NITROUS OXIDE ( nos / n2o ) advice forum

I am glad to say that despite the damp weather the old MGB went out last sunday and put down another 9.6 on its first proper test run this year.

We have done a few mods over the winter, mainly a new exhaust system as can be seen in the video attached. But another big improvement I think will be the new tyres. I've changed from Mickey Thomspon slicks to Hoosier slicks and they seem to perform a little better on my car. They seem a little stiffer on the sidewalls and make the car launch a little flatter as well with a lot less sidewall ripple at the same 12psi I normally run.

The new exhaust system is very free flowing now and I'm still running rich at 10-11 AFR with the timing knocked back by 8 degree's from theoretical ideal for the engine. Thats how we did the first test pass in this video.

http://www.youtube.com/watch?v=119ozwyI ... jw&index=3


Then I decided to advance the ignition by 3 degree's to see how she performed. I would say the hit off the line was great. But the custom made Moser shafts that were supposed be able to handle 700hp had other ideas

I think the added 3 degree's of timing may have gained me maybe 50hp or so to bring the engine up around 570hp. But the torque generated on the launch with 12psi of boost and a nitrous hit of 140hp with a build time to 175hp in 0.6 of a second on the new slicks was obviously too much for the shafts. The left shaft snapped within 2 feet and the other shaft held full power for as long as it took me to get off the pedal. The skid mark from the drivers side tyre was about 10 feet long and had a nice curve to the left as the tyre dissipated the energy from the spooled engine as I backed off the pedal. She had 4 inches of air under the front left as soon as i left the line

http://www.youtube.com/watch?v=dSKYSH6v ... GyG4tfRrjw


So I'm now re working my old MGB rear axle. I have dropped a shaft off at Webster racing as they had the shafts made about 3 years ago for me. But this time I have told them to ask Moser for a quote to remake two more shafts, but this time I want the splined drive ends made to Ford 9" 31 spline pattern because I have figured out a way to convert my old MGB diff into a hybrid Ford 9" spool using mym old diff cage and rear axle housing ????

It may work, it may not work. But it will deffo be better than what I have now while I save up for a Ford 9" rear end for 2015 ?

Perry

It's always good to start the new year as well as you ended the last, just a shame about the axles.

All the best for the rest of the year Perry.

Thanks Trev!!

Despite the broken shafts I am more than happy with the first test day. I think that the down time I will have from now on will ruin my chances of winning the RWYB challenge this year as I was possibly on track to take the trophy by default if I attended all 10 rounds and just ran a high 9 each time. I'm not going to get stressed about not winning the challenge as another possibility has just shown itself. And that is an 8 second timing ticket in 2014 ??


The new Hoosier slicks pretty much Dead Hooked off the line. The rear end let go in a few feet and I still coasted over the 60 foot marker with a ticket time of 1.4 seconds. I think this could have been my 8 second run ??

That would be a hell of an achievement Perry, so the best of luck for the rest of the year.

Thanks Trev

It wasnt that long ago that I was hoping to max the MGB out with an 11 second pass

And now the chance of an 8.99 timing ticket seems possible this year? Its a big ask for the old engine which started out as a stock Rover 3.9 but I have high hopes now as things seem to be slowly coming together since we built the engine last May. It has a lot of custom parts inside and it looks like my choice of pistons and the mods I did to them have worked ok?

I just need to sort out the rear axle in the next few months and I'll be good to go again

And more importantly I suspect is your current choice of head gaskets.

This is gonna shock you Trev!!!

On the last engine I went for Cometic multi layer steels which worked well.

On this modified 3.9 I have O ringed heads and have been using Elring Comp head gaskets since last May with no problems as the O rings settle down onto the steel rings around the compression chambers to pinch them up really tight just like tin gaskets

Who would have thought it ?? This wasnt by choice mind. It just happened that the heads I got were already O ringed. Or I would have gone back to tin gaskets.

It doesn't even surprise me Perry, as STEEL gaskets are much better than composite garbage, although I'd rather use the single layer original than multi-layer and the only thing better than that is using a wire ringed block/head (although again I'd go for a single layer gasket of copper in this case), so I'd expect you to get good results from those set ups.

If I remember correctly you were using a composite gasket without head/block wire rings, when you were having all those gasket failures?

Spot on Trev!!

I do have two pairs of copper head gaskets in the garage which are being saved for another day ??

They have been laser cut but have not been annealed. When the time comes I will soften a pair and get them fitted with the O ringed heads if needed.

At the moment I am working on beefing up the rear end. I think I have found a way to integrate Ford 9" 31 spline shafts into my old Salisbury diff with Ford 9" drive gears ??? If this works I guess I'll be breaking the prop shaft or gearbox next

That's the way it goes.

So far the Ford 9" hybrid diff and axle is looking good ???

I'm waiting for parts to arrive but it looks like I can fit Ford 8.8" diff side gears into the MG diff to take 31 spline shafts with no real hassle. I'm now working out what shafts I need. I know I need ford 9" 31 spline but its the length I need to sort out now. I've found a company that do replacement 31 spline shafts with extended splines. The idea is that the shafts are the longest length for the Ford 9" application in truck or bus axles, but they are splined long enough to be cut down to the shortest Ford 9" applications so they become multi use shafts !

I need to do a lot of measuring, especially for the bearing and wheel end to make sure I can re use all of my MGB brake system and fit my MGB wheels. Luckily I work for a company that can source any bearing I want so I should be ok to find one that will fit the ford shafts and hopefully the MGB bearing mount in the axle case. The important thing is the mating tolerance to the shafts. I can trim the bearing down to fit the case or mill the case out to fit the bearings as required?? Its going to be a fun project anyway. A Sleeper MGB rear axle