stunthanger.com
Engine basics => Engine set up tips => Topic started by: Paul Smith on October 26, 2007, 07:18:00 PM
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I got an ancient Merco .49 Multispeed in a bulk buy. The 5-digit telephone number on the tag indicates pre-1965.
I'm trying the decypher the bolt size. It's something in the area of 4/40, 5/40, or 3 mm, but not exactly any of these. Was another thread standard about in Merry Olde back then? I Merco still around? How about a head gasket for a bore of .875?
I'm a bit perplexed. The bolts are a bit buggered, maybe from the previous owner looking inside, bit the piston top looks un-run. I'm itching to bark this beauty out on the stand right quick.
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Paul,
"rustler" here on the board is the producer of the Mercos now, as I understand it. Maybe a PM to him will help. He does appear to know about all the older Mercos.
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Hi, I've got a few of the merco 49 engines and love them. They have a real nice 4-2-4 run, good power and a great stunt engine. I'm going to use one in my stiletto, I use one in a score and pulls the plane with out a problem. I believe you should use twenty-five per cent castor oil. Have a great day, Gary (Try search on this forum, type in merco and I believe you will get some info on this baby)
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:! Try a 4-48 bolt as it is a national fine thread and it fits my Merco engines (35 and 40) . Should be available at bolt supply houses..
Good luck... H^^
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The engine runs like a champ, 10,200 RPM down to 3,800 and back. The inside looks brand-new.
The tag from Joe's Hobby Center carries the phone number WEbster 3-6567, a number some of the older flyers around here can still recall.
Per Rustler's site, these units were produced 1961-1963. The phillips heads are an odd-ball size too, explaining why they're buggered-up, but not why the previous owner took 'em loose.
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Hi all!
I´ve used (and I´m using, althought not competing very hard lately :P because work and family responsabilities) a Merco 49 in a modified Indigo for more than 12 years (you read well) the engine is better than new and is a real beauty in the air. I recommend you to restore and use it, you´ll like for sure.
My 2 plug ancient bulldog uses withworth 1/8" screws, later versions used different ones (Merco suffered several owner changes in his story)
Hope it helps.
Regards from Spain.
Manuel.
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That sounds good.
I've heard of the Whitworth Thread for years, but this is the first time I've owned one. And they do mike out to .120".
I used my digital camera and Photoshop as a high-price magnifying glass and confirmed the 40-pitch. I'll canvas the industrial suppliers in towne to see if any still supports Whitworth.
I've alread confirmed that 4/40, 5/40 and 3MM are not close enough.
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There is a Whitworth 1/8-40, ling to chart below. The difference between it an SAE threads is the included angle. Whitworth being 55º and SAE 60º. What this results in is the Whitworth being a deeper thread than an SAE. Although a 4-40 might be close, there would probably be not enough thread engagement and a percieved "tightness" putting one in a Whitworth tapped hole.
http://homepages.tesco.net/~A10bsa/bswgo.htm