MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

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danmas
Dan Masters
Alcoa, Tennessee
(578 posts)

Registered:
10/28/2007 12:11AM

Main British Car:
1974 MGBGT Ford 302

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Re: Which rear end for 400bhp MGB
Posted by: danmas
Date: January 27, 2014 08:18PM

Quote:
How about Ted Lathrops 8" with Auburn possi (sp) with 32 spline axels and spyder gears ($$$$)?.

I have one of those. I'm only putting down less than 350HP, so I should be good to go.

That's good news, because you guys were starting to scare me.


mowog1
Rick Ingram
Central Illinois
(1523 posts)

Registered:
10/17/2007 09:36PM

Main British Car:
1974.5 MGB/GT 3.9l Rover

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Re: Which rear end for 400bhp MGB
Posted by: mowog1
Date: January 27, 2014 09:44PM

I also have a Lathrop Ford 8" with Auburn 3.27 posi.

Undercarriage 6-4-11.jpg


MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

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Re: Which rear end for 400bhp MGB
Posted by: MGBV8
Date: January 27, 2014 10:24PM

32 spline? Typo?


74ls1tr6
Calvin Grannis
Elk Grove,CA
(1151 posts)

Registered:
11/10/2007 10:05AM

Main British Car:
74 TR6 / 71 MGB GT TR6/Ls1 71 MGB GT/Ls1

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Re: Which rear end for 400bhp MGB
Posted by: 74ls1tr6
Date: January 27, 2014 10:30PM

Carl said:
Quote:
Until I get ready to jump into the 300+HP pool, I think Jim Nichols' 7.5" Ford would do just fine for me.

In the Miata/Ls1,2,and 3 world they prefer to use the Ford 7.5" rear end. Again they said the car is light enough to use with the swaps. the 8" is to big for clearance issues in Miata applications. Just a thought!

Same issue with the R200's in the drifting cars, said to be good for 550lbs of torque. In that application it would be the stub axles are the week link.

Just my thoughts, a 3500lb car and up would be looking closer to the 8.8" or 9" ring and pinion, and the 400hp in front of them.

Of coarse I'm talking normal and spirited driving with no clutch dumping. We all can spin the tires with out cars fairly easy!


74ls1tr6
Calvin Grannis
Elk Grove,CA
(1151 posts)

Registered:
11/10/2007 10:05AM

Main British Car:
74 TR6 / 71 MGB GT TR6/Ls1 71 MGB GT/Ls1

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Re: Which rear end for 400bhp MGB
Posted by: 74ls1tr6
Date: January 27, 2014 10:37PM

Quote:
32 spline? Typo?

They are normally 28 spline axles. I was talking to Ted and asked him about 400+ torque with his 8", he said you can go with the 32 spline axles and gears. I said I'll go for the 32 splined axles and spider gears. I'm also running 3.54.1 because of 6 speed T56.



Edited 1 time(s). Last edit at 01/27/2014 10:39PM by 74ls1tr6.


MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

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Re: Which rear end for 400bhp MGB
Posted by: MGBV8
Date: January 27, 2014 11:27PM

I think he meant 31 spline. I wouldn't use the 28 spline, either.


mgb260
Jim Nichols
Sequim,WA
(2461 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Which rear end for 400bhp MGB
Posted by: mgb260
Date: January 28, 2014 06:05AM

The 8" is right between the 7.5 and 8.8 in strength. Calvin is right on the lighter car being traction limited anyway. Carl's 300HP limit or use the 7.5 for 4 cyl,V6 or 215/3.5 V8. The 8" is perfect for 300 to a little over 400HP. Actually Torque is a better number. That is what breaks things The 8.8 if built right, is right up there with the Dana 44 and 9", should be good for 500HP. The 31 spline axles are larger diameter and stronger. For racing, I think the Dana 44 or 8.8 would be the answer.



Edited 1 time(s). Last edit at 01/28/2014 06:08AM by mgb260.



74ls1tr6
Calvin Grannis
Elk Grove,CA
(1151 posts)

Registered:
11/10/2007 10:05AM

Main British Car:
74 TR6 / 71 MGB GT TR6/Ls1 71 MGB GT/Ls1

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Re: Which rear end for 400bhp MGB
Posted by: 74ls1tr6
Date: January 28, 2014 08:19AM

You at right Carl 31 spline!


TXS67BGT
jay musgrove
low country
(15 posts)

Registered:
11/16/2008 10:12AM

Main British Car:
1967 MGB GT 1998 LS1

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Re: Which rear end for 400bhp MGB
Posted by: TXS67BGT
Date: January 28, 2014 09:57AM

just to add another option in the mix, and Jim Nichols I hope you chime in here, I bought a rearend from a wrecked 98 Camaro Z28, 3.43:1 with disks, Eaton posi, seemed at the time to be just what I wanted, during the rebuild bought new bearings, clutch disks everything I thought I would need. the bearings for a 7.5 did not fit, after digging around with the local Chevy Parts guy he showed me that it was a 7 5/8, only two ratios available, ordered the bearings for that and they fit. Local (Kent Washington at the time) rearend specialist did the cutting and welding said he had seen only one other 7 5/8, said the tube walls were thicker than the standard 7.5. now all this is from memory, thought at the time I was rather lucky to run across it, hope all I have said is correct, do know it had Aussie aluminum calipers. The shop I bought it from had it in a car they had been drag racing with, behind a 415HP LS1 and it held up fine behind an 4L60E trans.
REAREND 001.jpg


MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

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Re: Which rear end for 400bhp MGB
Posted by: MGBV8
Date: January 28, 2014 10:41AM

How many bolts holding on the cover, 9 or 10? Sounds like it could be an Australian 9 Bolt.

They are actually pretty stout. A friend of mine had a Third Gen Camaro with one. It survived his Paxton centrifugal blower equipped engine & a 5 speed.

Great info:

[www.thirdgen.org]



Edited 1 time(s). Last edit at 01/28/2014 12:41PM by MGBV8.


mgb260
Jim Nichols
Sequim,WA
(2461 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Which rear end for 400bhp MGB
Posted by: mgb260
Date: January 28, 2014 08:06PM

Hey Jay, GM 10 bolts after about 89 or so went to 7.625 ring gear and 28 spline axles. If I remember correctly,even the rear cover and outer bearings were the same as the earlier 7.5. The Australian 9 bolt was used in higher performance Camaro/Firebird. That rear cover looks more like a Dana and no C clips, also 7.75 ring gear. Another option for a narrow rear is the 89-92 GM S10 2WD. It is 54"wide and if you cut 1" off splined ends to eliminate C clips, narrow tubes and use Ford bearing ends comes out 52" same as stock MGB. 4.75" Chevy wheel lug pattern.


TXS67BGT
jay musgrove
low country
(15 posts)

Registered:
11/16/2008 10:12AM

Main British Car:
1967 MGB GT 1998 LS1

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Re: Which rear end for 400bhp MGB
Posted by: TXS67BGT
Date: January 29, 2014 04:06PM

counted, 10 bolt.
REAREND 005.jpg


waterbucket
Philip Waterman
England
(112 posts)

Registered:
07/30/2011 01:08PM

Main British Car:
1972 MGB GT

Re: Which rear end for 400bhp MGB
Posted by: waterbucket
Date: February 02, 2014 02:31PM

There is another axle available in the UK, the one from the Reliant Scimitar SE5. I think I am right in saying that it is only 11/2 inches wider than the original B axle, it has the brackets already for a four link location and a Watts linkage for lateral location. It takes Jaguar diffs (or Dana 44) so plenty of choice there for ratios and lsd. I guess it might be lighter than the Land Rover axle.


v8bloke
Mark Rawlins

(75 posts)

Registered:
02/02/2010 02:13PM

Main British Car:


Re: Which rear end for 400bhp MGB
Posted by: v8bloke
Date: February 04, 2014 07:01AM

Thanks everyone.
looking at the photos some have mounted the shocks just in front and some just behind the axle. The ford escort coil over kits mount the shocks on top of the axle. Is this as a result of packaging or is there an optimum position. I have room to fit them on top of the axle or just in front. Which would be best?
Cheers
Mark


Moderator
Curtis Jacobson
Portland Oregon
(4576 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

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Re: Which rear end for 400bhp MGB
Posted by: Moderator
Date: February 04, 2014 10:29AM

Putting the shocks in front of the axle leaves room for a Panhard rod or Watts linkage between the axle and fuel tank.



TXS67BGT
jay musgrove
low country
(15 posts)

Registered:
11/16/2008 10:12AM

Main British Car:
1967 MGB GT 1998 LS1

authors avatar
Re: Which rear end for 400bhp MGB
Posted by: TXS67BGT
Date: February 08, 2014 08:26AM

for your reference, shocks behind the axle. used Bill Guzmans setup as the basis
REAREND 081.jpg
REAREND 067.jpg



Edited 3 time(s). Last edit at 02/08/2014 08:34AM by TXS67BGT.


mgb260
Jim Nichols
Sequim,WA
(2461 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Which rear end for 400bhp MGB
Posted by: mgb260
Date: February 13, 2014 10:00PM

Jay, Nice looking setup. It'll be a smooth ride. Did you center or use aftermarket fuel tank? Curtis is right on front mount shocks/rear panhard , not a lot of room between the rear axle and tank . Triangulated like Jay and Graham have can be mounted either way. V8bloke(Mark) any progress pics?



Edited 1 time(s). Last edit at 02/13/2014 10:54PM by mgb260.


roverman
Art Gertz
Winchester, CA.
(3188 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Which rear end for 400bhp MGB
Posted by: roverman
Date: February 14, 2014 12:09PM

Mark, We are about "sharing", beneficial knowlegde-here. How about you tell us all about your TA headed, RV8 build ? You have not mentioned, if you will need different r & p ratios, for different circuits. If so,IMHO, you'll definately want a drop-out center section.Servicing a drop-out, on a bench, sure beats an "integral", in the car. Are you drag racing or road racing ? Drag slicks and drag tuned suspension, will shock-load a chosen rear, to the max. There are items to counter-act this. 8" Fords have 31 spline axles available, even hollow , lightweight full floater set-ups. 4 spider limited slip units, including gear only.What will be the r & p ratio, as this affects strength. More teeth in contact + stronger. Maybe a ring gear "thrust button", like 9 inchers use ? "Soft-lock" clutches, are available. Perhaps a rubber coupled drive shaft ? Good Luck, Now tell us, about your RV8. roverman.


v8bloke
Mark Rawlins

(75 posts)

Registered:
02/02/2010 02:13PM

Main British Car:


Re: Which rear end for 400bhp MGB
Posted by: v8bloke
Date: February 15, 2014 04:06AM

Thanks guys,
modifications are progressing at a very slow pace. Will post pics soon. Rather than work around the existing metalwork I have chopped out everything between the chassis rails inc most of the boot floor up as far as the rear seat kick panel. I seem to spend a lot of time just looking at it with arms crossed trying to figure out the best way forward.
The brackets for the Mumford linkage are made and am waiting for billet ally bell cranks to be made.
I will be using an MGB axle with stronger shafts for now but have made sure there is room to swap to a larger rear end if needed.
At the moment I am making and welding on all the housing brackets for upper and lower trailing links, mumford links and anti roll bar. I am still not decided exactly where I will be mounting the coil overs but it is likely to be behind the axle as the mumford link brackets will double up for mounting them.
Also I am having an aluminium fuel cell made that will fit upright with a built in swirl pot and baffles.
Although the car is road legal it is mainly used for track days and is stripped out so I am not at all worried about originality.
Will post some pics soon.

Mark
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