NITROUS OXIDE ( nos / n2o ) advice forum

I've broken the custom drive shafts now.

They have lasted about 3 years and were made from super material. But they were trimmed down on the spline end to fit the MGB diff side gears.

The side gears and the crown wheel gear has held up ok. But I need fatter shafts now. I cant afford a Ford 8.8" or 9" axle so I'm going to see if I can modify the MGB rear axle to accept Ford 9" 31 spline shafts. So far its looking quite possible, but it will mean some machining of the diff cage to accept Ford side gears and the fatter shafts. Then i will need to work out how to fit the MGB brakes and drums. I've been talking to Webster racing and they will be happy to assist me with the design of the Ford shafts as they will be a custom build. But unlike my old TOTALLY custom shafts. These will be off the shelf Ford shafts modified a little to my design. So that should save some money I hope ??

If it all goes as planned the axle will look totally stock from the outside, but will be much stronger on the inside

The Ford 31 spline diff gear set arrived today. Within an hour they were at the machine shop with a spare diff cage so my mate can make up a tool to bore out my V8 diff cage which is still in the car and also to trim 6mm off each side of the side gears so they will fit into the diff cage while still leaving enough metal to weld the side gears solidly into the diff cage.

I was so excited when the gear set arrived after paying for "express international shipping" which took 20 days that I forgot to take any pictures

Sounds good . I think the old MG axle's done very well to get this far (power/grip/et times) without major surgery any way!

Hopefully i'll get down to the pod a few times this year, and i'll see the black beast in action!

Ian

It would be great to see you again Ian.

I've stopped trying to make the Ford 9" side gears fit the MGB diff cage now..?

Mainly because I've now fitted a 900hp Ford 9" spool into the MGB diff case.

I'm AMAZED that gets anywhere near fitting.

Final measurements tonight Trev shows that the Ford 9" spool is only 20 thou longer than the MGB diff cage

So I need to get the shims either side of the diff cage trimmed just a tad.

The stock 9" spool leaves the crown wheel just 6mm short of where it needs to sit to mesh properly with the pinion. So a few mm off the spool flange and a few mm off the back of the crown wheel will see it lined up ok.

I will then need to re drill the spool to take the 8 bolts on the Crown wheel. The spool is a 10 bolt item. But there is so much metal on the spool flange and the bolt circle on the MG crown wheel is smaller than the 10 bolt PCD that I can get new holes drilled as required without having to remove much metal. Re drilling the flange would possibly put it out of balance. But as the PCD is only 6" I cant see that the rotating mass at this diameter would see me having to worry about re balancing the spool

QUICK UPDATE !!

I pulled my rear axle out this afternoon and the spool fits perfectly

I fitted the bearing clamps and its nice and snug with no sideways play and ZERO resistance when gently turned with my finger !!

I stripped the crown wheel and re fitted the old diff cage so I could put a straight edge across the flange face and scribe some marks on the diff casing. Then re fitted the spool and did the same. The difference is 7.9mm so I need to skim 3mm off the back of the crown wheel and 5mm off the flange face of the spool. The spool flange is about 22mm thick so with 5mm removed it will still be 5mm thicker than the MGB diff flange.

I rang my mate at 2pm to see if he was still at the machine shop and he was just washing up to go home. So I flew down there and dropped the bits off to him so he can do the machining and re drill the spool on Monday / Tuesday next week. So before the end of next week I can have the spool and crown wheel fitted for final testing by putting some gear marking compound on for rotation / mesh checks. I think this may just be a formality because I should be able get the crown wheel fitted back on within +/- 5 thou / the thickness of the line the scriber made

All looking good so far. UPS says the drive shafts have been in transit from California for 36 hours now Goodness knows when they will arrive but after weeks of messing around trying to get the ones I want I at least know they are on the way -- Hooray !!

The Ford 9" shafts are now here

First mock up trial fit and its looking very good indeed

Ford 9" 31 spline driveshafts in a MGB Salisbury axle ??

And the re drilled drums fit as well

Moved on a bit today!

Got the spool dialled in on the mill and drilled the new bolt circle. As the existing holes are where they are it was always going to have some holes close to each other. But I'm happy with the result so far. I still have to counter bore so 6 of the bolt heads will sit low down at the same level as the existing bolt surfaces. But the two bolts in the thicker section will stay as they are. The bolts are 12.9 strength cap heads and will be fine for the job.

I sat back in the sun today while my Son in Law and my mate Mike got to checking gear mesh. After 2 hours and lots of measuring we concluded that I need to move the crown wheel away from the pinion by 10 thou. I made a mistake when surface grinding the side shims DOH!!

To save the aggro of re grinding shims it will be easier to take the spool back to the machine shop and have 10 thou taken off the spool face

So I'm another step closer to getting the axle back in now !

The axle is now fitted and tested.

Did 5 test runs yesterday and it seemed fine. Then gave it some welly and ran two 9's with the best being 9.7 @ 141mph.

Excellent.

I think I'm getting there Trev!!

I'm now starting to unlock the hidden power I think I have in this engine I made. I wont go into too much detail about how I made this engine just yet. But it is still a Rover V8 3.9 litre based engine which i have tweaked at home.

My old PB of 9.6 @ 137mph was with the 175 shot coming in at 100 off the line with the other 75 coming in over 0.6 of a second. Last weekends 9.7 @ 141.68 was with a 50 shot off the line and the other 125 shot coming in over 1.7 seconds.

My old 60 foot times were all 1.3's. Last weekend the 60 foots were all 1.5's. Yet I was only a tenth slower across the line with an extra 5mph

If my calculations are in the right area I think the MGB with Rover V8 could run a low 9 or a high 8 this season ??

Dagnabbit!!

The new engine power now seems to be driving through the converter or the gearbox. I've run a few 9.6's and 9.7's at 140+mph. And now I'm crossing the line with the same rpm but MPH has dropped to 137mph.?

So something is slipping??

The converter is now 8 years old as is the gearbox.

Gearbox oil looks ok and does not smell burnt. The converter is a 3000 stall item, but the engine makes peak torque at 4000rpm now where it used to make peak torque at 3000rpm pre blower fitting ???

Sounds like 8s could be possible once you get it all sorted.

SERIOUSLY IMPRESSIVE for a Rover engine.

I just checked the website for my converter and its for engines up to 350hp. So I guess that may be the problem. Mine is now over 550hp. Time to start shopping around for torque converter advice ?

Hi mgbv8.

If you are looking to upgrade your torque converter or just want some advice then I'd suggest Mackie just outside Glasgow
http://www.mackie-transmission.com/.
I was at one of their open days a few months ago. looks like all high range franchise garages send either the car or gearbox to them to fix!!
I'll be having my GM 4L80E box and converter re-engineered by them. when I asked if the converter could be made to handle 1000hp answer was yes but would need 3 days to get the parts in!! as if this was a std mod

All the best

Brilliant Many thanks. Perry

I have used their contact form 3 times now with no response from them ??

I will attempt to call them this week to see if they can help or not ?

My first impression of this company who do not reply to requests on their own enquiry system is not that good so far !!

Perry

I got a reply but they cant help with uprating my converter. They suggested buying a new one, which makes sense I think