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MG MGB GT V8 Factory Originals Technical - Acceleration

I am in the process of building a 302/T5 Chrome Bumper Convertible, hopefully int he 350 hp range. I will never drive over 130 mph, so I am looking for the right gear setup w/ 16 inch rims to make it go from 60-130 like a BIG BIKE. Any suggestions?

Thanx In Advance
Geoff B.

Um, yes. Pay particular attention to your rear suspension. You did not say what diameter tires you plan to use, but a 24" diameter tire with the stock gearing should get you close to what you are looking for. The big problem will be traction, and a rear suspension that combines good cornering with dragstrip launch capabilities is a delicate balance. Sounds like some sort of traction device will be needed though, perhaps one of the "Y" bars discussed in the thread on panhard bars.

Jim
Jim Blackwood

Thanx, Jim. I am on the fence w/ a jag rr end or a Ford 8.8. I have both, but am wondering what the cost should be to graft in the jag vs. shortening the 8.8, but it will be one of those. Forgive my ignorance, but will that kind of power be breakin' em loose at 60?
And what is the stock gearing?
Geoff B.

Stock MGB gearing is 3.909:1 Which isn't always ideal for a T5 box. It will give you a lot of guts in the top end, but 'could' leave 1st gear absolutely useless.

You could go for the best of both worlds and go for
Ford IRS. =)

Justin
Justin

Also consider what gearing the T5 has, how many revs you want to turn, and what your engine is capable of turning. Several charts are online for calculating all the different combinations. I ended up with the 3.91, 25" tires(MGA) and a T5 with a 2.65 1st and .63:1 5th.
Scott

some 33 inch mud slingers should do just fine
steve

Geoff,

Tire size is very important part of the equation. Reducing the tire diameter has the same effect as using a lower (higher numerically) axle ratio, which gives you a faster acceleration. Increasing the tire diameter has the opposite effect, and gives you a higher top speed.

For example, a 3.5:1 ratio with 195/60/15 tires gives very nearly the same overall ratio as a 3.7:1 with 215/65/15 tires – 20.58 mph/1000rpm in 4th gear for the former, and 20.91 mph/1000rpm for the latter.

To maximize your performance, whatever speed range you are interested in, you need to juggle transmission ratios, axle ratios, and tire size (not to mention the choices you'll need to make for the proper cam, which will play a MAJOR role).

You might want to download a copy of the spreadsheet I created to play with the above items and see what you need.

http://www.britishv8.org/swaps/chart.xls
Dan Masters

Dan, I haven't gone v6/8 yet..but would like to get a little more speed (as opposed to power) from my newly rebuilt 4 banger with standard MGB gearbox and rearend. Is there a rearend I could easily install with in my 67B with lower ratio gears to give me more speed as opposed to switching gearboxes which will cost more. I guess larger tires will do what I want but would rather swith rearends if there is one that might work in a stockish B.

Thanks

Moe
Moe

note to Moe, if I were you, I would look at installing an overdrive gearbox in your 67B, there is no better improvement you can make (excepting V8 power) to a 4 cylinder. You won't acheive anymore top end speed, but it will sure seem like it!
Chris J.

Moe,

Dan Lagrou sells a converted Chevy S10 axles that bolt right in to an MGB. I don't know the cost, or how it would compare to the cost of a transmission swap, but you could give Dan a call and see.

D & D Fabrications, Inc.
Attention: Dan LaGrou, President
8005 Tiffany Drive
Almont MI 48003

Phone: 810-798-2491
Fax: 810-798-2777

If you can find one, I believe the 3.07:1 ring and pinion set from an MGC fits the MGB differential.
Dan Masters

Chris and Dan, Thanks for the info...I'll check them out !!

Moe

Geoff,
That'd be in the neighborhood of 300 rwhp or higher. At those levels you can expect traction issues anytime you are near the torque peak.

There have been some Jag conversions done, a couple are on the web. Justin has an 8.8 ready to weld in, and I have one under the bench awaiting time on the mill. Search the archives, as there has been some very detailed discussions of both, along with links to pictures. Justin's install requires the tank to be moved, I'm planning on doing it without that but there is a great deal more fabrication involved. That project won't be finished until the end of next winter. Most people go with a solid axle, there are a lot of good choices.

Jim
Jim Blackwood

This thread was discussed between 03/01/2005 and 05/01/2005

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