Jglisson

I am not familiar with the 4.6 enough to put it back together. I will probably have a shop do that.

1bd97cobra

i have a 97 cobra thats slightly modded but has no internal work done but was thinking about sprayin it with an nx kit. how many shot can a stock cobra motor handle?

asmall

The stock Cobra engine's weakest link is the piston ring lands, as I have shown above. Detonation will tear them apart. The good thing about Nitrous is that it acts like an octane boost... in other words, less chance of detonation. However, if it is not set up right, or if you give it a little too much, or if the engine runs lean on you, you will be doing a rebuild. Honestly the exact number that you can run is impossible to say. I would feel comfortable adding 100hp though. Your RWHP figures would be around 360. Ultimately, anytime you decide to do something like that to an engine not built up for it, you run the risk of causing damage... the more you want, the more likely the chance of damage. You can reduce the risk with good tuning and smart driving. However, you will have to decide how much risk you are willing to take while chasing the ponies!

Personally, I would feel comfortable giving it 100hp shot, but I have never run Nitrous, so I am kind of out of my league. There may be more factors that would make more thatn 100 possible. All I can say with certainty is that with 408 RWHP supercharged and a bit of detonation WILL damage a White 97 Cobra Convertible's engine!!! [:@]

Good luck!

asmall

I have begun porting the heads... let's just say that grinding 32 ports is going to take a while... I have completed the Intake bowls on one head so far. I'll post some pictures next chance I get. I'll show you the part that needs some work, and what I was looking to achieve.

1bd97cobra

what are some good stroker or forge kits i could get?

Jglisson

ebay

kcobra

If you go with a stroker I would definetly go with Diamond pistons. Their expansion rates are different then let's say manley. You will have a quieter motor with Diamond pistons. Trust me I've had many and a built motor, especially strokers have some slap in there and they sound like a diesel before warm up. I would also make sure you have plenty of fuel. Depending on boost, if you want to go big and run top end speeds often go with an aftermarket management like the Fast system which can do open loop at wot. You asked about the power you were making before and if it was high. I had a stock 97 cobra with SHM longtubes, s-trim, 8 pounds non intercooled and had 430 RWHP, my buddy had shorttubes and a intercooled set up at 10 pounds on his 97 with 484 RWHP. These lasted a long time with no issues about the ringlands. Once I had detonation on a top speed run once and boom, ring lands were gone on a few pistons. That is when I went crazy and soaked way too much money into the car. Set your goals because hp doesn't necessarily mean good numbers. Traction becomes a big problem and high HP can come at a cost. You have to run good fuel and be very careful. 500 RWHP is a very fun car, once you achieve 600 and above things get scary and hairy! Don't get me wrong I love speed and acceleration but when rebuilding an older cobra it cost big money. I should have bought an 03 because they already have the motor to handle boost. It's cheaper in the long run to modify an 03-04 cobra. Hell all you do it install a HP or Turbonetics Twin Turbo setup and you can get easily over 650-700 RWHP on pump fuel. You don't even have to install cams and your driveability is just as good as stock until you hammer on it.

asmall

Thanks for the good information, and I agree with you on every point. Before I suffered from the broken pistons, I was easily putting down 408 RWHP. Without any modifications to the suspension system, that amount of power is practically unusable. First gear was very hard to use as she would break free as the RPM hit 5500. I would have to ease it into second or else I would break free again. Third was much better, but by then you are going so fast... This was with the stock rear end, stock tires, stock suspension. It was great when the engine made 305 HP (260 RWHP), but kick it up and traction becomes a huge limitation.

If you plan to beef the engine, plan on a rear end suspension upgrade as well, or else all the money you spent on engine upgrades will put on a nice smoke show. [sm=burnout.gif]

Of course, if you get the rear end to stick really well, that means you will be applying more torque to the ground. That torque puts extra stress on the drive train (transmission, rear end, etc) so with a bullet proof engine that puts out huge numbers and a suspension setup that grips like a pissed gorilla, something else will have to give... Who know what that will be... but that is racing! Always trying to upgrade the weakest link!

Cheers!

1bd97cobra

thanks for all the great information it helps alot. about that twin turbo on the 03-04 cobra, you can run that amount of hp from the twin turbo on a stock 03-04 cobra without any problem? if so thats pretty impressive to me.

asmall

The progress so far has been focused on the heads. There are a lot of options when it comes to heads, and equally as many opinions. Here are some:
1) Keep the factory heads and don't touch them unless needed. This option is by far the cheapest since all you really are doing is slapping the old ones back on! However, depending on how many miles or on the engine, your valve guides may be worn (or getting there) or you valves may be worn. As a result, you could start seeing oil consumption as a result of the oil dripping in. Worse, this could cause detonation. At a minimum, I would replace the valve guides and have the original valves inspected, then get the seats relapped. Not quite as inexpesive as slapping them back on, but if you got it apart... why skimp?

2) Port and polish the factory heads. OK, there is almost no limit to how much you can spend on this. Some say send the heads to a company for a full blown C&C machined port job... $$$. Others say just polish them and call it good. I opted for this option, but am doing a lot of the work myself (at a savings of about 600 dollars). I am polishing the ports to remove the factory casting material (pictures to follow) and matching the ports to the IMRC and Manifols and exhaust headers. I want to make it clear, I am NOT gasket matching, nor am I completely matching the exhaust ports. There are some things to watch out for, which I will point out below.

3) Replace the heads with some newer, better, faster head. Yes, this may be the best way to make a ton of power... however, it is probably the most expensive as well. First, you need to buy the new heads (and trade yours for some cash back hopefully), which can easily run you 2K. Then, you need to get all the hardware for them (some come with it). Maybe a good choice... maybe not. I think there are a lot of opinions out there regarding this subject, so read up on it and make a decision based on how much you have to spend vs how much you think you will actually realize in HP an torque. With a blower things act differently. There are probably a lot of things you can buy with the money that will make your car faster. For example, you could use the money to buy stronger components, then raise the boost levels a bit more... or, instead of getting the supercharger, you could get the turbocharger (A GREAT choice in my opinion! I already have the supercharger though and I am on a budget!)

So, I decided to port and polish the heads on my own. Additionally, I am going to get a 3 angle valve job and have new vavle guides and stainless steel (Manley) valves put in. Total cost will be about 1500.

For the intake, I removed all of the factory slag and cut the small radius back to allow a more "straight shot" for the air to move into the cylinder while trying to maintain the general shape of the passage. I finished it with a 120 grit roll cartridge to make a "slightly rough to feel" effect.


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