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Loop Head interchangeability

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Simmoto View Drop Down
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    Posted: 03 Feb 2019 at 08:02
Folks,
 What other loop cylinder heads will fit the Eldorado? There is a table on ThisOldTractor that compares measurements and some appear to be compatible but hard to tell. Anyone able to clarify?
What the table does state is that Edlo cylinder heads have the part number cast in to the top of the head, so if correct that means some for sale offerings I've seen are not actually Eldo heads.
Thanks :-)


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Dave P. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 03 Feb 2019 at 11:06
According to This old Tractor the 750 and 850 heads are interchangeable. The part numbers are different though. I've seen heads on eBay advertised as being for 850GT models but having a stud fixing for the exhausts rather than a threaded port.I think some very late 850's did have stud exhaust fixings but I'm not sure. So.....I've been of no help whatsoever, your best bet is for Charlie (Amboman)to spot your enquiry and give you a definitive answer.
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
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ranton_rambler View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ranton_rambler Quote  Post ReplyReply Direct Link To This Post Posted: 03 Feb 2019 at 12:46
Have a look at the thread "V7 Special Heads".....
Ian
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Amboman Quote  Post ReplyReply Direct Link To This Post Posted: 03 Feb 2019 at 14:33
All of the heads after the V700/early Ambassador heads (which have smaller valves, single valve springs the odd bolt/nut at the top) will work. There are variations in the fin configuration around the sparkplug, but they have the same size valves and combustion chamber, etc. The last of the Eldorado/850GT heads had the casting "bumps" for studs, but weren't drilled and tapped for studs.

Bottom line: If you don't mind the heads not looking exactly the same, you can fit 750 heads to an 850 and vice versa.
Charlie
'69 V700, '69 Ambassador, '76 Convert, '85 Morini 350 K2
http://www.AntietamClassicCycle.com
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Simmoto View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Simmoto Quote  Post ReplyReply Direct Link To This Post Posted: 03 Feb 2019 at 21:29
Ian,Charlie, Dave

Great, thanks for clearing that up. Impatient beggars like me can't be choosers :-)

Cheers
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Simmoto Quote  Post ReplyReply Direct Link To This Post Posted: 28 Feb 2019 at 15:42
Hi Charlie,

Got a good Ambo head for my Eldo. The inlet port diameter is 30mm compared to 34mm fro the Eldo, is any carb modification needed?

Thanks
Dave
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Dave P. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 28 Feb 2019 at 16:47
Have a look here Simmoto.

http://www.thisoldtractor.com/moto_guzzi_loopframe_cylinder_head_comparison.html

It's got me confused.Larger inlet ports on earlier bikes with less performance?
I look forward to Charlie's reply.
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
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Simmoto View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Simmoto Quote  Post ReplyReply Direct Link To This Post Posted: 28 Feb 2019 at 16:56
No, its smaller inlet ports on earlier bikes. :-)

Also Charlie - I am only replacing one head so will have one with 34mm (Eldo) and one 30mm (1970 Ambo). Will the difference in port size affect engine balance etc - hadn't thought of this...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Simmoto Quote  Post ReplyReply Direct Link To This Post Posted: 28 Feb 2019 at 16:58
I just measured the exhaust valve guide, wiggles like a tooth so I thought it was bad, it has .32mm of play in one direction, book says 0.057mm So now need to decide if I can replace the guides myself or not... (and new valves)

Edited by Simmoto - 28 Feb 2019 at 17:02
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Dave P. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 28 Feb 2019 at 17:17
[QUOTE=Simmoto] No, its smaller inlet ports on earlier bikes.

Have a good look at the chart.The 700 and A series ambassador have 37mm inlet ports. The Ambassador was then reduced to 30mm. To speed up gas flow into the head perhaps.Then the last 750's and the 850 go out to 34mm.
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
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Simmoto View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Simmoto Quote  Post ReplyReply Direct Link To This Post Posted: 28 Feb 2019 at 17:26
Oh i see what you mean. yes bigger then smaller then bigger LOL but my Ambo 30 is smaller than my Eldo 34...
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Dave P. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 28 Feb 2019 at 17:33
Confusing aint it.I'm now wondering if my two have properly matched heads.
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
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Amboman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Amboman Quote  Post ReplyReply Direct Link To This Post Posted: 01 Mar 2019 at 14:45
Non-matching intake port sizes could definitely causing running issues.

The 37 mm ports on the early bikes was a mistake by Guzzi, reduction tubes were fitted to correct it.
Charlie
'69 V700, '69 Ambassador, '76 Convert, '85 Morini 350 K2
http://www.AntietamClassicCycle.com
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Dave P. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 01 Mar 2019 at 14:50
Hi Charlie. So did the move from 30mm to 34mm on the late V7 Special make much difference to performance?
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
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Amboman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Amboman Quote  Post ReplyReply Direct Link To This Post Posted: 02 Mar 2019 at 14:45
To be perfectly honest, I've never seen a pair of Loop heads with 34 mm intake ports. At least not that I've noticed anyway. This has made me curious and now I'm going to have to go out in the shed and measure all of the heads I have.

Before anyone asks if I have any to spare, most of those are "repairable" - exhaust nuts stuck in them, broken fins, snapped off bolts, and other damage.


Charlie
'69 V700, '69 Ambassador, '76 Convert, '85 Morini 350 K2
http://www.AntietamClassicCycle.com
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