Supercharger vs. N/A build!

[twobjshelbys]

People put Paxton on the 289. Shelby put two on his 427. I don't think cobras except Shelbys were official but I know of a couple on 289 mustangs. Pretty low boost at 4-6 psi is about all you can do with a carb fuel delivery. A friend had one on his 66 gt350h 289 hipo and said it was noticeable

[ct clint]

I have done the motor build big cubic inches tried turbos now on to a vortech charger. To much plumbing on turbo and heat. So now with vortech frees up room less heat can spray with meth for detonation and small wif of nos. But the biggest bang was gears in rear end and as much rubber as u can fit under it. Topend speed is a killer but grunt out of the hole puts the smiles on. Face it people freak out at speed let them feel her toqure out of the hole and that's what they talk about. Just my 2 cents

[olddog]

500 / 302 = 1.66 hp/ci That is difficult to do NA

500 / 347 = 1.44 hp/ci

My rule of thumb is 1.3 hp/ci is about as much a you can build, without going expensive parts and having a high strung peaky engine that is no fun to drive. From my rule of thumb 450 hp out of a 347 or 390 hp out of a 302 is about as much as practical, as you can get to NA.

A 302 can get to 500 hp NA, but not on a moderate budget. To get there the only part out of your existing engine you can use is the block, and I would recommend against using it. If you haven’t heard, the 5.0 block cracks between the main bearing and cam bearing oil galleries. There are pictures around, where the block split completely into two pieces. It’s partly Hp and it is partly rpm. As you go above 400 hp, the odds your block will split get worse, and the higher you go, the more rapidly your odds get worse.

Supercharged:
2 hp/ci is fairly attainable. A supercharged engine can be quite mild mannered, depending on how you build it. Again I wouldn't recommend any parts out of your current engine.

Not all superchargers are the same. Positive displacement blowers (lobbed or roots style and twin screw compressors) give you a very flat torque curve. Non-positive displacement blowers (turbine or fans) make pressure based of tip speed of the fins. Thus at low rpm they build, almost, no pressure. The torque curve goes up at about a 45 degree angle, in my opinion, making the engine useless for anything other than drag racing, and bragging. Others disagree.

Blowers can be used with a carb, but I wouldn’t do it. Sitting a carb on top of a roots blower (on the suction side) works, if you don’t mind it sticking up out of your hood. Putting a pan around the carb and pressuring it works, but then you have to vary the fuel pressure to match the pressure in the carb. This setup does not tolerate sudden throttle changes well, if the boost is high. In my opinion, EFI solves a bunch of problems and makes it much easier. Getting the timing and fuel right under boost is critical and an EFI computer makes it easy. Boosted engines act like a grenade, when the fuel or timing is off for a very short time. The higher the boost, the shorter the time and the less forgiving, on how far you can be off.

You might start by explaining what you want to do with this engine and how did you come to a 500 hp goal. Getting that type of power out of your 302 is not very realistic.

[Cobrat24]

Originally Posted by olddog

500 / 302 = 1.66 hp/ci That is difficult to do NA
.

You might start by explaining what you want to do with this engine and how did you come to a 500 hp goal. Getting that type of power out of your 302 is not very realistic.

Ok so here are my following reasons why..

1. I live in Reno, NV (5300 feet) power loss is typical up here due to elevation.
So when I tell you guys it's a little over 300 hp that's taking the elevation change, if this was sea level I may be having a different conversation.

2. The current motor is a 302 with GTP40 heads and a mild cam. Motor has 2800 miles on it. I bought it like that back in September. The original owner claimed it was 400hp, it's clearly not that. The power is decent out of 1st and 2nd but once you move from those two gears it just doesn't have enough power to my liking.

3. So to aim for 500hp would give me somewhere around 400 rear wheel at my elevation. I am aware added horse power creates added stress to other parts, however after doing some research it looks like this number is realistic on this block. I am seeing the mustang guys pushing more hp out of the same block.


Last thing I should tell you I do have a budget of 10k.

[twin turbo]

With a budget of 10k I would pull your 302 and put in a 408 (351 based) which can easily make 500 fwhp in a well balanced package.

[Phill Pollard]

Originally Posted by twobjshelbys

People put Paxton on the 289. Shelby put two on his 427. I don't think cobras except Shelbys were official but I know of a couple on 289 mustangs. Pretty low boost at 4-6 psi is about all you can do with a carb fuel delivery. A friend had one on his 66 gt350h 289 hipo and said it was noticeable

Huh? I put a Shelby-Spearco turbo kit on my 1967 Camaro with a 350 Target Master (i.e. "crate") engine in it and ran 12-14 psi of boost.

I'm not sure where the 4.6 psi limit comes from unless you're talking about one of the old tech/low tech blow-thru systems (mine was a suck-thru system). I've seen blow-thru's that seal the carb in a pressure box but you have to run foam floats in the carb because brass floats will collapse.

Even with the stock Target Master 350, it made a MONSTER out of that car. I immediately had to put disc brakes on it because it would get going SO fast, SO quickly. I did have to add a Edlebrock Vari-jection (simple water injection) system to my car because of the detonation created at that boost level but once that was on, I could hold full throttle until my balls shrunk. I had a blow-off valve for it but never added it after adding the H2O injection.

I became a BIG fan of super turbo charging after force feeding that car! The difference is amazing, like night and day.


Phill Pollard

[twobjshelbys]

Originally Posted by Phill Pollard

I'm not sure where the 4.6 psi limit comes from unless you're talking about

I'm not saying you can't do more boost only that the guy I know runs very mild. Not a limit except for self imposed. I recall it being consistent with the setups of the day. Also this classic vehicle did not have an intercooler.

I'm also not sure what you can get out of the centrifugal types like Paxton and ProCharger.

[Bernica]

I know that for those of you that had Patrick at Pro Systems build your carb, you can call him anytime and tell him what elevation you plan on running at and even other weather conditions. He will look up your build and suggest what to do with jetting, etc.