Help with engine issue!!!!
 

:mad: Help with engine issue!!!!

Tiring to get my RV6A off the ground but have some problems to solve. I have an 0-320 H2AD freshly overhauled in the aircraft. The first time I ran it it seemed fine but I did not do a mag check or run it over 1600 rpm. Cht,s where all in the mid 300,s and I had one cylinder with a higher EGT (#3) than the others, since then I have be told this is normal.

I borrowed a timing box and thought I would check the timing, what I found was the left mag was about 1 Deg ahead of the other. (H2AD has 2 mag,s in one) A local A&P told me it might not make much difference so try it as set, and see how much mag drop you get. So I timed to 25 deg advice and ran the engine up. It seemed ok but when I ran it up to 1800 I would a 25 rpm drop on one and a 200 rpm drop on the other I also got much higher CHT,s , The cowling was on this time which would account for some temp rise but when I did a high speed taxi (55-60 mph) the temps climbed to 450 (Lycoming says 500 deg is max but I think that?s too high) so I backed off put the plane away and when home.

The following weekend I removed the cowl and rechecked the timing which seemed ok. I replaced a suspect plug and ran it up again, same thing 25 ? 50 rpm drop on left mag 200 rpm drop on right, CHT,s were back to 350 ( No cowl) but when I tried to go above 1800 rpm the engine began missing. I now have the mag on my work bench, I made adjustments to the internal timing so that both contacts open within ? deg of each other at the 8 deg ?E? gap position. There are two windows where you can view the gear teeth, both left and right. When I line up the mag to the ?E? gap mark one red tooth is dead center of the window and the other is off by ? tooth.

Questions:

? Any Idea why my CHT,s would be getting so high with the cowling on
? What would cause the missing above 1800 rpm,s
? Why dont both red teeth line up in the center of there respective windows.

I was hoping to get my first flight in in the next few days but it does not look good, so any help would be more than appreciated.

Thanks

Remember one of the mags has an impulse coupling. You need to turn the prop through to discharge the impulse spring before setting the timing. Once pulled through, back up to the timing mark and set your mag. You may have the one with the impulse coupling set to far in advance or retarded, not sure which, but you will be many degrees off timing on that mag if you did not do this.

Roberta

Thanks Roberta
 

Thanks Roberta

I checked that and it is timed after the impulse spring releases. Both mag,s on the dual unit are retarded by the impulse coupling as they are drivin by one shaft.


Thanks for the input

John,
If I was there the first thing I would do is check the spark plug wires for proper installation. I'd follow each one all the way back to the mag and be sure it goes into the correct hole. Maybe you've already done this. If you have...do it again.

I can't help you on the mag timing. It's been years since I've worked on a dual mag and have forgotton a lot.

First, how long and hard are you running the aircraft on the ground? That might get the CHT's way up if you over do it. You should work very hard to minimize ground running a new engine.

Second, have you verified your CHT gauge accuracy? Do you have the correct thermocouples for your gauge?

Third, is your mixture set properly? It should be rich enough that you get a 25-50 RPM increase if you idle at 1,000 RPM and slowly lean the mixture.

Have not checked the mixture the way you suggest, will give it a try next time I run it.
Thanks

Mag drop
 

Mr. John,
From your experiences, checking timing did not help, and BTW, differences of up to 4 deg will not make as much difference as you are experiencing. Since only one mag is doing this, and assuming you have checked all the obvious suspects, the "bottom" plugs will tell you a lot. Remove them after a mag check, and hopefully you will "not" see a wet plug. If so, you'll need to look further.
CHT maximum as prescribed by Lycoming is 500 deg, max., although it would not be ideal. Somewhere between 300 and 375 and occasionally up to 425, is more in line. If you have multiple CHT, swap probes to check if readings are true.
You didn't mention make and model of magnetos regarding the red mark, but point gap can affect a mag drop, though rarely, due to engine speed for mag drop check. It would affect starting or top end.
Hope you find the problem, and that it is simple.
T88
RV10

The red lines rarely line up in the middle of the windows. The key is to time the mag to the engine with the "K" in the top window, and the red lines in each window. Once that is accomplished, the fine tuning to 25 degree can be accomplished an the mag tightened down. Once the mag is tight, attach the p-leads and the cap. MAKE SURE THAT YOUR PLUG LEADS ARE GOING TO THE CORRECT CYLINDERS, that was the problem that was similer to what you are describing on one of my customers airplanes. If that is all correct, next check that your baffles are sealing well, check that you do not have an induction leaks, but it sounds to me like something is awry with your plug leads.

Is the engine missing above 1800RPM one one mag or on Both?
Good Luck and Happy New Year,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at you own risk."

Its missing on both, spoke with A&P and he thought it might be that the oil was not hot enough, said the lifters are floating becuase they are not draining the oil fast enough.

Never heard of this, any comments.

Thank all for the great feed back.

John