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Baddest N/A NPI in Canada
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SVO have the NPI ports.

SVO will give the best flow numbers over PI and NPI heads. Are they the best head though? Well it really depends on what you want to do. They will have a lower compression ratio on the same motor as a PI head but will outflow the PI head. Which one will make more HP on the motor is something I don't know.
 

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svos are setup exactly like npi's, the best head to get ported is the one you can pick up for the cheapest and the one that gives you the c/r you want

lets say for example you want to use your 95 bottom end, if you went for pi's the c/r jump from 9.4 to 1 to 10 to 1 would be a big gain, that and the pi style intake (witch you can also use with npi's and svo's but thats a diff story) but if you had ported pi's on the stock bottom end it would put you probably close to 240 at the wheels, as my guesstimate with some minor exhaust and intake work.

then more problems come up though, the stock bottom end becomes weak around that rwhp range, so if your sticking with an npi bottom end, go for a ported npi, stock svo, or a non ported pi setup, and that will net you plenty of horsepower, i hope ive helped you at least some
 

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Baddest N/A NPI in Canada
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I should take back what I said about Ported SVO outflowing Ported PI's, check out T&J performance. Their stage 3 PI's flow about the same as Ported SVO's.
 

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Their peak flow numbers may be high, but I would be leary of a head with very high flow numbers because they are most likely giving up flow in the mid lift areas to achieve the peak numbers. Ask T&J for a flow sheet to see what they do across the lift.

But, I would prefer to have a head with less peak flow and more in the mid area because you only see peak lift once when the valve is open, while the other is used twice.

Pete
 

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The SVO is the ultimate NA head. The others cannot flow what it can on the intake side. Unless you do like T&J, and they will tell you not to use that head on an NA motor, the cross section is too large, so velocity will be poor, I've already talked to them about the heads they sell. Oh and the SVO is not exactly like the NPI, the chamber is totally different.
 

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Discussion Starter #9
kdanner said:
The SVO is the ultimate NA head. The others cannot flow what it can on the intake side. Unless you do like T&J, and they will tell you not to use that head on an NA motor, the cross section is too large, so velocity will be poor, I've already talked to them about the heads they sell. Oh and the SVO is not exactly like the NPI, the chamber is totally different.
So a ported and polished SVO is the way to go for N/A?

Does it need bigger valves or are they already big enough?
 

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That's why I am waiting for a few more months to get the new heads. You should look at those flow numbers on intake and exhaust. They put them all to shame. And yes, they will work on the 4.6L.
 

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BirdofPrey97 said:
That's why I am waiting for a few more months to get the new heads. You should look at those flow numbers on intake and exhaust. They put them all to shame. And yes, they will work on the 4.6L.
What heads are you refering to? Info taken from Fox Lake:

Stock unported '99- up P.I. castings flow a max of 163 cfm intake and
150 cfm exhaust on our bench @ .550"

Ford Motorsport 2V SVO heads flow 215 cfm intake and
147 cfm exhaust @ .550"

Fox Lake Stage 1 ported P.I. heads flow 200 cfm intake and
182 cfm exhaust @ .550" !
Stage 1 porting labor is $599 with valve job included

Stage 1 Assembled heads:
Includes Ferrea oversized valves, Comp Bee-Hive springs, bronze guide liners, Viton seals and Pro-Assembled (does not include cams)
$1495 with exchange

Fox Lake Stage 2 P.I. heads flow a whopping 223 cfm intake and
195 cfm exhaust @ .550" with Mod Max valves!
Stage 2 porting labor is $900 with valve job included


SVO's easily outflow the others on the intake side stock. A stock PI head outflows the stock SVO on the exhaust side though.

Intake flow is more important for a N/A application. I don't remember why though, there was a real good discussion on Modular Depot about it awhile back.
 

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If those are the heads he is talking about, GOOD LUCK with the swap.
 

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TGJ said:
Intake flow is more important for a N/A application. I don't remember why though, there was a real good discussion on Modular Depot about it awhile back.

Intake flow is more important for N/A applications for the same reasons forced induction artificially increases displacement, more [cold] air = more power. Since N/A don't have super chargers to "pack and compress" all that cold air into the engine, we need to mechanically alter the configuration of inner flow chambers of heads/intakes by using better flowing parts to increase cfm (throttel bodies, intake, heads, valves, etc). That's why folks would run dual quads or triple-duece carb set ups on older push rod engines, to get more air into the motor without fear of throwing a rod through the hood (as can happen when SCing/TCing older push rod motors, if not careful during build up).

just my .02 cents worth, hope it helps (you're just .27 cents away from a hamburger at McD's now, lol).
 
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