68 GTO...BACKHALF OR NOT? dilemma

[DM03]

Hey all, well yesterday i brought in my bare chassis to have boxed and cross-braced. After telling the fabricator what i was looking for(strength in the chassis for handling the motor, handling). I plan on running the Moser 12bolt, because ive heard the 10 bolt just wont hang. He called me a few hours later and said two options, The first being exactly what we talked about-cross-bracing, custom cross member, boxed frame, and running that 12 bolt with some hefty aftermarket uppers and lowers with coilovers. For that $2900 for just the metal work on the chassis (not including 12 bolt, arms or springs) or Completely Back Half the frame, mini tub it so i can run 315's or 335's, box and crossbrace like before, and fab up and 1 off 4 link system. Without the rearend, the price is $4900. Im not really sure where to go guys. I would love to fit some wider tires and have the rear suspension bullet proof, but at the same time its a lot to bite off. If you understand what i mean. The cars intention is to be a no BS street brawller, and will probably see the track here and there. Im just looking for your guys experience and knowledge. I realize im probably leaving a lot out, but im really kinda stuck here. Thanks for the help-Daniel

[ProdigyCustoms]

We have done a couple of these. Those frames narrow up real easy. You will need a $500 coil over conversion, We can order a Moser rear with the upper arm bosses attached and lower arm perches loose, about $2500. The $4700 if that is just labor and the frame is already on the floor is strong. I sent my brother to North Carolina to do one for another shop and he did it in 3 days start to finish, 24 hours, X $60, $1500 labor.

[Roadrage David]

[QUOTE=ProdigyCustoms;651014]We have done a couple of these. Those frames narrow up real easy. QUOTE]
Any pictures of that???

[ProdigyCustoms]

[QUOTE=Roadrage David;651805]

We have done a couple of these. Those frames narrow up real easy. QUOTE]
Any pictures of that???

Here is a 65, same deal

http://www.prodigycustoms.com/projec...s.php?album=15

[DM03]

hey guys, thanks for the feedback. As it turns out after i talked to Marcus at SC and C, and re-thinking where i am going with this car, im not going to back half it. I got wrapped up in the snowball effect and at the rate i was going this thing was going to turn out a full on race car.haha. So we did some engineering, and the frame is going to be boxed, new crossmembers, and some crossbrace work, We are also going to notch the rear about an inch to make a little room just as you guys said. Then off to be powdercoated gunmetal. Im trying to load pics but Im not allowed to for some reason. I will keep you updated, should be a really fun car.

[DM03]

Still cant seem to load pics! Help?

[Roadbuster]

Hey all, well yesterday i brought in my bare chassis to have boxed and cross-braced. After telling the fabricator what i was looking for(strength in the chassis for handling the motor, handling). I plan on running the Moser 12bolt, because ive heard the 10 bolt just wont hang. He called me a few hours later and said two options, The first being exactly what we talked about-cross-bracing, custom cross member, boxed frame, and running that 12 bolt with some hefty aftermarket uppers and lowers with coilovers. For that $2900 for just the metal work on the chassis (not including 12 bolt, arms or springs) or Completely Back Half the frame, mini tub it so i can run 315's or 335's, box and crossbrace like before, and fab up and 1 off 4 link system. Without the rearend, the price is $4900. Im not really sure where to go guys. I would love to fit some wider tires and have the rear suspension bullet proof, but at the same time its a lot to bite off. If you understand what i mean. The cars intention is to be a no BS street brawller, and will probably see the track here and there. Im just looking for your guys experience and knowledge. I realize im probably leaving a lot out, but im really kinda stuck here. Thanks for the help-Daniel

If all you want to run is 315s they will fit without a mini tub although some work would be needed on the fender lip. I tuck 305/35R18 rears on 18x11 rims on my 68 GTO with very minor work. It is tight but fits. A 335 on 18x12 will require a wider wheel well - either move the frame in or the fenders out.

The ten bolt is a BOP 10 bolt and is stronger than the Chevy 10 bolt and has positively retained axles (no C-clips needed). Problem is that it is not cheap to build up (since parts are less common) and still not as strong as the 12 bolt or a 9inch.



Jon

[MonzaRacer]

Well now I do have to disagree with a BOP 10 bolt NOT being strong as I bought he center section out of my old machinists 11 1/2lb per cubic in drag car, 4.88 gears/posi unit and he had a 400Pontiac with Crane Super Flow heads, and a custom set up Muncie.
Carrying nearly 5000lbs and on narrow slicks(fit a 64 Tempest stock body) and was carrying front wheels and held the record in that class and ran low 7s in the 1/8th mile (think 5k lbs and small slicks) with stock rear suspension with MAS traction bars and air bag inside right rear coil and what ever shock that were in vogue at time, probably 50/50s.
And this was slamming a 4 speed at 8000 rpm(yes 8k) on a Pontiac and actually consistent.
And he only broke on axle (actual fracture in middle of axle) and eventually took out some of the first "pro gears" ever made, the ones I had were plain old off the shelf Shiefer(sp) gears.
Weak link is axles, in road/autocross I doubt you would ever break it except with sticky tires you would twist axles.
As for BOP being stronger that corporate, nah, that BOP had a corporate 8.2 10 bolt R&P in it with spacer to take up for smaller diameter bolts.
Now as for making it handle, get you dimensions for the wheels and tires, make room on out side and simply move rails in till they clear, plenty of setups fix the Abody issues, slide in a set of ridetech Coolride air springs with individual lines and double adjustable shocks, its done.
Nothing fancy, if you want to do more for it set it up with parallel 4 link and a Fays 2 Watts link and its good and simple.
I put Cool Ride in back of my 71 Monte and some Poly bushings and and simple Sensatrac shocks and the handling was off the chart, then later on it got my Southside MAchine lift bars and older 64-67 12 bolt, then it got fun, I also had boxed my control arms before and the difference was down right awesome.

[nvmyss]

That price is high for the frame mods.
I have to agree with the tire size. I'm running 315/35- 17 on a 11" rim. It did take some triming of the wheelwell but it fits.

[BMR Tech]

I have a 315/20 (20" x 10" wheel) under my 70 Chevelle with no frame mods whatsoever. It's lowered 3" in the rear and all I had to do was order the correct offset wheel and trim the outer fender lips. It is definitely tight and anything wider will require frame and fenderwell alterations. I love the look of a 335 tucked under the car but for an extra 20mm of tread, it's hard to justify the expense. If you have to get 335's under it I have seen plenty of drag guys notch the frame and plate it. Both of these options would be much more economical than a back half and would allow you to keep the OE geometry so you could use stronger aftermarket control arms instead of a universal street rod or drag oriented 4 link kit....