Im new to this site and to the whole car scene. I have a 1975 camaro that me and my dad were building until I joined the military and since then its just been sitting their. I know its very difficult and alot of variables come into play but I want to get an idea of how much horsepower it makes. And my other question is how can I improve my fuel economy? I know about the gears im going to change them to 373 to help out. And its going to be used for street and at rare times for the strip. Feel free to recommend anything that could improve performance or fuel economy without losing to much hp. Any info would help thank you.
Here a list of mods the car has:
A rebuilt, high performance, balanced & blue printed 400 (6.6 L) engine.
Hyper-eutectic .030" oversize pistons.
Clevite cam, main & rod bearings.
The cam is .480 lift, 292 duration.
Melling high volume oil pump.
ARP bolts used throughout the engine.
Heads are original heads with new valves, springs & seals,
ported and polish by McKinny Racing Cylinder Heads*
Weiand intake manifold port matched to the heads.
Edelbrock valve covers & air cleaner.
Barry Grant Demon 750 CFM, double pumper, High Performance carburetor.
Carter high performance fuel pump.
Mallory electronic ignition system.
Certified Pro Race harmonic balancer.
Hooker headers with new dual exhaust, 2 inch pipes & 40 series Flowmaster mufflers.
Mike's Racing TH350 transmission, special modified drums with extra HP clutches,
manual shift valve body.
A 12 bolt differential with a new Eaton posi-traction unit and new Richmond 4.11:1 gears.
New Superior axles with long studs*
An aftermarket fiberglass 4" cowl induction hood.*
New Centerline rims: 3-1/2" with 165/60-15 Performance Radials up front ,*
8" with 255/60-15 Performance Radial tires on the rear.
New shocks all around, KYB fronts & Competition Engineering 3way adjustable rears.

 

Welcome to the forum!
Hard to say for sure, but I'll guess 400hp. The 3.73 will help overall mileage, and an OD trans would help highway mileage by about 25-30%. Not sure with a hi performance build you can do much else to improve mileage. Make sure the tune is spot on, and that's probably all you can do. 2nd gen Camaros are not light cars, so they will suck gas, and even more when you enjoy feeling the power you'll have.
If you wanted economy a smaller 350, with a milder build would have been a better choice.

 

Welcome. Guesses are just that. Best way to find out is dyno it or take it to the strip and run it. Then you can get real close with weight and mph. The factory heads and 2" exhaust are the hindering factors on your build, but I say around 400-420 too. 1.5 hp/ci is possible but built to the hilt. Also what's the actual specs at .050, advertised can be misleading. Are you running retro roller or ft. Sounds like a really nice build, and I agree with BB tune is where you will find mileage. That depends on your use though and where your tq peak is. Believe it or not I noticed a 1mpg increase with 3.42 over 2.41 gears bc my tq peak is up in the rpm's and around there is where motor is most efficient, plus I don't use as much throttle on take off. For ultimate mileage consider fuel injection, it's costly but will pay you back over time if you drive it a lot. Good luck look forward to pics and vids from you...hint hint....

 

I think it is a pretty good combo. It could use a set of heads but if they were done by someone that knows whats going on they can flow good. The 2" exhaust is choking it for sure. Probably pops like crazy when you let it engine brake. You didnt mention the header primary size or if the intake is single or dual plane. If your head porter got some flow numbers that would go a long way to help find the sweet spot for your cam and intake. It sounds like you got the old stand by 480/480 cam that almost every company offers. It almost always a flat tappet. Even though they differ slightly in lobe shape and duration, most are the same. I had one in my old pick up and hated it. It was 480 w/292* duration single pattern. It was cheap and did the trick but it was no where as refined as a new grinds are. But its already in the motor so I wont say get a new one. But it would be on my short list of future upgrades.

The only way to get MPG is with OD. No two ways about it even with a good tune I dont think it will get much past 12-15. Thats a real guess as I never tried to check MPG on my built engines. I do know of a 200-4R for sale from a member here. It is good to 650hp and in my opinion light years better than a 700r4. His name is Jason7504. I dont know if its still for sale as I could only find his shifter so far but I think Val (1971BB427) has had face to face dealings with him knows how to contact him. This is a pro built trans that I would have grabbed had I not got the T56. I have heard numbers as high as 24-26 MPG on the highway. The 200 wont drop prm's between 1st and 2nd like a 700 will. Plus it will bolt in place of the TH350 because the mount is in the same spot. 700 arent. Second would be a T56 but your looking to drop 3k doing that.

I'd like to tell you your making 400 hp but it think that cam may be too small in a 406. Also you didnt tell us the true comp ratio. Not what is on the piston box but what size the chambers are and how far in the hole the pistons are plus are the pistons flat top, how many valve reliefs? How think is the head gasket? These could all bring your CR way down from what you may think it is. A crappy quench/ squish area will rob power while a good one will give you free power. Roller rocker too! More info please. Guessing 350-375hp sorry.

Nevermind!!! Just found the thread on Nasty it sold last night.

 

What sold?

 

In the post I made I suggested that the OP to PM you to see if you could get in contact with Jason7504 about his 200-4R. It was an awesome trans that just happened to be for sale the day the OP was asking for options on gas milage. I remember he has stopped by your house WAAYYY back when to take a look at his car. I wasnt sure if you two had kept in touch but it was a good lead. Dont ask why I never forget the little stuff. IDK why. But the same day I posted was a day too late. The trans sold the night before. I edited my post so the OP didn't bother PMing you. I havent seen Jason around here very much but he is active on Nasty. He is going LS/T56 and the trans is sold. I dont remember if he is offing the 496 or not. I wish he would have posted a video for us. I remember when he was a punk kid asking about his Cragers. I honestly never thought he would get the motor he was talking about in the car but from what I have read the dude built a sweet ride. Must have graduated college by now.

 

No, I haven't seen or heard from Jason for years. I also wondered if he ever got the engine running. I knew he purchased it, and he contacted me about doing the install and hookup-startup, but nothing since then.