I just purchased a Factory Five Racing Roadster (Cobra Replica). The car is complete and a few things I know about the car is that it is a 1991 5.0 Crate motor with GT40-P heads Ford racing E303 cam, roller rockers, stock springs, cobra upper and lower intake. The car also has an aluminum flywheel, so the RPM's climb real fast. The car has a rev. limiter set at 5,000 rpm's and I am constantly hitting the limiter. What do you think it could rev to safely? What kind of power do you think this combo is making? Any input would be greatly appriciated. I had a 2006 Mustang GT with a whipple HO supercharger making 501rwhp that I traded on this cobra, I am missing the power but man is this cobra fun to drive.
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- Thread starter smeltz
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The "accepted" value for the factory rev limiter is 6250, though I've heard that some cars could be different. Your combo isn't making much power above 6250 anyway, so maybe start there.
If the car has "stock" GT40-P springs (Explorer springs), there might be a reason behind the 5000rpm limiter...
If the car has "stock" GT40-P springs (Explorer springs), there might be a reason behind the 5000rpm limiter...
Your combo should make peak HP at around 5200rpm so I'd set the rev limiter 500rpm beyond that i.e. 5700rpm.
Are you sure you do not have a high speed miss? A faulty TFI module would shut down a warm engine at high RPM.
The TFI module mounted on the distributor is usually the culprit for a high speed miss on a warm engine. If the problem does not occur when the engine is cold, the TFI module is definitely suspect. You may need a special socket to remove the TFI module, but most auto parts stores will have one for $5-$7.
Be sure to use plenty of the heat sink grease on the new TFI and clean the old grease off the distributor.
View attachment 204985
See Automotive Tools Specialty | Auto Mechanic & Technician Diagnostic, Testing Equipment | Thexton
The TFI module mounted on the distributor is usually the culprit for a high speed miss on a warm engine. If the problem does not occur when the engine is cold, the TFI module is definitely suspect. You may need a special socket to remove the TFI module, but most auto parts stores will have one for $5-$7.
Be sure to use plenty of the heat sink grease on the new TFI and clean the old grease off the distributor.
View attachment 204985
See Automotive Tools Specialty | Auto Mechanic & Technician Diagnostic, Testing Equipment | Thexton
How do you know you have a rev limiter set to that number?
I don't know of that many easy ways to set a limiter on these engines.
Most people would probably use an ignition box with a pill. If that's the case pull it out and put one in for 6 grand.
And E cam should be good for about 5500rpm.
I hope your "rev limter" isn't really valve float from the cam.
They feel very similar.
I don't know of that many easy ways to set a limiter on these engines.
Most people would probably use an ignition box with a pill. If that's the case pull it out and put one in for 6 grand.
And E cam should be good for about 5500rpm.
I hope your "rev limter" isn't really valve float from the cam.
They feel very similar.
I was told that it is limited to 5,000 RPM, I will need to call and talk to the previous owner. Honestly I am not real crazy about the whole set up. I think I may get a set of aluminum AFR heads and do the whole top section of the motor and have it retuned. I would like to be around 350-400 HP at the crank.
The car runs great until you get to 5K doesn't matter if its hot or cold. That is one thing tha worries me, I was told that it has the oiginal springs, I'm not sure if that E cam is to much for the stock springs.
The car runs great until you get to 5K doesn't matter if its hot or cold. That is one thing tha worries me, I was told that it has the oiginal springs, I'm not sure if that E cam is to much for the stock springs.
Eventually an e cam is too much for stock springs. Some cars take it for a while, some don't.
I just saw a car make 334rwhp with a custom cam, rpm II intake and 165's.
Honestly in a light cobra that would pretty much be equivalent to the 501rwhp in your old gt.
Also would give you a little more rpm to play with, something that you probably got used to with the new mustang, but lost when you went back to pushrods.
Your probably in the 260rwhp hp range now.
You do know those cars have there own forum.
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Very aware of ffcars.com, on it every day, I just figure I would get better advice on here when it comes to the 5.0 engine.
Very aware of ffcars.com, on it every day, I just figure I would get better advice on here when it comes to the 5.0 engine.
For what it is worth, I think you are right...
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