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907 vs 910  Rating:  Rating
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 Posted: 07-17-2006 03:15 pm
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OverdriveGear
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Hello everyone, I was wondering about the similarities/differences between the 907 series and 910 series.  I just recently saw you could "hybrid" the two together and I thought that was pretty neat.  Obviously the top end will be probably identical, but what about the bottom end?  Would a 910 crank fit in a 907 block, bearings different, etc?

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 Posted: 07-18-2006 02:56 am
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Judson Manning
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Erik Harkes put a 907 bottom-end on a 910 top-end.  I went the other direction and put a JH top-end on a 910 bottom-end.  My decision to build a 'hybrid' was driven more by available parts than any other reason.

Keep in mind the 9xx series engine continued to evolve through circa 1999(?), there were a LOT of running changes.  In general, most part are interchangeable without modification including the cranks.

The exception is the bottom half of the block.  Below the split-line of the main bearing panel is where the 910/912/911/920 depart significantly from the 907.

http://jhppg.com/gallery/album08/P1010012

Post ~1986 blocks (i.e. HCI, Excel SE, etc.) use aluminum liners with Nikasil coatings instead of the 907 iron liners.  The aluminum liners are 1mm larger in diameter so you can't put them in a 907 or vice versa.

Unless you are itching for a project, I can't suggest the 'hybrid' route.  Instead, I would suggest finding a 1988 Lotus Excel SE engine or an engine from a N/A Esprit to rebuild and transplant into your JH. 

These are really the most 'evolved' engines, and have all the HP goodies you will need.  The only problem is finding one as neither are exactly common.

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 Posted: 07-18-2006 05:15 am
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edward_davis
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I remember reading somewhere thet the 9xx slant fours were meant as a precursor to a V-8, but that eight was never built.  But that was an old source, and I know Lotus made an eight-powered Esprit near the end of its run.  Was that eight based on the 9xx, or was it a souped-up version of another company's engine, much like the four in the Elise?

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 Posted: 07-18-2006 02:34 pm
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Jensen Healey
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Lotus developed the LT5 Corvette engine for GM in the 1980's. It has the "bearing panel" design of the 907 as does the Northstar engine. These engines were certainly not two 907s grafted together but the technology carried forward.

The Lotus v8 was a product of Lotus and not another companies design. It used current racing knowledge to develop a lightweight v8 that would fit in the Esprit.

There's lots of info on the web.

Kurt 

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 Posted: 07-18-2006 02:48 pm
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jcdean
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Isn't the biggest issue with the 910 and later variants the fitting into the smaller mounting area in the JH?

 

Joey

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 Posted: 07-18-2006 03:55 pm
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Judson Manning
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Yes Joey, you are correct.  Click on the link I included above and you will see the 910 bottom end is significantly larger.  A 910 will fit, but some minor modification of the mounts and x-member are necessary.

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 Posted: 07-18-2006 04:54 pm
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jcdean
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Thanks for the confirmation.  I have looked all over for a 910+ engine with no results anyway.  Well, with results that make it affordable at least.  They are a rare breed.

 

Joey

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 Posted: 02-05-2012 07:21 pm
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JodyKerr
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Bumping this topic. Anyone have pictures or more specific information on the chassis modifications necessary to install the 910 block?

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 Posted: 02-05-2012 09:16 pm
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jcdean
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I have been looking for four years now for a US sourced 912. With the added statement that this has not been a full time search I have not found one. On the other hand there is Lotubits in the UK. They have everything I need including Dell'Orto's and the cost is not prohibitive. I have not found a real quote for shipping there though other than FedEx or UPS which doubles the cost. But, I can dream.

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 Posted: 02-06-2012 02:11 pm
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Jensen Healey
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Subwoofer did it.

http://www.jensenhealey.com/forums/view_topic.php?id=1209&forum_id=15&highlight=modified+sump

Scroll down to the 40th post

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 Posted: 02-08-2012 07:26 pm
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subwoofer
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Jensen Healey wrote:
Subwoofer did it.

http://www.jensenhealey.com/forums/view_topic.php?id=1209&forum_id=15&highlight=modified+sump

Scroll down to the 40th post


Please note that it is a later 907, NOT a 910/912, so it still has the narrow bearing panel.

--
Joachim

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 Posted: 02-08-2012 07:30 pm
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subwoofer
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edward_davis wrote:
I remember reading somewhere thet the 9xx slant fours were meant as a precursor to a V-8, but that eight was never built.

I have also heard rumours of that 907 based V8. I can't quote any sources, but I think I remember hearing that it actually ran and made lots of power, but they just couldn't make it keep the cam belt(s) on. Again, heresy and possibly faulty memory.

--
Joachim

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 Posted: 02-08-2012 08:53 pm
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JodyKerr
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Hey All,

 

I was able to find someone who had fit the 910/912 to a Jensen Healey in the past. Based on their information it apparently involves some shimming of the engine mounts and the cut of a small notch in the passenger side of the sub frame. And this information is reliable.

 

When I get my hands on said block I'll double check this information, make the necessary modifications and do my usual documentation of the process.

Jody

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 Posted: 02-09-2012 09:04 pm
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James Sohl
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Lotus did make a V8 based on the 907, it think is was the type 908.  At least one prototype was made, but no production.  There was also a prototype car, the Etna, a luxurious model that was never made, that would have been 908 powered.  This all occurring well before Lotus and GM got together on the GM 4-valve engine.

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 Posted: 02-11-2012 03:25 am
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Jensen Healey
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Thanks James! Here's some info and photos of the Lotus 909:

 

http://www.projectm71.com/Rudd.htm

http://www.lotusbuzz.com/forums/showthread.php?t=697 


 

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