MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Electropolishing and ceramic coating

Just polling the group to see if anyone out there has had there manifold/header electopolished as suggested on a recent thread and subsequently ceramic coated. Just trying to determine what gains might be achieved with such a move in addition to the heat reduction.
Frank

FWIW, Frank. There was an earlier thread about the ceramic coating stuff. Steve S and others remarked about how effective the JetHot was. I was pretty skeptical. I had a chance recently to experiment with the header wrap stuff and now I've got to eat a little crow on this subject. I don't have any experience with the JetHot (or others) but the header wrap heat & noise reduction was quite dramatic. The drawback, as I understand it, is that there will be a moisture accumulation under the wrap from post-run cooldown in humid climates. This will accelerate rusting of the header. The ceramic coatings do not have this moisture problem.
David

Contact Jet-Hot at http://www.jet-hot.com/ . They will send you a brochure and video at no charge. I plan to have all my MG's treated with their process, the coatings reduced engine bay temps up to around 20%. The coating they use will cover both the inside and outside of the manifold and it looks great even after many years. There was recent thread regarding Jet-Hot on the MGC BBS.

Regards
Rich
Rich Stinchcomb

Car Craft magazine has an article on header coatings in the August 2002 issue. They used a 454 GM HO engine for a test bed. Header surface temperature with painted Blackjack headers at idle was 524 degrees, at 3200 rpm the temperature was 533 degrees. With Cyclone coated headers the temperatures were, idle 215 degrees, 3200 rpm 265 degrees. The test was done under controlled conditions on a Dynomax Dyno. With the engine installed in an engine bay the changes may not be as dramatic as the Car Craft test, but it would appear that header or manifold coatings will make a very dramatic reduction in under hood/bonnet header/manifold temperatures. BTW the the Cyclone headers were Jet-Hot coated. Regards, Clifton
Clifton Gordon

Jet-Hot coating is a ceramic coating that can be applied to coat both the interior of the exhaust manifold as well as the exterior. The heat will have nowhere to go except out of the exhaust system, thus it will greatly reduce underhood temperatures. The big advantage of this is that the air being inhaled into the engine being denser, more fuel can be mixed with it to result in a more powerful fuel/air charge. Another benefit is that the setting of heat-sensitive SU HIF4 carburetors can remain more consistent. One word of warning to those considering Jet-Hot coating or any other type of ceramic coating: Be sure that the entire surface of the manifold, both the interior as well as the exterior of the manifold and the flanges is coated so that the heat of the exhaust gases will pass on through the system instead of being absorbed and trapped in the metal of the manifold, otherwise the manifold will warp just as in the case of wrapping the manifold with insulating wrap. Jet-Hot has a website at http://www.jet-hot.com/ . I highly recommend electropolishing to improve the flow capacity of a cast iron exhaust manifold. The advantage of electropolishing a cast iron exhaust manifold is that the process can get inside the manifold where human hands and mechanical tools can't reach. The smoother surface reduces turbulence, just like the smooth walls of a manifold constructed of tubular steel, and thus promotes efficient gas flow. I sincerely believe that a 1 3/4" tubular steel exhaust manifold won't flow any better than an electropolished OE cast iron exhaust manifold if they have the same basic design. Another technique for attaining a smooth interior surface in the exhaust manifold is called Forced Extrusion Honing. In this technique a dense mixture of abrasive clay is forced through the interior of the manifold, polishing the surfaces to an even greater degree than can be achieved on a casting through electropolishing. I've seen a head in which both the intake and exhaust ports have been subjected to this process and it is very impressive.
Steve S.

Steve,
I appreciate both you and Clifton responding again and I realize some of what you stated you had already said before....I was wondering if you had your manifold electropolished....where and how much? I went to the extrude hone web site and the price for that process is quite high...if money were no object...it seems that would be the way to go....they state they even do heads..wonder how this would compare to a Peter Burgess/Mike Brown job?
Frank

Frank-
I had my cast iron header electropolished by Notheast Electropoloishing up in Conneticut. They have a website at http://www.accuparts.com/electropolish/ They did my exhaust manifold two and a half years ago, so to get a current price you should Email them. They normally do surgical instruments, but can handle bigger items as well.

I briefly described Forced Extrusion Honing, so it's best that I describe Electropolishing. Stated simply, electropolishing is the controlled electrochemical removal of surface metal. The process has a leveling effect which produces smoothness and increased reflectivity. More importantly, the deformed, amorphous outer layer of the metal is removed, leaving a passive surface free of imbedded contaminants and work-induced residual stresses. Unlike pickling or acidic cleaning, it doesn't cause pitting or etching, or produce hydrogen embrittlement. Sometimes described as "reverse plating," electropolishing is accomplished by connecting the metal part to be processed to the positive terminal (the anode) of a DC power supply. The part is then immersed in a heated electrolytic bath that contains metal plates connected to the negative terminal (the cathode). The electrical reaction causes an ionic conduction resulting in the removal of particles of metal from the anode. During the process, the products of this anodic metal dissolution reacts with the electrolyte to form a film at the surface of the metal. This film is thinner over the micro-projections and thicker at the micro-depressions. The result is more rapid dissolution of the micro-projections causing micro-leveling at the surface. The amount of metal removed is influenced by the composition of the metal part to be electropolished, the temperature and agitation of the electrolytic bath, the spatial and area relationships of the anode and cathode, the current, and the length of time the current is flowing. Electropolishing can be used as a method for sizing parts to close tolerances within 0.0001 inch.

Electropolishing should not be done on intake ports. The ultra-smooth surface would eliminate the boundary layer of turbulence that keeps the gasoline suspended in the fuel/air charge and result in the gasoline condensing on the port walls. However, it can be beneficial to electropolish combustion chambers and exhaust ports (reduced carbon buildup, for example).

Electropolishing is in no way a substitute for professional headwork. A professional such as Peter Burgess actually modifies the contours of the ports and combustion chambers to improve and match their performance, much like Michaelangelo creating a sculpture from a block of crude marble. Precision measurements have to be taken, blueprints consulted, and repeated testing on a flowbench has to be performed to get the optimum results. If you don't want the extra expense of professional porting, remove your old valve guides, use a Dremel tool with a #80 grit and then a #120 grit sander to gently smooth the existing port contours. This should give you an increase in power output of about 3 HP. Peter, on the other hand, can give you about ten times this.
Steve S.

Steve,
Appreciate the follow-up. The comment regarding not doing the intake manifold was interesting as the extrude hone web site suggests under their automotive site that they do both exhaust and intake manifolds for high performance/racing applications. Could you enlighten me on why their ultra-smooth surface would not create the same problem on an intake manifold. I realize there is probably a significant difference between a V-8 racing engine and one on our "B"s however I would love to hear your opinion on this.
Frank

Frank:
I think the reason for Extrude Hone doing the intakes on modern V-8s, racing or street, is that they are fuel injected, and the intakes just flow air. Less resistance, more flow, and the computers adjust the amount of fuel metered to the injectors to match the available air.

Jerry
Jerry Causey

Frank-
Jerry is right concerning the fuel injection factor. Remember that our BMC B Series engines are carbureted, so because Forced Extrusion Honing does not produce an ultra-smooth mirror-like finish, the boundary layer of the flow charge is still turbulent enough to prevent fuel condensation on the port walls. Look at it this way: you can paint a sand casting with high-gloss paint and still have it be slightly rough (Electropolishing method) or sand it with an abrasive to make it even smoother (Forced Extrusion Honing method). It would be great to electropolish the combustion chambers and exhaust ports after forced extrusion honing, but what you don't want is a mirror-like finish on an intake port or the interior of an intake manifold, so the intake ports should be masked off before electropolishing the head if forced extrusion honing has already been performed on it.
Steve S.

Steve,
Thanks again for your reply....I have in the past followed your advice with regards to suspension modifications and have been quite pleased with the results so was pleased that you threw in your two cents worth. For some further clarification...I believe that I saw on a prior posting that for either the jet-hot coating or the electopolishing that you would recommend not having the machined surfaces (gasket mating) done...is this so for both processes? Also if one were to have this done to a combined intake/exhaust manifold (austin/marina) your suggestion would to be to have the exhaust part electropolished and both exhaust and intake parts jet-hot coated. Am I correct?
Frank

Frank-
Your memory has it backwards. I instructed that the mounting flanges be masked off to prevent erosion of the mating surfaces during electropolishing because it was, after all, a rough sand casting which took a fair amount of time in the bath. The Jet Hot coating should be applied to the entire surface of the exhaust manifold, inside, outside, flanges, the works. This will insulate the manifold from heat ingress. If the heat gets in there, the heat will build up in the metal of the manifold and the manifold will ultimately warp.

The single-carburetor one-piece intake/exhaust manifolds of the 1975 and later engines are fundamentally lousy breathers and the heat in the intake tract is so high that the density of the incoming fuel/air charge is ruined. (I'm seriously considering having my Maniflow intake manifold Jet Hot coated just to see what happens). My advice is to put it on a shelf so that you can later sell it some poor Rubber Bumper owner out in California who has to endure their visual inspection of the OE emissions control system. New ones are horribly expensive. If you're using HS4 carburetors and and their OE intake manifold, use exhaust manifold casting #12H 709. If you're using HIF4 carburetors and their OE intake manifold, use exhaust manifold casting #12H 3911. This is due to the need for compatability of the mounting flange thicknesses. Have the electropolishing and Jet Hot coating done. My best recommendation is that you get a Maniflow intake manifold and a cast iron HS4 exhaust manifold, mount a pair of UK Market SU HIF4s containing fixed-needle HS4 pistons and throttle plates (No poppet valve) and K&N 6”X 3 1/4” airfilters. Then slap on an Aldon-Modfied distributor and go have some real fun on a winding mountain road.
Steve S.

This thread was discussed between 11/09/2002 and 12/09/2002

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.