Triumph Sports Cars

As you may or may not know, I'm in the early stages of stuffing a ford i4 in my '63 spitfire. While currently I'm putting a carbureted engine (because it was gifted to me), my intention is to put a turbo EFI version of the same block at some point down the road. Currently I am aiming to have just over 200hp when all is said and done.

Now, in theory, how much power could I get away with before having to do serious frame construction. Also take into account that I intend to have a ford 8" rear end or something similar at the back.

would anything approaching 250hp start to twist the frame under load?

Short of a new frame, are there any discreet mods that can be done to increase rigidity? ex. a mini rollbar that would sit within the body, around the gas tank? I'll add a picture later to illustrate this idea...

I would essentially like to do as much structural modifications while doing the full restoration, running it with my current engine till I feel like upgrading rather than finishing it with this engine and then starting over later.

Of course, as this is all in theory, wild and zany ideas are more than welcome!

Ivan,

I only know the TR6 but I think the key is rust. How solid is your frame?

I'm amazed at how thin our frame material is and how crappy are the factory welds. A few welded cross members can only help. The mini rollbar also sounds like a good idea.


George

At a cursory glance, the frame looks solid. I've yet to do any body work or even remove the body from the frame. I need to sit the new motor in and make measurements for cuts and whatever else first.

I'm okay with reinforcing welds and putting braces, but I really don't want to tackle building a new frame.

just a quick sketch of what I was thinking

basically it would sit brace the gas tank, and I could hide it behind the trim. I would have to put more thought to its design though :p

I'll bump this up again.

Basically, if I put a turbocharged for inline 4 good for somewhere between 200 and 250hp along with a better rear suspension/diff, what would I need to do to stiffen the frame if anything.

The Spitfire frame is basically shaped like an hourglass so the twisting moment will be the strongest where the frame is the narrowest. If you can build up the frame at the narrow point it would help a lot. If you do away with the Spitfire rearend and go with a straight axle with four link then the torque effect on the narrow part of the frame will increase. To offset this effect if it is possible run some square tubing on either side of the car just behind the sill and attach to both ends of the frame where the frame begins to flare out. By doing this the bending moment now has to spread out along 4 frame rails rather than 2.

Hi, From my perspective the frame/ body assembly was plenty strong when new. However, when I pulled the frame from mine I was amazed at the amount of rust on the inside of the frame. A lot of it was paper thin and I feel it would have buckled at some point in the future if left alone. As BWA suggested I chose to use a pair of outboard frame riggers to make it strong enough for much more power. That also allowed the use of more reasonable size transmissions. A lot of support was added to the Diff area to support the BMW diff and Corvette composite springs.

[www.cardomain.com]

Bill

That seems like a good approach. I imagine using a live axle rather than solid would help a bit with the twist?

For the time being, I am going to assume that the frame is still solid. I'll have a better idea of the condition later in July when I get the body off.

From your pictures, Bill, I see you are using a automatic. I don't think that getting my transmission to fit is going to be quite as troublesome since I've got a "world-class" T5 that is already hooked up to the engine block.

on a side note, what would be a good affordable rear axle to start looking for? rx7, corvette, ford 8", etc...