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Old 07-10-2020, 12:59 AM
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Default 10 bolt and slicks

Im planning on running my 67 GTO at the local dragstrip in a few weeks. My buddy cant make it but offered to drop his wheels and slicks/skinnies for me to use. Assuming they fit, how much power can a factory 10 bolt modestly handle? Mine has about 5k miles on it with 3.36 gears and an Eaton limited slip. I dont know how much power the engine combo in my signature makes but it feels plenty strong enough to break parts if I start pushing it hard.

The slicks are 275/60/15 on 15x8.5 wheels. Theyre off his 70 El Camino so maybe they'll fit but I dont know the backspacing offhand. I don't intend on launching hard, just would like to limit wheelspin since my street tires are getting to the end of their life.

I'm going out there with a handful of friends to do a little racing but have no intentions of pushing my car to the point of breaking; just to have some fun.

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Old 07-10-2020, 05:42 AM
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In terms of maybe a track outing day of 4 to 6 passes with dropping the clutch I would be more concerned with my U joints or the driveshaft failing since you don't have a safety loop!

If the front joint lets go or the driveshaft snaps your in very deep pooju real fast!!

HP wise your making between 500 and 520 with your set up and You will be finding out real fast how good your fuel system is in feeding volume to the Carbs.

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Last edited by steve25; 07-10-2020 at 05:48 AM.
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Old 07-10-2020, 06:17 AM
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should be ok.. but make sure your u joints are fairly new. a driveline loop is a must too. On my firebird last year i had one of my axle tubes move on me causing my driveline to snap at mid track, but the loop caught the driveline for me. so on the new rear end i have the shop weld the tubes to the center carrier.

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Old 07-10-2020, 07:13 AM
sdbob sdbob is offline
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Weld perches also. You may be ok as is but why take that 1 chance and rear break s lose. I remember back in 60s friends didnt reweld rears nobody I knew broke one. Tires seem stickier today though.

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Old 07-10-2020, 08:17 AM
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If you are worried about parts breakage, maybe just run on the street tires. Especially with no safety loop and a manual. Look for a MPH number on the big end rather than the ET.


I agree with the above that you are likely to find out if your fuel system is sufficient. Especially if you do bolt on the slicks. Ask me how I know.

I would run with the better part of a full tank so you don't uncover the pickup on acceleration.

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Old 07-10-2020, 09:47 AM
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An 8.2 10 bolt? With a 2.64 ST-10? With a sticky tire? Eeeek.

With a 3.36 gear, and even the 2.64 first gear, it's only an 8.87 effective ratio. On top of that using a 28" tall sticky tire effectively killing some of the gear. It's going to be bog city unless you get aggressive and come out at a pretty high rpm and let it fly.

Personally I wouldn't do that with that setup. I'd be coming out easy to save parts, and just deal with the lousy 60 foot time, run it on down track and have some fun. 2.64 ST-10 aren't known for their strength. I'm not sure which I'd worry about first, the trans or the rear. I'd be more inclined to just run the car on regular street tires.

Buddy of mine ran the 2.64 ST-10 in his 69 Nova with a 427 and 4.56 gears. Not a torquey engine, but at the track with stickies, and 3,000 rpm launches, he lunched the ST-10, not once, but twice. Pop the clutch and rolled about 10 feet LOL. Went to a Nash 5 speed after the second time.

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Old 07-10-2020, 09:49 AM
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Quote:
Originally Posted by RocktimusPryme View Post
If you are worried about parts breakage, maybe just run on the street tires. Especially with no safety loop and a manual. Look for a MPH number on the big end rather than the ET.

^^^^^ This

Beat me to it. I'd just go out and have some fun with the car. MPH is more telling than ET in most cases on a street car anyway, as most don't have the suspension/converter etc... to use the power on the starting line effectively

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Old 07-10-2020, 09:54 AM
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NHRA rules require using a loop when running slicks.

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Old 07-10-2020, 10:30 AM
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The way I see it, with the power you are making, if you get down the track without running out of fuel (questionable) You aren't going to embarrass yourself and run like a 15 second ET. Even on the street tires, worse case you probably run a high 13? But at MPH that will show you can way exceed that in the future. Like you said, you are just going out to have fun. Its not worth the risk of picking up parts off the track. I mean, that's always a risk, but you can mitigate it somewhat. Traction is mostly what breaks things.

Also, I wouldn't call this sound racing strategy, but you know what's really fun. Driving around somebody when they got out in front of you off the line. Its a powerful feeling to be reeling someone in when there is absolutely nothing they can do about it lol.

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Last edited by RocktimusPryme; 07-10-2020 at 10:47 AM.
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Old 07-10-2020, 11:40 AM
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I've got a '67 Lemans with TH350. Same rear as yours, but 3.23s and a powertrax locker. My 400 making about 360 HP twisted the stock pass side axle on street tires. After about 4 passes I noticed the rear end was making noise. Likely the powertrax made the situation worse, but I dumped that whole setup for a Ford 9. I agree on running the street tires, better to spin the tires than dead hook on slicks and break stuff. IF you think you can walk it out on the slicks, you can try it, but it'd be hard on the clutch disc. The tracks I used to go to never checked anything. I was running ET streets and nobody ever looked under the car.

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Last edited by chiphead; 07-10-2020 at 11:55 AM.
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Old 07-10-2020, 12:04 PM
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Quote:
Originally Posted by RocktimusPryme View Post
Also, I wouldn't call this sound racing strategy, but you know what's really fun. Driving around somebody when they got out in front of you off the line. Its a powerful feeling to be reeling someone in when there is absolutely nothing they can do about it lol.
https://youtu.be/YYoXURd5rM0

https://youtu.be/XqEydRRRwqE


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Old 07-10-2020, 02:48 PM
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You have a stick ! If you try to leave hard you will definitely break something. I strongly encourage you at a minimum(!) a driveshaft loop.

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Old 07-10-2020, 02:57 PM
Chief of the 60's Chief of the 60's is offline
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Slicks, a 10 bolt and a stick? Should be interesting to see what lets go first.

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Old 07-10-2020, 04:01 PM
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Driving these cars with 4 speeds, 8.2 rear ends, and slicks/no slicks for over 40 years, I side with the guys who are telling you to run street tires and feather it out of the hole. If you want to not break parts. BTDT, and that was when junkyard posi 8.2's were $75 and Muncie's were the same. Last time I grenaded an 8.2 (1990) it cost almost $950 to repair it. Have fun, but no need to kill your car.

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Old 07-10-2020, 04:41 PM
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We didnt have a 4 speed. But a TH350 with a 3500 converter. 10 bolt and 10" slicks in a 68 firebird convertible. Only ran 12 flat at 111. But never hurt the 10 bolt.

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Old 07-10-2020, 05:23 PM
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Think it will be a moot point since backspacing on Firebird/Camaro is much less than what's needed on our GTO's. Think backspacing on our '68 Firebird was only 3-3/4" and that was pretty near the leaf spring. As said above, if the track is paying attention they won't let you run without a loop when running slicks.

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Old 07-10-2020, 08:11 PM
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Lots of reasons why 10 bolt rear axles di not live on the drag strip with a manual transmission. I blew up 3 of them in the 1st 5 years I owned the car but 10 bolt rears were cheap in the late 60s. Two of the three rear axle failures was from breaking the LEFT
CAP (that holds the differential in the rear axle). All of these failures were with a manual trans and slicks.

Lots of very good advice above.

Tom V.

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Old 07-12-2020, 10:33 PM
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A lot of great info here! I will answer a few questions:
- I do have a driveshaft safety loop installed.
- U joints have about 5k miles on them
- fuel system is a walbro 255 in-tank electric pump, 6-an feed line, regulator and 8-an return.

I'm doubting the wheels will fit my car anyways but figured if ask. Im sure my 60-ft times will be horrendous as i have no desire to launch the car hard and break anything. My goal is to drive it there and drive it home. My plan is an aftermarket 12bolt or 9" in the future, jist not in the budget now.

I really dont know what to expect out of the car but i would like to see mid 12s, even with an expected poor 60'.

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Last edited by 67gtospud; 07-12-2020 at 11:02 PM.
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Old 07-13-2020, 01:23 AM
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I say let em hang, and make a few passes.

It'll probably hold up for the day.

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Old 07-13-2020, 08:50 AM
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Right before covid struck I brought my car the track. Street tires and a stick. My drive shaft is 3.5" in diameter, 1350 U joints and a 10 bolt(3.42). 2nd pass snapped an axle like a twig. Put the car on the trailer. I was kinda glad in a way because I had 12 bolt laying around for 30+ years and this gave me a reason to put it in. So, for the 12 bolt, I bought Strange axles, ring and pinion (3.73), I studded the caps with ARP studs, a Strange forged yoke, ARP wheel studs and a girdle. I go back to the track and this time on the second run, which was about the time track started getting really sticky, I broke the spider gears which happened to take out my new R&P. With all that being said, the next time I go to the track I will be rolling out. I tried to get hardened spider gears but nobody seems to have them in stock right now and no production in the foreseeable future.

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