160 MPH in the 78 Grand Am

[gto78]

My Grand Am has a cammed 400, #670 GTO heads, headers, etc. Normally we 1/4 mile race it locally and run mid 12's. I had blown the rear end and temporarily stuck in the easiest thing I could find in the junkyard- a horrible 2.29:1 rear end. That totally took all the fun out of having a quick car with a big block...or did it? I hadn't driven it in months, then took it out for a punch ride to bring a friend home. Part of the trip is on an extremely long deserted road with noone around for miles.

I had decided to show him how 1rst gear goes to almost 75 mph when winding the engine to 5800 rpm, then decided to go for second since it still had gobbs of power, 2nd winds to around 130 mph, then 3rd. Then since it was clearly accelerating with no problem I let it keep winding up. Before I realized it the telephone poles turned into what looked like a picket fence and I decided that was enough when we just about hit 160 mph.

The car handled amazingly smooth. I held my lane without it feeling loose, very good road feel. The only problem was that at 150 mph the drivers window popped out about 1/2 inch at the very top where the rubber tab at the top usually holds it in position. Sometimes the window does that and you have to open it a little and then close it. That freaked me out a little bit at that speed, nothing else happened though.

Now that I've done it... probably never do it again. Well... actually did it one other time in the 350Z but the governor shut me down at 159, ok now never again Lol.

 

[Coveted]

which speedo gear is in the transmission? if its not the proper one for 2.29s and your tire size, your speedo was off, probabaly by alot.

 

[drogg1]

But off in the other direction though lol. Going from 3.73's to 2.29's would make it read low not high.

 

[pontiacgp]

what upgrades have you done to your suspension?...G bodies are known to get loose at high speeds with the air getting rammed underneath the car and lifting it

 

[shotgun]

First and most important, no self respecting Pontiac guy will refer to any PONTIAC engine a big block.

I agree with the others about your MPH being off.

Like pontiacgp said at those speeds you will be floating all over unless you have done some front end air management and suspension work.

 

[dogsht]

Both my Regal & my Cutlass got floaty around 140/145 and they both had factory front lower air dams as well as decent shocks the stiffer GN/442 springs and new poly end links. Although with especially a better front lower air dam and or lowering the car stability at 160 is certainly attainable. I am not negating your claim just saying in general and from my experience. Fun stuff to hear people talk about as you don't get to hear it talked about often as most of us don't have the power or road to test it out.

 

[Bonnewagon]

400 + 2:29 = top end unlimited. You're lucky you have a place to do that.

 

[RITTER]

Nice run man

I was in a '98 WS6 and we went like 155 and that was definitely scary, fun but scary aswell

 

[pontiacgp]

a friend of mine regularly drives his truck over 180 mph.......



in the Nascar camping world series... 8)

 

[megaladon6]

what rear was in the car? (or rather what speedo gear do you have?)