Cut'n'shut bellhousings

[dave1600]

Looking to cut'n'shut a Datsun L-series bellhousing onto a Nissan S15 6 speed gearbox.

I'm intending to make up a jig consisting of a mandrel that bolts through the main bearing caps of a spare block and continues through to the input shaft bearing / bearing recess in the bellhousing to keep it all aligned. The L-series bit of the bellhousing will bolt onto the rear of the spare block, and the bellhousing bit from the S15bellhousing will bolt onto the jig via a plate welded in the correct position.

Then take the whole lot to someone for welding.

Anyone see any issues / improvements / etc they can suggest ? What should I look for / ask for with regards to getting it welded up (my welding experience finishes at oxy/acetylene) ? Its been suggested to me that I need to pre-heat the lot prior to welding ? Anyone suggest an engineering place in Newcastle that would be happy to do this sort of thing ?

[15UZU]

whats the cost compared to getting a bellhousing and/or adapter plate fabbed up? and how strong do you need it to be?

cast or ally?

[no1200]

pre heat is a good idea.

All cast ally is different and some welds like shit, others OK, best to test first.

An adapter plate is a better idea just because more people can make one for you, whereas you will have trouble finding someone with a tig to weld such a large component cheaply.

[HoonBoy]

http://www.alloyrace.com/ have done almost the opposite with an adapter, FWD SR to L series block. It wouldn't be hard to modify that design to work the opposite way if they were so inclined..

[PLAYA]

I have done it with 2 plates slash ground with 4 doweled legs separating them, this is for sr to rb conversions, not that hard. I have measured up the result and is close to spot on.

[Momus]

That will work.

By far the cheapest and easiest way to go.

Needs to be TIG welded by someone with a decent amperage machine, probably 3 phase.
Pre heat a little and do a series of 8 or so evenly spaced tacks with no filler wire. That will get it warm, then weld.

[PLAYA]

nah 110 amps easy will do it

get an oxy, run acetylene rich and smoke up the ally, then turn it to the proper settings, heat it till all the black has burnt off, then it is hot to weld.

[dave1600]

Alloy.

Needs to be strong enough to handle all 70 horses from my L18

Don't know about cost of adaptor plates ? Could look into it. Although the "bellhousing" of the L-series box actually is integral with the gearbox case itself - ie the bellhousing extends backwards and encloses the gearset. Might make it a bit more complicated ?

Alloy Race Components. Mmmmm, nice gear there.

The reason I'm investigating is because it's at least $2K for a close ratio L-series box. If I put a low ratio diff in the car (4.44 or so) and ignore 1st in the S15 box, gears 2-6 in the S15 box are very nicely spaced. So, buy 2nd hand S15 box for $500 - $600 or so, get L-series bellhousing off the shelf in the shed, hack both bellhousings up and weld together should give a cheap-ish box with decents ratios to use on the track (no massive 2nd-3rd gap like an L-series box).

I'm happy to spend a reasonable amount on the welding as I can manage the rest myself.

Thanks for the suggestions gentlemen.

[fro]

If I put a low ratio diff in the car (4.44 or so) and ignore 1st in the S15 box, gears 2-6 in the S15 box are very nicely spaced. So, buy 2nd hand S15 box for $500 - $600 or so, get L-series bellhousing off the shelf in the shed, hack both bellhousings up and weld together should give a cheap-ish box with decents ratios to use on the track (no massive 2nd-3rd gap like an L-series box).

I've thought this for quite a while as well... interested to know how you go with it, as I reckon it's a good way to go. Keep me in the loop?

[Momus]

We did similar to what you are proposing to adapt an ex Gibson, Nissan HR 30 integral bellhousing CR box to a 13B.

Adaptor plating is ok, I've made a few, but they rely on the donor box having an input shaft longer than the original bellhousing.

[15UZU]

it`d constantly be in the back of my mind how good the welds where,but 70hp isn`t going to be stressing it too much

[dougmo]

saw this exact thing being done with L series to SR last weekend.
as you said adaptor through the main bearings and up into the bearing in the box.
Lots of initial preheating was required but once underway it held the heat.
You may find you cant have it bolted super tight to the block whilst welding to releive a little bit of the tension on the welds while cooling.

[dave1600]

I've thought this for quite a while as well... interested to know how you go with it, as I reckon it's a good way to go. Keep me in the loop?

Will do - I work slowly, so don't expect anything too quickly.

Need to find a cheap S15 box to play with now - there's a broken one on eBay I might have a bid on.

[HoonBoy]

Pic of adapter and l series box (with holinger 1-3 gears).

Is the shifter location of the six speed going to be OK?

[dave1600]

Plenty of people have put a complete S15 SR20 and 6 speed into 1600's, so I assume shifter position won't be too bad. Once I get a box, I can check.

SR20 5 speed boxes do normally need a bit of cutting and slight mods to the transmission tunnel, so I anticipate a little work.

The same basic box is available behind RX8's, MX5's, IS200's and S2000's so there may be some variation in shifter position between these that may be better ? I'm going with S15 box first because they are (hopefully) cheaper and easier to get, especially broken ones to experiment with.

If all else fails, I can use the 6 speed box in my 180B SSS as these have a much bigger transmission tunnel.

[HoonBoy]

I had an SR 5 speed next to the l series 5 speed today, the SR has the gearlever 5cm further back than the L series. Not sure how this compares to the 6 speed. The bodies don't look that different, the only space clearance may be an issue is around the shifter area. There is a pattern for making the plate for the gear lever in a 1600 around somewhere.

[dave1600]

Datsport's website has a template, and they also sell a cover - SR20 5 speed needs the hole in the tunnel elongated, and a bit of "stretching" with a jack to widen it slightly for the detent plugs around the shifter area.

From looking at pictures, the 6 speed looks a little less bulky in this area, but the gearlever housing will poke up into the car more. Will have to wait till I get a box to be sure.

Can't be too much difference between the 5 and 6 speeds, silvia guys swap between the two with no dramas.

[Paydirt]

Is there any possibility in using the bell housing from an MR30 stumpy box? They used them for a CA conversion using the S13 bellhousing and stumpy box, couldn't you go the other way?

[HoonBoy]

Don't take this as gospel, but I have been told that you can use the front half of an L series box with SR internal and SR rear half. Looking at the similarites of a lot of bits with my gearboxes today makes me think it may be possible.

[dave1600]

You can do this with the 5 speeds by just modifying the size of the selector rod holes in the L-series bellhousing (make them slightly larger), using an L-series countershaft bearing on the SR box and doing a little grinding inside the bellhousing to fit the slightly thicker countershaft gears in. I have a busted CA18 box in the shed that I fitted with an L-series bellhousing just to test this theory, never used it in a car but it seemed to go together allright.

In theory, you should also be able to do the reverse - put an SR20 or CA18 5 speed bellhousing on an L-series box - if you could work out how to stop the smaller L-series selector rods flopping about in the SR bellhousing (maybe drill the holes out much larger and fit a bush ?). I assume this is how they use the S13 bellhousing on the Skyline stumpy box.

This all works as the later "71C" type boxes (SR20 / CA18 / RB20 / etc) are just an evolution of the earlier "71B" boxes (L-series such as 240K / 260Z / pretty much any early-ish Nissan 5 speed), basically they are the same gearbox so swapping parts is fairly easy.

The 6 speeds are a completely different box, different manufacturer, etc, so it won't work

[Supercrown]

I've done almost exactly what you described in the first post 3 times with different engine/gearbox combinations. The only deviation was the method for centering the two. I centred using the gearbox input shaft, and what you have desciribed will give a more accurate position. (even using the gearbox method, all three I did came up within tolerance)

I had the bellhousing faces skimmed after to be thorough.

[dave1600]

I've thought this for quite a while as well... interested to know how you go with it, as I reckon it's a good way to go. Keep me in the loop?

Since you asked Things are progressing a little quicker than I planned as I broke the box in my 1600 at Lakeside a few weeks ago

I got hold of a busted S15 6 speed for virtually nothing, measurements have been made, calculations have been done, and it all seems as though its going to work nicely.

In "L-series mode" the 6 speed looks like it will fit better than the SR20 / CA18 5 speed as it'll end up a little shorter. Shifter will be a touch further forward (in between the position of a 240K box and an S13 box).

Only major difference is that the splined section of the input shaft is located a little further towards the motor. I don't think this will cause any issues, but will need to do a bit of measuring of where the clutch driven plate sits on this splined section, and how much movement there is when the clutch is depressed. That will have to wait till I get the old box out of the car.

I've sliced a few inches off the S15 bellhousing and compared it to the L-series box, looks like it'll line up OK for a cut'n'shut. Not a perfect match, but its workable. Even lashed out and bought special aluminium oxy welding lenses, they make it so much easier by filtering out the orange "flare" from the flux needed so you can actually see the weld pool. After a little practice on an old manifold, I'm confident enough to weld it all up with the oxy

Only other issue that will need sorting is that the clutch fork pivot point is in a different location (ie about 7 o'clock rather than 8 o'clock) and is a few mm too far in. I'll need to do a bit of welding, cutting and tapping to sort the location for the clutch slave to bolt on. Initial thoughts on the pivot are to turn up a new one the correct length so it will be in the correct spot.

A few interesting bits I've found so far are that different ratio 1st and 6th gearsets are available. Nismo makes a 2.9 1st gear, and pretty much any other version of this box (RX8, MX5, is200, Nismo) come with a 6th gear of either .84 or .86 rather than .76 as in the S15 box.

All four boxes - from left to right they are S15 6 speed, CA18 5 speed, skyline / 240K 5 speed and the original 1600 four speed.












S15 6 speed input shaft. Splines on shaft start at 30mm from the end, and continue on to 80mm from the end. 2nd pic is 240K one, splined section on thsi one goes from 45mm from the end to 92mm from the end. So the splined section is basically12mm less on the S15 box. By my calculations, the clutch driven plate ranges from 47mm to 71mm when engaged, so 9mm of travel should be plenty ??? Might turn a little off the boss that the throwout bearing carrier slides on, just for extra "peace of mind".






And lastly, the two halves line up pretty good, the only areas where the S15 is a little larger diameter (compared to the cardboard template matched to the 240K bellhousing) are circled. Should be near enough though.

[dogsballs]

adaptor plate would be soooo much easier!

[dave1600]

Adaptor plate won't work in this case.

The end of the input shaft protrudes about an inch outside the bellhousing face on the old box, but is about an inch inside the bellhousing face on the 6 speed. Add an adaptor plate as well, and the input shaft wouldn't reach the engine.

I'll actually be shortening the 6 speed box overall to make it work.

In the pics I posted, I've already taken 2 inches off the bellhousing of the 6 speed.

[dogsballs]

fair enough, have fun oxy welding the alloy.

[dave1600]

Oxy welding (I hope) won't be a problem, I've been doing it for 20-odd years (not alloy though) and have a Henrob / Dillon / whatever they're called this week torch.

A little practice the other night and I was turning out stuff like the manifold below, penetration is good and it didn't end up just a puddle on the floor.

More practice definitely required though before I attack my only 6 speed bellhousing - worst case, I can tack it up with the oxy and get it tig'd up professionally somewhere.

[dogsballs]

i think a crack or something in a manifold would be easier than joining two seperate pieces with different heating/cooling rates. as long as the fit is perfect makes things a little easier.

good luck.

[dave1600]

You may well be right - I'll find out soon enough

Practice will be to weld the "offcuts" of both bellhousings together.

[dave1600]

Progressing well - here's the almost completed jig for holding it all together while welding.

The three machined sections on the pipe locate in 3 of the main bearings of a spare block, the welded-on "collar" section locates in the input shaft bearing hole in the S15 bellhousing, and the flat section with the notch bolts up to where the front bearing cover goes in the front of the bellhousing.

Just need to whack it back in the lathe and take another light skim off the collar section to true / square everything up now that its welded up.