Oil Cooler Structural Failure
Posted: Tue Jan 16, 2018 12:30 am
by NWade
Hello All,
Tragedy struck today shortly after starting my AeroVee Turbo. Through 6 short engine runs it had provided smooth and strong power, hadn’t leaked oil, and the only sign of anything non-optimal was that I could only get ~36" MAP at WOT (but it was still making over 3000 RPM with my Prince prop).
On this run, I started the engine and got it idling for no more than ~5 seconds when my observer yelled “Oil! Lots of Oil!” I shut the engine down immediately and climbed out of the cockpit to see a HUGE puddle of oil below the airplane, and oil dripping from every item forward of the firewall.
After getting out the oil-dry and spreading it beneath the airplane, we started looking at the flow path of the oil around the crankcase to find the source of the problem. There were no obvious cracks, broken items, or loose hoses. But a bunch of the oil seemed to originate around the top-mount oil cooler itself. On a hunch, I double-checked that the mags & coils where off, then I slowly turned the prop by hand. After a couple of blades, a gob of oil burped out the front of the oil cooler - from somewhere between the first and second plates, down low on the pilot’s side. I waited until the cooler stopped “drooling”, then slowly pulled the prop around another 90 degrees of arc. Sure enough, another thimbleful of that green Brad Penn 20w-50 oil oozed out of the front of the oil cooler and dribbled down onto the crankcase.
After putting on my thinking cap while I spent 2 hours mopping up the worst of the oil in the engine compartment and scrubbing oil-dry around on the airport’s asphalt, I’ve come to the conclusion that I probably got a bad part from CBPerformance. The other likely explanation is that my oil pressure is a lot higher than I thought, and the system can’t take that much pressure. According to my VDO gauge, the oil pressure has been ~90 psi cold (air temps around 42 degrees F), with the pressure dropping to 50 psi once the engine has been running for 2-3 minutes. This seems a little bit on the high side, but not excessively so (unless my gauge is way off).
- Has anyone else ever experienced this failure?
- Does anyone have a recommended cleaner/degreaser that won’t damage the insulation on the electrical wires in my engine compartment?
- Anyone have a way to get oil out of the exhaust wrap?
(My guess is that I’ll have to remove it and buy new stuff, as a couple of sections are absolutely saturated) - Have a proven/approved method of slightly lowering the oil pressure in the AeroVee?
(Cut the spring on the oil control plunger? Get a different spring? Something else?)
Thanks,
–Noel
(…who’s not looking forward to removing the fence baffles and some of the wiring and the intake system and the aeroinjector to clean it all off)
Re: Oil Cooler Structural Failure
Posted: Tue Jan 16, 2018 3:22 am
by lutorm
Wow. At least it happened on the ground!
I’ve heard of VW oil cooler failures due to overpressure, but they have been to the ones mounted in the “full-flow filter circuit”, ie our bottom-mounted cooler. Since these are mounted before the pressure-relief valve in the case, they will see whatever pressure the pump is capable of putting out, which if the oil is cold can be very high (and does not show up on the pressure gauge since it is mounted after the filter.)
But it sounds like this is a top-mounted cooler, which should be after the pressure relief so shouldn’t ever see those unregulatedly high pressures. (Unless your pressure relief piston is stuck, which would be a good thing to check.) Did you happen to record oil pressure data on this very run? 90 psi is a lot higher than what we had on our bottom-cooled Aerovee at “cold” (ie, 75F…) starts before I tore it down, but with gigantic bearing clearances and complete flow through the oil cooler bypass this engine still saw ~70psi. 90 should not blow a cooler, I’d think, so maybe it was a bad cooler. It seems easy to get VW parts of questionable quality…
An easy way to lower the oil pressure is to switch to a less viscous oil. In the auto world, not many seem to run 20w-50 in their VW’s. 10w-30 seems much more common, certainly if the temperatures are down near freezing. Maybe since we run the engines at high power for long periods of time maybe they run at higher temperatures than in cars, so more viscous oil is warranted?
Re: Oil Cooler Structural Failure
Posted: Tue Jan 16, 2018 5:41 am
by rizzz
90 PSI is very high,
I think I get mid 60’s to low 70’s cold and mid 30’s hot.
Definetly check the pressure relief pistons, they can get stuck and if you find it is, GP has instructions on their website somewhere to get it out.
Re: Oil Cooler Structural Failure
Posted: Tue Jan 16, 2018 8:41 am
by Area 51%
Have you identified the type of failure yet? Thin material? Bad seam? Seal failure?
While dry-fitting my oil cooler to the engine, I noticed that the cooler was contacting the engine case bolt boss under it.
Re: Oil Cooler Structural Failure
Posted: Tue Jan 16, 2018 10:20 am
by marsolgp
Noel, I had the exact same failure last year… Makes a pretty good mess, huh?.. My oil pressures run about the same as yours… just chocked it up to another bad aftermarket VW part. I removed the cooler and blocked it off with the bypass plate and flew the rest of the ‘winter’ season that way. Don’t really need a cooler in the winter.
Re: Oil Cooler Structural Failure
Posted: Tue Jan 16, 2018 11:54 am
by 9GT
No help here with your oil cooler but something that REALLY works well for de-greasing and is safe for your wiring is Super Clean available at most big box stores including Wal-Mart. https://www.walmart.com/ip/SuperClean-T … 3=&veh=sem
Comes in a purple jug in various sizes right down to a squirt/spray bottle. Don’t confuse it with Purple Power which is lame in comparison. Once you try Super Clean you’ll want to keep it on hand at all times.
Re: Oil Cooler Structural Failure
Posted: Tue Jan 16, 2018 12:12 pm
by NWade
Thanks, all!
For the record, and to answer some of the questions:
An easy way to lower the oil pressure is to switch to a less viscous oil
The only “approved” oil for the AeroVee Turbo is Brad Penn 20w-50 Racing oil (semi-synthetic). :-/
Definetly check the pressure relief pistons
I’ll do that once things are cleaned up; but when assembling the engine I made sure that the slugs slid smoothly up and down in their channels with just a bit of oil on ‘em. But I guess that once they were installed with the honkin’ springs behind them, they might have gotten jammed… Will investigate and report!
Have you identified the type of failure yet? Thin material? Bad seam? Seal failure?
While dry-fitting my oil cooler to the engine, I noticed that the cooler was contacting the engine case bolt boss under it.
No, not yet. The failed area is between two of the horizontal plates, somewhere back from the “leading edge” so its not visible. I’ve brought some parts home - including the fialed cooler - to try to drain and clean them. I’ll see if I can find the exact point of failure once its cleaned up. As for my cooler, it never contacted the crankcase once it was mounted on the adapter plate with the oil seals in-place.
Will be calling Sonex momentarily to also get their opinion, and will report my findings here if there’s anything noteworthy.
–Noel
Re: Oil Cooler Structural Failure
Posted: Tue Jan 16, 2018 3:53 pm
by lutorm
NWade wrote:Thanks, all!
The only “approved” oil for the AeroVee Turbo is Brad Penn 20w-50 Racing oil (semi-synthetic). :-/
Indeed. I don’t think there are any “approved” methods of lowering the oil pressure… 
As long as you have sufficient oil pressure on hot idle, a less viscous oil is unlikely to cause a problem. (Some people even say higher-viscosity oils run hotter, because the increased viscosity leads to increased oil cooler pressure and more oil bypassing it.)
Re: Oil Cooler Structural Failure
Posted: Tue Jan 16, 2018 7:06 pm
by kmacht
Carefully with what you clean it with. Make sure it is safe for aluminum and use lots and lots of water. I like simple green but it has to be the one for aviation. The regular one found in home depot isn’t good for aluminum.
Keith
#554
Re: Oil Cooler Structural Failure
Posted: Wed Jan 17, 2018 4:35 pm
by NWade
Just for completeness:
I got a somewhat-brief response from Sonex today. Basically I was told that I can run a lower viscosity oil, but they have no suggestions/recommendations on what to put in. They also recommended I put in a mechanical oil pressure gauge to cross-check the VDO sender (the VDO sender I bought from them. The one which maxes out at only 80 psi, so you can’t truly tell if you’re seeing excessive oil pressure). They also noted that I can run without an oil cooler in cold temps (but no comment on what temp range might be recommended for that mode of operation, or how I would go about modding the AeroVee to do this). They also recommended I idle the engine until the oil temp is above 80 degrees (which, of course, is exactly what I was trying to do when the oil cooler blew out).
:-/
Not being incredibly impressed with the depth of information I’m working with, I also read a bunch and posted on some VW forums. Many VW automotive solutions & standards are inappropriate for an aircraft applications. However, I wanted to see what they had to say and then make my own judgments based on my experience so far with the AeroVee and with automotive (racing) engines that I worked on in my youth. I got some great responses and some pretty useless responses (hey, its the internet). The two notable things I took away are -
(a) 20w-50 is claimed to be “too heavy” by many VW folks and has been known to blow out oil coolers. This is due to a combination of the stock oil galley size around the oil pressure relief plunger (which tries to bypass the oil through bearings and other narrow orifices), the heavier-than-stock oil-pressure-relief springs that come in modern VW kits, and the thick cold oil itself. AeroConversions undoubtedly has a reason why they want a thick oil in the engine (either to maintain high pressures with hot oil at high RPM, or to retain a thick oil film when the engine is not used for weeks at a time, or for some other reason). However I had my ear chewed off about how 20w-50 is excessive and unnecessary in an automotive application.
(b) Early VW oil pumps were smaller than modern pumps and the bigger aftermarket pumps people use now often require (or are heavily encouraged to use) oil pump covers with special pressure-relief passages, or remote bypass valves that are daisy-chained to remote oil filters. I find this info germane since the AeroVee Turbo seems to be using something similar to this CB Performance pump and I believe that pump flows more than the old 26mm stock unit.
So, here’s my current plan:
(Note that I don’t claim to know that these are the correct steps to take; just putting it on-record as what I am going to try)
- Clean everything with Simple Green Aircraft Cleaner
- Get a replacement oil cooler
- Switch to Brad Penn 15w-40 oil (still semi-synthetic with high ZDDP). VW automotive guys are encouraging me to switch to 10w-30 but I want to make incremental changes and not suddenly find myself dealing with low oil pressure when the engine is hot.
- Replace the 80 psi VDO sender from AeroConversions with a 120psi or 150psi VDO sender. I might lose a little bit of precision, but doing this will allow me to see if the engine is running up to excessive pressure levels on engine-start without having to run an oil line into the cockpit and set up a mechanical gauge.
- Pull the oil control and oil pressure relief plungers out and check the bores for signs that the springs are scraping or not moving freely. I don’t think this is an issue but I want to check to be sure. I tested the plungers themselves before assembling the engine and they slid smoothly and freely so I know they’re OK.
- Optional Bonus Fun - I’m really not a fan of the hard-line for oil that runs from the pressure sender to the crankcase flywheel flange. I’m going to look at converting that to a -4 AN braided hose and using an cushioned (Adel) clamp on the oil cooler attachment bolt to hold the hose in the proper orientation/shape (so it has a high point for oil to drain back, and so its own weight doesn’t apply a torque on the fittings to loosen up over time).
–Noel
Re: Oil Cooler Structural Failure
Posted: Wed Jan 17, 2018 5:27 pm
by Sonex422
I also have had an oil cooler failure last spring right after I converted to a top mounted oil cooler. It occurred during initial run-up and leak test. Initially I thought it was high Oil pressure because of the 90 psi reading on my MGL Stratomaster.
On examination of the failed oil cooler it was discovered that there was a poor weld between the corrugated fins and the chamber containing the oil.
After replacing the top mounted oil cooler and before starting the engine again I bought a direct reading test gage from Harbor freight with a long hose. After engine start it read in the normal 50 psi range. So I did some more research and found out that the MGL stratomaster defaulted to Rotax settings (probably should have done that earlier). Rotax uses a 200 PSI VDO gage. So I simply had to set the correct scaling factor in the Stratomaster. Once completed, the readings matched that of the test gauge. There have not been any oil system issues since then.
I hope that this may help.
Re: Oil Cooler Structural Failure
Posted: Wed Jan 17, 2018 6:16 pm
by NWade
Sonex422 wrote:On examination of the failed oil cooler it was discovered that there was a poor weld between the corrugated fins and the chamber containing the oil.
…So I did some more research and found out that the MGL stratomaster defaulted to Rotax settings (probably should have done that earlier). Rotax uses a 200 PSI VDO gage
Thanks! Yeah, my Discovery Lite iEFIS defaulted to a 100psi gauge, and on my initial engine start I saw 100psi during the first few moments of running. Later on I realized I needed to adjust the EFIS and set it to the 80psi range of my VDO sender. From then on, I saw 80 psi during the first minute or two of each engine run. But I think my oil pressure may well be higher than that; its just beyond the max that the VDO sender can read. I’m curious to see what reading the 150psi VDO sender shows me on startup; if I can’t get a good consistent set of readings from it then I’ll grab a direct-read gauge from HF and see.
Either way, I’m making these series of changes just to be on the safe side. I’d hate to clean this mess up and then blow another oil cooler!
–Noel
Re: Oil Cooler Structural Failure
Posted: Wed Jan 17, 2018 7:00 pm
by daleandee
NWade wrote:The one which maxes out at only 80 psi, so you can’t truly tell if you’re seeing excessive oil pressure). They also noted that I can run without an oil cooler in cold temps (but no comment on what temp range might be recommended for that mode of operation, or how I would go about modding the AeroVee to do this). They also recommended I idle the engine until the oil temp is above 80 degrees (which, of course, is exactly what I was trying to do when the oil cooler blew out).
When I had my VW powered nose roller I was returning back home from my second time flying to the ASA meeting in Crossville Tn. I was coming down the valley and had just crossed over into Georgia when I noticed the oil pressure at 80 PSI. At first I thought it must be a bad sender and then I considered that there might be a few people in the graveyard that thought that too. Straight ahead about 11 miles was Dalton (DNN) so I decided to land there and find out what the problem was. After landing I took a look at what I could see without pulling the cowling & did a run-up. Everything was absolutely normal. Unicom had called and asked if I needed assistance. I told then the concern but all seemed well and I was taking off but depending on how it went I might be right back. It never did that again …
NWade wrote:20w-50 is claimed to be “too heavy” by many VW folks and has been known to blow out oil coolers. This is due to a combination of the stock oil galley size around the oil pressure relief plunger (which tries to bypass the oil through bearings and other narrow orifices), the heavier-than-stock oil-pressure-relief springs that come in modern VW kits, and the thick cold oil itself.
I’m in the camp that believes that 20W50 may be too thick. While it’s true that air-cooled engines have larger clearances & tolerances change more because they run at a higher temp, oils are much better than they used to be and oil that is thick can’t flow well. Pressure is important but so is flow. The factory says they want to see something above 40 PSI on the engine. Then builders get into thinking if 40 is good then 50 is better! So they tend to set the oil piston spring pressure higher & use a heavy oil and at start up on a cold morning the oil pressure can really shoot up high if the engine has to be spun up to keep it running in the cold. Resist the temptation to set the pressure too high or use oil that is heavy. I like your approach below about trying a viscosity oil that is one step below what you are currently running. I use 15W40 Rotella and it works well but I rarely will be flying if the temps are near freezing. (I’m turning into a wimpy old geezer).
My Corvair engine uses a stock factory oil cooler. We generally test them to 80 PSI before using them. You might consider doing that … even with a new one. If your oil system is correctly set up you won’t need a sender that reads over 80PSI. If it’s reading that high, how high it is is not really a concern but getting the airplane on the ground is!
With your experience you are aware that they make an Oil Pressure Adjustable Pressure Regulator so you can set your oil pressure where you want it. As the engine breaks in you can reset it if needed.
Dunno if this helps,
Dale Williams
N319WF @ 6J2
Myunn - “daughter of Cleanex”
120 HP - 3.0 Corvair
Tail Wheel - Center Stick
Signature Finish 2200 Paint Job
166.7 hours / Status - Flying
Member # 109 - Florida Sonex Association
Latest Video - “I Wanna Fly” https://www.youtube.com/watch?v=1VP7UYEqQ-g
Re: Oil Cooler Structural Failure
Posted: Wed Jan 17, 2018 8:21 pm
by hollandvw
Hi guys and gals The factory vws from the 70’s I.E. 1600 dual port (wich your engine is based on) recommended 10w30 in the winter and straight weight 30 in the summer changing bore and stroke has no effect on the oiling system or passages. I am not an expert but have built well over 50 vw engines in the 35 years I have been working on them and would never use anything but rotella 15w40 in the summer and 10w30 in the winter even on my turbo street engines. 20w50 in the winter has to be about like pumping 80-90 gear lube in the summer. Also I have never run a synthetic in a Aircooled vw as synthetics are designed to reject heat and 40% of your engines cooling comes from the oil. hope this helps Scott
Re: Oil Cooler Structural Failure
Posted: Wed Jan 17, 2018 9:22 pm
by NWade
Today I found out the hard way: mentioning 20w-50 on certain VW forums will get the sanctimonious a-holes there raging! sigh
Dale - I wasn’t aware of an adjustable pressure regulator for the VW; I’d be curious to see what that product looks like - have any links or product names I should look up?
My understanding (after dealing with some actually-helpful folks on the VW foums) is that the outflow of the oil cooler connects back to the main oil galleys, and there are no check-valves in the system. Therefore, even when the oil pressure spikes and the oil relief plunger opens up, the oil that bypasses the cooler still routes through the bearings and galleys and the end result is that the entire oil system still pressurizes. With no check-valves, oil can be forced to backflow up into the cooler until it reaches the same pressure as everywhere else. You get no real flow through the cooler; but you do get pressure in there.
Aftermarket VW folks have designed oil pumps that have pressure-relief ports that dump oil directly back into the sump, but those solutions are not usable on an AeroVee Turbo because of the double-stacked oil pump design we use.
Take care,
–Noel
Re: Oil Cooler Structural Failure
Posted: Wed Jan 17, 2018 11:25 pm
by daleandee
NWade wrote:I wasn’t aware of an adjustable pressure regulator for the VW; I’d be curious to see what that product looks like - have any links or product names I should look up?
https://www.ebay.com/p/EMPI-9198-VW-Bug-Adjustable-Oil-Pressure-Regulator/1974594347
NWade wrote:Aftermarket VW folks have designed oil pumps that have pressure-relief ports that dump oil directly back into the sump, but those solutions are not usable on an AeroVee Turbo because of the double-stacked oil pump design we use.
I haven’t seen what Sonex is using but I have a '74 Beetle with an Auto-Stick that has a double stack oil pump. They are stacked together but are separate in their operation as the outer one is used to drive hydraulic fluid (Auto trans fluid) for the torque converter part of the Auto-Stick transmission setup. It really is a pretty good German design. Here’s a link to the VW pump:
https://www.evwparts.com/vwparts/113115101A.html
Dale Williams
N319WF @ 6J2
Myunn - “daughter of Cleanex”
120 HP - 3.0 Corvair
Tail Wheel - Center Stick
Signature Finish 2200 Paint Job
166.7 hours / Status - Flying
Member # 109 - Florida Sonex Association
https://www.youtube.com/watch?v=1VP7UYEqQ-g
Re: Oil Cooler Structural Failure
Posted: Thu Jan 18, 2018 12:49 am
by NWade
daleandee wrote:
NWade wrote:I wasn’t aware of an adjustable pressure regulator for the VW; I’d be curious to see what that product looks like - have any links or product names I should look up?
https://www.ebay.com/p/EMPI-9198-VW-Bug-Adjustable-Oil-Pressure-Regulator/1974594347
Thanks! On the one hand that’s kludgy as hell; on the other hand its brilliantly simple. All that thing does is stop the oil control plunger from retracting all the way. So its good for helping keep the oil pressure higher. But sadly I can’t see how it would help lower the oil pressure below stock/standard levels; so it won’t help me at the present time.
Its good to know that exists, though. Thanks for sharing!
–Noel
Re: Oil Cooler Structural Failure
Posted: Thu Jan 18, 2018 1:55 am
by lutorm
NWade wrote:Thanks! On the one hand that’s kludgy as hell; on the other hand its brilliantly simple. All that thing does is stop the oil control plunger from retracting all the way. So its good for helping keep the oil pressure higher. But sadly I can’t see how it would help lower the oil pressure below stock/standard levels; so it won’t help me at the present time.
I think it actually pushes the bottom of the spring up, changing the spring preload. But that still means you can’t use it to lower your the relief pressure except by also switching to a lighter spring.
And about the pressure relief valve still pressurizing the cooler: yeah, the cooler will always see the indicated oil pressure. But that pressure will be set by the pressure control valve at the rear of the case, not by whatever pressure is needed to squeeze the oil through the cooler. It’s the latter that can get really high, since the control valve will dump oil back to the sump if the pressure is higher than something like 35psi (I may be misremembering the pressure it relieves at.)
Edit: there is another situation that can lead to overpressure: if you use a 30mm or larger oil pump, the relief passages are apparently not large enough to relieve all the excess flow, so the pressure can spike to very high levels.
There’s an interesting thread at thesamba here: https://www.thesamba.com/vw/forum/viewtopic.php?t=280293 where some guy took pressure readings at different places in the oil system for a bunch of different conditions. Really useful for understanding how the oil pressure behaves.
Re: Oil Cooler Structural Failure
Posted: Thu Jan 18, 2018 8:48 am
by Area 51%
CB performance has the oil cooler block-off/bypass plate. The part number is 1733 and it’s $17.95.
Re: Oil Cooler Structural Failure
Posted: Thu Jan 18, 2018 10:33 am
by SonexN76ET
Noel,
I believe you may be over thinking the high oil pressure you experienced. Likely it is one of two things. Either your pressure relief plunger stuck or you had a defective oil cooler. Your’s is the only top mounted cooler I have heard of that has burst. Most Aerovee builders have the issue of trying to increase their oil pressure. Also as your engine starts to break in you will likely start to see your pressure come down and you will start looking for ways to increase your oil pressure. The device Dale wisely presented is a very commonly used solution.
Finally, in regards to oil, please disregard the advice from automotive VW experts who have never flown behind or operated or maintained a VW powered aircraft and rather follow the recommendations of the factory. The flying environment is completely different than the road environment. Flying stresses on an engine are more akin to driving uphill in a fully loaded truck on a steep grade with a constant heavy load on the engine and at relatively high constant rpm.
As a side note, I recommend you take Robert Hoover’s VW blog with a grain of salt. He was an enthusiastic VW hobbiest and someone with strong opinions who loved to write. He had nowhere near the experience of John Monnett, Great Planes, Hummel, or Rev-master. Some of his advice is bogus. For instance, his advice on painting VW engine cases does not work. I tried it and my paint peeled right off.
Jake
Re: Oil Cooler Structural Failure
Posted: Thu Jan 18, 2018 3:00 pm
by lutorm
SonexN76ET wrote:As a side note, I recommend you take Robert Hoover’s VW blog with a grain of salt. He was an enthusiastic VW hobbiest and someone with strong opinions who loved to write. He had nowhere near the experience of John Monnett, Great Planes, Hummel, or Rev-master.
I couldn’t tell whether you meant the preceding paragraph to apply to Bob Hoover as well but, just to be clear, he was also in the business of converting VW’s for aircraft use. As for who has the most experience, I wouldn’t know. Like anyone’s advice, his should be taken with a grain of salt.
Re: Oil Cooler Structural Failure
Posted: Thu Jan 18, 2018 4:40 pm
by SonexN76ET
In regards to Robert Hoover’s VW blog, there is a huge difference between engineering and producing 1,500 plus engines like AeroConversions has with Robert Hoover helping to build a handful of engines.
I will give you another example of Robert Hoover’s bad advice. He recommends if your oil pressure relief plungers are sticking is to put valve grinding compound on them and to stick them back in your engine and spin them and push them up and down until they loosen up. Now, unless you are going to disassemble your engine there is not going to be a way to get that abrasive valve grinding compound out of the narrow oil galleys above the plungers.
Please be careful whose advice you follow.
Jake
Re: Oil Cooler Structural Failure
Posted: Thu Jan 18, 2018 5:13 pm
by kmacht
That specific advice was for during engine assembly when you could clean it out. I would treat every piece of advice as skeptical even if from the factory. They denied issues with the #4 bearing restrictor plug until they diddnt. Their mags were bad until suddenly they werent. They also have issues with the turbo but are still selling it without a fix in place. It’s always best to look at each piece of advice and see what their motivations might be. Sonex is trying to stay in business and sell motors. What was Bob Hoover’s motivation?
Keith
Re: Oil Cooler Structural Failure
Posted: Thu Jan 18, 2018 8:01 pm
by lutorm
In general, I’ve found most of Hoover’s topics to advocate a very careful, take no chances, approach to assembling a VW engine, arguing specifically that you can’t just buy a bunch of VW parts these days and think that they’ll go together without careful checking of all the specifications. Much more so than the impression you get from the Aerovee assembly manual. Is it all necessary? I don’t know, but you can’t fault the guy for being careless.
As an example, the Aerovee manual mentions nothing about checking the cam timing. Hoover does, and when I did, I found my cam to be 4 degrees off.
