lifted. I know it was hotter then I could touch.. temp gage said 170 and that was in the head with fluid..

 

NICE!

 

Groucho,
That header tape would ruin the look of your car! I'd make a heat shield,for the backside,between the headers and the body. Doesn't have to be real big. Kinda like those ones you can get for starters.

 

Yeah, that's what i'm thinking/HOPING

 

Well I will tell you this... I don't know what the heck went on to scorch the paint so badly and in such a big area of the outside of the hood Deuce posted above, but my 32 has smoothy hood sides, and the front tube of the driver's side header actually TOUCHES the inside of the hood. there's a rub mark about the size of a dime on the inside surface of the hood, but it doesn't even look burnt, just rubbed from vibration. The outside of the hood is perfect, and its been driven over 3000 miles so far with it like this... in fact it was driven 5 solid hours to Columbus last week, then 5 hours back and never hurt anything. My car is base/clear urethane rather than lacquer though, so maybe it's alot more durable in regards to withstanding heat. I agree that if it was gonna hurt anything it would have done so already. How does the temp on the paint in that area compare with the temp at the grill shell when measured with your infrared gun? If they're similar temps, i wouldn't worry about it. Heck, on a hot day my decklid can get too hot to touch just from sitting in the sun.

 

Great idea. I'll check next time i drive it. Today, i had zip ties holding half the car together, and a borrowed carb that ran like shit. Discolored the cyl head paint much differently from side to side, so i think it's junk. Mine's in the soup, and will go to get dyed tomorrow. Anyway, it'll be a few days before the next drive. I agree with the decklid thing. Anything out in the sun's gonna be HOT. I don't think i'll have trouble. I just thought i throw it out there for other experiences that you've had. Thanks ALL

 

you cant go by what has been said about other paint burning off motors. most are painted with the least amount you can put on. with a flake job your mill thickness is much higher and leads to greater problems of it failing due to the high temps.

if you can weld a tube with a 90 degree to the end cap that fits tight to the id of the cone just after the last primary tube. with the 90 cut to direct the exhaust flow out the flange.

to get it to stay in place you could weld 3 peices of rod to it and drill holes in the cap and weld the rods to the cap with out screwing up the coating on the headers.

 

I wonder if you could put an internal heat shield in the headers? Kind of a slide in air spacer (sleeve type) that would essentially work the same as an external shield, but you just wouldn't see it. I don't know if thats feasable, or if it would even really work, but just something that popped into my mind.

I also wonder if you could take a panel that's been primed and painted - perhaps even a 'test' panel, and then add a heat source like a torch from the backside, and then measure the temperature with an infrared thermometer on the outside of the panel. That should somewhat tell you at what temperature your paint would/should/could bubble, blister, and peel. You could then take that measurement and then check the temperature of the body where the headers are closest.

It sounds good in my head, but I don't know if it'd be practical or not.

 

heat wrap ?that wuold look amazing on the car ...in 1975 !

re cut the header .and re spray paint it.

done ,done...........