Over the past few weeks, it seems that my Z28 hasn't had as much power as usual. I had it dyno tested and the results were 288 hp and 317 lbs of torque. The hp rating seemed a little low to me considering the performance modifications on the car, which consists of Pacesetter mid length headers, Borla cat back with cutoffs, K&N cold air intake, electric water pump, cam upgrade, and a suspension kit.

I took it to a local mechanic to see if there might be anything noticeable causing power loss, he said the numbers from my dyno seemed pretty normal and that my loss of power is likely just the heat and humidity that we have had lately (I live in Texas).

I can see that, and I know that motors tend to lose horsepower with age, but from what I found on the internet, LT1 Camaros push about 275 hp stock. If that is so, then all of my performance modifications are giving me about 13 hp extra. I just wanted to get a second opinion on this to see if this sounds normal. My car has about 100,000 miles on rebuilt LT1.

 

The stock ratings are at the flywheel. Unless you pulled the engine and they put it on an engine dyno, yours were measured on a chassis dyno, and are rear wheel HP numbers, which reflect drivetrain losses and will be lower than flywheel HP.

Which type on dyno was used? If chassis dyno, what transmission do you have? The would allow an estimate of drivetrain losses.

Also, your dyno sheet should show that the results were corrected to a "standard", either SAE or STD, eliminating the effects of the temperature, humidity and barometric pressure.

 

What Fred said and also do you have a build sheet? What compression was it rebuilt to, what cam and springs do you have, full roller rockers? I've seen a local builder do performance LT1's to 9ish to 1 with a huge cam and that cars run like crap.

 

288 rwhp is not bad until I saw you had a cam upgrade. 288 rwhp is around 340-350 at the flywheel.

I make 309 rwhp with my mods listed in my sig.

Has the car been tuned ? What cam upgrade do you have?

 

Sorry guys, I have been checking my email for notifications to any responses to this thread and I haven't received any emails, so I didn't think anyone had responded yet.

@Injuneer - It was a chassis dyno and I have a 6 speed t-56. I will have to look at the spec sheet to see if SAE or STD.

@Bersaglieri - I wish I had a build sheet, but I do not. The LT1 was rebuilt and cammed by the previous owner and he didn't provide me with a build sheet, so I am not sure exactly what cam is in it.

@Matts97camaro - Like I mentioned above, the previous owner had the LT1 rebuilt and he didn't supply me with a build sheet, so I am not sure exactly what cam is in it. As far as the tune, I haven't tuned it and I'm not sure if the previous owner did either. I have been considering getting a programmer tuner, but after some research on this forum, it seems like the best option is to send my computer in for a mail order tune, which I will be doing soon.

Thanks for the replies guys. Again, I apologize that it took me a few days to realize that I had replies to my thread.

 

I checked the spec sheet and it was SAE.

 

Either standard tells you that the HP shown on the graph has been mathematically corrected to eliminate the effects of the high temperature and high humidity. It should show the actual calculated correction factor that was applied to the raw dyno HP. You might see a number like 1.05 on the dyno sheet. That would mean they added 5% extra HP to the graph to reflect the HP lost due to the heat and humidity.

Apparently your mechanic was not aware of this.