Taking the plunge: LS3 into '64 Tempest. Need help with shopping list. by b-man

5 minute(s) of a 224 minute read

Budget?

What's that?

I have decided to replace the '66 3.36 posi 8.2" 10-bolt Pontiac A-body narrow rear end with a much stronger '71 -'72 3.42 posi 8.5" Olds/Buick A-body (tapered bearing bolt-in axle) wide rear end. The strength of the GM corporate 8.5" rear rivals that of the Chevy 12-bolt, as an added plus the tapered bearing 28-spline bolt-in axles are best for hard cornering and overall durability.

I had been hesitating to replace the early narrow 8.2" rear end with a later wide 8.5" rear end (1" wider overall, 1/2" per side) mainly because of the way my steel 17X8s were built, they won't fit in the rear with 4-1/2" of backspace and a wide rear end. Now that I have decided to go for a set of 18X9" wheels all around I can buy new wheels that will fit with a wider rear axle.

The 17X8" steelies and dog dish caps will soon find a new home on my '64 Lemans convertible.

After doing some measuring I see that I will have 7.25" from the wheel mounting surface on the rear drum to the frame rail/inner fender and 4.50" to the outer fender inner body panel, for a total of 11.75" of room from side to side for a wheel/tire assembly.

A 9" wide rim is 10" in overall width, once you add the width of the outer wheel lips to the width of the 9" bead width of the rim. With the rim perfectly centered from side to side (looking from the rear) in the wheelwell, ideally I should have .875" of body/frame clearance on both sides of it (11.75" - 10" = 1.750", divided by 2 = .875").

After doing some internet research I have found a 18X9" wheel spec'd for a 2008 BMW Z4, the 5 on 120 mm bolt pattern is plenty close enough to the GM 5 on 4.75 to work (120.65 mm). I'm not first guy to use the 120mm bolt circle BMW wheels on a GM car.

I need a 9" wheel with close to 6.5" of backspace to center the wheel from side to side, the wheels I found have a 40mm offset which is the same as 6.57" of backspace. A tad toward the inside, but still very good.

After I upgrade to rear disc brakes on the car the rear wheel will move outward by about .125", moving the wheel pretty close to the exact amount I want to center it even better. I should end up with something like .805" between the inner wheel lip and the frame/inner fender panel, pretty close to perfect.

I can use this same wheel up front with a 1.25" thick billet aluminum wheel adapter, I have room to go inward by about 1" but almost no room to go outward. Using the 1.25" adapter effectively changes the 6.57" wheel backspacing to 5.32", moving the outer face of the front wheel lip outward by about .180" (less than 3/16") from where it is right now with the current 17X8" 4.5" backspace wheels.

I will run the same size tires front and rear, 245/40-18, 25.7" tall. This size tire will have very close to a 10" section width (sidewall to sidewall) mounted on a 9" rim, it is spec'd at 9.8" when mounted on an 8.5" wide rim.

I can rotate the tires from front to back by running the same size front and rear, plus I happen to like that look. There's still plenty of room to go up in size to a 275/40-18 that's 26.6" tall in the rear later on too if I change my mind.

My wheel choice, 18X9" O.Z Racing Ultraleggera, black painted of course.;)

40 mm offset/6.57" backspace, weighing only 20.8 pounds.







Spent some time today while it is still unseasonably warm out to get wet and dirty cleaning up the front suspension and engine compartment a bit. The front end cleaned up pretty nice.

The frame from the firewall forward, front suspension and inner wheelwells are coated with semi-gloss black POR-15. Note the junkyard 12" B-body rotors that have been redrilled from the 5 on 5" GM big car pattern to the 5 on 4.75" GM intermediate pattern.





Moving forward.