Hey all, just picked up my first mustang...a 97 GT. I've always been a 5.0 fan, but fell into a beautiful 4.6, and now I'm hooked. Anyway, she's all stock and never been used for anything but a daily driver by the old owner, so no shes mine to play with! I don't know much about the 4.6s(but my learning curve has been vertical since I bought, thanks mostly to this site) and was looking at heads on FordRacingParts.com. They have the PI heads of course, but they also have 'High Performance Heads' that are apparently made just for the 96-98 mod engines, and they are significantly more expensive than the PI heads. I cant seem to find any info on them. Anyone have the scoop on these heads? Anyone running them? Please pardon any ignorance on my part, I'm still absorbing information like a sponge. Thanks!
Ford Racing High Performance Heads??
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Jrgunn5150
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Those are what we all refer to as the "SVO" heads, from back in the day when Ford Racing Performance was called Special Vehical Operations. They are hands down the best Mod motor heads out there, and they allow the use of the SVO intake as well, which the BUllit was based off of. If you have the scratch, get them for sure.
DropTopPony
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I agree, if you can afford the SVO/FRPP Heads and intake then go for it...find some nice cams to finish it off.
voidfinger
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+1 !!! , well don't forget the 4v heads... pretty good mod motor heads 
quickstang_1994
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They are very good heads but the price hurts.
DropTopPony
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I've seen them sell for 700-800 used for a set a few times over the years...once just 2 days after i bought my VT PI heads...i almost bought them anyway.
DropTopPony
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the PI Intake does not fit as is but you can port match the heads to fit.
quickstang_1994
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It seem it would be best to p&p npi.
quickstang_1994
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p&p npi flow as good as p&p pi
Jrgunn5150
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Droptop is refering to port matching the SVO heads to the PI intake, which would be better, unless you can get a SVO intake too.
quickstang_1994
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I know but that getting to pricey.Jrgunn5150 said:
Jrgunn5150
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Right, which is why you would port match the SVO heads to the PI intake.
voidfinger
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well, i say if your going to do it then do it right the first time. If you spend all that money on the heads why not go on and get a killer intake to go along with it. just my .02
Jrgunn5150
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I would do it as a stop-gap personally. Intake swaps only take about 2 hours once you've done it enough :dancing6:
voidfinger
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Well, i wouldn't port the svo heads to the same as the pi intake, i would just leave the npi intake on till you do it... the port size is why the velocity is so good at higher rpm's. thats why the stock npi outflows at higher rpm and lift than the pi's. So you would kill it by doing the port work, but thats just me I don't have the money for them so i'm just doing the pi swap for now, then i'm doing a 4v motor swap they outflow the svo's lol.
I don't have the money for them so i'm just doing the pi swap for now, then i'm doing a 4v motor swap they outflow the svo's lol.steedastang
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I have the SVO heads/intake and have had them on my 96 for 7 years. They took almost 2 seconds off my 1/4 et with the addition of other bolt ons as well (no power adders). I am finally adding cams in 2 weeks and cant wait to see the numbers at my tuner. I will be using crower stage 3 npi's and am hoping for 315 to the rear or better. :naughty:
Shocker98GT
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voidfinger said:Well, i wouldn't port the svo heads to the same as the pi intake, i would just leave the npi intake on till you do it... the port size is why the velocity is so good at higher rpm's. thats why the stock npi outflows at higher rpm and lift than the pi's. So you would kill it by doing the port work, but thats just me
SVO heads have the largest port volume of the three heads. The PI intake port would actually be the hindrance.
A smaller port isn't going to help higher RPM power at all. Velocity is a two edged sword. Once the air speed (velocity) gets to about 7/10s the speed of sound the flow slows down terribly and the end result: the power dives. The NPI heads flow better at super high (hardly usable) lift mainly because of the bowl area behind the intake valve, it's pretty much a straight shot-opposed to the PI head. The PI has larger runners, but it also has the benefit of a port and combustion chamber design that does a better job of inducing mixture motion.
The NPIs won't outflow PIs at higher RPM, just because they outflow by a couple of ccs at peak lift, it has nothing to do with your peak horsepower. At any RPM the power you make will depend on how much air the engine can breathe at that point, and the few ccs the NPIs offer above .500" peak lift (which the stock cams don't even lift that high and aftermarkets are right at .500"), is negated considering the PI outflowing them by a good 20% or so at low to mid lift, which is where the valve stays at for the majority of the time it's open. Valve lift isn't like throttle, after all, you're getting full lift even at idle. Lift affects engine power, but doesn't really affect engine characteristics
