Need a 907 Motor Specification
Discussion
I need some assistance with a 907 specification that I do not have. What I need is the housing bore size on the big end of the connecting rod. I have the small end size, 1.0002/1.0004 inches, but my manual gives no specifications for the big end bore size. Any assistance you could provide with specifications on this would be great. My machinist is checking everything over in my motor for me and we’ve got some questions regarding this spec in comparison with some things we see in the motor.
Thanks,
Ron
Thanks,
Ron
Just to put some information out that I learned from Judson - it might make it easier on those who are considering a 9XX bottom end rebuild.
Judson suggested re-cutting the rods to accept Chevy bearings. My machinist checked that out and it looks like a spot on suggestion and there appear to be no problems. Not only that, you'd have a fantastic bearing selection and a set of bearings would be like $20, instead of $200. Cost to do it is cheap too, about $48, so future rebuilds would be cheap.
He also suggested re-doing the mains to accept Chrysler 318 bearings and that suggestion seems to work out well too. Again, same deal, cheap bearings, better quality, and inexpensive rebuilds in the future. Fortunately the Lotus crank used common size journals so it isn't hard to do.
Thanks for the help on these things Judson and I'll post back here on how this thing works out. This information should be good for any Lotus 9XX motor and a decent shop can carry out the work.
Ron
Judson suggested re-cutting the rods to accept Chevy bearings. My machinist checked that out and it looks like a spot on suggestion and there appear to be no problems. Not only that, you'd have a fantastic bearing selection and a set of bearings would be like $20, instead of $200. Cost to do it is cheap too, about $48, so future rebuilds would be cheap.
He also suggested re-doing the mains to accept Chrysler 318 bearings and that suggestion seems to work out well too. Again, same deal, cheap bearings, better quality, and inexpensive rebuilds in the future. Fortunately the Lotus crank used common size journals so it isn't hard to do.
Thanks for the help on these things Judson and I'll post back here on how this thing works out. This information should be good for any Lotus 9XX motor and a decent shop can carry out the work.
Ron
Cool, Ron. I'll file that little tidbit away. Ahh, the SBC: The generic motor. And, you can buy a set of rod bearings and have enough to rebuild two 9XX motors.
I think they were putting SBC rods into Toyota 4AGE's for high boost applications. Seems like I read of people doing that some time back.
I think they were putting SBC rods into Toyota 4AGE's for high boost applications. Seems like I read of people doing that some time back.
Dr.Hess said:
Cool, Ron. I'll file that little tidbit away. Ahh, the SBC: The generic motor. And, you can buy a set of rod bearings and have enough to rebuild two 9XX motors.
Even better, you can get change from a twenty! Set of rod bearings was $18.70, Clevite 77s, shopping around. So, that is $9.35 for bearings to do the motor. Haven't got the mains yet, but they'll be probably around $50.
Compare that with oh, the $122.50 Delta wants for the rod bearings and the $288.00 Delta wants for the main bearings. Not knocking Delta, I assume they are using standard markup, but that is a lot of cash for bearings.
R
I assume that is small block chevy. Are all SBC's the same or is there a particular year/model that fits best? Don't know my Cheby's.
Seitse K. in .NL made his own 910 pistons from either a Volvo or a Saab, I forget. Used a slightly smaller bushing on the small end for the slightly different sized wrist pin and cut valve reliefs on top.
Dr.Hess
Seitse K. in .NL made his own 910 pistons from either a Volvo or a Saab, I forget. Used a slightly smaller bushing on the small end for the slightly different sized wrist pin and cut valve reliefs on top.
Dr.Hess
Be careful with the Chrysler 318 bearings. As I remember there are either 2 or 3 different sizes depending upon which 318 saddle they fit in.
Also the 318 bearings I bought down the street for $50 were 360^ grooved. In my correspondance with the Clevite guys, they found a p/n for the individual shells, and a non-standard plain bearing...I'll see if I can find those p/n's.
Between the line boring, x-drilling and piecing together a 180^ set of special bearings; the cost of genuine 910 bearings may end up being cheaper.
Also the 318 bearings I bought down the street for $50 were 360^ grooved. In my correspondance with the Clevite guys, they found a p/n for the individual shells, and a non-standard plain bearing...I'll see if I can find those p/n's.
Between the line boring, x-drilling and piecing together a 180^ set of special bearings; the cost of genuine 910 bearings may end up being cheaper.
You might be right, but, my machinist is quite reasonable. $48 to do the rods, and the crank line boring is around the same he indicated. But, the big pay off would be in 2 years when it gets torn down again - the savings would be very high so I think it is worth it in the long run. Plus, hate to say it, but I've got more trust in good Chevy SB bearings than Lotus bearings. Since I figure as a race engine it'll be torn down relatively frequently I think the investment is worth it.
I'll call Billy in the morning to make him aware of the Chrysler bearing stuff as I'm not familar with Mopar madness, only Ford V8 details.
Thanks again,
Ron
>> Edited by rlearp on Thursday 9th December 11:14
I'll call Billy in the morning to make him aware of the Chrysler bearing stuff as I'm not familar with Mopar madness, only Ford V8 details.
Thanks again,
Ron
>> Edited by rlearp on Thursday 9th December 11:14
This is what I found:
Mains: Clevite p/n MB2035P (one Pair)
Chrysler318 position 1,2&4, component part of main set MS540P
std, .010, .020, .030 & .040 u/s
Shaft: 2.4995/2.5005"
Housing: 2.6925/2.6932"
Width: .867/.877"
Grooving: 180^ (upper half, full grooving available MB2283P which is two MB2035P-upper, ref set#1344P)
Rods: Clevite p/n CB745P/H (H for high-performance)
EARLY small block Chevy
std, .010" u/s
Shaft: 1.999/2.000"
Housing: 2.1247/2.1252"
Width: .832/.842
Grooving: none
Let me know how all of this goes...
Mains: Clevite p/n MB2035P (one Pair)
Chrysler318 position 1,2&4, component part of main set MS540P
std, .010, .020, .030 & .040 u/s
Shaft: 2.4995/2.5005"
Housing: 2.6925/2.6932"
Width: .867/.877"
Grooving: 180^ (upper half, full grooving available MB2283P which is two MB2035P-upper, ref set#1344P)
Rods: Clevite p/n CB745P/H (H for high-performance)
EARLY small block Chevy
std, .010" u/s
Shaft: 1.999/2.000"
Housing: 2.1247/2.1252"
Width: .832/.842
Grooving: none
Let me know how all of this goes...
Thanks a lot Judson, this might help him.
As you promised, nothing owrked out in my favor. Months ago when I told you my plans you said "nope, won't work". Well I had to try.
First I thought, I'll take it apart and see how she looks. Maybe clean it up, hone the cylinders, check bore, and re-ring it just to run a year.
Well, I got that far and noticed that #1 rod was mighty black, indicating heat issues. Off come the rod caps, dang, bearings really look worn. So off to the shop it goes.
It needs new bearings everywhere, but, maybe by a miracle, the bores are good and taper in spec. Pistons are pretty good to, so I can elect to overbore or not.
Still, it isn't costing a fortune, yet, but much more than I had budgeted for. I suppose I could have purchaesd a better Jensen Healey to start with, but that seemed a shame to pay 6x what I did for mine when I was going to gut and throw 50% of the car away. Plus, just because a fellow has a nice car and a running motor doesn't mean the motor is going to take race conditions - I could end up doing this anyhow.
I'll let you know how it comes out.
Ron
As you promised, nothing owrked out in my favor. Months ago when I told you my plans you said "nope, won't work". Well I had to try.
First I thought, I'll take it apart and see how she looks. Maybe clean it up, hone the cylinders, check bore, and re-ring it just to run a year.
Well, I got that far and noticed that #1 rod was mighty black, indicating heat issues. Off come the rod caps, dang, bearings really look worn. So off to the shop it goes.
It needs new bearings everywhere, but, maybe by a miracle, the bores are good and taper in spec. Pistons are pretty good to, so I can elect to overbore or not.
Still, it isn't costing a fortune, yet, but much more than I had budgeted for. I suppose I could have purchaesd a better Jensen Healey to start with, but that seemed a shame to pay 6x what I did for mine when I was going to gut and throw 50% of the car away. Plus, just because a fellow has a nice car and a running motor doesn't mean the motor is going to take race conditions - I could end up doing this anyhow.
I'll let you know how it comes out.
Ron
Judson, My machinist is with you on all the specs but he has a question on the 318 stuff. Are you saying just purchase 2 sets of 318 bearings or purchase those individually? He was confused with the working about position 1,2,4 etc. Hard to do this sort of thing on the road!!! Thanks,
rlearp said:
(Snip)... What I need is the housing bore size on the big end of the connecting rod. I have the small end size, 1.0002/1.0004 inches, but my manual gives no specifications for the big end bore size. (Snip)...
Ron,
Just in case you decide to stay with Lotus parts, here's the info you asked for...
(from Vandervell bearing catalog - this info is not given in the Lotus Manual)
Block & Main Bearing Panel Bore ID Specification
2.6652 to 2.6660 inch, Standard Bore ID Esprit S1/ S2
2.6655 to 2.6660 inch, Standard Bore ID All Others
2.6805 to 2.6810 inch, Oversize Bore ID +0.0150"
Connecting Rod:
2 grams Permissible Rod to Rod Weight Variation
5.500 +/- 0.001 inch Distance Between Centers
Std. Bore Diameters
1.9976 to 1.9982 inch, Crank Journal OD
2.1460 to 2.1466 inch, Rod Big End ID
0.0010 to 0.0032 inch, Static Clearance
0.0040 to 0.0100 inch, End Float on Crank Journal
1.0002 to 1.0004 inch, Small End Bushing ID
.............................. Ream to size AFTER installation
Crankshaft:
2.4995 to 2.5005 inch, Main Journal OD, 1, 2, 3, 4
2.5000 to 2.5005 inch, Main Journal OD, #5 (rear) only
1.9975 to 1.9985 inch, Rod Journal OD, All
Later,
Tim Engel
Lotus Owners Oftha North
>> Edited by Esprit2 on Friday 10th December 02:46
Hi Tim,
Thank you for that, I'll send these over to so that he has them for centering specs and for something to give the fellow that with make the bushings for the new bearings.
We are definitely going non-Lotus parts here, it fits beautifully. Bearings are bearings, and of course Lotus doesn't make bearings. Those expensive Lotus bearings fit another motor somewhere else in the world, maybe a farm tractor somewhere, and cost $22.99 for that application. But cost $400 for a Lotus.
Seriously, I would probably stick with the Lotus bits if this was a street rebuild and I didn't think I'd be back in there in 1-2 years. But, with a race motor it'll probably be torn down every two years (probably more in the 907 case) and I can't afford $400 for bearing refreshing each time. But, I can take $20! Plus, we have a wider assortment of bearings to chose from.
I hope the timelyness of the information doesn't foreshadow bad events. Jeff and I are taking our Esprits down to a Porsche track day event this weekend and I'm hoping nothing goes BOOM!
Thank you for that, I'll send these over to so that he has them for centering specs and for something to give the fellow that with make the bushings for the new bearings.
We are definitely going non-Lotus parts here, it fits beautifully. Bearings are bearings, and of course Lotus doesn't make bearings. Those expensive Lotus bearings fit another motor somewhere else in the world, maybe a farm tractor somewhere, and cost $22.99 for that application. But cost $400 for a Lotus.
Seriously, I would probably stick with the Lotus bits if this was a street rebuild and I didn't think I'd be back in there in 1-2 years. But, with a race motor it'll probably be torn down every two years (probably more in the 907 case) and I can't afford $400 for bearing refreshing each time. But, I can take $20! Plus, we have a wider assortment of bearings to chose from.
I hope the timelyness of the information doesn't foreshadow bad events. Jeff and I are taking our Esprits down to a Porsche track day event this weekend and I'm hoping nothing goes BOOM!
rlearp said:
(Snip)... But, with a race motor it'll probably be torn down every two years (probably more in the 907 case)...
Ron,
The 907 uses two dowels between the cylinder block and main bearing panel... one front and one rear. The 910 uses ten dowels... one for each main stud. If you will be using a 907 as the basis for a race engine, then adding the other eight dowels really improves to the assembly's rigidity. And longevity.
Add the dowels, then align bore/hone the bearing bores. If you're going to non-standard bearings you'll have to align-bore anyway, so it's a perfect time to add the dowel pins.
Have a great track day.
Later,
Tim Engel
Lotus Owners Oftha North
>> Edited by Esprit2 on Friday 10th December 20:45
Tim,
I've long heard the benefits of 10-doweling the 9xx series engines in high HP applications. However, Garry Kemp pointed out to me that the 910 only has 3 dowels (and the 1986 910 block I have has 3 dowels).
Of course the 910 has a much more stout bottom end compared to the 907 and might not need all 10.
Did Lotus adopt 10-doweling in later 910 blocks?
I've long heard the benefits of 10-doweling the 9xx series engines in high HP applications. However, Garry Kemp pointed out to me that the 910 only has 3 dowels (and the 1986 910 block I have has 3 dowels).
Of course the 910 has a much more stout bottom end compared to the 907 and might not need all 10.
Did Lotus adopt 10-doweling in later 910 blocks?
Judson,
I have manuals for all the FEDERAL Turbo 4-cylinder engines, 1983-87, 1988-92 and 1993-97. All of them indicate 10 dowels per engine/ main bearing panel assembly.
I've rebuilt FEDERAL 910's from 1983 thru 1988 and I have yet to find one without 10 dowels.
I don't "know", but I suspect it's the difference between Fed-spec and DOM/ROW spec engines. Garry Kemp's 910's would most likely be DOM-spec. Where did you get your '86 block?
Regardless of all that, 10-pinning a 907 is a worthwhile improvement. I've 10-pinned my street engines and I'd strongly advise it for anyone building a 907 into a race engine. Of course the best foundation for a naturally aspirated race engine would be a 910 block with 10 dowels.
Later,
Tim Engel
Lotus Owners Oftha North
I have manuals for all the FEDERAL Turbo 4-cylinder engines, 1983-87, 1988-92 and 1993-97. All of them indicate 10 dowels per engine/ main bearing panel assembly.
I've rebuilt FEDERAL 910's from 1983 thru 1988 and I have yet to find one without 10 dowels.
I don't "know", but I suspect it's the difference between Fed-spec and DOM/ROW spec engines. Garry Kemp's 910's would most likely be DOM-spec. Where did you get your '86 block?
Regardless of all that, 10-pinning a 907 is a worthwhile improvement. I've 10-pinned my street engines and I'd strongly advise it for anyone building a 907 into a race engine. Of course the best foundation for a naturally aspirated race engine would be a 910 block with 10 dowels.
Later,
Tim Engel
Lotus Owners Oftha North
Hi Tim / Ron,
that's very interesting about US 910's having 10 dowelled mains - the only ones in the UK to get 10 dowels were the 910 dry sump motor - of which there were less than 100 made. I've probably pulled apart 100+ 910's and 912's (same block) and they have all had 3 dowels.
As an aside - the main bearing bores on the early engines - particularly the 907's usually have really poor alignment and roundness - once you get to the late 80's cars they start to get better and once into the 90's are pretty good. In my opinion the often refered to weakness of the 2.0L block had little to do with ridgidity and more to do with plain old shoddy workmanship from the factory machinists.
that's very interesting about US 910's having 10 dowelled mains - the only ones in the UK to get 10 dowels were the 910 dry sump motor - of which there were less than 100 made. I've probably pulled apart 100+ 910's and 912's (same block) and they have all had 3 dowels.
As an aside - the main bearing bores on the early engines - particularly the 907's usually have really poor alignment and roundness - once you get to the late 80's cars they start to get better and once into the 90's are pretty good. In my opinion the often refered to weakness of the 2.0L block had little to do with ridgidity and more to do with plain old shoddy workmanship from the factory machinists.
I found this info when looking for oil pump parts.
For Jensen Healey 907. New crank and bearings adapted from a Holden 2L or 2.2L motor. Aparently the same crank apart from the rear seal which the supplier in Tasmania does for them.
BTW Holden is Australian arm of GM. They offer stroker kits for the 2L engine to 2.2L.
www.jhps.com/html/detail/2.2_details.html
For Jensen Healey 907. New crank and bearings adapted from a Holden 2L or 2.2L motor. Aparently the same crank apart from the rear seal which the supplier in Tasmania does for them.
BTW Holden is Australian arm of GM. They offer stroker kits for the 2L engine to 2.2L.
www.jhps.com/html/detail/2.2_details.html
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