I have a 305 with a 700-r4 in my 83 z_28 right now. what would be the most cost effective modification I could do to the engine to get more hp/torque? It is a factory 305 with crossfire injection mated to a 700-r4. I haven't done any mods except for a shift kit coming up.

 

Exhaust..... every single piece, from the heads to the street, but NOT for LU5.... if any of it fits to what's already there, it will preserve the bottleneck, namely the tiny Y-pipe.

Get chassis-specific headers such as Edelbrock or SLP, I'd suggest getting the ones for about a 88 350 TPI; and a cat and cat-back to match from any of the mfrs such as Flowmaster, Hooker, Dynomax, SLP, Borla, etc.

 

That's a good place to start, but can get more costly than some other modifications. In raw terms of the question (best HP gain per dollar) I wonder if it would be as cost effective as replacing the CFI with a bone-yard intake and carburetor for the same vintage engine. Then again, I supose the carb is going to want better exhaust flow, too, as well as an improved inlet side.

The next closest HP/$$ value is likely the camshaft, especially with an older, flat-tappet cam like yours.

 

I agree the headers with y pipe, high flow cat or I pipe, 3" cat back is the best mod for the money. Expect at the lowest 20hp and 20tq and about $500-700 on parts.

 

To expand a bit further...

Unfortunately, there's not a huge bang for the buck in the exhaust itself; but, no other mod will be able to do its job without it. Anything else you might do instead or in addition, such as a better cam, head work, intake porting, etc. will be unable to reach its full potential without the exhaust being de-restricted. So, although you won't get just a huge world of difference type of result from it, it is essential for any other mod to have its desired effect.

 

Thanx for the info, Im thinkin I will go for the exhaust then camshaft, any suggestions for a cam? its a daily driver for college but moonlights at the strip. Ihave been told an RV cam is best but at the age of 20 Im still learning whats best. what is an RV cam and/or is there anything better??

once again thanx for the help

Lil Taz

 

Usually when people say "RV cam" they mean something designed to put in a motor home or something. That's not what you need.

Look at Comp or Crane or Lunati, at their cams that are specifically designed to work with computer-controlled fuel injection. A good typical sort of thing would be the Comp 252AH-12, grind # 12-388-4

 

What RB and Vader said, But I'd like to add something, since I have been down this road (with the Crossfire specifically).

BANG FOR THE BUCK, a cam will get you the farthest, IMO. In my first TA('83 LG4 Auto), I installed a $69.99 summit cam and lifter kit, and a $14.99 timing chain set. I mean, I went CHEAP. Everything else was stock. This dropped my 1/4 mile time by a second (16.3 to 15.3).

$100 Dollars for 1 second is tought to beat. And swapping from CFI to Carb (as Vader suggested) on an other wise stock CFI car wouldn't get you those results. But the cam was a good call.

Now, like RB said, the exhaust is the SMARTEST first mod, and it'll show you similar gains as the cam, while making the engine a MUCH more efficient system because the stock exhaust in that car is as bad as it gets. Exhaust on that car WILL make a huge improvement, even with everything else stock;

On my second TA ('83 305 CFI 5 speed) I installed Edelbrock headers and "Y", '86 and newer cat, and SLP 3" cat back. Combined with "free mods" and nothing else, it ran 14.5 @ 95 in the 1/4. So the engine will definitely respond VERY well to exhaust, but exhaust IS semi pricey.

After doing just about every thing to the CFI engine that can be done, I would recommend the following in order of importance;
1. Exhaust
2. Port the stock intake!! And mod the fuel distibution vanes (free)
3. "free mods" (cooler T-stat, no smog pump, dial in fuel presure and timing)
4. Cam -The CFI engine already comes with the L69 "HO" cam, which ain't great, but it's way better than the LG4 cam, so you probably won't realize the full second I did on my first car. Even though it is the cheapest mod, and it is effective, the other mods are more important, and the car will run better overall.

 

Yes