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Old 03-09-2002, 02:15 PM
pylut pylut is offline
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Default 440 Lift versus duration 1.6 rockers

I have a 72 440 HP motor with 8.2 comp (previous owner put mopar thin metal head gasket on so comp may be higher) and as best I can tell I have the mopar 268/284 duration cam.
To my question.
I want to put the 1.6 ratio roller rockers on this engine because it will increase the lift and effective duration goes up a bit but mopar says its lift that makes power and most cam builders seem to indicate that durations the power maker?
Can someone clarify?
Also, any ideas on what this will do to my already low compression motor operating at 5200"?
Thanks.
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  #2  
Old 03-09-2002, 08:00 PM
Jims451 Jims451 is offline
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The 1.6:1 rockers only make the cam "look" bigger at the valve, about 2 to 3 degrees bigger @ 0.050", so they should not hurt low RPM power very much.

The "power" is really airflow. The more air you can pump through the engine the more power it will make. The higher valve lift allows the heads to flow more air and make more power, up to a point, as at some point the port size/shape will limit flow no matter how far the valve is opened.

Adding duration does several things, mainly it lets the valve remain open longer (more airflow) and moves the power band to a higher RPM.
Because HP is derived from torque times RPM, moving the power band (torque peak) higher in the RPM range the engine makes more peak HP.

The caution is alaways the same when increasing the valve lift: Check for valve spring coil bind, Valve spring retainer to valve guide clearance and piston to valve clearance. With a mild cam, I think you may be OK on these clearances with your current setup, but check to be sure.

I think the change should work out good on your 440, even at 5,200 ft.
The easiest way around (fix) a low compression performance engine (low torque at low RPMs) is a high stall torque converter
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Old 03-09-2002, 09:18 PM
pylut pylut is offline
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Default Thanks for info

Thanks for info 451.
I know that you know about altitude 'cause your not to far away.
I was hoping that you might respond to the post.
On the converter, can you recommend a stall for this engine?
I am currently running a3.23 open but am planning a change to a suregrip maybe a 3.53 or 3.91.
I dont drive this everyday and no highway is envisioned.
Also car is a se with no electric anything no power brakes etc so it is not the heaviest Charger out there.
Thanks in advance for your help.
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Old 03-10-2002, 01:33 PM
Jims451 Jims451 is offline
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With 3.55:1 gears and about 27" tall tires, you could use a 10" (about 3,000 stall) converter, which is a pretty good combination for mostly street driving with some drag racing.
At 65 MPH, Engine RPM should be right around 3,000 RPM with this combination.

With the 3.23:1 gears or taller tires the 10" converter is just a bit too loose for street driving. I tried this last year, and you have some slippage below 65-70 MPH. 65 MPH would be about 2,700 RPM, but pulling a hill or ao the converter will go up to 3,000+ RPM, so I don't like the extra slippage with this combination. A tighter converter would reduce slippage, but that would also hinder performance.

With 3.91:1 gears, the 10" converter is still a good choice for a dual purpose car. The only draw back is engine RPM will be about 3,300 RPM at 65 MPH.

As for Brands, I really like my Dynamic 10" converter. I hear they have a new 9.5" converter that works like the 10", but can be made even more efficent?
There are sone other good brands out there, but avoid the cheap GER converters.
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Old 03-10-2002, 02:15 PM
pylut pylut is offline
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Thanks for your input 451.
I will make some changes to the car with this in mind.
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