Proud Cobra Owner - SP01862
 

Hello everyone,

I just wanted to introduce myself to the group and ask for a little regional advice.

I bought my Superformance Cobra back in April. It's a 2004 roller originally built by Dynamic Motorsports in Ohio. It has a 351W and a Tremec 3550. The dyno run at the time of the build was 470 hp/435 ft lbs. I was actually looking for more of an enjoyable driver rather than the most extreme build I could find, so this was perfect. The car is everything I'd hoped for, but it's set a new bar for high maintenance as compared to any other sports car I've ever owned.

In fairness, I'm pretty clearly dealing with a lack of good maintenance from the previous owners. Even though the car only had 8,520 miles at the time I purchased it, eleven years of nothing can take it's own toll. In time, I plan to get it back in good shape.

Almost immediately after receiving the car, it needed a new water pump and a cam shaft (more radical than the original). One of the original cam's lobes was ground down from a bad roller. Also, it was originally running a 750 CFM Demon Street Demon carburetor (mechanical secondaries) that wasn't tuned well. At the same time as the other work, the Demon was switched to a 650 CFM Holley Street Avenger (vacuum secondaries). The car has hated this carb from the beginning. Two "experts" have worked with it and everything that can be tweaked (jets, squirter, power valve, springs, etc...) have been changed out, but the car still runs very poorly. It leans out terribly under hard acceleration and the power delivery is neither smooth nor linear, both on the primaries and the secondaries.

This brings me to the advice part... I live in Aiken, SC. I understand a lot about my car (mostly how much more I still have to learn), but I'd really like to find a very competent, detail-oriented shop to work with just to help me get it back to reliable running where I can take over. On the Georgia side, I know about Southern Automotive (in a transition currently?) and Cobra Restorers. On the NC side, I know about Olthoff's Racing. Am I missing any place? Does anyone have any experiences with these places that they'd be willing to share? Who would you trust your car with?

Thanks, and I'm happy to be part of the forum.

I have to guess that what you really mean is "I am aware of the existence" of Olthoff Racing. Obviously, you don't really "know about" Olthoff Racing. Map quest says you are 177.89 miles / 2hrs, 50 minutes driving time from Mt. Ulla, NC. You are a very lucky guy. Give Dennis a call and talk with him about your Mk III. (704) 647-9924. You'll get the picture pretty quickly. And, congratulations on your new car!

DC,

After driving 1359 from New Mexico back to North Carolina, I made it a point to have Dennis and his crew give my car the once over. These guys are passionate about these cars and will get your car sorted out. Good luck and congratulations.

You should also consider the SCOF forum as it has proven to be a great resource for me.

Jamie

First, welcome to Club Cobra, you'll find a wealth of information here.


Second, Olthoff is an excellent place to bring your car, they know it inside and out. I can also suggest Mason's in Spartenburg, SC,(they are a large, old school, very Ford friendly shop) forget about Cobra restorers as the owner passed away two weeks ago, and the shop is in flux at the moment.

Third, having had the same engine in three of my cobras, and having the benefit of unlimited access to a chassis (not engine) dyno, your first carb was way too much for the car, no way to jet it down enough to get it to work well, the second is (670cfm Avenger part # 0-80670) a "show and go" (IE: street rod/ ice cream cruiser) similar to the Edlebrock car line (that is what Holley was going after when they came out with the "Avenger Series"), and was never meant to be a true performance carb. In your case, and with your engine specs, I highly suggest a 650cfm Holley, PART# 0-76650BK, right out of the box you'll love it.

Hope you find this helpful......


Bill S.

PS: Greenville Cars & Coffee is tomorrow at the Michelin building just off RT85, if the weather is good, why not take a drive up......

Everyone,

Thanks for the welcome and for your comments. I appreciate it.

jcam,

Agreed on SCOF. They helped with the ownership history prior to me buying my Cobra and their Owner's Manual has been a pleasant surprise, too.

Thanks!

mrmustang,

Great! That's exactly what I was hoping for.

I didn't want to put that out there to prejudice people's responses, but that's the carburetor I've been looking at (and that all my research points to). One question for you, though... Choke or no choke? I'm not a huge fan of the electric chokes, and I don't want to clutter things with a manual choke (though I'm definitely a manual control kind of guy). We live in a fairly warm area, so I'm leaning towards no choke.

Very much, so.

Thanks for invitation! I'd like to see that 289FIA of yours. Maybe next time when my car's running reliably. Raincheck? Is it always the last Saturday of the month?

DC,

I have a similar engine and I a Holley 750 double pumper (rebuilt (late 90's)) with an electronic choke. The 750 made a huge difference at lower RPMS and a noticeable as you stand on it. The electric choke is sometimes a PIMA. I am contemplating installing manual choke and mounting it under the dash (near the 12 volt outlet).

Enjoy your new car.

Thanks, jcam. I love the idea of a manual choke. It suits my personality better, but I'm just not ready for the clutter. I may try choke-less first. Right now, I'm just looking forward to having a carb that gives me smooth power through the circuits and transitions.

If the car has an electric choke pre-wired, stick with it, the newer style is a far better set up than the previous century set up. Straight out of the box this carb will make your car run better.


Ah, the 289FIA is now living in Germany, I'm currently on the hunt for my next Cobra (will be my 30th ;))

Yes, fourth Saturday of the month......You are more than welcome to stop in when you are up in the area.


Bill S.

30th!?! My car collection and addiction isn't seeming so bad now! :LOL:

I'd support mrmustang's recommendation of an electric choke. I have a 770 CFM Street Avenger on my BBF and it was WAY too rich on cold starts - a gigantic PITA that had to be babied until it warmed up. I figured out the choke pull-off wasn't properly set for an engine of that size and wasn't opening far enough. It has been 'night and day' since I got the pull-off set properly.

Thanks, cycleguy55! The car is currently wired for a constant 12V electric choke.

One less than the other forum you know me from :D

If the Holley Street Avenger was brand new, it should have worked fine right out of the box. There are differences between each carburetor model, of course, but they are not so great to cause the engine to run like crap. You likely have a different problem.

And if you really made 470HP with a 750CFM, and you switched to a more radical camshaft, you are going the wrong way by using a 650CFM carburetor.

You need local help from someone that knows what he is doing. Carburetor tuning isn't difficult, but it is a dying art.

My favorite carburetors are from Quick Fuel Technology. They build excellent carburetors based on Holleys. Another good choice is the Holley HP series. I'm suggesting this over the others because you said you have a more radical camshaft. They carburetor and camshaft need to work together.

My favorite carburetor tuning website is this: Carburetor Tuning the Scientific Way

There is a section near the bottom where he explains how to tune using an O2 sensor and a vacuum gauge. I did this on my car (non Cobra), and it made tuning a piece of cake. The O2 sensor eliminates the guesswork.

wkooiman,

It was brand new, and the shop who choose it was the same shop who chose the Trickflow Stage 3 cam. I couldn't agree with you more about the cam and carb needing to work together. Given everything else was better (not perfect, but better) prior to the cam and carb switch, it's not a stretch to say the carb choice was very poor, especially going in the direction of a more aggressive cam.

I do need to look into the fuel pressure more. I know that.

Dyno from the time of the original build is attached. The car was not dynoed again after the new cam.

I'd love that, but haven't found it yet. And that's not for lack of looking. The second "expert" I worked with was careless with his lift arms and cracked the fiberglass slightly under each exhaust outlet. *#^&@#?<%!!! :mad: With help like this, I know I'm better off on my own, even if that's groping in the dark much more slowly.

I'm really more interested in finding someone to work WITH so I can learn more rather than have someone just do it for me so it forever remains a mystery. I hate it when I ask questions and people get defensive. I kind of feel like if you can't explain your idea/plan, it might not be such a good one.

I only have some limited experience with Holley and Demon (Barry Grant). I know a lot of others share your appreciation of Quick Fuel, though.

I'm still digesting the link, but I appreciate you sending it! That's exactly the kind of educational stuff I've been reading up on lately. I wasn't aware of that site, so thanks!

Cool.

I've had pretty good luck with this approach.

0. Start with a good carburetor - preferably one that is brand new and matched to your combo.

1. Make sure the fuel pressure is correct, the carburetor is level, no leaks, and the floats are set correctly. If any of this is wrong, it will throw everything else off. Also, don't forget that many problems are diagnosed as a carburetor problem, when it is actually something else.

2. Set the timing. If you have the timing off, it will act like the carburetor is misadjusted. I like 16-18 initial, plus ~20 advance, so that total advance is 36-38. Of course this varies from engine to engine. Newer, more efficient combustion chambers require less timing.

3. I prefer to run w/out a choke. If you are running with one, disable it while you are tuning the car. Deal with one variable at a time. You can adjust the choke later.

4. Set the idle screws for max vacuum at idle. As you lean it out, it will increase the vacuum. Stop leaning it out when the vacuum stops increasing. Take your time, and go in and out with the idle screws until you get the feel. As you screw them out, the engine will run slower (and vacuum will decrease) As you screw them in, it will run faster. Find the point where it stops increasing as you screw them in, and don't go any further. Make sure they are set the same on both sides of the carburetor.

5. Drive it several days, just working on the idle screws. It runs on the idle circuit 100% of the time, so get this right first. The main circuit (jets) add fuel. It doesn't replace the idle circuit.

6. Drive with a vacuum gauge. When you gradually give it gas, you'll see your vacuum drop. At some point, your engine will stumble. You want the power valve to open right above that point. The stock power valve is usually 6.5, which means it opens when the vacuum drops to 6.5. Above 6.5, it is closed.

7. Run with a vacuum advance distributor on the street. When you are not under power, the power valve is closed - which means the carburetor is running leaner. As you lean the carburetor, the fuel burns slower, so you need more advance. If you run w/out vacuum advance, it makes the exhaust much hotter. This doesn't hurt drivability, but it isn't fun driving a car that always runs hot.

8. Tune the main jets with an O2 sensor. The O2 sensor will tell you your AF ratio at cruise and at power. Max power is somewhere around 12.5. You want it to lean out to about 16 at cruise. If you are too rich at cruise, you'll foul plugs. Add fuel by going up 3-4 jet sizes. Remove fuel by going down. You can do this on a dyno if you want, but you need to find a shop that knows what they are doing.

9. Here's the fun part. When your car is running bad, what does your O2 sensor say? Is it lean or rich? Your O2 sensor will tell you what's going on.

10. At this point, it should be running pretty good. You can fine tune air bleeds and the accelerator pump circuits, but you usually don't have to mess with them to get a car that is enjoyable to drive. You fine tune to get rid of that annoying flat spot over 6,000 RPMs, or perhaps a bog when you leave the starting line.

This, and the link you sent before, makes it sound fairly easy. If nothing else, I'll know a Hell of a lot more about my car after this. Thanks, wkooiman!