Longevity & Reliability vs. Power
for a street driven FE 427, at what point do power modifications begin to seriously degrade longevity & reliability? 500 HP, 550 HP, 600+ HP ?
Z. |
For an engine of that displacement, it's not hard to get 500hp with good cylinder heads, hydraulic roller cam, etc.
When you start approaching 600hp, you need to start using the larger, rowdier cams, little higher compression, etc. Peak horsepower rpms go up, better valvetrain components are necessary, etc. Of course the larger the displacement, the easier to make more horsepower. The 428FE that I built for my own Cobra used Edelbrock heads, a Tunnel Wedge intake, a solid roller camshaft, and it was about 11:1 compression. Peak horsepower was about 550 @ 6500. If you were running this car hard, you would need to shift at about 7000. A solid roller cam needs a little more attention than a hydraulic cam and the lifters don't live as long. I would consider that a minus in the longevity department. Where reliability starts becoming an issue is if you're drag racing with hard launches, spinning the engine really high, etc. |
At about 5,500 RPMs
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“5,500 RPMs”, I agree.
The higher the RPMs the greater the cost to build and the longevity goes down. It’s literally diminishing returns. |
I wouldn't call it diminishing returns since rpms make horsepower, but in terms of reliability, I would say anything over 6400-6500 would start to see a decline.
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If you put Royal Purple oil in it with a ZDDP additive, it may physicaly break, but it will never wear out! :rolleyes:
:3DSMILE: . |
Personally, for a predominantly street-driven car, I think the "sweet spot" is mid to upper 400's in horsepower at the flywheel, measured with all accessories and pipes attached.
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(just giving you a hard time). ;) |
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EDIT -- *streetability, longevity, or increased maintenance. (I need the last one like a I need a hole in the head.) |
So, it all boils down to:
Performance, Reliability, or Cost. Pick any two. |
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Perhaps you should ask Santa for a new set of Avons or Billboards for your ERA.;) You could get a bit more performance out of your FE with a better set of tires.:cool: |
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Are you suggesting that--ceteris paribus--a Cobra with 525 FWHP would accelerate as quickly as the same Cobra with 700 FWHP (assuming decent tires and suspension setup)?:confused: |
It's about the clearances, rpm limit, and oil pressure
zrayr Z this will turn into a questionable answer. From my own personal 14 years of owning a cobra and abuse at the track 95% of the time, here is what I have found. Matching parts for an rpm range is most important. If the power range is between 2,000 rpms and 5,800 rpms you build a motor for this range with parts. Intake manifold, compression, exhaust system and most important, CAMSHAFT design and valve springs. I built a shelby block and head motor with a 9.2 compression, 501/533" hydro camshaft and stock ERA exhaust. Car made 368 HP and 420 ft of torque at the rear wheels. This was with a stroker crankshaft from a stock 428 motor. 3.98" The cylinders are bore of 4.25". I build torque motors, this is was moves the cars, HP is for topend speed. I also believe in a peroiler system for the motor. Car will pull just under 1 "G" on a skid pad. I have learned that anything over 500 rpms past max hp numbers is all you need to spin the motor up to. ANY THING more than tis is just wasting motor life. Maintainance of checking bearings each sprring and looking for any damage or metal flakes in the oil pan are important to longer life of the motor. If you are running an FE bottom end, which I was, I run high oil pressure when racing. Between 65-80 psi hot on the track. I ran this motor for 8 years and have no failures. I run a 15w-40 oil and Lucas oil suppliment and small bottle of EOS. 75% of the wear to a motor is on startup after the motor has been sitting for a week. prelube with giving the motor a 35 psi pressure before starting saves alot of wear and tear. I have only $14K in this motor. The motor now with the same block and heads is a 482 motor. Same principles apply to this motor. I have gone to a hydro roller camshaft with a .586-.607". I have also gone to beehive springs that have less weight than the stock valvesprings and top caps. The couple of oz's has increased the rpm range 300 rpm more and raised the valve float to 5,800 rpm, the motor just pushes through this spot. Max rpm is 6,200.
Here's the thing, if you want to build an FE motor, stroker it with a 4.25 crank and chevy rods. This will make it just about bullet proof. I would still not rev this over 6,500 rpms. HVHP oil pump with an #80 pound spring. This will work good for street and a little track fun. Having ports on the intake and heads will make 10-30 hp more that stock. The exhaust is the big choker of the power. If noise is not an issue, go for loud pipes, low back pressure, and ear plugs. forget about talking and driving. Watch out for the cops with DB meters in town after dusk. You can also buy 2 sets of pipes, one for track and one for street. Run a lite flywheel on the car 20-22 lb one,not the 40 pounds that comes stock on most motors. Rearend ratios and trans ratio need to work togeather to get the most power to the ground. Barry R. has a book out about max hp from an FE motor. BUY IT and read. Jay Brown is also coming out with a book in a couple of weeks with more info on each part and which ones work better than others. You can build a nice 445-482 make great power, run on hightest gas 91 0ctane. Smoke the rear tires in 3 gears. Make about 600ft, of torque and 540hp. This is what my 482 makes. idles at 750 rpm with a little lope sound. running for 5 years now and no problems. I did have 2 failures of rocker shafts and have fix this with running ersons now. limit to 6,000 rpms, motor will last for many years with basic service. Have to remembeer the car ownly weights about 2,500 pounds. TOO much power is as bad as not enough, only different is one makes you look silly the other one could get you kill.:eek:%/;):) Rick L. |
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