4-Valve camshaft selection

[Dookie]

I am in the process of casting a port fuel injected single plane intake for Ford's 5.4L 4-valve V8. I am trying to determine the correct lift & duration cams to use for this application. If anyone can have a look at my engine specs and provide some assistance it would be greatly appreciated.

Engine - 5.4L double overhead cam
Bore & Stroke - 3.50 x 3.54
Heads - fully ported 38mm intake & 31mm exhaust valves
Cylinder head flow - 300cfm @ 28" H2O
Intake manifold Port flow - 300cfm @ 28" H20 (average)
RPM range - 3000 RPM to 7000 RPM
Compression Ratio - 9.5:1 flat top pistons
Exhaust - full length headers, hi-flow cats, & mufflers
Gas - 92 octane pump gas
Fuel injection - computer programmable, 42lbs. injectors, with 1200 CFM throttle body

Like I said this engine is a test bed for my single plane intake. Thus, exact vehicle weights, transmission, Rear gears, are not entirely relevent since I have no idea what my customers will be putting these engines in, but for testing purposes here is the information on my test vehicle:

Weight - 3300 lbs
Transmission - automatic/overdrive 3300 stall converter
Rear end ratio - 433

Stock cam specs - Intake: 196 degrees duration .397 lift
Exhaust: 206 degrees duration .397 lift

I am leaning toward an off the shelf grind with the following specs: Intake: 217 degrees duration .474 lift
Exhaust: 217 degrees duration .474 lift

Am I in the ball park? What would you suggest? If you need any more information please post. Thanks in advance.
DOOKIE

 

[SWB]

Can you give flow numbers in stages? 300cfm doesn't mean anything if it happens at .700" lift! Also, at what point are those timing figures made, .050"? Also, what is the rod length, center to center?


Sean

 

[Dookie]

Sean,
Thanks for your reply. Sorry I made a mistake on the stroke. It is actually 4.170. Rod length center to center is 6.657. Flow figures are as follows:

.20 190 CFM
.30 255 CFM
.40 275 CFM
.50 300 CFM
.60 307 CFM

Cam stats are at .050

I'm starting to think I need more cam. What do you think?
Thanks for taking the time to have a look!

Regards
DOOKIE

 

[SWB]

I'll take the time to look at the numbers and see what I can. Good news is that the flow comes in early, so it's not peaky. One thing you will really need to look out for though when you get this done, is to spend the time to dial in the LSA of the two cams. Hopefully you will have adjustable sprockets available for this, otherwise you'll have to make a best guess and then go from there.

With 4-valve engines it's really easy to get the low-lift flow up, so if you are using a 108 separation on a standard SBC or similar, you'll probably find you need to widen that to around 110 or even 112 with what you have now.

I don't think your duration is too far off, but I'll look into it. Remember that you've set a limit on compression so keeping the intake open for too long will kill the lower end, which if it's too long will happen above your stall speed. Then you'll just have a peaky engine with no real power..

Sean

 

[Dookie]

Sean,
Thanks for the reply Sean, you have given me a couple things to think about. Looking forward to your response.
Anyone else want to chime in?
Regards
DOOKIE

 

[SWB]

I went through and did some Q&D calculations to come up with a closure point of around 45-55 degrees after bottom dead center (like advertised closing point). Point is, if you close the intake too late, you'll largely be pushing air out until you get up to your torque peak and above. If you know the mean inlet cross sectional area, then you can figure your theoretical torque peak using piston area and mean velocity. But in general, you need to keep the timing short and I wouldn't go above what you have now based on the references I have. If you had a way to bump the compression up, then you'd be in fat city, but you've got a bit of a challenge going with the lower CR. I'd start conservatively myself..

Sean

 

[Marquis]

This is an interesting post , and the question is alot more complex then alot of people realise.
Just for the record it's what I do for a living, working out the correct Combustion chamber and camshaft selection and port design for a wide variety of engine and criteria and conditions for an OEM.

It's the kind of question companies pay consultancies large sums of money to do.

I hate to answer a questions with more questions,but I feel I must.

Dookie, you have mensioned cam shaft degree duration, but I'm not sure of the convention used over there. What are these durations quoted at? What lift is it measured at?
I typically quote periods as measured at "top of ramps".

The process I would use if this was an official project would be to put all the information into a 1 Dimensional eng sim code
Before Eng sim codes exsited, the mathematics was done by hand, and it is very complex. The 1 d Sim code predicts Volumetric efficiency. It's usually accurate to within 6 percent envelope of the dyno measured curves. It involves knowing measured exhaust backpressures and intake manifold depression at wide open throttle. The geometry of the whole intake and exhaust system would have to be known to.

Now I can't do a project for you, as this is alot of work. I could nudge you in the right direction, based on engines I've helped develop.

Where are you hoping to get peak power? Peak Torque?
With this in mind appropriate cam timing can be arrived at.I have a data base of lots of engines of different configs with cam data.