SFI specs 10.2 vs 10.3

I was getting ready to order the SFI specs rulebook for an altered.

I was told to build to 10.2 specs by the chassis guy in our club and by the guy that certs chassis for NHRA in our area.

After looking at the guideline that SFI has listed it seems that what I have in mind is more lkely to fit into a 10.3 rules (7.50 and slower). Other than the obvious 7.49 versus 7.50 difference what other differences are there between the two specs? Mild vs Chrome Moly? extra bars/ different geometry? Etc...


Here is just a few things that will be:

Motor: 6-71 blown, 2 port injected alcohol, cast iron head SBC motor. Nothing exotic. Power glide trans to a narrowed 9". Low compression (8.5:1) mild boost (7-10lbs) motor built for longevity.

Chassis: Mild Steel, center steer, solid mounted rearend. Coilovers on the front tube axle. American Racing 17" spindle mounts up front and 15 x 12 Ansens in the rear with a metal body.

This thing will never touch an 8. More like a 9.20 on a good day.

 

First thing you have to relize is that if you build with mild steel that you have to over build because
1) Mild steel tubing does not come in .118 wall. Even tho they call it .120 it will measure .114, which will not pass sonic.
2) Since you cant step down tubing sizes(telescope) you must run continuess which adds weight.
3) Depending on how or where you buy materials, building out of moly shouldnt cost more than $200 extra for an altered.

The only advantage to mild is. for the home builder who does not tig weld

 

Thanks,

I assume the difference between the two specs is MS/CM then?


I'm not opposed to using CM I just figured weight was not that big of a deal to me....if it was I need to go on a diet (5'10" @ 260 lbs).

It seems most people I talk to about the MS /CM debate runs about 50/50.

 

If at all possible build a moly chassis, but as stated it has to be tig welded
If tig welding is not possible you could consider D.O.M. tubing which can be mig welded, using the correct wire and a 75-25 gas mix.
But our experince is the cost is about the same as moly. This could be that we buy more moly than any other type of tubing.
If possible build to the quicker spec. The car will hold its value much longer, if for some reason you ever sold it.
Speedy