300hp possible from NA 4.1L?

[unboostedV6]

JD, here's the deal. Checking over your current parts list - the Weiand manifold is excellent, carb is too small - suggest 600 -650 Holley, your headers will restrict your top end with their 1-1/2" primaries, but will still do quite well on the street, needs 2-1/4" duals, or "y" your 2-1/2" collectors into a single 3"...an "H" or "X" pipe is not tremendously helpful on a v6,IMO. In order to make 300 crankshaft hp, you need to move 300hp worth of air and fuel. This means, your 252+ci will need to make peak hp around 6000 rpm. Because of the small valves, the Buick requires 10-15 degrees more camshaft than a typical SBC for a giver power range. Of course, porting helps tons, as would T/A, or Champion heads. That said, one of my pump gas engines used a custom ground Comp hydraulic flat tappet stick that spec'd at 246-256 @.050" and .510"-.507" lift w/ 1.6 rockers. They also like very narrow lobe centers, which adds bottom end, but decreases idle vacuum. I shifted it at 6500 and ran mid-high 13's at 3250 lbs. Yes, this stuff requires custom cams and pistons. You definitely need compression. The stock crank and rods easily handle 7000 rpm runs with the stock oil pump shimmed to 70psi. I even spun the roller motor up to 7500 a couple times, but it wouldn't go any faster. GB

 

[joedirtmcd3]

Thanks

Thanks for the very informative response. I definitely want to add Roller Rockers and eventually will put in a roller cam of some type. As for the higher compression i will not be bothering in that pursuit as eventually i want to go with forced induction. The aluminum heads and new set of headers might be something to look into though...

Things I need:
Roller Rockers
Roller camshaft and lifters
Ported intake/heads
opened up exhaust
600 or 650cfm carb

 

[Kovmat]

600 Carb

I have a Holley 600 that I ran on my 4.1. I am switching to a Turbo setup and no longer need it. It needs to be cleaned up and re-built. If you are interested, let me know.

 

[49-blues]

I have a complete almost new headers back to the tailpipes custom bent true dual catback system-i think they re 2.50" in dia. with two cats and custom crossover pipes. i paid about $1000. for everything -i will let it go for $500. shipped. or trade for parts. will include a homemade crossover bracket for free.

 

[joedirtmcd3]

headers/exhaust system

by new set of headers, i meant ones that would bolt up to a set of aluminum heads. that would be a different bolt pattern than what i already have so are your headers meant for GN aluminum heads or the stock iron heads for a 4.1L?

 

[eastwoodad]

Any production (turbo or NA) or stage 1 head whether it is aluminum or cast iron has the same header flange and bolt pattern. Only when you go to the stage 2 will there be a different flange. I hate to say it but you won't have a choice on production headers that are larger than the now discontinued Hooker header system you already have. You could keep what you have and pay nothing but not be quite ideal, or have someone custom build a larger header and pay some big money.

You will also need to mill the heads/block and/or run a steel shim head gasket to bump compression up to really take advantage of this combo. I know you want to add a power adder later but to take full advantage of your NA combo you WILL need compression.

It seems you will really need to determine what you want to do with the combo. If you truly will be adding a supercharger keep the compression low and you just probably won't get the 300 NA HP. But oh well, you'll have a supercharger later that will more than make up for that.

Your best bet in the short term will be the 600 vacuum secondary carb, porting the heads, and maybe getting a better header-back exhaust setup. These are things that will help no matter if it is NA or supercharged.

By the way, check out FULL THROTTLE SPEED - Store Front Page for roller parts.

 

[joedirtmcd3]

stage 2 hear flange

When I see these champion aluminum heads their exhaust ports look alot more circular than then rectangular ones I have now. This is the difference I was referring to and I guess that's what you are saying is stage 1 vs. stage 2?
Also, I definitely don't want to go with custom pistons but i understand the need to up compression.

Iv'e been looking around on Full Throttle's site but their descriptions are not very detailed, perhaps I will have to call them to be sure I find the correct Roller Rocker (T&D or TA??) setup for my heads as well as possibly a Hydraulic Roller Camshaft kit (with lifters, pushrods, springs, etc.)

Eventually I will most likely run the exhaust dual 2.5" from the collectors to a dual 2.5" in/dual 2.5" out Flowmaster super 40. Does anyone think this might act as a makeshift crosspipe because I believe the muffler's chamber is open to both pipes. Main reason I wanted this muffler was weight and space savings from only one muffler. I could try to run a cross pipe before this muffler but I don't think it would be very easy to fit.

If you are taking two pipes into a Y, do you compare cross sectional areas of the sum of the two pipes from Y input to cross sectional area of Y exit? if so, I will have 2[3.14*(2.5"/2)^2]= 9.8 square inches versus [3.14*(3"/2)^2]= 7.1 square inches, assuming I went with a 3" exit. I didn't want to take the exhaust into a Y if I could avoid it, but maybe it would be worthwhile. What do you think?

 

[eastwoodad]

The only style head that Champion makes is the factory/stage 1 style, whether it be ported stock heads or their aftermarket aluminum head. The exhaust port is larger because it has been ported. You could use this with any production or aftermarket header provided you ensure both are matched to the gasket.

The stage 2 is a totally different head that requires a different intake, header, rockers, valves, etc.

For the factory head or the champion heads, you could use T&D's, Harland Sharp's, or the T/A style designed for stock heads. For the T/A head you have to use a proprietary T/A designed rocker stand and rocker assembly.