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557 doesn't rev
good morning,
We stroked a FORD Motorsport 514 to 557. Kept the cam and timing, went to 12:1 CR and ran out of revs (only 5500 instead of 6500). Do we have to retard the cam more (amongst other possibilities)? We use a 1050cfm carb. 6200 RPM would be perfect with the current diff ratio. Dominik www.capetownskies.com |
You can retard the cam timing, but frankly, you're out of cam and possibly head flow.
When you increase the displacement of an engine, it takes more cam to fill the cylinders in the allotted time. You have to have head flow to back that up. Also, I don't know the particular strokes for a 385 series engine, but increasing the stroke could also damper the hp peak a little due to the fact that you're swinging more weight. Retarding the cam timing may move it up about 500 rpm or so...but it's not the correct solution. For a peak hp of 6500 in a 557ci engine, you're gonna need LOTS of duration. |
thanks!
I check the "basics" soon, like fuel and air supply, monitor A/F ratio, power and torque peak on the chassis dyno. we are quite happy with all the torque and power the engine makes up to 5500 and I forward your advise about head flow and cam to the driver/owner. he will be happy to put another diff in and leave the cam as it is. this is a "low performance" country and this car is the fastest, by far! Dominik, Cape Town |
Good luck with it! How much hp/torque did it make?
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With a 557 you really shouldn't need anything much above an idle, surely?
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Good day,
we got about 900Nm (660lbft) and 605 hp as a 514cui and 1000Nm (740lbft) as a 557, with not too much more hp. I have to check, but if I remember correctly 625hp. I don't have the dyno sheets here, so I can't recall the corresponding RPM. Impressive numbers, no matter how you look at it and what the error may be. The car did easily low 10s (sorry, this is not a Cobra, rather a FORD Fiesta) and we think about adding a wing now for better high-speed traction. The track is actually too short for braking, the driver lifts off at about 350 yards. I don't want to know what happens with that engine in my Cobra... Yes, I agree: 5500rpm is enough! Dominik |
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very cool!
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557 doesn't rev
Dominic,
Is your 1050 carb a 4100 or 4500 series carb? What type of intake are you using? What are your cam specs? Are you running a breather? How close is your hood to carb? It sounds like you are not getting enough flow into the engine assuming all other areas like fuel pressure and volume, spark, timming etc. What is your vacuum at WOT? If the carb is sized right you should have less than 1#. I have a similar problem with a 545, 13.5 compression in a Mustang except it will keep accelerating but slows down in high RPMs. My is a two prone problem: 1- jet extension need in secondaries causing high A/F #s, 2-the 850 BG carb on a dual plane intake not big enough causing higher vacuum #s at WOT. Food for thought. Mike |
cylinder cracked
Hi Mike,
thanks for your input to my thread from months ago :-) Unfortunately, a cilinder liner cracked and ever since it has been "fixed" the engine seps water into that cylinder. The owner of the car lost interest, but we look into fixing it some time. He ran it to not much over 5500rpm, definitely less than 6000 and was quite happy. Dominik |
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