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Ceramic coating pistons, exhaust ports, valves, combustion
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1975 Kombi
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PostPosted: Mon Oct 04, 2010 11:15 am    Post subject: Ceramic coating pistons, exhaust ports, valves, combustion Reply with quote

I just spoke with my powder coat guy and he quoted me a price of $250 to ceramic coat the top of the pistons and apply a moly based lubricant coating to the skirts, ceramic coat the combustion chambers and exhaust ports along with the valve faces and partial stem and coat the rest of the stem with the moly coat. Also treat the outside of the head with a heatsink coating and the outside of the barrels. Coat the valve springs and retainers.

Has anyone ever done this and is it worth the $250.

Picture from Jake's web site.
Image may have been reduced in size. Click image to view fullscreen.


He also mentioned that the heads might be able to be re heat treated to bring them up to a T6 aircraft quality. If the seats and studs are removed they may be able to be strengthened back to better then factory. Not sure if that is possible but I thought I would throw that out there.

Any thoughts. I am seriously thinking about having it done.

Here is his web site: http://www.fireballcoatings.com/index.php?option=com_frontpage&Itemid=1
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Last edited by 1975 Kombi on Mon Oct 04, 2010 11:52 am; edited 1 time in total
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aeromech
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PostPosted: Mon Oct 04, 2010 11:22 am    Post subject: Reply with quote

I have no knowledge on this but would love to see what happens if you try it.
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1975 Kombi
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PostPosted: Mon Oct 04, 2010 11:43 am    Post subject: Reply with quote

He said the heat reduction would be substantial. Which I think is the number one issue with the older air cooled stuff. He has constant business for the pistons and heads on all makes.
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PostPosted: Mon Oct 04, 2010 11:59 am    Post subject: Reply with quote

$250 seems like a good price to me, worth a try i say.
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1975 Kombi
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PostPosted: Mon Oct 04, 2010 12:54 pm    Post subject: Reply with quote

I wish I had new AMC heads but $250 is not bad. I might pick up new valves that could be transferable to another head in case the seat drops.

Just a couple of questions:

1. Should I balance the pistons before the coating. My powder coat guy says the addition of weight is negligible.

2. Should I also lap the barrels into the head after the coating.
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raygreenwood
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PostPosted: Mon Oct 04, 2010 2:47 pm    Post subject: Reply with quote

Yes, youshould lap the pistons into the barrels.

You can always rebalance the pistons again later...as the removal of material is done inside under the dome...and the ceramic coating is on the outside.

There are some fantastic heat "shedding" coatings out there....but just be absolutely sure they have been tried and used successfully on the outside of a VW head....not an aircraft head...a VW aircooled head and make sure you talk to someone actually using it....not selling it...before you have the head coated on the outside.
There are some definate advantages to this....but there are also some potential issues. Do a lot of reserach.

The wrong coating on the outside of the head (or even just the wrong application method)can actually decrease heat shedding because of the airflow characteristics. The ACVW does not have the same constant speed airflow as an aero engine.

The moly coat is excellent. The Kolbenschmidt pistons always used to come with a moly coating on the piston skirts.

Other than that, the prices seem reasonable. I would go for it. Ray
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PostPosted: Mon Oct 04, 2010 3:01 pm    Post subject: Reply with quote

1975 Kombi wrote:
I wish I had new AMC heads but $250 is not bad. I might pick up new valves that could be transferable to another head in case the seat drops.

Just a couple of questions:

1. Should I balance the pistons before the coating. My powder coat guy says the addition of weight is negligible.

2. Should I also lap the barrels into the head after the coating.


1. Yes; even the heat-rejecting coating on a piston top is only about 0.015" thick.
2. Yes, for the best fit and heat-conduction, since the combustion chamber surface will have been finely sandblasted before the coating was applied.

Just aluminum flame-spraying the outsides (finned regions) of the cylinder barrels dropped my engine's cruising oil temps 30 degrees F. Seems like the additional coatings for reduction of friction, as well as for lowering heat migration into critical areas, could really add to engine longevity.
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PostPosted: Mon Oct 04, 2010 6:56 pm    Post subject: Reply with quote

the supervee folks were doing this 35 years ago. Just make sure the guy has done this type work for well known racers in the area who are winning.
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PostPosted: Tue Oct 05, 2010 1:07 am    Post subject: Reply with quote

Without new amc castings and Len's magic, you are pissing in the wind.
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1975 Kombi
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PostPosted: Tue Oct 05, 2010 7:49 am    Post subject: Reply with quote

Hoody wrote:
Without new amc castings and Len's magic, you are pissing in the wind.


Ya I know but I'm wearing a rain coat. I don't quite have the money for the AMC's with the Hoff magic and I'm in Canada so the cost is a bit more. So what is the next best thing. Well I thought maybe extending the life of what I have for a $250 investment and for the knowledge for the future. From what I can tell the seats and guides look ok and I had the head checked by a machinist. So I did some homework but how do you tell if the aluminum in the head is fatigued and if any head from the factory had T5 or T4 strengthening done anyway. T6 is aircraft quality and what is the factory rating. So ya, I'm going in not knowing but looking to learn something on the way.

This guy has been doing performance stuff for a couple of years but I will check with his clients.
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PostPosted: Tue Oct 05, 2010 10:22 am    Post subject: Reply with quote

Yes, re-hardening the heads works great, but you will need to then check virtually every machined surface for flatness and remachine....which is not too far off what is needed anyway.

Heat cyling does not destroy every centimeter of the head. What it does do is change the elasticity of areas that have been machined into the grain of the casting.
More accurately put...in places where you have an interefrence fit...the part that is fitted is under tension....i.e....valve seats.
With repeated heating and cooling the aluminum around that valve seat reepatedly expands and contracts until it fatigues and loses some of its ability to re-expand properly. In general...simply replacing your valve seats with slightly oversized ones with a proper interefrence fit will restore new metal contact around the seats.

I would only worry about heat treating if the heads have been cracked and welded or seriosuly overheated and alot of warpage is present.

"Aircraft Quality"...is an often overused or misproperly used word. T-6 is a hardening standard used in far more places than the aircraft industry...and not all aluminums used in aircraft are hardened to this standard. In fact...only a few aluminum types are actually what could be described as something directly aircraft quality....and it has "0" to do with teh ardening....its the alloy.

be really careful about what you are being told by yoru machinist...unless he has LONG experience with many ACVW's...and not just occasional performance with somone building a racing engine or aircraft engine. It is not the same. Ray
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PostPosted: Tue Oct 05, 2010 11:03 am    Post subject: Reply with quote

Good luck with it.Let us know how it turns out.
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PostPosted: Tue Oct 05, 2010 5:29 pm    Post subject: Reply with quote

you said one thing that concerned me - that the seats and guides looked Ok. That is not how you decide whether they need to be done. You can't turn them into good heads just by coating them. The guides, seats, valves etc all need to be co-ordinated with the machinist. You also need to look for cracks and possible bad studs. The cylincer mating area needs to be flat also.
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1975 Kombi
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PostPosted: Tue Oct 05, 2010 5:35 pm    Post subject: Reply with quote

Ya I hear you. I need to be there when the machine shop guys checks the heads. I hate taking the guys word when I don't know if he checked everything possible. He isn't a Len Hoffman.
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PostPosted: Wed Oct 06, 2010 12:58 am    Post subject: Reply with quote

Put the 250 towards new amc castings.Those valve guides and seats are spent.
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1975 Kombi
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PostPosted: Wed Oct 06, 2010 5:10 am    Post subject: Reply with quote

Hoody wrote:
Put the 250 towards new amc castings.Those valve guides and seats are spent.


I am still thinking about the new AMC heads. $1650 from Len.
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PostPosted: Wed Oct 06, 2010 6:05 am    Post subject: Reply with quote

1975 Kombi wrote:
Ya I hear you. I need to be there when the machine shop guys checks the heads. I hate taking the guys word when I don't know if he checked everything possible. He isn't a Len Hoffman.



Your head machinist does not need to be Len Hoffman. Any very competent cylinder head machinist...even one who has never worked on VW's...can do the work you need....as long as they KNOW and are TOLD what needs to be done and are willing to listen.

You need to have the head crack checked, looking carefully around seats, spark plug holes and in the exhuast valve pockets.
You need to have the cylinder openings chekced to see that they are parrallel...or need to be flycut slightly for clean up. All studs, therads and spark plug holes need to be checked.

Personally...unless the guides are very new and are dead on in spec....its false economy to not replace them. Its also false economy to not to replace springs and valves.
The seats on type 1 are less worrysome than a high milage type 4...but personally I would get new seats, and have them carefully blended at teh top edge.
Make sure the centers of the guides are properly drilled out for relief...before pressing them out. New guides must have proper clearance. The clearances for aircooled are slightly different than watercooled. Check all work yourself...and have it corrected before use. Ray
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1975 Kombi
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PostPosted: Thu Oct 07, 2010 9:57 pm    Post subject: Reply with quote

Well I got the word from the "Hoff" himself on the coatings. He wouldn't coat the combustion chamber or the top of the pistons. Reason being the heat tends to build greater then normal on the section of the piston just under the top and above the top ring and causes severe heat issues and possibly welding the top ring to the ring land. Instead of the heat being absorbed into the head casting it just bounces around until it finds something to transfer into. He recommends exterior heatsink coatings on the head and cylinder fins only.
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--
Rust In Pieces: 72 Bug, 73 Bug, 81 Rabbit LS D 2D, 83 Rabbit D 2D, 84 Jetta TD GL, 85 Jetta D, 68 Z28 RS 302, 91 Passat 16v


Last edited by 1975 Kombi on Fri Oct 08, 2010 11:43 am; edited 1 time in total
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PostPosted: Fri Oct 08, 2010 8:25 am    Post subject: Reply with quote

1975 Kombi wrote:
Well I got the word from the "Hoff" himself on the coatings. He would not coat the combustion chamber or the top of the pistons. Reason being the heat tends to build greater then normal on the section of the piston just under the top and above the top ring and causes severe heat issues and possibly welding the top ring to the ring land. Instead of the heat being absorbed into the head casting it just bounces around until it finds something to transfer into. He recommends exterior heatsink coatings on the head and cylinder fins only.




Did he recommend a particular heats shedding coating? Ray
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PostPosted: Fri Oct 08, 2010 4:56 pm    Post subject: Reply with quote

raygreenwood wrote:
1975 Kombi wrote:
Ya I hear you. I need to be there when the machine shop guys checks the heads. I hate taking the guys word when I don't know if he checked everything possible. He isn't a Len Hoffman.



Your head machinist does not need to be Len Hoffman. Any very competent cylinder head machinist...even one who has never worked on VW's...can do the work you need....as long as they KNOW and are TOLD what needs to be done and are willing to listen.

You need to have the head crack checked, looking carefully around seats, spark plug holes and in the exhuast valve pockets.
You need to have the cylinder openings chekced to see that they are parrallel...or need to be flycut slightly for clean up. All studs, therads and spark plug holes need to be checked.

Personally...unless the guides are very new and are dead on in spec....its false economy to not replace them. Its also false economy to not to replace springs and valves.
The seats on type 1 are less worrysome than a high milage type 4...but personally I would get new seats, and have them carefully blended at teh top edge.
Make sure the centers of the guides are properly drilled out for relief...before pressing them out. New guides must have proper clearance. The clearances for aircooled are slightly different than watercooled. Check all work yourself...and have it corrected before use. Ray


I think for type 4 heads, you should have a special process done on the valve seats so they don't drop out. From what I know this involved having a tigher fit than spec - installing by freezing the seat to contract it and heating the head to expand it.

Mark
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