Will I lose low end torque by using an B303 cam with a mild 306?

[ssp.interceptor]

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[boominXplorer]

1.7s on the stock cam is a good option instead of going aftermarket in my opinion. Yes more lift does decrease low end torque but when your only starting at .450 lift to begin with a little extra lift will help a ton.

 

[ssp.interceptor]

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[TBMounty50]

Just out of curiosity, anyone know what the point of diminishing returns is for lift on stock size valves in the P heads? Is there a simple formula to figure it out using the diameter of the valve, or is it more complex than that?

 

[ssp.interceptor]

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[boominXplorer]

The main reason people choose 1.6s over 1.7s in our trucks is fitment. A valve cover high enough would require an intake spacer or header issues if you use the FMS headers. Not sure about Torque monsters.

Funny thing is I have had a set of 1.6 pedestal mount roller rockers for about 4 years, just waiting on cam swap to use them. I never felt like installing them on the stock cam since factory is 1.6 already.

 

[TBMounty50]

Putting all the other details of this future engine of mine aside and also the other properties of the camshaft mechanicals(duration, overlap, lobe profile...) and focusing solely on valve lift, there is a point where the intake runner will simply not flow any more air with more valve lift. The maximum flow would also be affected by the intake runner itself of course. This theoretical would need to be determined with all the multitude of variables eliminated(as ssp mentioned) by, lets say, a flow bench. Put the head on a bench, progressively increase valve lift and flow numbers will progressively increase, to a point. I just thought there might be a known lift value for the stock size(1.84?) P head valves where the flow "peaks". The reason I'm curious is if I do chose to use an aftermarket cam, there would be no use in choosing one with a valve lift greater than this number and putting extra stress on the supporting valvetrain components. And to clear something up, new valve springs will get installed even if I stick with a stock cam.

I know what most of you are thinking, why are you beating this horse? Aftermarket cams have been done thousands of times over and most just pick a popular grind, slide it down the bore and drive it. Well, my curiosity gets the best of me and takes me down these weird roads sometimes. I pulled the head off of my air compressor to replace a broken valve and while it was off I thought to myself, "Bet it would fill up faster if I smoothed out these ports." I almost did it! That's just where my mind goes, always looking to improve something.

 

[TBMounty50]

The main reason people choose 1.6s over 1.7s in our trucks is fitment. A valve cover high enough would require an intake spacer or header issues if you use the FMS headers. Not sure about Torque monsters.

Funny thing is I have had a set of 1.6 pedestal mount roller rockers for about 4 years, just waiting on cam swap to use them. I never felt like installing them on the stock cam since factory is 1.6 already.

How would the roller rockers affect header fitment?

 

[boominXplorer]

How would the roller rockers affect header fitment?

I was actually talking about valve cover clearance. The drivers side fms header on my truck does not allow for much extra clearance over stock valve cover.

I also notice most people are running cams on basically stock gt40p motors have at least .500 lift.

 

[TBMounty50]

I was actually talking about valve cover clearance. The drivers side fms header on my truck does not allow for much extra clearance over stock valve cover.

I also notice most people are running cams on basically stock gt40p motors have at least .500 lift.

Gotcha, that makes sense. Can't the oil baffle be removed on stock valve covers to clear rollers?

 

[ssp.interceptor]

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[ssp.interceptor]

Rear (and possibly Front) end gearing, transmission gearing, tire size, TC stall and vehicle weight (or intended towing max weight) all play a role also. Always keep that in mind.

 

[TBMounty50]

Rear (and possibly Front) end gearing, transmission gearing, tire size, TC stall and vehicle weight (or intended towing max weight) all play a role also. Always keep that in mind.

Agreed. Tires and axle ratio are still up in the air. I found a Comp Xtreme Energy with 206* int. 212* ex. duration @0.050, .480 lift on both and 114* LSA advertising a 1,200-5,200 RPM operating range. With the shorter duration, more lift and probably more aggressive ramps, it seems like this one would perform better than the ex. cam. Especially for what I'm trying to achieve. Essentially an "RV" cam as you described. (Like the stock explorer, only "better"?)

 

[ssp.interceptor]

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[boominXplorer]

Gotcha, that makes sense. Can't the oil baffle be removed on stock valve covers to clear rollers?

I think you have to do a good bit of hammering to the stock stamped covers to get roller tip 1.6's to fit so I am sure 1.7s will be a no go under stock cover. Also with a taller valve cover and no intake spacer you will be all over the PCV hose under the intake on the drivers side also if I remember right.

Also I am right with you on all the research you are doing for a cam swap. I did all this a few years back and for what an explorer needs is a RV cam. Once you go over .500 lift you loose alot of torque down low. I Tow my car trailer with my Mounty on rare occasions (never have a car on it, just stuff) and need all the down low I can get. The 4.10s I have just made up for the torque loss from headers and 3" exhaust.

 

[Joe Dirt]

I had 1.7 Cobra's on my P motor, under stock Mustang covers with the baffle removed. Not sure if the Explorer covers are different though, never investigated that...

 

[ssp.interceptor]

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[Joe Dirt]

I had the E7 covers on mine... I know they were close, I think we ground a couple of places to gain clearance...

 

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