Exhaust Manifold coatings
rumblephish
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- Location
- Central California
- Vehicle(s)
- 1978 Jeep CJ-5 "Levi's" edition, original AMC 304 V8, T-150 transmission, Dana 20 transfer case, AMC 20 rear end. All stock except for a hotter ignition.
While prepping to install the Howell TBI kit I just got in I decided that the first order of buisness was to remove the air pump and injection tubes from the exhaust manifolds on my AMC 304 . Well, after 32 years of heat and rust 3 of the 7 bolts decided that they didn't want to be removed and snapped off inside the exhaust manifold. ARRRGH! I hate broken bolts! But you know what I hate more than broken bolts? Broken bolt extractors!! I should have known that I wasn't getting these out when the lower jaw of my 12" Crescent wrench snapped off while trying to turn the bolt extractor (which also broke!). So I decided to take it down to a local exhaust shop and have them just weld up the air injection ports on the manifolds. Ugly welds but hey, for $20 I wasn't complaining as long as they worked 
While I had the manifolds off I found that a freeze plug at the rear of the left (driver's side) head was leaking coolant. 32 year old steel freeze plug had rusted through. I'm really glad i checked it out because as I was wiping the rust and coolant away to get a better look at the plug my finger pushed right through it! So after 2 hours of fighting with it I got all the remnants out and replaced it with a brass plug. I also found that the return line on my power steering was leaking right at the clamp. I guess as I was moving things about to get the manifold out I had moved the line which cracked the old, brittle rubber around the clamp and viola! PS fluid leaking! yay!! So another repair while I had the manifolds off.
Anyway, back to the manifolds... I got them home and heated them up with a propane torch to burn off any residue left from the BreakFree and WD40 I doused it with to losen the bolts. After that I used a HD degreaser and a wire brush on my drill to prep it for some paint. I wanted to try the "Extreme High heat" exhaust manifold coating from VHT. It's a silicone/ceramic based paint that is heat cured and can withstand temps up to 2000 degrees. It's also supposed to cut surface temps on the manifolds by 400 degrees and engine compartment heat by 200+ degrees. I was pretty skeptical about those claims and was going to be happy if it just made the manifolds look better. Well, look better they did. This stuff was very easy to apply and the coats would dry to the touch within 10-15 minutes. I waited 30 minutes between coats (3 coats all together) and then let'em air cure overnight before reinstalling the manifolds.
The next day I reinstalled the exhaust manifolds and cleaned up the wiring in the enigine compartment a bit. I replace the spark plugs and custom cut some good 8mm Accel spark plug wires. After getting everything buttoned up I fired up the engine. In about 5-8 minutes the headers were smoking like crazy! At first I thought "
, this stuff is going to burn right off! " But apparently this is what they meant by "heat curing"! The longer it ran and the hotter they got the more they smoked, but the color never eally changed (silver-gray). As the smoke dissapated a bit I checked the heat of the manifolds and engine bay by "hand" (no, I didn't put my hand directly on them! 
) after running for 30 minutes straight I noticed significant reduction in the temp of the engine bay. I was suprised to say the least! Before the heat was considerable and now it was negligable. Amazing. I ran it for another 15 minutes and then shut her down. Within 5 minutes of shutting down I went back and checked the heat. Usually the temps will rise a bit after shutting down (is this called heat soak?). But now the heat was MUCH reduced. Even the manifolds themselves were not nearly as hot as before. I also noticed the exhaust temp at the tailpipes is much greater now and I would assume that the velocity of exhaust gas in the system is greatly increased as well. I would hope that this increased velocity would help with the scavenging effect but I have no way of knowing, just assumptions.
So the moral of this story is... if you want to clean up the look of your stock manifolds or even headers while reducing engine bay and manifold/header surface heat, VHT Exterme High Heat Exhaust manifold coating is the ticket!
While I had the manifolds off I found that a freeze plug at the rear of the left (driver's side) head was leaking coolant. 32 year old steel freeze plug had rusted through. I'm really glad i checked it out because as I was wiping the rust and coolant away to get a better look at the plug my finger pushed right through it!
So after 2 hours of fighting with it I got all the remnants out and replaced it with a brass plug. I also found that the return line on my power steering was leaking right at the clamp. I guess as I was moving things about to get the manifold out I had moved the line which cracked the old, brittle rubber around the clamp and viola! PS fluid leaking! yay!! So another repair while I had the manifolds off.Anyway, back to the manifolds... I got them home and heated them up with a propane torch to burn off any residue left from the BreakFree and WD40 I doused it with to losen the bolts. After that I used a HD degreaser and a wire brush on my drill to prep it for some paint. I wanted to try the "Extreme High heat" exhaust manifold coating from VHT. It's a silicone/ceramic based paint that is heat cured and can withstand temps up to 2000 degrees. It's also supposed to cut surface temps on the manifolds by 400 degrees and engine compartment heat by 200+ degrees. I was pretty skeptical about those claims and was going to be happy if it just made the manifolds look better. Well, look better they did. This stuff was very easy to apply and the coats would dry to the touch within 10-15 minutes. I waited 30 minutes between coats (3 coats all together) and then let'em air cure overnight before reinstalling the manifolds.
The next day I reinstalled the exhaust manifolds and cleaned up the wiring in the enigine compartment a bit. I replace the spark plugs and custom cut some good 8mm Accel spark plug wires. After getting everything buttoned up I fired up the engine. In about 5-8 minutes the headers were smoking like crazy! At first I thought "
, this stuff is going to burn right off! " But apparently this is what they meant by "heat curing"! The longer it ran and the hotter they got the more they smoked, but the color never eally changed (silver-gray). As the smoke dissapated a bit I checked the heat of the manifolds and engine bay by "hand" (no, I didn't put my hand directly on them! ) after running for 30 minutes straight I noticed significant reduction in the temp of the engine bay. I was suprised to say the least! Before the heat was considerable and now it was negligable. Amazing. I ran it for another 15 minutes and then shut her down. Within 5 minutes of shutting down I went back and checked the heat. Usually the temps will rise a bit after shutting down (is this called heat soak?). But now the heat was MUCH reduced. Even the manifolds themselves were not nearly as hot as before. I also noticed the exhaust temp at the tailpipes is much greater now and I would assume that the velocity of exhaust gas in the system is greatly increased as well. I would hope that this increased velocity would help with the scavenging effect but I have no way of knowing, just assumptions.So the moral of this story is... if you want to clean up the look of your stock manifolds or even headers while reducing engine bay and manifold/header surface heat, VHT Exterme High Heat Exhaust manifold coating is the ticket!
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