Your typical M6 full bolt-on car is going to be somewhere around ~295 rwhp with LT's, cold air, a bolt on tune, etc through a 10 bolt.

Your best bet is to estimate the loss % from going to a 9" from a 10 bolt and go from there.

FWIW, back in the day with bolt-ons and a 2800 stall my car put down 272 rwhp untuned through the 10 bolt.

I'd say you're slightly down on power, but nothing too extreme. The 9" on the bolt on car is definitely hurting you at this point, but at least you're set for future power upgrades.

 

You really need a tune even on a stock LT1, and that rear is way overkill for your mild setup. 9" is way too much drivetrain loss for a CAI/exhaust LT1 - that is probably why your numbers havent changed much.

Of course you should datalog to check for things like false knock and running rich(which you probably are since the exhaust leak), but nothing is probably wrong with your car.

A bit off topic, but a 12 bolt is not an easy rear end to break. I cannot think of three people I know who have broken them myself...Were they on adjustable suspension components and self installed gears? Sounds like user error to me. Bad pinion angle or not properly meshed gears will grenade a rear in no time -much more likely IMO. Of course everyones experiences will vary, and autos are a lot more gentle then a stick, but I have ran 11's on my 10 bolt(knock on wood). A 12 bolt upgrade will be in my future, but I see no need for a 9" on a street/strip LT1.

**edit*** For reference my Z barely touched 265 to the wheels when it had all the bolt-ons(except for EWP) through a 3k fuddle and a 10-bolt. That is also including things people miss like 1.6rr's, ignition, tune, etc. I can't believe how many people get(or claim) 300+ to the wheels with just headers/cai/exhaust - but I am not there so what do I know *shrug*. That modest rwhp ran consistant 12.8's all day though **edit**

 

<Puck> - Most of the 300RWHP Bolt On cars are M6's, I have seen a few auto's claim it but have yet to see it in person.

 

id change out your o2 sensors and do wires..eliminate the simple things first. and a good dyno tune will really help out your engine. im in a similar situation as you tho,.. no local places to do em

 

http://www.1slowformula.com/images/dyno_cutout.jpg

Just under 300RWHP and that was before RR's, Headers and Exhaust, and it might have been over 300 if the dyno operator actually spun the car up over 160 (had 2.73's at the time)...

 

get a tune, my madz tune was awesome, cheap, and he did it and shipped it amazingly fast.

 

Proof?
Of course it will. How much?

A LT/ORY install doesn't need to be tuned to see a significant gain.

 

It will still help a lot. Even a bone stock LT1 can get 10 to the wheels from a basic tune.

 

So I've read. Regardless and as stated before it still doesn't need to be tuned to see a good gain. Personally I don't believe in 10rwhp gains. Reason being a gain/loss can happen simply from heat soak/coolant variance from the same dyno session.

 

8-10rwhp is a fair number... or based on my experience, good for at least 1 MPH or so.

Back in my bolt-on days I gained a consistent mph out of a bolt on tune in same conditions.

 

I put down 303rwhp through an auto with just boltons.... well I thought I was just boltons at the time.

 

What's significant to you? For the price of a mail order tune, that's some pretty cheap HP. Not to many other ways to pick up 5-10 HP for that kind of money that I know of. But hey, I'm all ears.

 

Now, I do agree that the 35 spline axles are overkill...For now

 

I went from going 110mph to 114mph simply going from Edelbrock shorties w/ stock y-pipe (cats included) to LT's and ORY with no tune to accommodate the LT's. I think that's pretty significant. As stated I really don't believe in noting 5 or 10rwhp gains. Way too many variables come into play.

 

That is a nice gain, but maybe weather played a part in it. And maybe some of your other mods were waiting for the LTs to help the overall picture? But I'll still take those 5-10 HP gains any chance I get. It's the little things that add up, as you already know, right?
And one last thought. Maybe your tune was off a little, and benefited from the header swap. Free updated tune? Thats pretty cool.