How can I tell if I've been modded?

[Paul G]

We just got our CE home. The mods I can see are Edelbrock TB, powdercoated shorty headers and a Power Effects Exhaust.

My real concerns are internal. I am wondering if it might have a different cam or programing. How can I tell?

What puzzles me is the mileage. On the 1000 mile trip home the average economy as read on the display was only 21.7 MPG. Seems too low to me for highway driving. I kept the speed at or under 85 the whole way.

Paul

 

[Fabinatl]

That is odd. My CE LT4 gets anywhere between 27 and 30 mpg on the highway at 70 ish mph. Now that's non stop driving. In town with stop and go I get about 15 mpg. Maybe you have a different rear end!

 

[FX GS]

We just got our CE home. My real concerns are internal. I am wondering if it might have a different cam or programing. How can I tell?
Paul

Excuse me for asking, but I am assuming you just bought this car(?) If so, didn't you ask the seller any info about the car before you bought it?

 

[Paul G]

The seller told me what he new which wasnt much. He is second owner and not mechanical. He bought it from a Corvette dealer, not the original owner. He kept the car very clean and neat. He took it to the Chevy dealer for all the service work including routine oil changes. He told me about the TB and PE exhaust on the phone. He didnt even know it had headers. I pointed that out when we saw the car. He was kinda surprised himself.

What concerns me is if the first owner installed headers and exhaust with a bigger TB the natural course of action would be to modify the computer and cam also.

Is it possible to change the programing for the worse rather than better which would explain the poor mileage. How can I tell if the the programing has been changed?

 

[Shriker]

Get it on a dyno and you will know right away. Typical LT4 will make 290-300 rwhp . With shorty headers and PE exhaust (open all the way) and the TB it should make ~10-15 more (TB is worthless until you are at least heads/cam).

You should be able to recognize a cam by the way it idles and drives .... any lope at idle?

 

[atmmac]

sounds like you may have gotten a great deal!! If it has a cam thats awesome!

 

[Paul G]

You should be able to recognize a cam by the way it idles and drives .... any lope at idle?

No lope at idle. It idles nice and smooth. The car goes like stink though. I am very pleased with the performance.

 

[3TT3V]

If you post what your RPMs are at 70 MPH ; then someone here will tell you what rear end ratio you have. If it's like a 4:11 - 1 ratio; that would be reason enough to get low stated gas mileage.

 

[Edmond]

Would there be any possible way to track down the original owner?

 

[Evolution1980]

No lope at idle. It idles nice and smooth. The car goes like stink though. I am very pleased with the performance.

I would expect it to be pretty smooth, as the base LT4 has a beautiful, flat torque curve through the RPM's. I'd probably go out and make a note of RPM's @ MPH and see what it compares to others LT4's. Then you'll have a better idea if the rear end was swapped out.

And yes, a good dyno shop that deals in GM's should be able to tell you if you have a different cam. I would feel confident that Dynotech or LPE could tell you with a single pull on the DynoJet.