NA or Supercharged?

[Hapnyny]

Hi CR Family,

I’m looking for some feed back. Currently have a 1992 CR with a 289 from the 60’s and a C4 with a manual trans. I was think of upgrading to a 347 Stoker and recently found another option. The question I have, would you go with a Stroker or a Paxton Set up if you had a choice? My 289 is probably pushing about 260HP and the Paxton is claiming 110 to 150 HP increase. The Stoker is 500 HP.

https://paradisewheels.biz/65-66-twin-paxton-dual

https://www.prestigemoto.com/custom-...347-hr-c3.html

[Tommy]

How do you want to use the extra torque and power? Track? Street driving? Car shows? Just because?

[rustyrims]

Someone else recently posted a link to that 347. it says as cast aluminum heads, 10 to 1 compression ratio and a hydraulic cam. It does not say the brand of the heads. It would be very difficult if not impossible to get that horsepower with those parts. You should check with a engine builder to see if they think it is possible. If you can get the brand of cylinder heads you can make a better guess. With ported heads if done right it's possible. Power adders like superchargers or turbo's are always cheaper if your current engine will stand up to them.

[Chicagowil]

As far as the Paxton S/C, they are /were not very efficient. And there is quite a bit of noise. It is an interesting config, more period-correct looking, when you add the Paxton. Funny thing is, I just sold a complete rebuilt early Paxton 2 months ago. And it will be very tight under the hood (ask me how I know with my CRI) to get that airbox on a carb.



You would actually be way ahead, IMO, with a later front mounted S/C from a Fox Body Mustang or go with a new/rebuilt 5.0 roller short block with really good aftermarket alum heads and a throttle body EFI system like the Holley.

I have a low milage 5.0 that I added TFS Twisted Heads, extrude honed early EFI lower, port matched to the heads (which have a stage 2 porting job), Much larger fuel rails & injectors, bread box upper, 75mm TB & 80 mm MAF, and the CR headers (modifying the CR mufflers to more free flowing mufflers)

I can now return to a more stock style hood scoop. I am expecting somewhere around 325HP since it is the stock cam.

Click on photos to enlarge

[twobjshelbys]

Originally Posted by Tommy

How do you want to use the extra torque and power? Track? Street driving? Car shows? Just because?

Along this theme - what deficiency are you trying to correct??? Most Cobras have way more HP than the originals and can't use it anyway because the tires can't transfer it to the road.

[incoming]

c-4 with a manual transmission? I'm confused?

[Hapnyny]

Hi CRG!

I’ll answers the questions above.

Hi Tommy, the car is mostly used for Track events and some times a morning drive. I belong to the BMW Club of NY.

Hi rustyrims, the 347 is a stage three from Prestige Motors, you can look them up on YouTube. 347 Stroker 500HP, they use AFR heads. They just recently built a 363 Stroker out of a 302 pushing 580HP with 7K RPM. They know how to build a motor.

Hi Chicagowil, thanks for pointing out the issues with the supercharger. I was going to go with a single 4 barrel but the air box issue is a pass.

Hi twobjshelby, the Cobra is under powered with the 289, the set up is coil overs all around with 10.5 rear tire and a 8.0 in the front. Car handles and brakes well but is about 100hp short of being a balanced vehicle.

Hi incoming, the set up is a C4 with a manual trans body and a Lokar Modified Shifter.

Everyone thanks for the feed back and I look forward to the responses.

[Tommy]

Good info. If I were going for visual impact, I'd choose the supercharger. But for track use I'd prefer the NA engine for simplicity and reliability. The biggest issue for high HP engines is that they are typically optimized for the 3K-7K RPM range, making them less fun on public roads. Depending on your personal priorities, you could go for an all out, wide open throttle track beast, or something a bit tamer that is still tolerable for occasional street use. When building the engine for the multi-use Cobra I used to have, my guiding principle was to have the biggest, flatest torque curve in the range from 2500 to 6000 RPM.

[eschaider]

Centrifugal compressors need turbine speed to produce boost. That means at idle, you will have little to none, and the car will drive and feel that way. Depending on your installation and your equipment, you can usually get around 8, maybe even ten psi by 2500 to 3000 rpm. That number will vary based on your engine size, compressor size, compressor trim, and, in the case of crank-driven units, the overdrive ratio you elect to use.

The boost delivered by a centri design is based on turbine size and the square of the turbine speed. That means initially, the boost will be very moderate and then come on in a rush as turbine speed increases. This can provide for some exciting driving experiences. In fairness, the belt-driven PD blower will provide an immediate rush as you push on the accelerator, but it is predictable and manageable, with experience.

A belt-driven positive displacement compressor (KB, Whipple, Eaton, Roush, Magnuson etc.) produces immediate boost the moment you push on the throttle. The driving experience is night and day different.

When it comes to modulating engine power, the centri's may or may not be as responsive as you intuitively expect. Throttles placed after the compressors will provide the best modulation. Throttles placed pre compressor (this is not common) will provide the least modulation.

Belt-driven PD blowers will provide you with 90% or more of your maximum torque from throttle tip in through max engine rpm. The effect is a very intoxicating driving experience and the kind of control you need to minimize the number of crashes you might experience when driving a supercharged Cobra aggressively on a road course.

Using a centri compressor and using your clutch pedal to disconnect the engine from the final drive, you can still mitigate the trailing torque oversteer problem a Cobra can induce. For precision torque management control, the PD blower design does a better job, although you can still get yourself into enough trouble that you will still need to push in the clutch.

Neither path is inexpensive. Both are exciting — and dangerous.

Pick your poison ...

[Hapnyny]

Thank you both for your input.

I’ve always had very high HP cars. Feeling the car is underwhelming and 500hp is on the lower side of the HP car’s I have had.

[eschaider]

The difference is your other cars probably were not 90 inch wheelbase cars that weighed 2300/2400 lbs with 52% of the weight on the rear tires. That makes a big difference ...

[incoming]

Get in touch with "Aggressor". He has a close copy of the Super Snake. Running his car without air filters is louder than Bubba's Cummins Dodge with the silencer ring removed from the turbo.

It's really cool for a few minutes.

Why not get a '94 351 truck block and stroke it to 393? Off the shelf parts and will stay together.

[Hapnyny]

I’m keeping the headers so I went with the small deck. Picked up a 363 Stroker.

https://www.prestigemoto.com/custom-...363-ss-c3.html

[twobjshelbys]

Are you having them put on the carb too? Just as well get it all. The EFI system might be worth a more detailed look. I'd want to know which system they use and if it is MAF based

[Sycraft]

Originally Posted by Hapnyny

I’m keeping the headers so I went with the small deck. Picked up a 363 Stroker.

https://www.prestigemoto.com/custom-...363-ss-c3.html

Let me know how you like it. This is the one I am considering too.

[Hapnyny]

Went with the 347 Stroker I felt based on all the feed back that 500hp would probably be around 440 RWHP in a light car. I didn’t want to over build and I’m thinking the car will stay hooked. I do like the C4 in the car, that was a surprise to me I was ready to convert to a T56.

I’ll keep you posted on the results!

Thanks everyone for your input, I took everything into consideration.