What is the theoretical top speed of an 05 SS with stock diameter tires? Looking around google you get answers from 143-207mph. I know one of yous can tell me definitively.

 

From the factory, the stock limit on most L67 cars is 126 via electronic limiter. Beyond that gets a bit mushy as often if someone is flashing the pcm to remove the limiter, they're generally also modifying it for power, sometimes raising the rev limiter (which impacts top speed).

For someone just disabling the speed limiter and doing nothing else, top speed is in the range of 145-155 depending on final drive ratio. Essentially the physical limit is the top of 3rd. The engine doesn't make enough power to pull in 4th (I actually don't think the stock pcm will even command a shift at WOT) and the stock 4th parts aren't strong enough to hold WOT.


Not sure what places are saying 207, but that's nonsense for a stock L67. Maybe thats numerically the limit at the top of 4th at max engine rpm, but you'd never see that in the real world with air resistance. As a point of reference, there was a Bonneville back in the early 00s with a 3800 / 4t65 set up for top speed runs that managed to just barely break 200. But it also had custom gearing / custom transmission and made "over 600 hp" with a Kenne Bell twin screw blower on it.

 

Ok good info. I was talking about if there was no drag and enough power to make it to the top of 4th.

Funny, the Bonneville youre talking about is where that 207 number came from.

I guess I worded the question confusingly by asking what the "stock" top speed it. Either way, thats the info I was looking for.

 

Oh yeah, I'm not sure about that. They've got gear / speed ratio calculators online that you can plug the info into (max engine rpm, FDR, tire height, gear ratio) and it spits out a speed that could come up with that pretty quickly. There's a decent span of FDRs even stock across the various 3800 vehicles, but Id suspect they're all around 200ish at the engine limit.

The hard part with talking about modified stuff is there are several changes that would likely happen at the same time. IE if someone is pulling the transmission apart to build up 4th gear to handle power, they're likely making enough power to upgrade the drive chain (which can be had in different sprocket ratios that impact FDR). Theres also options for swapping differentials which also has an impact on FDR.

Notwithstanding that, max engine rpm has an equally big impact. If the engine is modified enough to make 4th gear pulls, it'll almost certainly have the max rpm upped. For example, a 6k rpm engine limit (where it would normally shift up in a lower gear) with one FDR combo mechanically tops out at 210. Simply bumping engine redline to 7500 (not crazy for a big 3800 build with a big cam) pushes that up to a hair over 260.

I could be wrong, but Im almost positive he had a custom FDR (2.5x?). That build was before 3800 modding really took off so a lot of his stuff was one off. No clue what other custom parts (custom gear ratios?) he may have had as I never saw a deep dive into the build. But I'm sure he wasn't banging it off the limiter to get there.