Torque/power Vs. MGBtube axle.

Anybody have any experience with the torque/power capacity of the MGB tube axle. I'm doing a conversion with a GM HO 2.3l Quad 4 engine and T5 trans. Torque about 165#-ft and 210-220 Hp.

Ecotec engine? If so tell us more.

Capacity of the axle - I think it should be fine aslong as the ratio suits your needs.

No- Quad 4 was an engine introduced in the mid-90's (?), 4 cyl 4 valve. Precursor to the Ecotec in the US. Notable because the cam coverlooks alot like an Offenhauser

As Greg noted the Quad 4 is an iron block 4v aluminum head engine originally designed and produced by Oldsmobile in the Olds Calais and Pontiac Grand Am in 1988. The HO versions were factory rated at 180 Hp in 1990-91 and have a race version, W41 at 190. The W41 is what I am using with tube headers, ported head, and no catalyst. The Ecotec was designed in the mid to late 90's as a world engine for many GM brands and vehicles. It is all Al. and quite robust as well as lighter. If I do another similar conversion it may very well be with an Ecotec. Greg Fast, please give me a call as I've misplaced your number. 970 564 5822. I have a question for you. Dave

I have a 3.9, 9.35 comp. rover with a C rear with 3.07 gears with 450,000 miles on it & no problems. Had a 4.8 with a TON of tork & a 3.9 rear, drag raced it to 13. 1/4 mile.

The MG rear will be fine.

Wasn't the Quad-4 known for blowing head gaskets & cracked heads? A friend had a Quad-4 Pontiac Grand Am, lots of problems.

Carl --youre right the Quad 4 is a piece of junk--I had an Olds Quad 4 --they throw the timing and are too expensive to fix --mine had only 68K miles one of GMs absolute worst designs in trying to compete with foreign engines

The Salisbury MGB diff'/axle was originally destined for a light truck, or van. They shortened the axle and put it in the B. Way too heavy duty for a light weight sports car. I saw a post by someone with 300 plus BHP who managed to break the spider gears, while dragging off a turbo Porsche. Dropped the clutch I suspect. I think Bullet proof is a good description.

...and if you break it, replacement parts are widely available - many times free.

The only one on BritishV8.org:

http://www.britishv8.org/MG/Bob.htm

Greetings David,

Welcome to the V6/V8 forum. As you well remember my first conversion was a quad 4 that I traded some items for when you lived in Ohio.

For all who read this column, David Headly is a very capable individual with years of engineering experience and has been associated with the Quad 4 as a great part of his career life at GM and on a personal basis.

David, my only real contribution to your thread would be a comparison witness not based on anything but experience. We have customers that have been using the 3500 FWD engine as an engine conversion option. This engine when installed with a cold air flow system and a fair header arrangement is capable of producing a conservative 240 HP at about 220 ft. lb. of torque. Most of the conversions are done on later model cars that use the one piece rear housing and the stock 3.90 gear. In my experience from hanging around with some of the MGB racers was they preferred the tube axle over the one piece for it's strength. I'm sure you have heard the same thing in your racing career. We have customers who use the 3400 engine in the tube type applications, that have up to 230 HP and 207 ft. lbs. of torque and no reported failures. Of all the conversions we have done and all the customers we have out there we had one sheared axle with a one piece rear end housing. This was a 3400 application using a one piece rear gear housing. After removing the axle and thoroughly examining it we discovered that it was either a substandard replacement or a defective part. It was at least 30% under size in comparison to all other axles we've seen and the other axle in the same housing was a normal size. We replaced it with a normal OEM part and has not shown any signs of failure. I realize this is not the answer you seek but it may have some value in your quest.

Yours truly,
Dann Wade

Dan, thanx for your input. I'm not sure what you are refering to when you talk about 1-piece axle vs tube axle. I was only aware of the tube and banjo type which is prefered for racing due to weight and ease of gear changes.

The Salisbury (late model) is a stronger housing than the banjo type, but also heavier. IIRC it has about a 7-7/8" ring gear and is quite strong. It should hold up very well in all applications under 200 ft/lbs of torque. Once you go above that you should expect to see the life span decrease, and in the range from 250-300 you can expect to see accelerated wear. Over 300 all bets are off. I wore out a ring and pinion gearset in one, but that was behind a 215 running 16 lbs of boost and it had lived a hard life before that. Many people select the 8" Ford axle for strength and light weight but it is actually not that much bigger. The Dana-44, at 8-1/2" is reputed to be good for 500 hp in a full sized vehicle. This should give you a useful frame of reference. Does 1/8" make that much difference? It can. Do you need it for a motor that puts out less than 200 ft/lbs of torque? Absolutely not.

One other thing to consider. Banjo housings are known to flex under heavy power. For decades drag racers have added internal stiffeners to counteract this flex, which can cause the tooth contact patch to be altered and wear out a set of 9 inch Ford gears in as little as 10 dragstrip passes. Any banjo housing can benefit from these stiffening modifications, in much the same way that salisbury type axle housings can benefit from the use of a girdle type rear cover with jackscrews to load the bearing caps. So for the ultimate lightweight axle why not consider the early banjo axle with aluminum hogshead and internal stiffeners? It will probably hold up well in your application.

Jim

Dave ,
I meant that the whole rear axle housing was one piece. I had forgotten that the called it a banjo. Now that you remind me I do recall. :-)

Dann