Supercharger vs. N/A build!

[Cobrat24]

Well here goes!

I just registered yesterday and accidentally stumbled upon the forum via Google.

I have been lerking posts for the better part of 24hrs straight, needless to say the wife is irritated. Lol..

Let me first say this website is amazing and you all have so much knowledge here. I enjoy reading all the threads. The one thing I can't seem to find in a search is what my subject title speaks of..

I am on a quest to make a decision on increasing my little 302's ponies. Let me first say the motor is carb'd and I have no plans for FI.

I have been debating on a carb'd supercharger kit to get me the desired realm of 500hp give or take. However I've been kicking around the idea of just changing carb, manifold, cam and heads as well to get the same number of hp.

My question to you fellas, if you had to choose which direction would you go and why? I'm curious to see what some of you would do in my shoes.

Your input is greatly appreciated.

[patrickt]

Originally Posted by Cobrat24

Well here goes!

My question to you fellas, if you had to choose which direction would you go and why?

If you have a very tight budget, and you have to have more horsepower, then just bolt on a nitrous kit. It will likely put an undue stress on your engine, but it will deliver your horsepower, for a while.

The better solution is to pull your engine and ship it to one of the reputable engine builders and have them give you an upgrade. At a minimum, head work and a cam... but if you can afford it, maybe a nice stroker crank for increased cubic inches -- the builders on here do it all day long.

Personally, I wouldn't even consider the blower option until you had maxed out your engine build. Pulling your engine and shipping it off may seem like a PITA, but it will turn out to be the easiest option for you. Of course, while it's out, new clutch, pressure plate, TOB and pilot. Most of the reputable builders can give you a non-binding "quote range" after a reasonably short chat.

And what would I do? Sell the 302 on Ebay and put in a big block.

[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.

[Morris]

With a power adder engine.....you need better brakes.......no engine braking.....

[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.

[olddog]

I agree that those heads on a 302 is not likely to give a true 400hp. Be aware that talk is a way to make huge Hp for very little cost, with little effort. So when you hear what the Mustang guys are doing, remember the Bull Chit factor on the HP. They may be about 100 hp less than what they say. Also not too many tell you that their engine only lasted 10,000 miles after their big hp modifications. Often times much less.

Also all dyno tests are corrected to what the engine should make at sea level. At 5000 feet you are going to be missing a lot of power. We just pulled a camper to Yellowstone with a new Ford F350 diesel. The power loss at high altitudes is huge. So I understand your situation.

500 hp at the crank on an engine dyno, will be lucky to get 400 hp to the wheels. Exhaust, air cleaner, all the belts on, drive train losses all add up. Then you will take the extra loss for elevation.

If this is a Cobra, the exhaust is fairly restrictive in most side pipes, unless you want to wear ear plugs. More likely to get 375 to the wheels at sea level on a 500 hp at the crank.

The old saying "there is no substitution for cubic inches" is correct when talking NA. Supercharging is like adding cubic inches. For every 15 psi of boost you are doubling the cubic inches. If you think of boost as adding cubic inches then "there is no substitution for cubic inches" is absolutely correct.

First can you drop a 351 Windsor block in your car? It can be stroked to 400 cid. If you go with a aftermarket block 4.125 bore you can easily stroke to 427 cid. You can get to 460 cid but there is no meat left on the bones for a rebuild.

If not, your 302 block can be stroked to 347 cid. If you go with an aftermarket block 4.125 bore you can get 364 cid. With some boost, say 5 psi those added cubic inches is 1/3 more than what you added. That 364 is like adding 82 ci if boost is 5 psi. So even if I was going to add a blower, I would at least stroke it out. The aftermarket block is much stronger and can take a lot more hp than the factory block, but you are talking $3000 in the block.

If you can drop in a Windsor block you can get there with a NA engine and still have a decent mannered engine. If you have to stay with the 5.0 block, I would go with boost. To keep it in your budget, stroke it for sure. I would go with aftermarket 4.125" bore block and keep the same heads, if I could afford it. Then blow air into it's nose. In your heat you are going to have to have an after cooler if you push much air. That is why you want as much cid as you can get to keep the needed boost down. With boost I wouldn't worry about the heads. You may want to drop the compression for boost. Keeping boost under 5 psi and dropping the compression to 8:1 you may not need an after cooler, which is about $1500 savings - last I priced one.

Someone suggested laughing gas. It's relatively cheap to install. It just costs every time you burn it up and have to buy another bottle. Put a 150 hp wet shot on it. You need a way to back timing out. It is the cheapest option. Then save money for the big engine, when this one grenades. You shoot enough into it and it will break, so start saving.

See what Blylins can do for you with that budget. He actually builds engines for a living. I just talk about it.

[Cobrat24]

Here's the 302-

[ct clint]

What rpm does it cruise at on hwy? How much time do u spend on the hwy? What rear end does it have? Sounds like u tear it up at lights don't drive it much so rear end gears are by far the cheepest. Nice charger with meth spray will help with bad air and get. Go to a dyno day see what other guys are using saves a lot of time and it's nice to see what else is out there. Most guys will tell u everything if u ask then look at there dyno numbers don't take long to see who's full of it. Nice car for sure

[mikeinatlanta]

gonna have a hell of a time pulling 500 hp NA through the skinny air filter. I'd go injected turbo and pull the air elsewhere. Nothing beats a turbo at altitude.

[Cobrat24]

Originally Posted by mikeinatlanta

gonna have a hell of a time pulling 500 hp NA through the skinny air filter. I'd go injected turbo and pull the air elsewhere. Nothing beats a turbo at altitude.

Yea I agree, I saw your post in the other thread. That hood setup is sick. When I first bought my cobra I envisioned a big blower out of the hood for rat rod sake but then as I drove it I realized I wanted to keep it all under the hood, it's just a sexy car all around and I felt like a big chrome blower would change the look.

[cycleguy55]

There is a school of thought that says you can't really use more than 400 HP in a Cobra - at least for street use.

Regardless, if it was me making the decision using the parameters you've given, I'd go with a 427W build. You'd be able to meet your goals and still have something drivable. I'd also be inclined to go with EFI to better handle the changing fuel/air mixture requirements with changing elevation.

[Cobrat24]

Originally Posted by ct clint

What rpm does it cruise at on hwy? How much time do u spend on the hwy? What rear end does it have? Sounds like u tear it up at lights don't drive it much so rear end gears are by far the cheepest. Nice charger with meth spray will help with bad air and get. Go to a dyno day see what other guys are using saves a lot of time and it's nice to see what else is out there. Most guys will tell u everything if u ask then look at there dyno numbers don't take long to see who's full of it. Nice car for sure

I do maybe 45-50% freeway the rest is in the street. As I was talking about earlier the power really flattens out from 3rd on, which makes sense for the hp.

The one thing I refuse to be ok with is knowing any stock corvette could pull away on the freeway if they wanted to, which is he current case. Yeah sure my cobra looks great but I would like to have the bite as well as the bark.

[mikeinatlanta]

500 NA is one thing. Doing it with a small block within the confines of the stock hood and with sidepipes won't be cheap. Lots of guys think they have 500, but that's with dyno headers and a big air cleaner. In cobra trim it gets tougher.

[Cobrat24]

Originally Posted by mikeinatlanta

500 NA is one thing. Doing it with a small block within the confines of the stock hood and with sidepipes won't be cheap. Lots of guys think they have 500, but that's with dyno headers and a big air cleaner. In cobra trim it gets tougher.

Yea I am well aware the chink in the armor so to speak is the air filters/sidepipes.

So let me ask you this, you yourself, small motor with super charger or big motor n/a. I have a feeling 10k would get me there on the 302 with the super charger kit carb'd with changing out the pipes to the 3 inchers. Not sure it would happen with the 351.

[ct clint]

Your best bet is ride in a car with a charger they just keep pulling. I am stepin up to a v4 vortech and use pro m efi his suff realy works even can control the meth and nos. Had v2 but bad things happen when u abuse them lol. I would go charger and efi it realy works.

[mikeinatlanta]

In GA I'd NA, but at 5,500' with the best local roads even higher I'd be all over the blower.

[Cobrat24]

Originally Posted by ct clint

Your best bet is ride in a car with a charger they just keep pulling. I am stepin up to a v4 vortech and use pro m efi his suff realy works even can control the meth and nos. Had v2 but bad things happen when u abuse them lol. I would go charger and efi it realy works.

Been in a few cars with chargers, love the feel. It sounds if I went the way of 302 with supercharger with my elevation it would just make since to step up to FI. That's why I was asking about supercharged using a carb version, I don't know of anyone who has gone that route. I'm not sure 10k can get me the supercharger, FI, and side pipe fix. I'd have to price it out.