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i have a '71 mustang convertible with a 351c-4v, wide ratio toploader, and 3.25 traction lok rear-end. to my knowledge, the only modification is a pertronix ignitor in place of the points/condenser. i had it tuned on an analyzer and the mechanic set the timing at 6 initial, 34 total. he also blocked off the vacuum line going into the front of the vacuum advance, and did some basic adjustments on the carburetor and said that it was fine except the accelerator pump is weak. this probably explains why it hesitates before the secondaries kick in.

the car doesn't seem to be particularly quick, and it quits making power around 4000 rpm, and will not rev much higher than that. my rear tires are 255/60 on 15x8 magnums with a tread width of about 10 inches. without a high-rev, clutch-dumping takeoff (i've only done this once just to see what it would do), it will barely slip the tires. it takes a really hard shift after revving to 4000 rpm to break them loose in second, and then it's not much more that a chirp. i'm not hung up on breaking the tires loose, but without access to a drag strip with accurate timers, i don't have much of a reference point on how well it performs.

one suggested explanation for it sitting down at 4000 rpm was that it has weak valve springs. this mechanic said he didn't think so because it doesn't miss and act up, it just quits revving. could this be fuel delivery? i've replaced the filter located on the fuel line going into the carburetor.

are my expectations too high, or should this drivetrain combination perform better? any comments or suggestions would be appreciated.
 

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It should rev higher than 4k. Make sure the secondaries are working correctly. Tire spin is not much of a measure of proper performance, but I would not expect you to be smoking the tires when you hit second with a stock vehicle.

Deal with the RPM limiting problem and you will find your "seat of the pants" performance improves also.
 

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I just finishd tearing into my motor for the first time. Mine would never rev higher than 4k and ran like a dog! I'd been through all the other systems, still ran crap.

All was revealed when I pulled off the front cover! The timing chain had jumped a tooth and the cam was 10+ degrees retarded!

How many miles are on your motor? Hope yours isn't the same problem...
 

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From the sounds of it your not coming close to what you should be getting. The 351C 4v should have no problem running higher than 4,000.

Start off by running a compression test on all 8 cylinders boith dry and wet. This will give an overall health reading of the engine. As already stated check the secondaries. Next if it were me i'de rev it up to max in the driveway watching a taometer. If it revs out at 4,000 i'de give it a shot of starter spray. If the valves are floating it shouldn't do much, if your starving for fuel the sudden rush of starter spray will make the engine spike up. Use care, you don't want to over rev.

The ignition system could also be the problem.

I doubt it is the fuel suply (pump, filter, line) it should rev up all the way then die which is not what your describing.

If you don't mind paying to have the problem go away you can have the car dyno'ed and have them monitor the mixture when they do it.
 
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