5.0 rpm limitations?

levs302 · Mar 28, 2008

In stock trim our motors are pretty clogged up, and seem to start falling off around 5500 RPM. If I were to match together a H/C/I combo that was good for peak HP and torque numbers in the higher RPM’s, maybe around 6500, where am I going to run into problems? Can the rotating assembly take the high RPM’s? If not, what is the reasoning, is it just not high enough tolerances out of the factory? Would the block be at risk of splitting at the higher RPM’s? (keep in mind I’d be using a stock 302 block.) Would the longevity of the block be severely decreased by the higher RPM’s? I’ve seen plenty of bigger intakes and cams that are said to make power up to 7500RPM. Where are the 5.0’s that are spinning this fast? Are these purely race oriented parts? Or would the motor be durable enough for a street/strip car?

Sorry for so many questions and thanks for the help,
Joe

Rick 91GT · Mar 28, 2008

First the stock EEC is going to shut fuel off at 6250rpms, so to go over that you'll need a chip or tuner to disable the factory limiter.

The weak part in the stock bottom end is the rod bolts, the crank, rods and forged pistons are really pretty decent. The higher rpm does put added stress on the block, and that is why usually when you spin the motors higher you increase certain clearances when you build the motor. If you were building a new bottom end there are a lot of things done for higher rpm motors to gain power and reliablity.

One of my first set-ups which consisted of a stock bottom end I shifted at 6700rpm for years, no issues even at the 50oz balance, made about 340RWHP. Bearings looked good after a lot of abuse, NA and N2O.

I find most stock 5.0L actually lose power around 4800rpms, after that you really are not gaining anything in stock form.

Fast63 · Mar 28, 2008

I agree with Rick, the weakest part is the rod bolts. The purely stock shortblock can take 6000 all day, and probably 6500 when you feel like it, but good insurance would be to have some ARP rod bolts installed. I've taken my 85 to 6000 a lot, but mostly when I was younger because I've realized my setup is mostly out of steam at 5500, except in first because it's so low of a gear.

mustangfan1990 · Mar 28, 2008

i have taken mine to 7000 when it was stock. I never had to the rev limiter on my car when I bought it I even changed the the computer and still no rev limiter. I heard though with the little bar bolted into the valley that a stock block could hold up to 9000 rpms

Rick 91GT · Mar 28, 2008

Well I can tell you the stock limiter is there, if your seeing 7000rpms on the stock tach it could be the tach, they are notoriously off.

5.0 rpm limitations?

levs302

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Rick 91GT

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Fast63

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Rick 91GT

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5.0 rpm limitations?

levs302

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