1970 Pontiac Grand Prix, too HEAVY?

[silvermonte]

In my local SCCA autox group there is a kid that just graduated high school and he runs a fairly stock 70 monte carlo. He does decent but mainly he has tons of fun and people are always asking him questions about it.

[Later-A-body]

Well as an owner of a big Pontiac that still weighs 3960 with an LS7, don't let that stop you. You don't have to go completely overboard spending money to upgrade your car to have a ton of fun. Smart investments in good quality suspension such as Global West, adjustable shocks, 17" or 18" wheels and a 200 treadwear tire will get you pretty far. You already have either a 400 or 455 in the GP so that's handled. Spend wisely and go have fun.

[Peanut1959]

Love those GAs and GPs!

[MonzaRacer]

So a Chevelle runs 3600ish pounds and your worried about 400lbs?
GTFOI Get The F Over It!
Ihave had two first gen Monte Carlos, want another and right now have a 4dr 66 Caprice,
With todays performance innovations who cares just add anther 50 hp shot or couple pounds of boost.
Honestly build a nice solid fat torque curve Pontiac, gear accordingly and adapt a decent od trans or gear vendors and dont forget Bret Voekels from ridetech, his wife has a 67 Bonneville and I saw it run through the cones at least once or twice.

[TanMan]

Thanks again for everyone’s feedback! I’m new to this, as in, I haven’t even gotten started. Trying to understand the pro touring big picture before I simply start ordering parts. I’ve had my ‘70 GP for 25 years and it turns 50 next year, so there’s a bit of a timing goal. We used to race these models at Nashville Motor Raceway but I think road course driving could be even more fun (and maybe break less?).

Also, glad to hear a bunch of you are running some heavy steel around the track- and even a big ole Pontiac or two, awesome!

[TanMan]

Trying to preserve (to some extent) the classic beauty of a GP with Rallye II wheels while at the same time understanding the need for massive brakes.

I found a 17” aluminum Rallye II look-alike but I can only fit 12.19” rotors which is not ideal. Should I bite the bullet and switch to more modern looking 18” wheels in order to squeeze in 12.88” (or bigger) rotors? Not forgetting 4,000 lbs won’t slow down without putting up a fight.

[68Formula]

Here's some affordable cast 18s like the Rallye IIs. http://us-mags.com/bandit-u109-w-3303.htm Not sure if they're ideal backspace for your vehicle, and the width has limited choices. A few people on here have them if you search for USMAGs Bandits. Here's an example from the manufacture's site:


They also have a couple 2 piece forged and machined which are available in custom backspacing with more width options, and I believe lighter. But much more expensive (since it's not cast)
These are similar looking to the 109s
http://us-mags.com/bandit-u304-w-1318.htm

And these are closer to the original Rallye II design than the Bandits
http://us-mags.com/trans-am-u722-w-5713.htmAttachment 166937

[TanMan]

Wow, in my everlasting quest for wheel options, I had found exactly those. The US-MAG Bandits are some of my favorites so far, if I indeed need to go 18”.

On the other hand- since they really aren’t Rallye II’s, I may need to dive all of the way in and go for an entirely different look.

The ‘70 GP is a long, distinguished, chromed-out kind of classic as opposed to a sporty, aggressive muscle car. So maybe a multi-spoke, less-chrome-approach could work as well. I just can’t quite imagine how that would play out on this vehicle.

Any wheel-tire visualizers out there that have worked for anyone?

[TanMan]

68Formula, damn those Trans Am U722 wheels are killer, but damn, $3,400 for a set!!

[68Formula]

Wow, in my everlasting quest for wheel options, I had found exactly those. The US-MAG Bandits are some of my favorites so far, if I indeed need to go 18”.

On the other hand- since they really aren’t Rallye II’s, I may need to dive all of the way in and go for an entirely different look.

The ‘70 GP is a long, distinguished, chromed-out kind of classic as opposed to a sporty, aggressive muscle car. So maybe a multi-spoke, less-chrome-approach could work as well. I just can’t quite imagine how that would play out on this vehicle.

Any wheel-tire visualizers out there that have worked for anyone?

They are not chrome, just polished. They don't look quite as reflective in person. If you wanted, you could even brush them to dull it a little.

I think that's what was done on this one:

[cdrod]

I have the U109 Bandits on my 442 convertible project. I didn’t like the flat centers that came on the rims, so I modified the stock retainers to mount the factory Olds SSI center caps.

[TanMan]

Awesome, I was immediately drawn to the center caps, very nice touch. I have a friend who did a phenomenal, frame-off restomod on a ‘70 442 and it is absolutely gorgeous.

Did you go 18x8 front, 18x9 rear? I’m wondering if I can squeeze 9” in the front without potential issues.

BTW, I fully intend on putting original style PMD center caps on there;)

[68Formula]

Hard to say as there isn't a lot of information on backspace versus width for you vehicle. But if it'll fit on the rear, you can buy 2 and test fit on the front before you buy the other 2.

I'm thinking it'll work, and would look pretty sweet, not to mention perform better. On A-bodies there's some decent room. A lot of people stick with 8s, but the 9s have 8mm more offset, effectively pushing the tire more towards frame, and away from the outside fender lip (improving clearance to the fender lip).

The 9s would perform better with a 245 or 255 tire, than 8s. Here's some information from another thread on this site, about advantages to going to the wider side of the rim width for a given tire (especially on the front) in terms of performance.
https://www.pro-touring.com/threads/...size-questions
If you do a general web search you'll find similar information on other various competitive boards.

[Interceptor5588]

Do what you can for weight -- aluminum intake, water pump, & rad, headers & maybe a smaller modern ac compressor. Suspension mods as discussed. Biggest brakes and tires you can afford. Don/t worry about the rest.

[OLDFLM]

http://us-mags.com/bandit-u109-g-20509.htm

235/40R18 | 265/40R18

http://us-mags.com/bandit-u109-g-16592.htm

235/50R18 | 295/45R18

And it looks like Hotchkis at least makes rear arms and sway bars for your GP...

These should give you some more ideas:

After a quick search on here, I'd contact UMI!

https://www.pro-touring.com/threads/...-Touring-Build

Other big Pontiacs with the wheels you like:

https://www.vanguardmotorsales.com/i...-prix-restomod

https://www.pro-touring.com/threads/...972-grand-prix

And since yours is black: https://www.youtube.com/watch?v=C9gAI0nDJRo

http://fastmusclecar.com/best-muscle...d-prix-type-j/

[TanMan]

Man, you guys are a wealth of information. Much appreciated.

[c4racer2]

That car is simply bad ass

[cdrod]

Awesome, I was immediately drawn to the center caps, very nice touch. I have a friend who did a phenomenal, frame-off restomod on a ‘70 442 and it is absolutely gorgeous.

Did you go 18x8 front, 18x9 rear? I’m wondering if I can squeeze 9” in the front without potential issues.

BTW, I fully intend on putting original style PMD center caps on there;)

TanMan:

I've seen a few cars with the PMD center caps installed on the Bandit rims; they look really nice, I think even better than the Olds caps. The Olds caps are taller, the PMD caps are more flat. I'm running 245|45 tires on 18x8 on the front & 285|40 tires on 18x9 on the rear. I don't think the 9" wide cast U-109 Bandits will fit on the front of an A-body, the offset will push the tire 5/16" farther out into the fender. The forged version U-304 can be ordered with custom offsets, but they are considerably more expensive than the cast U-109s

[68Formula]

From the post by OLDFLM, this guy is running 9s in the front: https://www.pro-touring.com/threads/...972-grand-prix

I saw a same vintage Monte Carlo this weekend with 255 fronts. Don't forget, switching from discs to drums pushes the wheels out around .25", so make sure you have your brakes mounted before you measure. Worst case, if the 9" U109s were too deep (which I highly doubt), you could stay with a 245 and use a 1/4" to 5/16" spacer.

Remember to take all your wheel/tire measurements with the correct brakes and suspension components you intend to use. And then it doesn't hurt to take them again once the wheels are in, before you mount tires.

[TanMan]

Interesting that you mention spacers. Are those a bit unsafe, or can they be done properly? I would guess longer, stronger studs would be a must.