S14a conversion

richiep

Club Member
That looks fantastic. I'd be up for one of those for when I get around to installing the S14 box I have. Bear in mind that design appears to be for an early car, 70 to mid-71 vintage, where the crossmember bolts vertically to the tunnel, as opposed to the later crossmember with horizontal bolts. Good for me, given my car is early-71! Would need a redesign for later applications.
 

MaximG

Well-Known Forum User
That looks fantastic. I'd be up for one of those for when I get around to installing the S14 box I have. Bear in mind that design appears to be for an early car, 70 to mid-71 vintage, where the crossmember bolts vertically to the tunnel, as opposed to the later crossmember with horizontal bolts. Good for me, given my car is early-71! Would need a redesign for later applications.

Yep exactly the same as John and I. Not sure when the change took place but my car is a 72.
 

richiep

Club Member
Yep exactly the same as John and I. Not sure when the change took place but my car is a 72.

Was yours manufactured in 71 though and registered in 72? I though the change in crossmember occurred with the 72 model year, starting in autumn 71...

Whatever, it's definitely a cool piece. Although, it's worth noting that for the early crossmember the S14swap is actually much more straightforward. You don't actually have to cut the crossmember up and weld like you do with the later one. You can simply drill new holes in the ears of the crossmember to the side of the original holes. This, combined with turning the gearbox insulator mount so it is facing backwards, gives you the necessary mounting offset of about 25mm.
 

johnymd

Club Member
Mine's an early '72 and I think pre July '72 has this type.

I read that about the early mount Richie but couldn't work out which part you turn round. Do you know?
 

richiep

Club Member
The actual rubber mount. You bolt it to the gearbox backwards. It has an offset in its design between the top and bottom that, once reversed, gets you some of the way there. You can then offer up your crossmember and drill the holes when fitting.
 

rnblakey

Forum User
I would also be interested in one of those mounts Jonnny, if you get a batch made up.
My car has the early gearbox mount, with vertical bolts, and I welded the mount for the larger S14 gearbox. (It didn't occur to me to reverse the insulator). I Always considered the welds temporary as they will crack and fail at some point. That looks like a great solution.
Roger
 

SKiddell

Well-Known Forum User
Always considered the welds temporary as they will crack and fail at some point.

Why, there is little load on the cross member which is cusioned by the rubber mount, ive done nearly 20 of these conversions and if done properly the mount is the strongest componant.
 

rnblakey

Forum User
Hi Steve, I expect cracks to initiate from the welds, and grow due to cyclic loads, eventually resulting in a fatigue failure. Probably not during my lifetime, but it will happen. I would much prefer to have a part from a single pressing, or machined from one piece. Just better that way.
 

johnymd

Club Member
Reminds me of my of go carting days when only certain parts of the frame could be welded and others had to be braised due to the above. Not sure the gearbox mount will be stressed as much but it will suffer a cyclic twisting force.
 

SKiddell

Well-Known Forum User
Yay lets make everything out of aluminium.........

I expect cracks to initiate from the welds
decent fabrication, minimal weld undercut and appropriate stress relief will produce something equally as strong as a bit of milled alumininium...... (a material that has its own unique fatigue profile), but it won't be as shiney ;)
 

Albrecht

Well-Known Forum User
I don't think Roger needs any lessons on fabrication or materials science, given his occupation...
 

SKiddell

Well-Known Forum User
I don't think Roger needs any lessons on fabrication or materials science, given his occupation...

:bow: I could only gauge from his reply that he seemed overly concerned about potential failure and I was trying to alay his fears by giving the benefit of experiance and that the gearbox cross member is only supporting pivoted weight and that any "cyclic" or "shock load" that would induce weld cracking is primarily absorbed by the rubber damper mount.

Point in case are the lugs or shackles that the OEM mount bolt up to, is there evidence of these cracking and falling off due to "cyclic" stress or fatigue, if so we're all in trouble.......the only problem ive ever seen or heard of in that area is through everyday corrosion.
 

rnblakey

Forum User
Hello Sean,
Yes, I am the same Roger.

Hello Steve,
As I said, I don`t expect it to fail in my lifetime, but a welded part for that appication is not good practice. the original part was not welded. If a welded part was OK an OEM could save a huge amount of investment is presses and dies, but they don`t.
 

SKiddell

Well-Known Forum User
Hello Steve,
As I said, I don`t expect it to fail in my lifetime, but a welded part for that appication is not good practice. the original part was not welded. If a welded part was OK an OEM could save a huge amount of investment is presses and dies, but they don`t.

But Roger you miss my point, the ear shackles that the existing OEM cross member bolts up to is welded to the tunnel, is that considered bad practice.....QED

To add, you say
the original part was not welded.
but it is...all be it spot welded.

RE your argument that
If a welded part was OK an OEM could save a huge amount of investment is presses and dies,
is somewhat flawed, the "presses and die" are used to in order to optimise production (I have taught continuous improvement programs) to achieve a cost point whilst staying within safety frameworks where as welding is time consuming and comparatively costly....no quiet a fair argument.

Anyway each to their own.

Apologies to the OP for going off topic
 
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