Has anyone found a source to buy used PI cams???????????

 

iron horse,

Ebay motors. Parts car and truck. After getting to that page do a search on 4.6. There is usually some PI heads on there for sale.

This weekend someone probably got a very good buy. There was a pair of Ported and Polished PI heads complete and newly rebuilt. When I looked they were going for less then $800 with about 30 mins left.

 

Has anyone else bought the afore mentioned MM&FF issue this month? Someone has already posted the fact that the stock heads outflow the PI heads at .500 and .510, but the numbers after porting both PI and NON-PI heads are even more interesting. The NON-PI heads outflow the PI's on both the low end and the top end! I forgot to bring my copy in to work, but if anyone is interested I can post the numbers tonight or in the morning. There are quite a few interesting facts in it. I for one, did not realize all five mains were crossbolted on the 1996 and newer 4.6 engines. Curiouser and curiouser!
Rick

 

lilricky2 - from what I've read on stangnet and corral, the intake on the non-PI heads are good (as outlined in the magazine article), the problem area on the non-PI heads is the exhaust.

In addition to a better port design, the PI heads get larger exhaust valves.

So even thought the non-PI heads can flow better on the intake, it doesn't do as much good if you can't get the burned gases out of the cylinder.

I am still heavily leaning towards doing the PI camshaft swap. An online Ford dealer wants around $200 for PI camshafts. From what I've read, it should take about 6-8 hours to swap cams. Not as much down time and cost as swapping heads, but you can still pick up 10+ HP and 15+ foot pounds of torque.

 

Ted'98,
I guess I misunderstood what the article was saying. The cam swap sounds promising. Seems like a good investment for the $$$. I have a set of 5.4 NON-PI's that I can't figure out what to do with. I am hoping this thread will eventually provide enough answers to help me make up my mind.
Rick

 

Here is something else to consider about swapping the heads. No one seems to know where the torque curve is going to be on the swaps. Be it the non PI heads with PI cams, or the PI Heads with PI Cams. Unless you stick to the Truck PI cams you can not be sure where the curve will be using other cams. Remember 90% of the torque is available at 2000 rpm. If you do a swap and change the torque curve you could have 90% of the torque at a substantially higher rpm. If memory serves, the stock torque converter has a stall speed of about 1800 rpm. If you raise the torque curve you may find that you do not have as much torque at the stall speed and the truck will not launch as well.

Regards

Jean Marc Chartier

 

JMC - I had the same concern, I made certain that the price quote I got was for 5.4 truck cams. Even though everyone says that modular cams are modular cams, I didn't want to invest all that time and money I find out that my torque curve now looks like a Mustang.

 

This article was posted by Ted'98 earlier.
http://www.babcox.com/editorial/ar/eb40228.htm
What is interesting it lists the differences in all the modular engines since Ford started making the 4.6. In the article they list all the cams with the cam numbers (it won't let me cut and paste here). According to that list, all PI cams are the same reguardless of if they are for Mustang engines or F150 engines.

lilricky2,
The Non-PI heads you have will work but the intake will not. They are different for the 4.6 and 5.4.

 

Holy valvetrain Batman! This is starting to get a little complicated. I rebuilt a couple of Pontiac engines in the seventies. I know that gives away my age, ahem. Even transplanted a 455 Olds engine into a 1971 Lemans, but this modular stuff is grinding my brain into cheese. O.K. does anyone know for sure if I will gain anything putting the 5.4 heads on my 4.6? Will simply swapping cams accomplish as much as anything else? For those of us contemplating the head change, should we just hold out for a set of PI heads? I definately don't want to push the torque curve out. I started with 2.5 inch duals and the power factor sucked big time. I'd rather not do anything to lose bottom end power.
Rick

 

lilricky2:

Since your 5.4 heads are non-PI, bolting them on to your engine won't do anything (the 5.4 non-PI are the same thing you currently have on your engine).

Putting PI cams in your current heads will give you an increase.

Your sig says your are saving for a supercharger. If you bolt on PI heads, your compression ratio will increase (I think to the point where it will cause problems with a supercharger). So you are better off not putting PI heads on.

My advice (for what it is worth) take the 5.4 heads, have larger exhaust valves put in and have some mild porting done. You should be able to find some companies with track records of doing this kind of work if you search on the 4.6 car forums.

Then swap in PI cams, and then bolt that set-up to your engine. That way you will have a better breathing engine now and when you get your supercharger. Plus your compression ratio will be compatible with the charger.

 

Ahhh, a plan I think I can live with. Thanks.
Rick

 

I wish someone would be able to get the specs on each cam. I looked at part numbers for Mustangs and trucks and there seems to be 1 PN ofr the 4.6 truck PI cam left and 1 PN for the right for the Model years 2000-02 . The 5.4 also has 1 each for the same years. The 1999 truck cam numbers are different from the 2000-02 numbers. The Mustang cam PNs are different from the trucks. A lot of it mught be due to the pressed on or bolted on cam gear. 1 exception is the Cam PN for the Right side of the 2000 Mustang is the same number as the PN for the 1999 5.4 My eyes statred to cross so I stopped looking. If indeed the cam specs, lift diration etc, are identical then the difference in the torque curves would be dependant on the intake configuration. So I will take the 260 Hp and the 302 lbs/ft from the mustang and slip my clutch to get the power to the wheels.

Regards

JMC

 

Well it’s time to through a couple of monkey wrenches into this mix.

First, on the flow of the heads.
The fact that Non-PI heads flow better at cam openings over .5 inches does not mean the heads will out-flow PI heads if you install PI cams. That is a static reading with the valve opened to that point. Head flow is dynamic and has to take into consideration the valve flows completely through the cycle of opening and closing. The valve only spends a little time fully open so even if it flows more at valve openings over .5 inches, it does not flow more during the entire cycle. Since most of the time the valve is open less then .5 inches (remember cams are elliptical not square), the net flow is less. Through the entire cycle, PI heads flow better period. That said, the installation of higher lift cams may increase flow over stock cams, but only slightly.

The data from MM&FF magazine indicates the non-PI heads benefit most from porting and polishing, out flowing non-ported PI heads and almost matching ported and polished PI heads. That makes sense given the PI heads are essentially already ported or opened up almost to their potential. The flow is also improved with cam lifts that match the PI cams. Porting and polishing may be the best way to get PI performance from your pre-99 engine.

The next thing to address is if PI cams will fit the non-PI heads. The PI heads had the intake valve moved closer to the center of the piston. It seems to me this will change the Cam Lobe location and so these cams may not work with non-PI heads. That has to be determined before you just bolt one into a non-PI head. The MM/FF article mentions Ford Motorsports heads that have Cams with lifts that match the PI heads. That may be the way to go. It also mentions Ford Motorsports used stiffer springs for these increased valve lifts so do you trust using higher cam lifts without changing the springs?

The next thing to think about is the engine management. If you bolt on Ford Motorsports heads you have to use their engine management system to correct for the increased flow. If you open up stock heads (or install PI heads for that matter), I think a call to the Superchips distributor (Mike) may be in order to see if a custom chip can be burned to compensate for this increased flow.

So what do we know…. This is not a simple bolt on.
For me, I can work out most of these problems given I am building a new motor. For those who are looking for a Saturday upgrade, a lot more may need to go into this then is worthwhile.

Any thoughts, corrections?

 

WLF - You've got some good points and questions. I've spent a lot of time reading about head and camshaft swaps on the other 4.6 forums and can answer a couple of things based only on what I've read and not on personal experience.


Some mustang and crown vic owners have already put PI cams into their non-PI heads, so if the valve geometry is off, it isn't off by enough to create problems (I think one T-Bird owner has put over 15K miles on his '96 heads with PI cams and stock springs without any problems).

Regarding the valve springs, it is only a concern if you are using very early 4.6 heads (which were available on cars, but not trucks), so it should be a non-issue for Truck owners.

You are right about a headswap not being simple or cheap (in addition to the heads, you need a PI intake, misc items (new heads bolts add up quick) and you are forever destined to run premium fuel and a supercharger isn't going to be an option unless you change pistons.

I do agree that porting/polishing non-PI heads may be the best compromise.

I am still looking hard a camswap, I just need a couple of hundred bucks and a free weekend.

 

putting a used head back on an engine without a valve job is like taking a shower and putting your dirty underware back on, dont do it!

never take the low bid on head work, there is a reason that joe blow is so cheap. never let someones dad grind your valves on a valve machine he got at an auction.

porting a throttle body is one thing (you almost cant scew it up), porting 8 intake and 8 8 exhaust ports is a whole nother ball of wax. "makem big" dont work here, shape, size, velocity and volume come into play.

NEAL , since you have such a problem with blowing the wheels of and all that low end torque, why not switch over to a mustang intake and shift the power up in the rpms? for that matter any one with a blower thats intersted in speed, not pulling, could do this and it would be a whole lot less work than a head change.