Leaky exhaust valves
Posted: Sun Mar 26, 2017 11:24 pm
by rizzz
Went for a flight the other day and before going out I manually rotated the prop.
I noticed considerably less compression on 2 (#4 and #3 I believe) of the cylinders, also, I can hear a hissing in the exhausts during compression.
Leaky exhaust valves? Certainly showing all the symptoms…
I took the plane out for a flight hoping the problem would go away on a hot engine and while it was much better when the engine was hot, the difference in compression was still noticeable and the hissing noise was still there.
I’ll have to remove the heads and take them to my VW guy for a service/valve job, hopefully they can be saved.
In any case, it looks like I’m grounded for a while 
FYI, my heads are Mofoco 042’s, machined for 94mm and dual ignition.
Re: Leaky exhaust valves
Posted: Mon Mar 27, 2017 7:56 am
by kmacht
If you haven’t already, check your valve adjustment first before pulling the heads. I have had similar issues and it almost always was due to the engine needing the valves adjusted back to .006. It doesn’t take being off by much for the exhaust side to be too tight and cause the valve to open too early.
Keith
#554
Re: Leaky exhaust valves
Posted: Mon Mar 27, 2017 10:42 am
by intoaircooled
I would agree with check the valve adjustment first. I would go with the .008 on the exhaust valve and .006 on the intake. As everything heats up and expands the exhaust valve could use the extra clearance for good valve seal. Just my 2 cents.
Re: Leaky exhaust valves
Posted: Mon Mar 27, 2017 1:32 pm
by N190YX
Guys, if your airplane is not 100%, please don’t fly it! The notion of flying an engine that is not 100% to see if the issue will correct itself is a recipe for a disaster! Leaky exhaust valves result in the valve overheating and burning, and can also result in the valve failing. Which happened to me with a 1969 VW Bug I bought new, and kept the valves adjusted properly, but at 39,000 miles it swallowed an exhaust valve and seized, the head of the valve broke off (#3 cylinder that gets a little less cooling air due to the oil cooler in the plenum). TCM Continental allows no leakage past an exhaust valve, if leakage is detected in a compression test, the engine is not airworthy, the cause must be corrected. I repeat, please do not fly if your entire airplane is not 100% operational. We have got to keep our safety record as good as we can!
Re: Leaky exhaust valves
Posted: Mon Mar 27, 2017 5:57 pm
by rizzz
Thanks guys,
I will check the valve adjustment first.
It’s now been about 15 hours since the last one.
If that does not fix the issue I’ll remove the head(s).
N190YX, I hear what you’re saying.
The wise thing to do would have been to just go for a run-up to get the engine warm.
Re: Leaky exhaust valves
Posted: Mon Mar 27, 2017 6:59 pm
by intoaircooled
Calm down N190YX, I didn’t see anyone offer anything but advise on valve adjustments. Next course of action would be a good warmup and full power run up then and a leak down compression test. Just before you decide to push it off a cliff 
So far the only problem that ever fixed itself is our government,if u can believe that I have some health insurance I would like to sell you.
Re: Leaky exhaust valves
Posted: Mon Mar 27, 2017 8:37 pm
by gammaxy
N190YX wrote:Guys, if your airplane is not 100%, please don’t fly it! The notion of flying an engine that is not 100% to see if the issue will correct itself is a recipe for a disaster! … TCM Continental allows no leakage past an exhaust valve, if leakage is detected in a compression test, the engine is not airworthy, the cause must be corrected. I repeat, please do not fly if your entire airplane is not 100% operational. We have got to keep our safety record as good as we can!
TCM Continental no longer has the strict “no leakage” rule for valves–they replaced it almost 15 years ago with SB03-3. They have a calibrated orifice that seems to correspond to around 45/80 on most testers. They recommend you do a borescope inspection, fly, and retest if you fail it. I think they got smart and realized the previous rule was unrealistic.
https://www.aircraftspruce.com/catalog/ … lletin.pdf
Re: Cylinder Heads
Posted: Mon Mar 27, 2017 10:18 pm
by Eisenflyer
Hi, has anybody in the Sonex community checked out the new cylinder heads from cbperformance, “Panchito 044”
they look like the right design for the Sonex, much better cooling features than the regular VW heads.
Re: Leaky exhaust valves
Posted: Tue Mar 28, 2017 12:54 am
by mike.smith
rizzz wrote:Went for a flight the other day and before going out I manually rotated the prop.
I noticed considerably less compression on 2 (#4 and #3 I believe) of the cylinders, also, I can hear a hissing in the exhausts during compression.
Leaky exhaust valves? Certainly showing all the symptoms…
You don’t have the Nickasil cylinders, do you? If you say yes then I’ll tell you what may be up. If you say no then disregard
Re: Leaky exhaust valves
Posted: Tue Mar 28, 2017 1:14 am
by rizzz
mike.smith wrote:
rizzz wrote:Went for a flight the other day and before going out I manually rotated the prop.
I noticed considerably less compression on 2 (#4 and #3 I believe) of the cylinders, also, I can hear a hissing in the exhausts during compression.
Leaky exhaust valves? Certainly showing all the symptoms…You don’t have the Nickasil cylinders, do you? If you say yes then I’ll tell you what may be up. If you say no then disregard
I have the Nicom cylinders from Hummel, they are essentially Nikasils (nickel silicon carbide) but I believe the NiComs have chrome in them as well or so I’ve read somewhere.
I did ask Scott about them when the whole AeroVee Nikasyl issue happened and he said he never had issues with his brand, he still puts them on his engines as far as I can see now.
But yes, the thought has crossed my mind… you had problems with yours didn’t you?
Re: Leaky exhaust valves
Posted: Tue Mar 28, 2017 10:43 am
by Klimek
Gentlemen,
At 37 hours I replaced the exhaust valves on my AeroVee. Being an old VW tech, I have rebuilt too many VW engines due to a burned or broken #3 exhaust valve.
I had an excessive amount of leakage from two cylinders. Now at 80+ hours and at least 6 valve adjustments, it seems something needs to be done again. The exhaust valves were always tight. I set the exhaust at .008 and intake at .006. The exhaust valve clearance closed 3-4 thousandths after 10-12 hours of operation. I kept the temps below 400f on climb out and they run 310-325 in cruise. The face of the first set of exhaust valves were dished and seats seemed way too wide and evidenced leakage. I run 100ll and am considering using MOGAS from now on, as I set the compression ratio at 7.5:1 so I could run either fuel.
I have called about the “Panchito” heads but CIP no longer gives out info on the machine shop that can drill and tap for a second set of plugs, for liability reasons.
IF I could find someone who can and will do the machine work, I would consider installing a set of these heads. According to CIP they run cooler and have air flow on both sides
of the exhaust port. Looking at there website (California Import Parts) they are available in the same valve size and bored for the cylinders as used in the 2180 cc
AeroVee. Check them out, on the surface they look great.
If anyone has any ideas or suggestions or any reason I should not try them please chime in.
Other than being skittish about the valves, I love my AeroVee and AeroInjector.
Frank
ONEX 090
N1970T
At home polishing, painting, new windscreen, adding Aero Conversion hyd. disc brakes.
Re: Leaky exhaust valves
Posted: Tue Mar 28, 2017 11:09 am
by Area 51%
Not 100% sure, but I think Great Plains offers that service.
Re: Leaky exhaust valves
Posted: Tue Mar 28, 2017 11:22 am
by airscribe
Gotta chime in on the recommendation against flying if you believe the engine has issues; a ground-run, taxiing around, should warm the engine sufficiently to recheck for valve leaks and compression levels… Don’'t fly. There’s nothing to be gained in terms of warming the engine…
And feel compelled to comment on the prospect of the engine swallowing a valve…it’s not an automatic disaster…it is a challenge.
While there’s never, ever, a good place to suffer an in-flight engine problem, most pilots who suffer such a failure do survive…in fact, total engine failure for a swallowed valve isn’t an automatic outcome…many times the engine continues to run, albeit – and obviously – at far below normal power.
Three good friends of mine suffered such a failure…one in a Lyc-powered Cherokee, one in a Continental-powered Champ, one in a big-bore Continental powered Debonair…the latter two were at cruise altitude when their failures occured – luckily for them – and both found an airport close enough to nurse the plane to a safe, no-damage landing. The third fellow was doing pattern work; the engine made barely enough power for him to declare an emergency and cut from downwind directly to final…he ground-looped and damaged on gear and the wingtip on the same side as the gear.
In all three cases, cool heads and prior practice/training kept their incidents from unfolding into something worse.
And personally, suffered a seized exhaust valve in an O-200 in a Cessna 150 – a considerable distance from an airport…the engine continued to let me stay level; my decision: slip over to above a four-lane road that lead back to my departure airport, a decision requiring me to fly a longer return leg while keeping a landing option right below me until the last mile…going direct would have put me over urban and industrial landscapes with few-to-no open-space options…
It was a tense 12, 13 minutes, worrying that the engine might fail completely…the observer pilot flying with me told me later he would’ve gone direct – but when making the airport – I stayed at 2,500 agl all the way back – was a given he saw the point of the longer route…my fault for not verbally sharing my logic, but my attention was on flying the airplane and communicating our situation to the approach controller handling me…
All’s well that ends well…and to end well, we gotta fly the airplane.
Dave
Re: Leaky exhaust valves
Posted: Tue Mar 28, 2017 12:16 pm
by NWade
airscribe wrote:Gotta chime in on the recommendation against flying if you believe the engine has issues; a ground-run, taxiing around, should warm the engine sufficiently to recheck for valve leaks and compression levels… Don’'t fly. There’s nothing to be gained in terms of warming the engine…
While I know everyone on this forum is well-meaning, I really do wish people would post their qualifications or experience when they make a recommendation for or against a procedure.
Lots of well-meaning people repeat old-wives-tales or information that they believe to be correct; but is actually incorrect, or at least misunderstood. As Kerry said in an episode of the Sonex Flight podcast: Newer builders & pilots tend to believe that anyone handing out advice automatically knows more than they do. This can lead people down the proverbial garden path, regardless of your intentions…
When it comes to warming the engine: Heat causes metal to expand, and therefore it can change the way the engine behaves and the result of tests (like compression and leak-down tests). So yes, it makes a difference in the strictest sense of the word. The question is: should you use the “cold” or “hot” readings as the “true” answer? And what does a difference between a cold & hot reading mean? Something may be gained; or it may not indicate a safe condition for flight at all. Without knowing more, none of us can say for sure. A blanket admonishment (or endorsement) is not helpful or wise.
Personally I defer to Mike Busch, an award-winning A&P who has lots of experience with air-cooled engines. Here’s one of his articles on compression, leakage, hot vs. cold tests, and a couple of other items.
Blanket statements on the internet without a careful explanation of why should always be considered suspect. Even if a line of reasoning is explained, the qualifications of the person doing the explanation should also be factored into how much value you place on the information.
Let’s use facts, not fear, to guide our decision-making and our safety.
–Noel
P.S. For my own experience: I’ve helped build and operate race cars - from 2.0l 4-cylinder Fords, to Miatas, to a 750hp V8 GT-1/Trans-America Series car. And a lot of the same theory and basic information carries over to any Otto-cycle gasoline engine. However, I’ll freely admit that I am at the beginning of my experience with AeroVees in particular and cannot offer specific advice about how they wear and change over time; or best practices with VW aircooled engines.
Re: Leaky exhaust valves
Posted: Tue Mar 28, 2017 1:57 pm
by N190YX
gammaxy wrote:
N190YX wrote:Guys, if your airplane is not 100%, please don’t fly it! The notion of flying an engine that is not 100% to see if the issue will correct itself is a recipe for a disaster! … TCM Continental allows no leakage past an exhaust valve, if leakage is detected in a compression test, the engine is not airworthy, the cause must be corrected. I repeat, please do not fly if your entire airplane is not 100% operational. We have got to keep our safety record as good as we can!
TCM Continental no longer has the strict “no leakage” rule for valves–they replaced it almost 15 years ago with SB03-3. They have a calibrated orifice that seems to correspond to around 45/80 on most testers. They recommend you do a borescope inspection, fly, and retest if you fail it. I think they got smart and realized the previous rule was unrealistic.
Note you can only fly a TCM engine (and this should be considered for any aircraft engine) with leakage past an exhaust valve is after a boroscope inspection shows a normal exhaust valve. Leakage past an exhaust valve is really bad, think about it, the hot gasses going through a closed valve that should be in total contact with the head for cooling between exhaust strokes of the engine.
Re: Leaky exhaust valves
Posted: Tue Mar 28, 2017 5:24 pm
by NWade
N190YX wrote:Note you can only fly a TCM engine (and this should be considered for any aircraft engine) with leakage past an exhaust valve is after a boroscope inspection shows a normal exhaust valve.
Excuse me, can you please provide a citation for this? Saying you can “only” fly the engine implies that the procedure is mandatory.
If your source is the “Service Bulletin” that was referenced in the previous post, its worth noting that Service Bulletins are not mandatory (with a few narrow exceptions - including when they are incorporated into an AD and incorporated into a Users/Owners/Maintenance manual).
Thanks,
–Noel
P.S. I’m not trying to be a jerk; but the claim goes perfectly to my earlier point about well-meaning facts and careful explanations.
Re: Leaky exhaust valves
Posted: Tue Mar 28, 2017 5:57 pm
by rizzz
For those who have had to replace the valves and service the heads on your VW conversion,
Did you need to replace/recut the pushrods as well after this or would the old ones still fit?
Re: Leaky exhaust valves
Posted: Tue Mar 28, 2017 6:14 pm
by Brett
Old pushrods were fine. I’ve had different heads done 3 separate times. My local machine shop usually cuts the seats for me on the exhaust valves and my bill often is around $40-$100 depending on time taken to do all 4 valves and test for leaks. So far I haven’t actually needed to change any valves yet. This would no doubt bump the cost up.
Re: Leaky exhaust valves
Posted: Tue Mar 28, 2017 6:59 pm
by rizzz
Klimek wrote:I have called about the “Panchito” heads but CIP no longer gives out info on the machine shop that can drill and tap for a second set of plugs, for liability reasons.
IF I could find someone who can and will do the machine work, I would consider installing a set of these heads. According to CIP they run cooler and have air flow on both sides
of the exhaust port. Looking at there website (California Import Parts) they are available in the same valve size and bored for the cylinders as used in the 2180 cc
AeroVee. Check them out, on the surface they look great.
If anyone has any ideas or suggestions or any reason I should not try them please chime in.
Scott Casler at Hummel engines will do that, his website states $150 for a pair:
https://www.hummelengines.com/price-list
Re: Leaky exhaust valves
Posted: Tue Mar 28, 2017 7:05 pm
by Corby202
Here’s one of his articles on compression.
That is an interesting link that Noel posted. For us Jabiru owners (in Aus anyway) regular leak down tests are required. I also believe there are so many variables doing that test. I think the best practice is to have your own leak down tester with a known orifice size and keep that tester along with a compression tester for all tests.It is the best way to know the condition of YOUR engine as you can compare test to test correctly.
Re: Leaky exhaust valves
Posted: Tue Mar 28, 2017 7:29 pm
by mike.smith
rizzz wrote:
mike.smith wrote:
rizzz wrote:Went for a flight the other day and before going out I manually rotated the prop.
I noticed considerably less compression on 2 (#4 and #3 I believe) of the cylinders, also, I can hear a hissing in the exhausts during compression.
Leaky exhaust valves? Certainly showing all the symptoms…You don’t have the Nickasil cylinders, do you? If you say yes then I’ll tell you what may be up. If you say no then disregard
I have the Nicom cylinders from Hummel, they are essentially Nikasils (nickel silicon carbide) but I believe the NiComs have chrome in them as well or so I’ve read somewhere.
I did ask Scott about them when the whole AeroVee Nikasyl issue happened and he said he never had issues with his brand, he still puts them on his engines as far as I can see now.But yes, the thought has crossed my mind… you had problems with yours didn’t you?
Yes. The walls of the cylinders were too thin to stand up to normal temperatures and torque values. The tops of the cylinders, where they contact the heads, were rolling over and mushrooming. So the heads were getting closer to the engine block each time I reset the torque, and that would decrease the gap between the valves and the rocker arms until they were in constant contact, making the valves leaky (they would never fully close). That also burned my first set of valves, but at the time I didn’t understand what was happening, so I put the heads back on the bad cylinders after replacing the valves.
The real clues were twofold: 1. Every time I checked the torque on the heads the nuts had to move to get the torque to specs (on my cast iron heads the torque has stayed put, and the nuts have never needed tightening), and 2. regular oil analysis showed high levels of things like nickel (the nickasil) and iron (piston rings) and aluminum (the cylinder walls under the nickasil).
Here’s my Kitlog entry.
http://www.mykitlog.com/users/display_l … 380&row=38
Absolutely no issues since changing to cast iron cylinders.
Re: Leaky exhaust valves
Posted: Tue Mar 28, 2017 8:08 pm
by rizzz
mike.smith wrote:Yes. The walls of the cylinders were too thin to stand up to normal temperatures and torque values. The tops of the cylinders, where they contact the heads, were rolling over and mushrooming. So the heads were getting closer to the engine block each time I reset the torque, and that would decrease the gap between the valves and the rocker arms until they were in constant contact, making the valves leaky (they would never fully close). That also burned my first set of valves, but at the time I didn’t understand what was happening, so I put the heads back on the bad cylinders after replacing the valves.
The real clues were twofold: 1. Every time I checked the torque on the heads the nuts had to move to get the torque to specs (on my cast iron heads the torque has stayed put, and the nuts have never needed tightening), and 2. regular oil analysis showed high levels of things like nickel (the nickasil) and iron (piston rings) and aluminum (the cylinder walls under the nickasil).
Here’s my Kitlog entry.
http://www.mykitlog.com/users/display_l … 380&row=38Absolutely no issues since changing to cast iron cylinders.
Hmmmm looks bad,
I’ll be heading to e airport tomorrow to find out what’s going on, we have a borescope in our local SAAA chapter so I will use that first before pulling anything.
It’s a shame about the quality of those nickasils currently on the market. Most are cheap chinese knock-offs.
I’m not sure where Hummel sources their NiComs though but I’m hoping for the best. They look quite different from the AeroVee and GP ones.
If I had the money I’d by a set of the original LN Engineering “Nickies” (http://lnengineering.com/products/airco … ?limit=all), everyone on the VW forums raves about those, but at almost $3500/set they darn expensive, too expensive!
Re: Leaky exhaust valves
Posted: Tue Mar 28, 2017 11:08 pm
by radfordc
Is there any value to the Nickasils other than the weight difference?
Re: Leaky exhaust valves
Posted: Tue Mar 28, 2017 11:47 pm
by rizzz
radfordc wrote:Is there any value to the Nickasils other than the weight difference?
It is claimed they cool better.
Re: Leaky exhaust valves
Posted: Wed Mar 29, 2017 1:54 pm
by N190YX
NWade wrote:
N190YX wrote:Note you can only fly a TCM engine (and this should be considered for any aircraft engine) with leakage past an exhaust valve is after a boroscope inspection shows a normal exhaust valve.
Excuse me, can you please provide a citation for this? Saying you can “only” fly the engine implies that the procedure is mandatory.
If your source is the “Service Bulletin” that was referenced in the previous post, its worth noting that Service Bulletins are not mandatory (with a few narrow exceptions - including when they are incorporated into an AD and incorporated into a Users/Owners/Maintenance manual).
Thanks,
–Noel
P.S. I’m not trying to be a jerk; but the claim goes perfectly to my earlier point about well-meaning facts and careful explanations.
I wrote about exhaust valve leakage based on my experience of owning an IO-470 TCM Continental engined airplane for 37 years (still flying it) and doing my own maintenance (under the supervision of an A&P IA), and having had a VW engine swallow an exhaust valve head that broke off the valve stem (the engine seized immediately with metal throughout the engine, the valve head caused a hole in the piston), and on following what I consider to be reasonable guidance from TCM regarding leakage past an exhaust valve. Hey, we can’t pull over to the side of a road when our engine fails, and to read that, well, you can survive most engine failures in flight - If you think taking an unnecessary chance on an engine failure in flight is OK, you should not be flying, you don’t have the judgement. Blunt statement, but we pay higher insurance rates due to pilots doing risky things. Please think about this.
Re: Leaky exhaust valves
Posted: Wed Mar 29, 2017 5:13 pm
by SonexN76ET
One possible way to protect your valves from leaking early due to carbon fouling is to use Decalin or TCP fuel additives. I checked with Sonex before I started using it and while they do not explicitly recommend it, they did say people had reported good results with it. (Just be careful to read the directions as you put very little in to mix with ten gallons of 100LL, I am talking just a tablespoon or so per the directions. One guy mistakenly poured a whole bottle in his Sonex’s fuel tank and had some bad results with reduced power output). On a SportCruiser with a Rotax 912, it was required to use the Decalin fuel additive when using 100LL to prevent fouling). So far, I have noticed no ill effects using the Decalin over the past fifteen hours.
http://www.aircraftspruce.com/catalog/appages/Decalin.php?recfer=1914
Sonex had also recommended that I ensure that I was not running too rich and warned that a too rich mixture can lead to valves and sparkplugs fouling. I now lean my mixture after landing when taxiing back to the hangar. I do not lean my mixture when taxiing to the runway for takeoff because of the off chance that I would fail to go to full rich for takeoff which could cause the engine to fail on takeoff due to a too lean of mixture. I lean in flight to stay in the upper range of the green for my CHTs and EGTs.
The other thing you can do is make sure your cooling baffles are adequate and do not leave any gaps that the air can escape through. You want pressurized air going through the cooling fins and ducts on your engine. High pressure on the top of the engine flowing through the cooling ducts and fins on the cylinders and heads and into the supertins on the bottom and into the low pressure below the engine and out into the slipstream. One thing I did not initially pay attention to is that gaps at the front of the engine in your baffles can cause a significant amount of air bypassing the engine. Another place that allows air to escape is in the corners of the baffles at the rear of the engine. The reason head cooling is important and related to valve fouling is that some people run their mixture excessively rich in an effort to keep their CHT’s in the green. That excessively rich mixture used to offset poor head cooling causes the valves and sparkplugs to foul with carbon and lead.
I also wanted to make a comment on the proposition in this thread to look at different cylinder heads. On the surface the CB Panchito 44 heads look promising. I do not think I would like to be the first one to try them in flight though. One configuration issue I saw was the intake ports are milled significantly more inboard than the conventional heads. This would require probably using a spacer like the one Sonex uses with the MOFOCO heads but having them machined to create a smoother joint with the Aerovee intake elbow or having custom intakes made.
I agree with N190YX that you should not fly with any known deficiencies. Always double check everything and if something needs fixing then fix it before you fly.
On that note, pulling the heads on an Aerovee is very easy and very simple. It takes me about 15 minutes per head. My local machine shop will do a valve job on the pair of heads for around $150. Then when you reinstall them all you need is new exhaust gaskets, new push rod tube seals (I highly recommend the white silicone ones. They do not leak!) and new copper cylinder head gaskets. It might take an hour per side to reinstall them. You will have to adjust your valves again when you reinstall the head and then again at 5 hours, torque the heads and adjust valves at 10 hours, and 25 hours, just like when you first built your engine. You will also have higher CHTs as the valve job breaks itself in over the next few hours. I am tempted to get a second set of heads and just change them out whenever I suspect a fouled valve (with a valve job done when I pull the heads and then have them ready to go for the next time). Aerovee heads are very inexpensive compared to certified heads or Rotax heads.
Anyway, this is just my two cents on my experience so far. Please put safety first when you fly. These planes are lots of fun, but they need to be treated with respect.
Jake
Re: Leaky exhaust valves
Posted: Wed Mar 29, 2017 8:06 pm
by mike.smith
SonexN76ET wrote:One possible way to protect your valves from leaking early due to carbon fouling is to use Decalin or TCP fuel additives. I checked with Sonex before I started using it and while they do not explicitly recommend it, they did say people had reported good results with it. (Just be careful to read the directions as you put very little in to mix with ten gallons of 100LL, I am talking just a tablespoon or so per the directions.
I have run TCP for 220 hours on my AeroVee engine and it works great. But the instructions are 30ml for every 10 gallons. That’s quite a bit more than a tablespoon. They sell a syringe for the TCP that is marked in ml; that’s what I use.
Re: Leaky exhaust valves
Posted: Wed Mar 29, 2017 8:08 pm
by mike.smith
rizzz wrote:
It’s a shame about the quality of those nickasils currently on the market. Most are cheap chinese knock-offs.
I’m not sure where Hummel sources their NiComs though but I’m hoping for the best. They look quite different from the AeroVee and GP ones.
I think if the cylinder walls were thicker then they would have worked fine.
Re: Leaky exhaust valves
Posted: Wed Mar 29, 2017 8:10 pm
by mike.smith
rizzz wrote:
radfordc wrote:Is there any value to the Nickasils other than the weight difference?
It is claimed they cool better.
I found that the Nickasil cylinders were VERY good at cooling. When I changed to the cast iron cylinders my temps were higher, but after break-in and a few minor modifications even the cast irons have run quite cool even in the dead of summer. (My cooling modifications are on my Kitlog site under the “Engine” heading.)
Re: Leaky exhaust valves
Posted: Wed Mar 29, 2017 11:05 pm
by rizzz
OK, just got back from the airport, despite trying the many suggestions, in the end the heads had to come off as nothing seemed to improve the situation.
Here’s what they look like, not pretty.
Right:
Left:
The cylinders look good though but the piston faces have the same burnt look.
Took them to my VW guy, his reaction:
Holy $#&!!" these have seen some heat, how lean are you running this thing???!!!
My response to that was, what do you mean? I always thought I was running too rich?
