Ok guys need your help. I have a 1990 RS with the 5.0 TBI not planning to convert to TPI so need some input. My current dream set up is boring out the block about 40 over and cam it out. I want to rebuild and port the heads. I have hedman headers and have a complete customo cold air intake and a complete custom 2 3/4 inch exaust system with thrush welded mufflers. I will later tune and dyno the car and install a venom 400 performance module. i want to be hitting about 400 horses to the wheels. I need to know what you think and any input you have on it, i also want to know any recommendations for a good priced cam.

 

Forget porting the swirl-port heads you already have. NO potential.
Next, even if you do ported LB9 heads, you're not getting anywhere near 400 horses, not even 350 horses. At the crank. 400 at the wheels, from a 305, is NOT happening. Period. Don't even think it again.
If 400 at the tires is most important to you, I'll cover that in a minute. If keeping it a 305 is most important to you, here's the scoop: With a stroker crank, forged custom pistons, TFS 175cc heads, and nitrous, you might get close to 400 rwhp, but you'll spend more to get there than the stuff I'm about to discuss. Plus, the block itself is suspect at this power level. You're on the verge of an undriveable combination.
What you can expect of the 305 you describe, assuming ported LB9 heads, is about 300 rwhp with nitrous.
Now, to get 400 at the tires, you can do a nitrous 383 with aftermarket heads, you can do a 454 with aluminum heads, or you can swap in an LS1 with ported heads and a mild cam. The 454 is federally illegal for street use, so forget that one.
Welcome to reality.

 

If you're going to be pulling the engine out for a rebuild anyway, then you should just build a 383 and keep your 305 as a spare.
If you decide you don't want to pull and build the 305, but still want more power, you should swap your heads for some ported 416's (LB9 heads) and install a stock LT1 camshaft. Then you need to look into PROM tuning as there is a lot of power on the table there with the typical TBI calibration.
400 horses is too high of a mark to shoot for with a streetable 305 build, but you could add a 100hp shot of N2O.
There is some information about stock head improvements in my signature.

Edit: Forgot to mention that you'll want to upgrade the intake manifold to something like the RPM or Air-gap design for a carburetor, but use an adapter plate for your TBI.
Basically the biggest restrictions you have are the TBI heads, the TBI camshaft, and the TBI intake manifold. Upgrade these and get the tune right and you'll have a completely different engine.

 

No, the #416 heads are LG4 heads, and not as good as the later LB9 heads.

 

Just to clarify this, many, many LB9 engines came with 416 heads as well. I have several sets in my shop.

 

Okay chief, it is a fact that the '85 and '86 LB9s did use 416s, but I can't remember the last 3 digits of the casting number for the '87-'92 non-swirl 305 heads. If you have some sitting around with valve covers off and intake valves removed, please get me those 3 digits so I can be more specific from now on. It'd be appreciated.
BTW, the '87 LG4s also used these relatively good heads. They are better than 416s. Just looking at the chambers it's obvious. More power with less spark advance.
If there were enough of these to go around, everyone running 416s should swap to these.

 

well said

 

Hey man, sounds like you got a pretty fun car. Yes, i would def change that camshaft in there. You could possibly go with a cam that will work with your ecm like a crane computer cam. But do your homework on the max lift of your springs if you go with something like an LT1 cam or a cam that is not designed for a computer controlled car. So, basically you should work the heads and get them milled too. Port work is expensive and i would not try it yourself. You may ruin them. If you can afford aftermarket heads then go for it. I have also heard that the intake on TBI cars is very restrictive and you should probably replace that TB with one that flows better. After all is said and done you will prob need your ecm customed tuned. What gear ratio do you have? Ever thought about going with a carb? Well all in all , you have a cool car anyway. http://www.camaroz28.com/forums/showthread.php?t=296716 check out that link too.

 

You may be talking about the 081's. Next time a set comes through the shop I will measure everything very closely to compare to the 416's. I don't remember any big differences between the two, and small differences don't matter much to me since either casting requires extensive modification for performance applications, to include some chamber reshaping. I don't have flow numbers for stock 081's yet, but maybe some day I'll get some.

I can tell you that 416's and 083's are identical besides valve diameter and chamber volume. The change to center-bolt valve covers really didn't make any difference to the port design or flow potential, but I'll check out the 081's as soon as I get the chance.

 

The 081s don't flow the least bit better than the 416s, but they do dyno higher because of the improvement to the shape of the combustion chamber and the revised spark advance to go along with the improved shape. You shouldn't be re-shaping the 081 chambers at all, beyond whatever the sweeper cut does to reduce shrouding, in the course of cutting the heads for 1.94" intake valves. Maybe light polishing, but no chamber porting.