MGB & GT Forum

Hey just toying with the idea of doing this anybody ceramic coated their exhaust manifold ??? Is it worthwhile on a stock engine ??

I've done two it reduces under hood temperature a fair amount as far as performance I don't know if does much .

I did it for my MGA. With the cramped engine bay the MGA has, the ceramic coated manifold definitely reduced under bonnet temperatures, manifest by a reduced tendency for fuel vaporisation in the carburettor bowls, and less heat transfer into the cabin. I thought it a very worthwhile cost effective thing to do.

For my MGB, with its more capacious engine bay, double skinned bulkhead etc I have never sensed the need.

Patrick-
I hade my exhaust manifold Jet-Hot coated. Jet-Hot® coating is a ceramic coating that can be applied in order to insulate both the interior of the exhaust manifold and its exterior. However, while simply ceramic coating the exterior surface of the exhaust manifold will reduce the radiation of heat into the engine compartment, it needs to be understood that applying the ceramic coating onto the interior of the exhaust manifold and the mounting flanges is also of significant importance. This will prevent the heat of the exhaust gases from becoming absorbed and trapped inside of the exhaust manifold by the exterior coating, which can not only result in warpage of the exhaust manifold itself, but can also result in the heat being conducted back into the area around the exhaust ports. Since the center exhaust port receives only marginal cooling due to the fact that its coolant flow passageways have the same coolant flow capacity as the outer two, but handles twice the volume of hot exhaust gases, this can cause the cylinder head to warp. Ceramic coating of the interior of the exhaust manifold not only effectively mitigates this problem by insulating the metal of the exhaust manifold from the heat of the hot exhaust gases, it also reduces the temperature of its exterior surface by reducing heat conduction, with further positive effects upon engine compartment temperatures. This is a significant factor as uncoated exhaust manifolds often reach temperatures exceeding 400 degrees Fahrenheit (204.4 degrees Celsius). Reducing temperatures within the engine compartment is beneficial for power output, as well as presenting less potential for both preignition and detonation. It is worth noting that for every 5.4 degrees Fahrenheit (3 degrees Celsius) decrease in temperature that the air that is ingested by the engine, power output is increased by 1%. Although most carburetors do not have a thermal sender unit in order to measure temperature, all carburetors function similarly in that it is pressure decrease across a venturi that is the mechanism that pulls fuel into the venturi. The pressure decrease itself is a function of air density, therefore air temperature also enters into the equation. In operation, carburetors are quite effective at functioning within the limited range of operating conditions that we subject them to. Without cold air induction, a carburetor must accommodate a significantly wider range of air temperatures than if cooler air is supplied from outside of the engine compartment. Another benefit is that the reduction of radiated heat permits the metering of the thermosensitive 1 1/2" SU HIF4 Series carburetors to remain more appropriate. You can leave the car in a hot parking lot after a run on a hot summer day, and have no problem restarting it. Be aware that Jet-Hot® coats the interior surfaces as a matter of routine, while some others do not. The application process of Jet-Hot® coating does not contribute to hydrogen embrittlement, a condition that is associated with chromium-plating and other coatings, the result of which is microscopic cracking that can lead to premature failure of the metal of the exhaust manifold.

The Emissivity Value of 0.2 of Jet-Hot's ceramic coating is very good considering the fact that a 'perfect emitter' holds a value of 1.0. As a general rule, the reduction in the surface temperature of the exhaust manifold when using Jet-Hot's 'Sterling' coating can be relied upon to exceed 300 degrees Fahrenheit (148.9 degrees Celsius), while the reduction in surface temperature when using the 'Extreme Sterling' coating can be relied upon to exceed 400 degrees Fahrenheit (204.4 degrees Celsius). Consequently, the cooler charge of air that is being inhaled into the engine being denser, the more fuel that can be mixed with it in order to produce a more potent Air/Fuel charge. At the same time, it decreases the deceleration of the exhaust gases, the sustained exhaust gas inertia thereby enhancing the pulsed-vacuum scavenging effect upon the cylinders. This is due to the fact that the increased exit inertia of exhaust gases that is produced by their higher velocity not only clears each cylinder more quickly; the resulting improved vacuum effect within the cylinder draws in the next Air/Fuel charge more efficiently. This is especially beneficial when employing a long-duration camshaft.



Edited 1 time(s). Last edit at 2021-12-11 05:53 AM by Steve S..

Thanks to Steve for such a thorough explanation of the benefits.

Agreed. Here’s the Reader’s Digest version. Yes, it is worthwhile.

---

I was addicted to the hokey pokey but I turned myself around.

The problem with doing nothing is not knowing when you’re finished.

As Steve explained, doing the inside is important. As the exhaust gasses cool. they contract and become turbulent. That reduces the ability of the flowing exhaust gasses from one cylinder to help start the exhaust gasses from the next to start moving. Keeping the gasses flowing smoothly until after all the pipes merge helps you make power in a race car and must be of at least some benefit in a street car. Best of luck. Basil 707.762.0974 basiladams@yahoo.com

---

Basil C. Adams
1956 MGA Coupe (Show Car)
1957 MGA Roadster (Driver)
1958 MGA Coupe (Racecar)
1959 MGA Coupe (unrestored)
1960 MGA Coupe (unrestored)
1960 MGA Roadster (Driver)
MKIII Elva Courier (E1056)
1967 427 Cobra
1972 Alfa Romeo Montreal
A coupla late MGBs
1960 Austin Healy BN7
More Cars than Brains

More than a decade ago, I put a ceramic coated exhaust and intake manifold on my B. It looks great, much less heat and runs better! Do it.

---

1st Place Winner ABFM Portland Oregon 2008, 2010, 2011, 2012, 2013, 2014, 2015 & 2016!
Email me for questions or needs, I'll respond promptly! dan@allpointsorganized.com
Life. Positively in order.

Now is a good time to do your port matching before you send the manifold off. It just takes a few minutes with a die grinder or a Dremel tool to smooth out any restriction.

Many years ago my brother port and polish his head on his 79 B, then he broke a valve as I recall him telling me. He overdid it and the engine broke. Is that a pretty difficult job to do?

About 15 years ago, he got another MGB, a 78, and took a load of the parts from a 79 B and made that car great. However, sadly for the last 6-7 years, he's had that B stored in someone's barn. Everytime I bring it up, he gets angry.

---

1st Place Winner ABFM Portland Oregon 2008, 2010, 2011, 2012, 2013, 2014, 2015 & 2016!
Email me for questions or needs, I'll respond promptly! dan@allpointsorganized.com
Life. Positively in order.

I'm a fan; I've been using ceramic-metallic coatings on exhaust manifolds/headers since the 90s. I started doing my own polymer coatings around '92 (1st was the engine for the 74-1/2 GT I had at the time).

Besides manifolds, thermal barriers, thermal dispersants, and dry-film lubricants can be beneficial to internal parts too.

The "blue" headers are a higher temp Jett-Hot coating for engines with forced induction (or nitrous, apparently, but I've never messed with it). Everything else is stuff I've applied/cured using TechLine products (link to their FAQ page: http://www.techlinecoatingswebstore.com/FAQ.html ).

@#4.

So Steve Jet Hot (or its equivalents) is not DIY and needs to be applied professionally? Am I right in assuming that your explanation of heat inside applies just as equally to an EFI car? I've had my through the guard V8 manifolds ceramic coated but only on the outside - maybe I need them done on the inside too. I assume down to the yellow line on the collector below is all that's needed (as after those my exhausts are stainless steel).

---

Mk1: CKD 11/66 first registered 8/5/67; owned since 3/77. 18GB +40 balanced. Peter Burgess BVFR head. Piper 285. 123. FidanzaFW. 4synch c/r box. Superpro. Nut and bolt rebuild 2010 - 2015. Tartan Red.

GT: 12/78. VW Golf guards, flush fit front and rear valances, frenched indicators, Mk1 rear lights - LED lights. 'Worked' Rover V8, Monsoon ECU for EFI. Commodore VSV8 GM4L60E, Lokar tiptronic shifter & Quick4 controller. Vintage Air A/C. FC IFS. CCE 4 link rear. Salisbury with Quaife. Jaguar Storm.

Barrie-
Yes, Jet-Hot coating needs to be performed professionally. EFI has nothing to do with its function. It should be applied to both the interior and the exterior, as well as onto any sealing flanges.

Thanks Steve. My reference to EFI was in relation to your comment "Another benefit is that the reduction of radiated heat permits the metering of the thermosensitive 1 1/2" SU HIF4 Series carburetors to remain more appropriate"/ I didn't think it would have but I thought I should check.

---

Mk1: CKD 11/66 first registered 8/5/67; owned since 3/77. 18GB +40 balanced. Peter Burgess BVFR head. Piper 285. 123. FidanzaFW. 4synch c/r box. Superpro. Nut and bolt rebuild 2010 - 2015. Tartan Red.

GT: 12/78. VW Golf guards, flush fit front and rear valances, frenched indicators, Mk1 rear lights - LED lights. 'Worked' Rover V8, Monsoon ECU for EFI. Commodore VSV8 GM4L60E, Lokar tiptronic shifter & Quick4 controller. Vintage Air A/C. FC IFS. CCE 4 link rear. Salisbury with Quaife. Jaguar Storm.

I had mine Jet-Hot coated a long time ago. Still very happy with the results. Looks super forever and prevents vapor-lock.

---