How much PSI are you running on stock internals? - Page 2 - Ford Mustang Forum
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Quote:
Originally Posted by ironmike666 View Post
stl, so what are the %'s that are deducted off crank hp for the different ttransmissions? How much more hp could you see if whiplash7 had a manual trans?

silverstang, what size lt's you running? 1.75"?
It's about 12% for a manual and 15-18% for an auto.


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I dont think there is really a "safe" level. Ford will warrenty there SC with 400hp at the crank. What does that tell you. Even Roushs 427R is only HP at the crank and it is warrentied also. Thats only 375 or so at the wheels. I think the rods are terrible and manufacturing consistancy is worse. Some get good ones and some dont. All it takes is one bad rod.
The fellow who blew a motor at 24psi made me laugh. You can blow any motor. Its only as strong as the weakest part.
From what I have read I think RPM is more important in keeping your motor alive than a pound or two of pressure. Im a chicken and even though I can probably aford a built motor I dont want to go thru that agrivation. So I picked a low 7psi and set my RPM limit at 6k. Only time will tell. GA
+1 on the RPMs. The stock cast crank and powdered metal rods are really good pieces for up to 550 crank HP with boost as long as your not gonna try and turn 6K for 4 hours. The cast pistons are really the weak link when it comes to boost. With boost detonation is deadly to the cast pistons and since we have no control over the true quality of pump gas it can be a game of Russian roulette when you get to 10/12 psi on a pump gas tune.

Over revving the PM rods seems to prove to be disastrous even in non FI engines. Most every PM rod and pictures of PM rods that I have seen have failed where the beam of the rod begins to expand out to the crank journal. When a rod fails at that location it is normally a tension failure (when the crank is pulling the rod and piston down on the intake stroke) from over revving. There is thread in here with pictures of a 3V engine that broke all 8 rods and they are all broke in the same place. There was never an explanation of what caused the failure but I would put my money on to many revs.


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Quote:
Originally Posted by ironmike666 View Post
stl, so what are the %'s that are deducted off crank hp for the different ttransmissions? How much more hp could you see if whiplash7 had a manual trans?

silverstang, what size lt's you running? 1.75"?


Yes sir, 1.75 ceramic coated from lethal perf.
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10 psi here. 458 RWHP with 449 RWTQ, Automatic tranny with stock interns. 10K miles and no problems.

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8.5 psi here with a 2.6l Kenne Bell. Put down 440 rwhp and 401lb-ft of torque.

I always hear the manual is right at 15% loss where auto is about 18% (whipple and KB sites state that, I don't know for fact).

As long as you don't ping or just plain push more power to the rods than they can handle, it's RPM that will kill your motor. On the dyno this weekend the tech running the dyno asked if I wanted to do a pull to 6800 since power was still climbing steady at 6500.. My limiter is set to 6500 but even so, I would not push an FI setup that hard on a factory short block. Stress on the rods goes up exponentially so you end up with almost double the stress on the rods at 6800 then you have at 6500. I usually shift at 6300 and my shift light goes on at 6150..

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9.4 lbs - Whipple.... no prob.... but it's not about the boost! boost is just a relative term telling you the increase in air pressure from one setup to another (additional pressure in manifold before compressor to after compressor); the number by itself doesn't really mean much - almost every single variable you could think of could change the boost reading... it's about the tuning.. as said the internals are reported to be good for about 500 hp (450+ to the tires); if you tune it correctly, maintain it correctly, and leave a reasonable rev limiter in place, you are really no more prone to engine failure than any other car
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Quote:
Originally Posted by dtuna42 View Post
9.4 lbs - Whipple.... no prob.... but it's not about the boost! boost is just a relative term telling you the increase in air pressure from one setup to another (additional pressure in manifold before compressor to after compressor); the number by itself doesn't really mean much - almost every single variable you could think of could change the boost reading... it's about the tuning.. as said the internals are reported to be good for about 500 hp (450+ to the tires); if you tune it correctly, maintain it correctly, and leave a reasonable rev limiter in place, you are really no more prone to engine failure than any other car
+1 dtuna42 gotta tune em right

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