Author Topic: Twin Cam block grading  (Read 4634 times)

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Offline Pete Gossett

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Twin Cam block grading
« on: Wednesday,August 29, 2012, 05:25:03 AM »
I was reading about the LA, LB and LAA grading used on the twin can engine blocks last night. One of my engines was partially disassembled when I hauled this mess home, so I popped out to the garage this morning for a quick look. I was surprised to discover my block has no markings. This engine is from my '73, and as far as I know is the original lump. Was Ford no longer stamping the blocks by then?

For that matter, is there a way to determine whether this is the original engine?

Offline cal44

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Re: Twin Cam block grading
« Reply #1 on: Wednesday,August 29, 2012, 08:53:50 AM »
Pete,

Look for casting numbers.  They will be on the left side.  Stamped numbers will be Vin numbers, right side, if present.  If I have written in error someone please correct me.  Throw us some pics of the block/s.  There will be something on there for I.D.

As for the LA, LB and LAA. I would need to do homework as I am not familiar with those letters.

Mike
"Be Polite, Be Professional, But have a plan to kill everyone you meet"
General "mad dog" James Mattis
United States Marines

Offline Pete Gossett

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Re: Twin Cam block grading
« Reply #2 on: Wednesday,August 29, 2012, 09:31:56 AM »
It was related to the thickness of the cylinder walls, but I don't know much beyond that.

I'll grab some pictures of the engine from the '73. It's mostly apart and on my bench. The '72 is still in the car.

Offline Pete Gossett

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Re: Twin Cam block grading
« Reply #3 on: Wednesday,August 29, 2012, 05:12:19 PM »
Here are a couple pics from the '73. I really couldn't see the numbers on the left side, but I think they read 282?






Offline cal44

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Re: Twin Cam block grading
« Reply #4 on: Wednesday,August 29, 2012, 06:59:07 PM »
Pete,

I should have written the side of the block, towards the front.  Sorry.

Mike
"Be Polite, Be Professional, But have a plan to kill everyone you meet"
General "mad dog" James Mattis
United States Marines

Offline EuropaTC

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Re: Twin Cam block grading
« Reply #5 on: Wednesday,August 29, 2012, 11:06:03 PM »
Just to chip in my 2d's worth (or should that be 2cent's worth  ;) ), I can add a bit about the thicknesses from the Brian Buckland manual on rebuilding an Elan. He shows lots of engine block identification marks and comments that the stamping on the left front face should be LAA, LA or LB, and as you say it's related to casting thickness.  He says the LAA was the thickest and hence most suitable for large bores, with LB being the thinnest.

He also has pictures of a cast "L" between the 4 holes where the engine mount goes and says that although cast by Ford this denotes a block made primarily for Lotus & Ford Twin Cam engines. He splits the blocks into 3 categories;

1 early Mk2 engines, the Ford 120E was ground off and overstamped with 3020 leaving it as 3020 6015
2 Later Mk2 blocks (probably our TC ?) left the ford identification casting marks, he shows an example as 681F6015-A (which means nothing to me !)
3. The last blocks, presumably the 73 cars, also had Ford markings. He shows an example as 701M6015 EA (the E looks like a damaged B though ?)

Brian