Technical P&J split wishbone on 40 Ford question

I'm in the process of my latest build.

I'm using P&J split wishbone kit.
Superbell Axle with 36.5' perch centers.
Posie 2037-40L spring.

I cut the stock bones at 38.75" Measuring along the top of the bones. This places my axle about 2" too far forward.

Before I cut agin, I was hoping to talk to someone who has done this with the same setup as me.

Thanks in advance.
Phil

 

I've never done it but if it were me I'd hook the spring up to the bones even if I just used a leaf or two and set the spring up in the frame so I had my exact location.
Too long beats the hell our of too short though. Remember that you want about half the threads on the rod ends screwed into the bungs when you do all the measuring.

 

Yeah, that's the next step. But 2" is a lot. So I'm hoping someone can confirm or point out something I screwed up. Thanks.

 

Double check, that you have the trans mount / wish bone mount in the correct place.

 

I have. But I’ll triple check. Thanks

 

Is that length measurement for the wishbones intended for a stock perch width axle as compared to the narrower perch width axle you are using.

When I did mine, I set the axle up with just the main leave and pulled it down to ride height with a ratchet strap. Then figured out the length for the bones, welded, and mounted them. After that removed the shackles and squared the spring perches. Don't neglect to check the caster when you get most of the car put together.

 

Mine were split when I bought the car and it has the tci kit in it which calls for 38 3/8 yet they are at 37 3/4 with plenty of thread engagement. I can see the 5/8 difference but 2 inches seems much.

 

I would suggest 3/4 of the threads screwed in. - with 1/2 screwed in, if you have to adjust outward you could potentially end up with very few threads holding it in place.
My reasoning is that half the threads should be holding it in at a minimum, so the adjustment should start at 3/4, to give 1/4 of total threads adjustment either way.
careful measuring is the key.

 

If the axle is narrower than Pete & Jake intended, that could lead to this problem. But it will also lead to a spring width problem.

But, I would rather try to overcome those problems and have a slightly narrower axle to give more tire clearance under the fenders.

 

I contacted P&J, they said the narrower perch centers should not change the length. It was my first question.

my plan, so far, is to mockup and cut were it needs to be cut.

There’s also a difference when you measure the top of the bones, compared to the bottom. Because of the caster angle of the perch holes. But their diagram show’s measuring along the top.

 

If that kit is for a SBC/th350 in a 40, the measurement seem long. Our kit, which is quite similar call for 36 1/2". That would make this kind of difference.

 

That makes no sense. The wider the bones are spread the further back the axle is going to be.

 

As it is a P&J kit I would consider this post - he is probably the guy that wrote the instructions in 1984

Cheers Turns