How fast will these things go, anyway?

[Oberon67]

The subject line says it. What's the fastest you've gone in a square body, either in acceleration or top speed?
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[flashed]

Mine is a 74 short step with 3 on the tree and a 250 /6 cylinder so not very fast .

[Oberon67]

Originally Posted by flashed

Mine is a 74 short step with 3 on the tree and a 250 /6 cylinder so not very fast .

I have the same drivetrain in an '81 long bed. A grocery-getter for sure, but I think I could bury the 85mph speedometer if I wanted to.

I haven't tried it. The reward doesn't seem worth the risk to me.
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[TwoFiftyShifter]

100 in my 87 V20. 4 speed 350. It wouldnt pull anymore after that;

[KQQL IT]

1/4 mile

[Oberon67]

Originally Posted by KQQL IT

1/4 mile

Wow... Not too shabby!
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[Malo83]

Originally Posted by Oberon67

Wow... Not too shabby!
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That's nothing, I can do that coming down the grapevine from LA to Bakersfield

[KQQL IT]

Originally Posted by Malo83

That's nothing, I can do that coming down the grapevine from LA to Bakersfield

Malo83 I have that double hump transmission crossmember, free to a good home.

[Malo83]

Originally Posted by KQQL IT

Malo83 I have that double hump transmission crossmember, free to a good home.

PM sent.

[Jake Wade]

Originally Posted by KQQL IT

1/4 mile

That's impressive for a Small block truck if NA

[KQQL IT]

Originally Posted by Jake Wade

That's impressive for a Small block truck if NA

Yeah, for now.
Just rebuilt it with better rods and opened up ring gaps.
Try a hundred shot out of the hole is the plan.

[chrismoore701]

I had my speedo pointed straight down. Put two quarts of oil back in after that run

[esbstuff]

Originally Posted by Oberon67

The subject line says it. What's the fastest you've gone in a square body, either in acceleration or top speed?
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1990 or so... 78 k10, 350, 4-speed, 205, 3.07's. I had the speedo pointed straight down and bouncing one night. 3 wide on a 2 lane interstate with a couple buddies. I think the story was the last one at the party had to buy beer... I didn't have to buy! Too afraid I would go splat now.

[D13]

1982 250 3ott 3.43 geared 3/4 ton, 80 is absolute limit.
1987 6.2 diesel 7004 3.08 geared 1/2 ton, fastest is 75, truck felt rock solid, issue was the noises under the hood.
I would suspect with a reasonable motor and OD trans with good gears that 120 would easily be possible. I read somewhere (Jim Feuling in CC in the 90's maybe?)that if the tailgate is open over 120 or so the vacuum bubble will close it - so I sure wouldn't want to try higher speed corners without some rear down force.

[phillip123hastings]

So not really fast whatsoever.

[KQQL IT]

Originally Posted by phillip123hastings

So not really fast whatsoever.

3.08's @ 5500 with a 27" tire was way way faster that they should ever go on a S rated tire.
Thought the driveshaft was coming thru the floor when I lifted off the gas.

[Matt Man]

I had mine at about 90mph to test out driveshaft vibration when I had it rebuilt and shortened. Felt stable, but the wind noise was awful. I tried to push it farther as well but wouldn't go any faster. Oh well its a 81 4x4 pickup, not meant for speed haha.

[foamypirate]

Calculator says I should have been doing about 112 based on RPM (about 4200) in my 305/TH350/3.08/29" tire 84' LWB, but I have no idea how much converter slip was going on. Pedal was on the floor for several miles (sick baby in a truck with no AC in 97* temps, was trying to get home to get her cooled down ASAP). Wide open toll road, thankfully. Realistically, probably closer to 95mph based on how quickly I was passing people.

In my 88' R20 crewcab, max I've been is 90mph, testing acceleration with the LQ9/4L80E/4.10 combo. Speed limiter is 98mph, and the driveshaft is only good until roughly 115mph anway. I feel no need to take this one any faster than 90mph.

[Oberon67]

Originally Posted by Matt Man

I had mine at about 90mph to test out driveshaft vibration when I had it rebuilt and shortened. Felt stable, but the wind noise was awful. I tried to push it farther as well but wouldn't go any faster. Oh well its a 81 4x4 pickup, not meant for speed haha.

I'm thinking someone... Not me, someone who can build... should put together a square-body for Bonneville.

The World's Fastest Squarebody.
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[mongocanfly]

There's already a square body salt truck...210mph.http://67-72chevytrucks.com/vboard/s...d.php?t=473510

[Alex V.]

Fastest I've had my '85 C3500 (454/TH400, 4.10's) is 85, but it wasn't done yet. 90 wouldn't be too hard, and I think it'd break 100 but everything under there is spinning so fast at that speed I'd rather preserve the truck than take the chance.

[mongocanfly]

My 81 c30 with 6.0, nv4500 and 4.10s will hit a 100 before you know it..when they had it on the dyno they had it showing 140..

[foamypirate]

Originally Posted by mongocanfly

My 81 c30 with 6.0, nv4500 and 4.10s will hit a 100 before you know it..when they had it on the dyno they had it showing 140..

I hear ya! I hit that 90mph number awfully quick with the LQ9! I finally got a license for HPTuners, so I'll be bumping the limiter up to just under my max driveshaft speed so I can see how she does.

[mr.chevyblack]

came across montana with the cruise set at 115mph. on the dyno rwmph was 137mph it would do it but a lifted suburban has no business doing that on the highway lol

[MikeB]

Originally Posted by foamypirate

I'll be bumping the limiter up to just under my max driveshaft speed so I can see how she does.

Max driveshaft speed is something that I wouldn't have thought about. How did you determine it?

Recently had my truck's stock driveshaft straightened and balanced, but I have no idea how many RPM it's good for.