2.0 mag case main bore measurements
 

Hi all, here are the results of my dial bore measurements on my '68 2.0 mag case. All measurements are in the order "10-4 o clock diagonal bore", 2-8 o clock diagonal bore", and "3-9 o clock diagonal bore"

I set my dial bore gauge to 62.019mm or 2.4417", and then measured the below differences from that. So, things generally do not seem too loose, with the exception of #8. If anything, they seem a bit tight in places. But that may be operator error with the gauge also, LOL.

#1 .0015"(.038mm) under, .0002"(.005mm) under, n/a (couldn't fit gauge in)
#2 .0004"(.010mm) under, .0001"(.003mm) under, .0005"(.013mm) under
#3 .0003"(.008mm) under, .0006"(.015mm) under, .0008"(.020mm) under
#4 .0007"(.018mm) under, .0011"(.028mm) under, .0010"(.025mm) under
#5 .0006"(.015mm) under, .0001"(.003mm) under, .0006"(.015mm) under
#6 .0001"(.003mm) over, .0007"(.018mm) under, .0010"(.025mm) under
#7 .0014"(.036mm) under, .0007"(.018mm) under, .0014"(.036mm) under
#8 0, .0010"(.025mm) over, .0007"(.018mm) over

Opinions? Can I use this case with no work? Crank journals are in the middle of standard spec, and green plastigauge was around .05mm for all journals with old bearings. (I have new bearings to put in it).

Thanks.

Mike

Bore measurements alone will not tell you if the case needs resizing. The alignment of the bores is critical. Mag cases tend to warp and even though the bores are round and the correct size, they may be out of alignment. This will cause the crank to bind once you've torqued up the case.

I've been told that you can check the alignment if you have a std/std crank with new bearings. You can install the crank/bearings and torque the case down. If the crank spins freely, then the case should be good.

Check with some of the experts on this board to validate this case check process.

Tom, OK, I will plan on doing just that. Thanks.

More opinions would be good......anyone?

:D

FWIW,...each & every mag case that we do gets align-honed to see if the main bearing saddles are straight and if not, the case parting lines get re-machined and the mains are bored back to standard.

Almost every mag case needs it due to heat stresses,.... :)

Thanks Steve.

I am trying to stick with my 2.0 rebuild, to have a period but non matching numbers engine for my '68. But as more costs tally up, I think I may be better off finding a 2.7 core motor to rebuild instead......:confused:

Mike,

JMHO, but ANY mag case will require the same level of preparation so budget accordingly.

My experience tells me that all 2.7's need the same case machining operations to be reliable.

Mike, if it's not the original numbers matching case I would get a 2,4 7R. Harder to find but Steve is (as ever) right on the money. Few but the most experienced cognoscenti can tell the difference on casual inspection.

Steve, thanks. I guess I wasn't clear, what I meant was that if I am going to start spending all this $ on a 2.0 non matching numbers engine, I may just as well get a bigger displacement motor.

How much is a core 2.7 anyways? I see SC AL case motors and later are $2500 and up, 2.7's are cheaper, no?

I'd agree,....:) :)

2.7 core motors seem to go for around $1200-1500/complete. 2.7's ARE cheaper but need $1000-2000 worth of case work to be durable and reliable. That said, a properly built 2.8 runs VERY well,... :) :)