Sprite Race Gearbox Rebuild

Yeah, one of the detents was sticking - probably some tiny bit of errant swarf I didn't get completely cleaned out even tho I cleaned the living crap out of it - works fine now.

 

Delivering this box to the owner Wed AM, we're all going up to Jesse Prather Racing to put the white race car that I built the engine for on his dyno and see if we can get the last bit of power out of it - even tho it runs really well right now there might be a bit more left. We're also going to put a Bugeye on that I built a 1275 engine for last year and a Morris Minor pickup that belongs to a friend of mine.

The Bugeye has a Weber on it - he just hasn't been able to find someone who knows what they're doing to tune it properly. Jesse and Kent Prather are both really sharp on Webers, they should be able to get it shaped up.

The Mo has a 1275 too, but he's running an SU HIF44. I have a few needles for it but not many, we should be able to get it close tho.

Going to be a fun morning. The race car is leaving for the race at Grattan in Michigan as soon as we're done on the dyno.

Going to be a hot day tomorrow so we're getting an early start, first runs are at 8 am.

 

The race car is running twin HS4's, those are right in Kent's wheelhouse - his favorite carb setup so he'll be tuning it.

Both Jesse and Kent have extensive experience tuning Webers, and a BIG box of jets and such - which is essential to getting them tuned right.

Today I'm starting on gearbox #2 while all the pitfalls of the first build are still fresh in my mind, and I'll do the third one right after that assuming Moss gets the last bits I need delivered in time.

That will be it for gearboxes this year. Well, for Sprite gearboxes anyway.....I have two Mini gearboxes to build too. They mostly just need synchros but of course you have to disassemble the entire box to get to them.

 

The next one came to me in chunks - it's on the bench now ready for teardown, I have all the new parts tho there could be the odd bit missing - he says he has everything I might need tho.

I believe him - he has a two car garage FULL of crap! so much so that he has to work on the racecar in his driveway or in his trailer if the sun's too hot.

 

Got the case stripped out and cleaned up, there was a lot of corrosion on the gasket surfaces so I removed all the studs and counter sunk the holes a bit, then took a large flat file tot he surface, lastly a twisted wire wheel brush in the angle grinder cleaned off all the corrosion.





I also disassembled the mainshaft and got it ready to rebuild. I'll be gone tomorrow so may not get back to it till Thursday. When this one is finished it's going into the little white racecar - he thinks it might be good for 1-2 seconds a lap just from having better ratios. Not to mention the straight cut gears are a whole lot stronger so he can bang on it harder if needed to get past a competitor.

 

The next step in this build is to clean and tap all the threaded holes - I remove all the studs to make it easier to clean the gasket surfaces, and in this case the studs were also coated with gasket sealer and rust. I think this gearbox either sat outside or in a humid garage for quite a while as there was rust in some very strange places.

So with the case all cleaned up I found there was a broken bolt - never fun to get out of an aluminum case. It's very easy to drill off center and tear up the aluminum and not get all the steel out.....this was one severely corroded in place.



To start with I used a small file to try and flatten the broken end as much as possible, but it was below the surface of the case, so all I accomplished was to take a nib off the end. Next I carefully center punched the end of the bolt, then got out one of the best tools I've ever owned, a set of left handed drill bits. I didn't think this one would wind itself out, but you never can tell. I used a small bit to carefully drill a pilot hole and it was centered nicely. Next I went after it with a finish bit and as you can see by the pic, I got out a lot of rust along with the steel. Once the hole was done I picked out what threads I could, then used the correct tap to clean up the rest of the threads. It came out nicely!







I also cleaned up all the rest of the bits and pieces, and put the mainshaft together.....as always, installing the pin keepers on 2nd and third gears is always the hardest part of putting the mainshaft back together, but the more I do the better I get at it. Doesn't mean I'm any faster tho......it's still a PITA.

I installed and shimmed the two main bearings so everything is now ready to go back in the case. Assembly is the reverse, as they say.....

 

I finished his race box today and he'll pick it up and put it in the racecar before the next event in mid-September.

Today I also started on the last of the three boxes, this one for a guy in Houston. He'll be at the September race too but I think this is a spare gearbox for him.

This box is in very good shape, 1st gear isn't even roached up badly so it should be a fairly straightforward build.

First thing I did after getting it disassembled was to remove all the studs, chamfer all the holes, tap all the threads and clean off all the gasket mating surfaces. After that, into the tank for a thorough cleaning in the solvent and a good blow dry.








Next - disassemble the mainshaft - always a "fun" job.





Once that's done, all the bits go into the tank for another cleanup, I'll wire brush the threads on all the studs and bolts, clean all the little plungers and such and get it ready to put back together. I think I spend more time cleaning than dis-assembly and re-assembly!

 

This one went together pretty smoothly, I got the gear assembly into the case with no issues, but when I went to install the shifter I noticed it didn't want to move - it was locked up with a big mud dauber nest! I took the back plate off and dug out the mud, cleaned it all up and now it shifts well.



although it wasn't completely roached like most of them, I did put a new first gear in this one too along with a new shift fork. You can't but a shift fork or shift sleeve for 3rd/4th....all you can get are used ones and hope to find one that's not too bad. The owner had a new hub and shift sleeve made in Australia (or was it new Zealand?) and while the sleeve was good, the hub did not fit the shaft, I don't think the splines were cut correctly.....the sleeve is the part that wears out anyway, so I did use it.

I cleaned up all the studs and bolts - I always use new nuts and lock washers as they get grungy and are difficult to clean - new ones are not expensive. Still have to tap all the threads in every hole to get a good clean assembly tho, can't skip that step or you pay for it later when something won't tighten properly.



So this one is ready to go back to Texas.....there is a race at Eagles Canyon in mid Sept, that Clancy will go to and the owner will be there that weekend too, so Clancy will transport it for him.



Looks like there are two more coming in over the next couple of weeks.....it's getting to be almost routine now, tho never easy, but at least there are fewer mysteries with each one I complete.

 

You're probably right!

 

So.....this next one is done - sort of. Everything inside is finished and it shifts beautifully. Clancy brought me a front cover - he has a guy who machines them and puts a lip seal inside so they don't leak oil thru the mainshaft. Originally, they have a sort of reverse thread that's supposed to scroll the oil back into the box, but the front covers wear and the gap gets big enough that they leak thru and it gets on the clutch, this helps eliminate that.



However....

He brought me the wrong one - he brought one for a smooth case gearbox, and the bolt hole pattern is different.

So I have it all done save for that. He was supposed to get it on Tuesday so they could put it in a car for the races at Hallet, if they can work out the pick up schedule OK they still have plenty of time to get it in the car.

All I have to do is measure the cover so I know what size shim to put in it and bolt it on, won't take 15 minutes once I have the right cover. In the meantime I have a small bracket bolted on to hold the input shaft bearing in place.



With this one done I can now get back to work on the Mini gearbox as all the parts are here for it. I'm hoping that the various machine shops will be done with their work on the engine block, head and crank by tomorrow afternoon, but I have plenty to do in the meantime.....

 

I threw a coat of paint on it - I wouldn't normally paint one white but that's what color it was when it came to me, so......



Just heard from one machine shop - block, pistons and crank are done for the Mini engine, I'll go get them tomorrow.