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Do I Have A 6.6 Or 7.6 Engine.


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#1 L81966 OFFLINE  

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Posted December 20, 2012 - 11:32 AM

I have had this L8 for years, and just noted the serial #2M37322, J3207 places it in the 7.6 years. The casting on the trans case is dated 2/23/66. There is no tag or plate on the PTO casting. It has the slanted Spark plug. Zenith aluminum carb has forward inlet, and the air filter is on the L side of the engine above the carb. The oil gilter is PH8 screw on.
I ask for clarification as this serial number is very near the cusp of the switch to the 7.6 engine, and there are some differences in valve adjustment (.012 vs. .015) and magneto timing procedures and plug gap (though I have the large 7/8" thread size).
Any comments? Is this a 7.6 that has had the head changed or is it a 6.6??

#2 Cat385B ONLINE  

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Posted December 20, 2012 - 12:38 PM

With the slant plug, but having a filter, I'm guessing a 7.6 with a head swap. But according to your serial #, you should have a 6.6 on there.

#3 HowardsMF155 ONLINE  

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Posted December 20, 2012 - 01:29 PM

Hey Cat, according to the gravely club site, that serial number does occur in 1966 at the supposed beginning of the change over to the 7.6 engine. Do you have another source?

L81966, WELCOME TO GTTalk!! Great to have another Gravely guy on here. I think it is generally recognized that Gravely continued to use old stock even though "officially" production of the new engines started in 1966 (or whenever). Also, unless you've had that tractor since it was new, things could have easily been updated. I know Gravely was very keen to try and have tractors updated whenever they came in for service, so things like the oil filter could easily have been done by the dealer. The carburetor seems less likely to have been changed, so that plus air filter location argues more for a 7.6 configuration, the head certainly argues against it.
One change that is often overlooked it the cylinder jug was reworked slightly. I don't know how to tell you exactly what the difference is, but the threaded section where the head bolts go was beefed up somewhat.
Post some pictures of all this stuff and let's see if anything else comes to mind. (Besides, you HAVE to post pics. Its in the contract you signed when you joined up LOL)

#4 Cat385B ONLINE  

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Posted December 20, 2012 - 01:34 PM

This is what I was going by:

1963 M-90897 14738 2M4745 L, LI, LS, L8
1964 2M4745 2M18900 H
1965 2M18900 I – 11552 I Large Bearings
1965 2M34215 I – 11553 Small Bearings
1966 2M34216 J-7600 J 6.6
1967 J-7600 J-23680 C, CI, CS, C8 7.6 HP

#5 L81966 OFFLINE  

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Posted December 21, 2012 - 11:07 AM

Found another "answer" http://oldgravelys.n...SD_19660100.pdf, It states that through 2M51800 L engines had slanted plugs. Dated jan 1967.

#6 Bmerf ONLINE  

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Posted December 21, 2012 - 02:50 PM

L81966, don't know much about old Gravelys, but :welcometogttalk: and don't forget :camera:




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