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Post by kennyw on Jun 13, 2018 12:52:50 GMT -6
I have a 1835 type I on 994SP. I believe it has around 225hrs on it. I know it has 70hrs since I bought the airplane.
It was built by a guy in the Spokane area for a Quickie then removed and sold.
The last 2 25hr oil changes, I pulled the rocker arms to check cylinder head torque. And, now both times, I’ve gotten about 45 degrees of turn on all lower stud nuts to get final torque.
Is this normal?
I have plenty of jet helo wrenching experience. But, none previous on VW conversions.
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Post by Supervee on Jun 14, 2018 16:20:24 GMT -6
Kenny, I am not an engine guy, hopefully some of the participants will make a comment. I know that in the past I had that happening, and the studs were stretching I believe. We installed case savers and the problem went away....Ed
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Post by kennyw on Jun 14, 2018 20:14:46 GMT -6
Kenny, I am not an engine guy, hopefully some of the participants will make a comment. I know that in the past I had that happening, and the studs were stretching I believe. We installed case savers and the problem went away....Ed I snapped one of the rocker arm mount blocks (stupid mistake) and had to go buy a new one from the Bow Wow guys out in Monroe. I talked to them about it. They have a lot of experience with Type I engine performance builds according to their website. And, there were several cool looking old bugs and a bus or 2 in their shop. They said that with a performance build, using various combinations of aftermarket and OEM parts, it is most likely that they're actually loosening just a bit, and not stretching all that much. They recommended that I continue to do 25hr retorques and to measure the threads showing on the studs each time. So, for now I' guess I just keep on flying it. Got it back together today. And, did a good runup & leak check. It fired right up, just like always. |
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Post by dmar836 on Jun 15, 2018 15:37:47 GMT -6
Kenny, a lot of early conversions used the single relief T-1 case. Some early engines might have appeared better for this as they had larger diameter studs. They lacked the case savers that Ed mentioned and most have failed with the studs eventually pulling through the soft cases. This happened in the auto world as well and VW began installing case savers at the factory at some later point and returned to the completely adequate smaller studs(I think 8mm rather than 10mm). Cases can and are often retrofitted with inserts and the smaller studs. Nothing else changes but the engine needs to be apart. No car guy would think of starting a build nowadays without them.
Might be worth looking at your case. It should be fairly obvious if there is a threaded insert for each of the studs(except #3 which is recessed and the insert not visible. Threaded inserts sound redundant but the extra diameter of the insert’s threads fixed these issues.
What you describe sounds like a lot of stretch for an engine that’s broken in already.
JMO,
Dave
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Post by kennyw on Jun 19, 2018 23:04:27 GMT -6
Kenny, a lot of early conversions used the single relief T-1 case. Some early engines might have appeared better for this as they had larger diameter studs. They lacked the case savers that Ed mentioned and most have failed with the studs eventually pulling through the soft cases.... After a long work week, I finally got back down to the hangar today. Pretty sure I have the case savers. I'm gonna put another 25 hours on it and check the torque again. If its loose, I may just pull the jugs and get a closer look. Maybe I'll go ahead and buy new studs.  |
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Post by dmar836 on Jun 20, 2018 6:52:06 GMT -6
Yep, those are case savers. You might paint mark everything and/or have a helper watch when you torque them next - just to see if anything untoward is happening.
I’d fly it too!
Dave
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Post by chuckerf14 on Jun 28, 2018 12:29:06 GMT -6
Kenny,
One known issue with head torque occurs when the steel jugs deform the aluminum heads. As the engine gets hot your jugs grow and the clamping force on your heads can increase to nearly 20,000 pounds! If the head temperature is high enough the aluminum will become more ductile and the jugs can physically deform the heads. When the engine cools and the jugs return to their original size you will lose some of your original torque. During the next run it is possible to have compression gasses blow by the head seal....and then the big problems begin. With blow-by you will soon lose all compression in the affected cylinders.
Why didn't street bugs have this problem? I can't say for sure. Some did, perhaps. Most bugs were 1600cc's or less with a small carburetor and a pretty good fan shroud system. VW spent $2M in R&D on the cooling system before the upped the displacement to 1600.
Since you hand prop your engine I recommend you pay close attention to balanced compression between cylinders. I would also recommend putting paint on your cylinder head nuts and bolts to check for rotation (which I doubt is happening). At your next oil change, if the torque is once again low, pull your heads and check for deformation. If you want to remain on the conservative side, PULL THE HEADS NOW!
I have found GPASC, Hummel Engines, and Joe Horvath (Revmaster) to be very helpful... although Joe may only be helping me because I have one of his engines. Give those guys a call. I know your bird will get home on three cylinders....but will it make it on two?
All the best,
Chucker
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n84tw
New Member
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Post by n84tw on Aug 6, 2018 7:22:22 GMT -6
In the day my 1600cc heads would loose torque. I attributed it to insufficient cooling. In the worse cases the cylinder jug would deform the head contact surface ever slightly but still seal when hot. My cylinder head spark plug thermocouples always ran high. I never felt like I had good enough cooling. Some of it attributed to too much engine compression.
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Post by dmar836 on Aug 8, 2018 6:36:40 GMT -6
Tom, Do you remember what compression ratio you were running?
Dave
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Post by Supervee on Aug 8, 2018 9:52:28 GMT -6
All in good humor,.....Usually when I ask a FV guy that, I just get a nice smile back...and no answer.....!! Some of these guys are still competitive even today!!!
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Post by dmar836 on Aug 8, 2018 10:21:45 GMT -6
Lol. Well, I figured that as I typed it. I asked cause I’m in an engine displacement/HP downsizing spiral. I was at 9.5 CR with a W-100 cam and 2110cc. Nice new Panchito heads. That would be a tractor motor but maybe choked with the 34mm Revmaster carb. I will have enough on my plate besides having to tune something that might have considerably more torque than the motor mount was designed for. Now I might need smaller heads, type A pistons and on and on. While I’m at it I’ll shoot for lower CR. Not looking to outperform anyone yet... just perform with minimum hassle. I’ll be a parts VW parts house soon!
Dave
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n84tw
New Member
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Post by n84tw on Aug 11, 2018 8:29:23 GMT -6
Checking in this AM.. How much compression? I would have to check my old notes to answer with clarity. But there is no secret:). I would mill the heads for an estimated density/altitude. Normally I missed the estimate and put too much compression by over milling the heads. As an example the heads were reasonably priced and somewhat sacrificial, so I would keep milling and test flying until the engine would detonate at full throttle. A lot of work but it was interesting. During heat races if detonation occurred, and it did many times, I would reduce throttle slightly until detonation ceased. All this happens very quickly and continue the heat/race. There was a lot of risk in what I did because if the heads became to hot and detonation was really bad reducing throttle would not stop it. This happened in one heat and I was forced to land. The FAA was not happy. It was "Ëxperimental" and we pushed the limit.
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Post by Supervee on Aug 11, 2018 10:17:11 GMT -6
Tom, thanks for your input here. It is great to hear from you, a former FV winner. I appreciate it.
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Post by dmar836 on Aug 11, 2018 14:43:00 GMT -6
Yeah. That’s great stuff for sure!
Thanks!
Dave
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Post by kennyw on Aug 25, 2018 11:18:15 GMT -6
I wanted to thank everyone for their input. I just finished the annual 994SP. And, found no problems! compression tests were very close on all 4 cylinders. And this time, the heads didn't lose any torque over the last 25hrs.
I did managed to mangle a rocker arm stud by brain-farting and allowing the rocker arm shaft to rotate 180 degrees when reinstalling. But, I bought new studs and replaced both on that side, no problem.
The test flight was great! No leaks, temps and pressures in the green and full power on takeoff. So, I'm good for another oil change.
I recently found Rex Taylor's (HAPI) engine articles in the back issues of Sport Aviation Magazine. It was a 10 segment series that ran from Dec '79 to Sep '80. This was really the most informative stuff I've read on VW engine conversions.
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