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| early or late model head | Rate Topic |
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| Posted: 10-25-2005 02:28 am |
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1st Post |
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dbarton62 Member
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hello all first post to this group........is the following part # for the lotus cylinder head a early or late model head or were they all the same part#C907E 0311Y. regards dave
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| Posted: 10-25-2005 04:23 pm |
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2nd Post |
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Judson Manning Member 
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Dave, Casting numbers aren't always the best indicator. The easy way to tell is looking at the dimensions of the intake ports compared to an intake gasket. Here is the link to a photo I took comparing an earlier version to a later version used in a S1/S2 Esprit. http://jhppg.com/gallery/album08/907Intake_comparison Judson
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| Posted: 10-25-2005 04:57 pm |
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3rd Post |
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Mark Rosenbaum Member 
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All JHs, and early Lotus cars with the 907 engine, originally came with the A907E0311Y head casting. At some time after the JH ceased production, Lotus changed the casting to the C907... version. This occurred somewhere after engine S/N 12009 and before engine S/N 14302, but I don't know exactly when. It's my understanding that the C907... head has larger ports with an improved shape for better gas flow. Presumably at around the same time, the intake manifold used with Stromberg carbs was changed to accomodate these larger ports. I would suppose that a similar change would have been made to the intake manifold used with Dellorto carbs. If your question involves an actual cylinder head, I'd be interested in knowing all of the numbers stamped or cast into it -- not only the serial number and casting number, but any numbers to be found on the intake and exhaust manifold faces, head gasket face, or elsewhere.
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| Posted: 10-25-2005 10:21 pm |
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4th Post |
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dbarton62 Member
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thanks judson and mark i have a line on this head ........i am assuming this will fit onto my jh block? i will let you know the stampings if i get the head regards dave
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| Posted: 10-26-2005 02:07 am |
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5th Post |
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Judson Manning Member
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Dave, I don't believe there is a documented case of a 9xx series head not fitting on a different 9xx series block or vice-versa. I for one have a 907 head mated to a 910 block. There is at least a 99.9% chance any 9xx series head you find will fit your block. Mark is pretty close about the Stromber manifolds, but what I've seen is that the early manifold castings are just terrible. Not only are they small, they don't line up very well. By the 1974-1/2 MY, quality was vastly improved. It only got better with subsequent versions. Both the ports and manifolds can be fixed with a grinder, so there's no real need to buy an extra head unless you just don't want to do the work! Judson
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