Ok, my friend has a 95 Mustang 5.0(302) and he has done some mods to it including GT40 heads and intake and bigger cam, and Cobra ECM. He claims that it can turn out 300 horses. I've rode in the car and its pretty fast.
Now, I have a 87 TransAm 5.0(305). Why can't I get that much horsepower out of it with some mods like he did? Everyone says ditch the 305 and get a 350, but if I can get more horses out of it I would rather keep it. Everything in the car is original and works, so I would like to keep it close to original in appearance under the hood. What should I do? Only mod I know that has been done to the car is the Edelbrock long tube headers and exhaust. How much horsepower do I have now with these?

 

Wow, this has been discussed often.

Edelbrock "long tubes"? Hmmm, not familiar with them. All I thought they made for our cars were TES, which is shorty headers with a y-pipe. If that's what you have, it depends upon which ones you got. The LG4 TES (I assume that's the 305 you have) maintain the restrictive EFE valve and cat inlet, which really limits power potential. But, on an otherwise stock 305, they'll increase power by about 10%, which will be proportional as you do other power improvements up to a point.

Okay, the 5.0: It has a 4" bore vs. the 305 3.736", and only 4 cylinder heads bolts around each cylinder vs. the SBC 5 (understanding that adjacent cylinders share the bolts that are between them). The net effect of those two things is that the air flow into and out of the cylinder can be much more efficient on the SBF. But, that comes at a price - as in, blown head gaskets (very common with SBFs), and engine blocks that have a habit of splitting in two (becomes common when power adders are used).

Can you get a Chevy 305 to put out 300 horses? Yes, and pretty easily. It takes cam, headers (yours will probably do), air cleaner upgrade, and some head work (porting at a minimum, and 1.94" intake valves a big plus). Expect driveability to suffer, and economy to go down slightly. You'll also have to do other things (torque converter, gears) to be able to effectively use the new power. You can find all of this information (not the Ford stuff) in a 305 thread on the FAQ forum.

Now, if in fact you have TPI, it gets a little more complicated and a lot more expensive, but it can still be done.

Oh, the fox-body is lighter than thirdgens, as well.

 

Thanks 57Kid,
I'm not sure what kind of headers they are. I know this much, there is a stamp on the passenger side header that just says Edelbrock. They are crammed in there too. Makes changing plugs a nightmare. Had to saw down a spark plug socket to get it to fit onto the plug at #1cylinder. I looked and you are right, it does have what's left of the stupid EFE valve on the passenger side. I can move a little tang that sticks out, but don't feel like anything is moving inside. How would I know if it's still in there? And another thing I noticed is that the pipes are smaller going into the cat than they are coming out and running to the rear. Hmmm.

 

Yep, sounds like a TES. Not all that bad, but not good in the LG4 configuration.

I see you've updated your information. 4bbl, that's good for the power stuff.

Get the exhaust upgraded, upgrade per the recommendations above (and the FAQ forum thread, "Differences between 305's, and power upgrades"), and you'll be able to keep up with them.