[b-man]

Originally Posted by DaleO

I'm not set on a 12 bolt. My only issue with it is when somebody would notice it they would then really expect me to be able to perform and I'm just not there. Not worthy. I really want to see what I an do and need drag radials to do that and am pretty sure I'd break the 10 bolt pretty quickly. Besides, I want a little steeper gears.

Thank you for your input. I've been looking at the Quick Performance site. The thing I need to study next is brake size, I have drums and they list 11" drums which I am not sure will fit 15 inch wheels. I suspect so because I think 11" drums were on the station wagons which likely had 15 inch wheels. The other issue I might have is with having larger brakes on the rear as I still have 9 1/2" drums up front. I think that is the size Pontiac used.

I’d opt for the 11” Ford drum brakes if you decide to the pull the trigger on a 9” rear, as I see it you’re overdue for a front brake upgrade. I ran the 11” rear drums on my ‘64 GTO bracket car equipped with a 9” and ‘69 GP spindles/11” discs up front, no problem with fitting those 11” drums inside a 15” wheel.

I was bracket racing launching off of a transbrake with slicks and it was nice to have a strong 9” under the car, however it wasn’t really a high strength unit and only had a stock cast iron housing, a Detroit Locker and shortened/resplined stock 31-spline axles. This was an old 1987 vintage Currie 9” that came in the car when I bought the car in 1989, built off of a salvage yard housing like most back in those days. It wasn’t that uncommon for my competitors to break their stock 12-bolts on the starting line which made me like the 9” even more.

For my street only ‘64 Tempest with the 430 hp LS3/4L70E I decided on the ‘71-‘72 Buick/Olds GM corporate 8.5” 10-bolt. My reasoning at the time was because those units are equipped with bolt in axles and tapered roller axle bearings to better handle cornering loads. Also the lower friction 8.5” gears as well as the lighter axle housing, for better suspension control since the axle housing is unsprung weight. I’m running fairly heavy 13.4” C6 Corvette rear disc brakes (and corresponding 14” front discs) so I thought compensating for that with a lighter rear axle assembly might be a good idea.

Maybe I’d have been better off with a new aftermarket 12-bolt but what’s done is done. I did upgrade the 8.5 with an Eaton posi and 30-spline Moser axles so I’m sure it’ll handle whatever I’m doing during spirited street driving and occasional canyon carving.

[DaleO]

Originally Posted by b-man

as I see it you’re overdue for a front brake upgrade. I ran the 11” rear drums on my ‘64 GTO bracket car equipped with a 9” and ‘69 GP spindles/11” discs up front, no problem with fitting those 11” drums inside a 15” wheel.

Thanks b-man.

Without a doubt, it is embarrassing actually. At least I don't drive like an idiot : ) tailgating speeding around town and such and very cognizant of what is going on out front and to the sides. But I totally agree. In fact I have the A arms, spindles, tubing, prop valve, master cylinder and booster out of the 1969 GP I took the 428 out of. But then this brings up what HO did way back when with the 1964 GTO, Kern's I think, where they used I think A arms from a 73-77 or so A body with which the improved geometry made a handling improvement. For all these parts including a 8.5 I could part out my 1974 LeMans! Ugh, that would make me sick.

Did you happen to run your car for a short time with smaller front drums?

[b-man]

Originally Posted by DaleO

Thanks b-man.

Without a doubt, it is embarrassing actually. At least I don't drive like an idiot : ) tailgating speeding around town and such and very cognizant of what is going on out front and to the sides. But I totally agree. In fact I have the A arms, spindles, tubing, prop valve, master cylinder and booster out of the 1969 GP I took the 428 out of. But then this brings up what HO did way back when with the 1964 GTO, Kern's I think, where they used I think A arms from a 73-77 or so A body with which the improved geometry made a handling improvement. For all these parts including a 8.5 I could part out my 1974 LeMans! Ugh, that would make me sick.

Did you happen to run your car for a short time with smaller front drums?

Never had drums in the front, when I got the car it had the H-O Racing tall spindle setup using 1975 Firebird spindles and 11” discs. I switched back to stock height spindles (GP) to drop a little weight but mainly because of the crazy toe-in when the car was launched off the starting line. That H-O tall spindle setup was known for bump steer, and after I saw a picture of the car with the wheels pointed in I made the change.

The only special item needed for the tall spindle conversion was a matching lower ball joint that had the diameter turned down so it would press into your lower A-arm and the correct outer tie rod ends that matched the spindles. The original setup used offset upper shafts and a pretty big stack of alignment shims, later the aftermarket came up with tubular upper arms that corrected this.

Do yourself a favor and get those GP spindles and discs installed.

Being able to stop for the idiots you will encounter out on the road is very important.