Home » Public Forums » GMCnet » Ignition Timing Question
| Ignition Timing Question [message #254465] |
Sat, 05 July 2014 19:01  |
Jon payne
Messages: 495
Registered: May 2008
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Guys,
I recall this past winter a discussion about how to "properly" set the ignition timing. It was discussed if following the GMC MM you may have have some mechanical advance being that the MM ask to set the timing at 1100 RPM and to to see if this is happening check the timing at a lower RPM. Well I just did this and found that the timing was only 2deg at ~550 RPM (Vacuum advanced removed and plugged). As soon as I touched the throttle the the timing would advanced. So I slowly increased RPM until I reached 8degs, which was 1100 RPM where I have previously set per MM).
So based on this previous discussing I have 6deg less timing and I should. Do I understand this correctly? If so looks like I need to advanced the timing to 8deg at the lowest RPM possible, correct?
Note that I have a Dick P distributor and I suppose the springs on the counter weight are lighter then the OEM. Could explain why I have been thinking the GMC has lost power some years back (could be when I installed the Dick P distributor).
Please would appreciate if you guys could validate the above and confirm if I should set the timing to 8deg (or higher) at as low of RPM possible.
P.S. As you can see I got the GMC back up and running! Got the tanks out and fuel pump fixed, brakes fixed and so on. Don't have time now but I will share what I found and provide some pics.....and thanks again for the moral support the other day!!
Jon
Jon Payne
76 Palm Beach
Westfield,IN
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| Re: Ignition Timing Question [message #254466 is a reply to message #254465] |
Sat, 05 July 2014 19:08  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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Jon, If you have a disk Paterson distributor you need to look a the chart he sent with it. Mine said to set it at 12 BTDC. I have mine set to 13 BTDC. ROB Mueller has his chart posted on the photo site. I believe it was also 12 BTDC at the slowest practical idle speed and with the vacuum advance disconnected. I'll see if I can find Rob's chart.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
[Updated on: Sat, 05 July 2014 19:08] Report message to a moderator |
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| Re: [GMCnet] Ignition Timing Question [message #254468 is a reply to message #254467] |
Sat, 05 July 2014 19:46 |
Jon payne
Messages: 495
Registered: May 2008
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Bought mine through Applied and never got a chart but I imagine it should be the same. And based on that mine is probably okay but I'll check it at 1250 and see if I get 10degs per the chart.
Thanks!
JP
Jon Payne
76 Palm Beach
Westfield,IN
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| Re: [GMCnet] Ignition Timing Question [message #254474 is a reply to message #254468] |
Sat, 05 July 2014 20:08 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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Jon Payne wrote on Sat, 05 July 2014 19:46Bought mine through Applied and never got a chart but I imagine it should be the same. And based on that mine is probably okay but I'll check it at 1250 and see if I get 10degs per the chart.
Thanks!
JP
You are reading it wrong. Look at the top. At 1250 rpm the timing is 12 initial PLUS 10 mechanical for a total of 22 degrees BTDC. Time it at 12 BTDC at the slowest possible idle speed. (500 or 600)
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Ignition Timing Question [message #254479 is a reply to message #254465] |
Sat, 05 July 2014 21:37 |
Steve
Messages: 506
Registered: September 2013
Location: East Greenville, Pa
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Jon, glad to hear you are up and running again. Given your pending Yellowstone trip I felt so bad and wished I could help get you on the road. Enjoy and be safe. Can't wait to hear what you found with the brakes. Would also like to see pics of the GMC in Yellowstone.
1978 GMC Royal
Eastern Pennslyvania
1968 Chevrolet C20 396 Camper Special
1969 Chevrolet C20 Camper Special
1985 Buick Electra Park Avenue
1992 Camaro 25th Anniversary Heretage Edition Black
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| Re: [GMCnet] Ignition Timing Question [message #254488 is a reply to message #254465] |
Sat, 05 July 2014 23:47 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Jon,
I was going to point you at the photo I posted of the chart I got with my Paterson dizzy; however, Ken saved me the effort and did
that already.
I would like to point out that Dick custom builds his dizzies to specs that you send him, note the DISTRIBUTOR SPECIFICATIONS at the
top of the chart. Double Trouble is a 455 with a 3.07 final drive, and do not tow.
I would suggest you give Dick a call and ask him how you should set yours.
Regards,
Rob M.
The Pedantic Mechanic
USAussie - Downunder
USA '75 Avion - Double Trouble TZE365V100426
AUS '75 Avion - The Blue Streak TZE365V100428
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Jon Payne
Sent: Saturday, July 05, 2014 7:01 PM
To: gmclist@temp.gmcnet.org
Subject: [GMCnet] Ignition Timing Question
Guys,
I recall this past winter a discussion about how to "properly" set the ignition timing. It was discussed if following the GMC MM
you may have have
some mechanical advance being that the MM ask to set the timing at 1100 RPM and to to see if this is happening check the timing at a
lower RPM. Well
I just did this and found that the timing was only 2deg at ~550 RPM (Vacuum advanced removed and plugged). As soon as I touched the
throttle the the
timing would advanced. So I slowly increased RPM until I reached 8degs, which was 1100 RPM where I have previously set per MM).
So based on this previous discussing I have 6deg less timing and I should. Do I understand this correctly? If so looks like I need
to advanced the
timing to 8deg at the lowest RPM possible, correct?
Note that I have a Dick P distributor and I suppose the springs on the counter weight are lighter then the OEM. Could explain why I
have been thinking
the GMC has lost power some years back (could be when I installed the Dick P distributor).
Please would appreciate if you guys could validate the above and confirm if I should set the timing to 8deg (or higher) at as low of
RPM possible.
P.S. As you can see I got the GMC back up and running! Got the tanks out and fuel pump fixed, brakes fixed and so on. Don't have
time now but I will
share what I found and provide some pics.....and thanks again for the moral support the other day!!
Jon
--
Jon Payne
76 Palm Beach
Westfield,IN
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Ignition Timing Question [message #254492 is a reply to message #254488] |
Sun, 06 July 2014 01:53 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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USAussie wrote on Sat, 05 July 2014 23:47Jon,
I was going to point you at the photo I posted of the chart I got with my Paterson dizzy; however, Ken saved me the effort and did
that already.
I would like to point out that Dick custom builds his dizzies to specs that you send him, note the DISTRIBUTOR SPECIFICATIONS at the
top of the chart. Double Trouble is a 455 with a 3.07 final drive, and do not tow.
I would suggest you give Dick a call and ask him how you should set yours.
Regards,
Rob M.
The Pedantic Mechanic
USAussie - Downunder
USA '75 Avion - Double Trouble TZE365V100426
AUS '75 Avion - The Blue Streak TZE365V100428
He has a generic distributor from Jim K. but built by Dick P. It was not fine tuned for his coach. The base timing should be the same (around 12 degrees BTDC). From what I read he has been setting the timing at some some rpm where the mechanical advance has already started to kick in. That is his basic problem. I made a posting telling him NOT to do that but he has not responded. So I have to assume he has not seen any of our notes since his last posting.
Based on his last note I have to assume he is about 10 degrees retarded.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Ignition Timing Question [message #254501 is a reply to message #254492] |
Sun, 06 July 2014 08:24 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Ken,
I agree with what you've noted makes sense vis-à-vis a "generic" dizzy.
For the record Double Trouble came with a Holley carb and OEM dizzy. It wouldnt get out of its own way so I replaced it because the
Holley had the same size secondaries as primaries with one of Dick's Q-Jets. That did improve performance so I decided to get one of
his dizzies. I could not believe it but that made a bigger difference than the carb!
With those parts installed I reckon that this engine (built by Ken Frey 70,000 miles ago) is as good as it will get. John Sharpe has
commented that it starts and runs almost as good as his GMC that has fuel injection.
In case you're wondering what kind of mileage I get, I have NO idea, I have NEVER checked it. The reason is I drive the speed limit,
if it's 60 that's what I drive, if it's 75 that's what I drive. Obviously if you want to get good mileage driving 75 is
counterproductive.
Regards,
Rob M.
The Pedantic Mechanic
USAussie - Downunder
USA '75 Avion - Double Trouble TZE365V100426
AUS '75 Avion - The Blue Streak TZE365V100428
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Ken Burton
Sent: Sunday, July 06, 2014 1:54 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Ignition Timing Question
He has a generic distributor from Jim K. but built by Dick P. It was not fine tuned for his coach. The base timing should be the
same (around 12 degrees BTDC). From what I read he has been setting the timing at some some rpm where the mechanical advance has
already started to kick in. That is his basic problem. I made a posting telling him NOT to do that but he has not responded. So I
have to assume he has not seen any of our notes since his last posting.
Based on his last note I have to assume he is about 10 degrees retarded.
--
Ken
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: Ignition Timing Question [message #254622 is a reply to message #254465] |
Mon, 07 July 2014 12:59 |
Chris Tyler
Messages: 458
Registered: September 2013
Location: Odessa FL
Karma: 7
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12 degrees initial sounds about right. Keep in mind if you advance the initial on a stock distributer, you also increase the total centrifugal advance. Normally when recurving, you either use a bushing or braze up the slot to limit travel.
22 degrees total sounds too far retarded to me.
A QJet has spark ported vacuum that has no vac until you open the throttle a bit. Most Holleys don't, and will give you way too much advance at idle
Its hard to find anyone with a distributor machine these days.
Highly recommend a quality 'dial back to zero" type timing light esp if youre going to roll your own
76 Glenbrook
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| Re: [GMCnet] Ignition Timing Question [message #254706 is a reply to message #254492] |
Tue, 08 July 2014 11:52 |
Jon payne
Messages: 495
Registered: May 2008
Karma: 1
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Senior Member |
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Hi guys,
Sorry i have been out of pocket sense monday and i have not been able to respond, specifically to KenB. Strange but on this thread Ken's posts are hidden for some reason. Have no idea why that is. Anyways, to share with everyone what I ended up doing is set the timing to 10deg @ 1250 based on the disrib card Rob got from Dick as I have the same set up.
Would you all agree that is where I should set it at? Again I originally set the timing per the MM (8deg@ 1100).
Still owe you guys what I found from on my brakes and fuel pump. I will try to post something this afternoon.
Jon
Jon Payne
76 Palm Beach
Westfield,IN
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| Re: [GMCnet] Ignition Timing Question [message #254718 is a reply to message #254706] |
Tue, 08 July 2014 13:32 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Jon Payne wrote on Tue, 08 July 2014 09:52Hi guys,
Sorry i have been out of pocket sense monday and i have not been able to respond, specifically to KenB. Strange but on this thread Ken's posts are hidden for some reason. Have no idea why that is. Anyways, to share with everyone what I ended up doing is set the timing to 10deg @ 1250 based on the disrib card Rob got from Dick as I have the same set up.
Would you all agree that is where I should set it at? Again I originally set the timing per the MM (8deg@ 1100).
Still owe you guys what I found from on my brakes and fuel pump. I will try to post something this afternoon.
Jon
NO! Read the posts above and set it at 12 degrees BTC at the slowest practical idle. You might want to unblock Ken B. He has a LOT of good advice.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: [GMCnet] Ignition Timing Question [message #254725 is a reply to message #254718] |
Tue, 08 July 2014 13:52 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Carl S. wrote on Tue, 08 July 2014 13:32Jon Payne wrote on Tue, 08 July 2014 09:52Hi guys,
Sorry i have been out of pocket sense monday and i have not been able to respond, specifically to KenB. Strange but on this thread Ken's posts are hidden for some reason. Have no idea why that is. Anyways, to share with everyone what I ended up doing is set the timing to 10deg @ 1250 based on the disrib card Rob got from Dick as I have the same set up.
Would you all agree that is where I should set it at? Again I originally set the timing per the MM (8deg@ 1100).
Still owe you guys what I found from on my brakes and fuel pump. I will try to post something this afternoon.
Jon
NO! Read the posts above and set it at 12 degrees BTC at the slowest practical idle. You might want to unblock Ken B. He has a LOT of good advice.
Thanks Carl. That is exactly what I said. The way you set now, you are about 12 degrees retarded. That is good for starting the engine but terrible for power and fuel economy.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Ignition Timing Question [message #254731 is a reply to message #254725] |
Tue, 08 July 2014 14:49 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
Karma: 0
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What do you guys think about locking down the advance weights with a zip tie or something to set the initial?
Or is that a bad idea?
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| Re: [GMCnet] Ignition Timing Question [message #254735 is a reply to message #254731] |
Tue, 08 July 2014 15:22 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Keith V wrote on Tue, 08 July 2014 12:49What do you guys think about locking down the advance weights with a zip tie or something to set the initial?
Or is that a bad idea?
No need if you are adjusting the timing with the engine idling at around 600 rpm the advance weights won't be advancing the only concern would be vacuum if you are using manifold vacuum rather then port.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Ignition Timing Question [message #254739 is a reply to message #254706] |
Tue, 08 July 2014 15:32 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Jon,
I must apologize, I did not explain the chart when I sent it to out, I'll do so now.
http://www.gmcmhphotos.com/photos/aa-miscellaneous-photos/p32021-dick-paterson-s-distri.html
Notice INITIAL 12° in the third row down.
Notice the column titled CENTRIFIGUAL and the following info under it:
800 = 2°
1000 = 5°
1250 = 10°
1500 = 12°
1750 = 13°
2000 = 14°
2250 = 16°
2500 = 18 °
Notice the column TOTAL@ CRANK
2500 = 30°
I have completed the form below, hopefully the email program won't mess up all the columns!
RPM CENTRIFUGAL INITIAL TOTAL @ CRANK
800 2° 12° 14°
1000 5° 12° 17°
1250 10° 12° 22°
1500 12° 12° 24°
1750 13° 12° 25°
2000 14° 12° 26°
2250 16° 12° 28°
2500 18 ° 12° 30°
TOTAL @ CRANK is what you would set the timing at the crank
http://www.gmcmhphotos.com/photos/misc/p30454-timing455.html
with the vacuum advance disconnected.
Set the engine rpm to 800 with the vacuum advance disconnected and see the timing at 14°. Increase the RPM 1000 and it should
advance to 17° take it up to 1500 RPM and it should read 24°.
I trust this is now clear.
Regards,
Rob M.
The Pedantic Mechanic
USAussie - Downunder
USA '75 Avion - Double Trouble TZE365V100426
AUS '75 Avion - The Blue Streak TZE365V100428
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Jon Payne
Sent: Tuesday, July 08, 2014 11:52 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Ignition Timing Question
Hi guys,
Sorry i have been out of pocket sense monday and i have not been able to respond, specifically to KenB. Strange but on this thread
Ken's posts are hidden for some reason. Have no idea why that is. Anyways, to share with everyone what I ended up doing is set the
timing to 10deg @ 1250 based on the disrib card Rob got from Dick as I have the same set up.
Would you all agree that is where I should set it at? Again I originally set the timing per the MM (8deg@ 1100).
Still owe you guys what I found from on my brakes and fuel pump. I will try to post something this afternoon.
Jon
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GMCnet mailing list
Unsubscribe or Change List Options:
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Ignition Timing Question [message #254744 is a reply to message #254739] |
Tue, 08 July 2014 17:06 |
Jon payne
Messages: 495
Registered: May 2008
Karma: 1
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Senior Member |
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Wow, thanks Rob that is clear to me now. Man so my timing is way off! I imagine I should see a bit more performance with the timing set correctly! Basically I'm going from ~2deg @ 800 to 12deg at 800. So I will go out and set the timing after dinner and report back my results.
Hey all, how did Ken get blocked? I keep seeing a message on this thread that Ken is ignored. Ken, really I didn't intentionally block your posts!! Anyone know how to unblock or un-ignore?
Jon
Jon Payne
76 Palm Beach
Westfield,IN
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| Re: [GMCnet] Ignition Timing Question [message #254747 is a reply to message #254744] |
Tue, 08 July 2014 17:23 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Jon,
You're going to be "blown away" when you correct the timing! ;-)
When logged on to the Forum click on "Control Panel."
When the next page opens click on "Ignore List."
Ken should show up in a list.
Regards,
Rob M.
The Pedantic Mechanic
USAussie - Downunder
USA '75 Avion - Double Trouble TZE365V100426
AUS '75 Avion - The Blue Streak TZE365V100428
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Jon Payne
Sent: Tuesday, July 08, 2014 5:06 PM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Ignition Timing Question
Basically I'm going from ~2deg @ 800 to 12deg at 800. So I will go out and set the timing after dinner and report back my results.
Hey all, how did Ken get blocked? I keep seeing a message on this thread that Ken is ignored. Ken, really I didn't intentionally
block your posts!!
Anyone know how to unblock or un-ignore?
Jon
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GMCnet mailing list
Unsubscribe or Change List Options:
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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