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(By popular request - Thank-you Don McKinnon & group)
For all years being the same, and replacement cams having identical performance specs and construction method; These are my best info
All cam measurements at .050” lift
Intake lift at valve: .350”
Exhaust lift at valve: .340”
Lobe Center 112°
Valve overlap -9.0°
Intake Duration 215°
Exhaust Duration 215°
Base circle: ?
IVO (BTDC) -4.5°
EVO (BBDC) 39.5°
IVC (ABDC) 39.5°
EVC (ATDC) -4.5°
Intake Valve 1.299"
Exhaust Valve 1.063"
BTW: I think these specs are from Doug Lewis but they could be from Vadim, I CRS. So thanks to both.
This car, or rather the cam timing was designed to operate with a certain amount of backpressure. Remove the backpressure and the intake charge doesn't stay in the combustion chamber long enough to properly and fully ignite.
Sounds like then that cam sprockets would be very helpful in this situation just like they are on the Gen1/2 engines with staged cams. I wonder if there are any aftermarket applications from the SVT Duratec that could be used?
The way that our cams are made there is no way possible that a set of cams could be made like they make for the older years.. we would need new cams done
Kirk, I'm not talking about grinding cams, but about adjustable cam sprockets. Adjusting the intake or exhaust cam timing relative to the other cam can help with reducing intake blow though as Carter mentions below.
For those that do not know, when a stage 2 cam (stage 1 cams too) is installed in a 3.0l/3.2l Gen1/2 engine low end TQ suffers a hit with nice gains with top end power. Others have used adjustable cam sprockets to help with gaining back low end TQ while losing a little of the top-end power, you are shifting or sliding the TQ down the rpm scale.
As stated in the FAQ: "based on simulation studies the factory cam is very radical for a street motor. It is already what old timers call 3/4 race cam. A more radical camshaft would require headers, a lighter car, deeper final drive ratio and a manual transmission so the engine would always stay on the pipe. Crane Cams confirmed that recent Ford performance cams leave little (as in none) room for improvement. Ford has them developed to the nth degree."
So if the Gen 3 cams are analogous to Gen stage 1 or 2 cam then adjustable cam sprockets could help tune in the low end if the blow through is really an issue. Street could have one setting, track can have another setting for maximum top-end
BTW, has anyone ever had the cams spec'd for actual lift, duration, etc.?
On that, what is the overlap on our cams, large amounts of "blow through" would be very bad for emissions, I doubt it is as much as has been suggested here. I am more inclined to believe that our stock 3.4 motors don't require much if any more flow than the stock exhaust can handle, thus leading to small if any power gains when changed.