first thing i need to get off my chest is why can't ford build a stronger small v8 if nissan's v6 has 265hp why doesn't my 4.6?

ok that said my 4.6 is a 97 150. so i'm looking for a set of pi heads. will this increase my compression ratio (will i have to use high octane). somewhere here i read 5.4 heads will work is there a bigger advantage to this over 4.6 heads. what else will i need to change. please set me straight

 

Moved to proper forum.

 

PI heads will gain you 1 point in compression, around 10.0:1 - 10.4:1 compression ratio. You should run higher octane for that. 5.4 Heads are the same as 4.6 Heads. Now I am not sure if the 97 4.6 in a truck had a Romeo 4.6 or Windsor 4.6, and that does matter as it affects what other parts you require.

 

Check your 8th digit in the vin for the W or 6 to tell us whether you have a Windsor (W) or Romeo (6) motor. The PI heads do raise compression as TGJ mentioned, but you have to get the PI intake to match. Many mod motor Mustang parts places online sell machined and ported PI heads for better/higher flow characteristics. You could take your existing heads in to do something similar, but I don't beleive you'll see any stellar results

Here's the run-a-way effect that the mod motors have... If you're going to swap heads you might as well get a set of cams for those new heads that go beyond the factory grinds. Then while you're in there you could even go with larger valves. Don't forget you'll need reprogram the ECU. Now the motor flows better, but what about the intake and exhaust? There's no half way here.... to get the truck running right you need to find where you're willing to stop then reprogram after all the mods have been made.

Another problem with these mod motors is the parts can be so expensive you only want to do the job only half way. Slapping a set of PI heads on a non-PI motor won't exactly give you huge gains... and won't get you to your goal of 265hp or more, they will help, though.

-Kerry

 

I more inclined to know what your intentions for this truck are?

 

That is very good question, i've asked myself that several times:> I just got a set of 315's and plan to stay w/ the stock 3.55's (we'll see how it goes) but I also haul fire wood, pull a 5000lb. camper, live in an area with lots of hills, and also tired of getting passed by mini vans:{ Now I will probably be putting shorty headers on( depending on info from another post) and plan on going with some sort of tuner. I dont want to get into changing cams,maybe porting.

 

oh, i almost forgot. as for the heads raising comp. ratio i've heard of people using a thicker copper head gasket will this work for this situation? as for the 265hp, i dont need that exact number, just more than i have now.

i dont have the cashola to get too fancy like cams(those things are outrageous, unless you know anybody that has a good used set for a really good price )

 

The pricey part is just how these motors are for now. The thicker gasket will lower the compression ratio some, but not more than a tenth or two. If you keep the heads as is, you'll definitely be in the market for a higher octane gas using the stock timing set-up, even with a small porting job and seat job you aren't going to lose much of that compression ratio. That tuner may be a good investment, but be forewarned, you'll lose power when you advance timing to compensate for those heads using 87 octane.

-Kerry

 

Increasing the airflow by adding larger cams and or porting/larger valves will also move your power band up higher in the rpm range which will give you even less torque once you install the 315's with 3.55 gears. pulling 5000lbs, you may get passed by granny's electric wheelchair on a decent incline. I would leave the heads alone and go to either 4.10 or 4.56 gears. 4.10's with 265's or 285's and 4.56's with the 315's. and add a programmer.

 

i think your right ,i'll get the programmer first, then look for the gears not hauling anything for a little while. has anyone used the summit/jegs brand gears or do they even make them?haven't chaecked yet