In order to get say 400HP or more HP out of a 350 engine using fuel injection I have listed what I consider the most important items. Again this is for a street car with a couple of trips to the track each year.

1. Heads: Don't go cheap here. In my opinion this is the most important part. If you don't have good flowing heads you are doomed. Try for something around 250 CFM at .500" lift on the intake. I would also recommend staying under 195cc on the intake ports. The 200CC Edelbrock E-Tecs would be included.

2. Exhaust: Must have a good free flowing exhaust. Quality headers with at least 1 5/8 pipe with 1 3/4" being better. Then 2 1/2" in the next section. Must have a quality "Y" pipe and not factory. This can be good for 15HP alone. Then at least 3" back to the muffler.

3. Intake: Here you wil need something that will flow 270 or so CFM. This is to feed the heads. There will always be losses to the head so you need something that flows greater than the head to make up for the losses.

4. Cam: To me this is the least important on the list. I believe with good flowing parts as described above you can make 400HP with a cam as small as the ZZ4 and 1.6RR.


Opinion???

 

Too much head flow for the horsepower target. The port is likely to end up larger than you (*er the motor*) wants. A head with say an honest 230/235cfm on a 170+/-cc port will make more torque on a 350ci motor and easily make 400+ peak HP.
A ETEC 170 head Or simular like Vortec or Perf RPM would be a better choice on a 350.
Any intake that flows 270cfm is *likely* to be too big internally, again giving up torque (volocity). You can't select a intake manifold from flow bench results (alone). the induction charge tuning is too important.
The total air flow of the intake/cylinder head is more important. As long as the combination does not loose more than say 4% overall your fine.
First order of business is trash the Stock TPI intake and runners. Going to a hi perf short(er) runner intake like a Mini ram, super ram, ramjet or holley street ram style intake will get you a lot further for less $ over all.
A modded LT-1 manifold swap is a great way to slay a few birds with one stone for low $$$
get the compression ratio up. Up to the *practical limit* of the best available pump fuel.
on a 350ci motor, especially a mild(er) street motor a good 1-5/8" header usually will make as much or more power and almost always more torque than a 1-3/4 header. Long tube headers are better.
As for the cam I basicly agree less is often all you need.
But you'll just flat out make a lot more power with a Hot-Cam or simular. (and run faster) Cost is basicly the same. If you want lift, get a cam with the lift you want.
You'll get way more basic bang and $bang for the buck$ from getting the right cam with 1.5:1 rockers than trying to soup up a lesser cam with 1.6:1 rockers. Not a good HP/$ return. Ther are many benefits to sticking to a 1.5:1 rocker. You can easily make over 400HP with .450" lift.
Proper cam timing events and lobe lift rate that augment the induction/ exhaust combo is much more important.
Don't get wrapped up in high lift numbers.

 

Too much head flow is like too much money, or a car thats too fast. No such thing, velocity is a different thing. If I could get 180cc intake ports to keep velocity up and still get 250cfm, I would be in heaven!!! Oh wait.... AFR 180s :hail:

Even AFR advertises that their heads flow so well you can go with 10-15 less degrees of duration and make the same power.

I love AFR heads, only beef I had with them is the RA on my heads when they milled them for me. It was about a 100-120, must have had that baby set at 8 or 9, It looked like they used the cnc machine to mill it, I could see all the lines from the cutter moving too fast to cut it smoother. So I had to have someone local cut them again to get me a nice 50 RA

 

A Head as good as a AFR head is kind of a waste for 400-425HP though. Cost is always a factor.
A smaller port volume will make more torque and accelerate the car faster. A larger port will make more peak power most times but will be RPM hungry.
Often... it makes less power or gives up too much mid range torque. A 180cc port would be my limit for this type of motor. If the motor was bigger like a 383-406 then things would be different.
Seen too may examples of 350ci engines with smaller ports make more overall power in dyno tests and get down the track as fast or faster with less flow.
A recent magazine test comparing the etec 170's and 200's back to back on a mild 350ci motor is a perfect illistration. the 170's walked all over the 200's at every rpm on the chart. The etec 200's flow 250cfm. The smaller etec 170 flows right about 232cfm.
A Edelbrock performer RPM head flows about the same.
Can be tweeked up to 255-260cfm with suprisingly very little hand port work. Nothing special required.
They'll be less than 180cc finished and really rock on a street 350. and for $Less$ Great bang for the $$$'s
A head like a AFR is better suited to a 383 or large motor and a 460+HP goal. I like them too.

 

Amen, preach it brother.... lol

At this level of HP I would stick with the 1 5/8" again another velocity issue, also helps overlap work and getting a good intake charge.

And if you cant decide on a which cam, error smaller, not bigger. Nothing is a bigger Turd than an overcammed engine.

EX: My first motor EVER... 350, 8.5:1, #882 heads :ugh: and a solid cam 254/262 @ .050 with ~.525 lift 106 lca. It was free my dad had it laying around so I threw it in. He said "it will definatly have an erratical idle, but it isnt the best cam for ya"

Yeah it sounded cool, but was the biggest DOG off the line.

 

A set of $low buck$ home ported/ shaved 305 heads with big valves would have turned that thing into a whole different animal.

 

Just a change to a set of ported #461s (2.02/1.6) made a HUGE difference.

I found out I have a set of #416s that Im going to redo(sitting in corner for years). I have engine machining right now, so I have to replace guides and install new valve seats, cut my 3 angle, cut for bigger springs, screw in studs. I hot tanked em, crack tested em, ground the valves and all that good stuff so far.

When I get into HP Fuels, Ill port em, flow em, and mill them a few .001s

Should be a decent set of heads when Im done. And its a good use of time since I have access to everything.

 

that test in carcraft on the e-tecs used an engine with i think 8.9:1 compression. thats just too low for high performance heads. whether higher compression would make the 200cc heads perform better than the 170cc is another question.

 

if the compression was raised on each engine , each engine would show a aproprriate and predictable gain in torque and horsepower. The 200cc head would not suddenly jump ahead from a compression ratio change.

the 200cc head with its larger ports and more high lift flow would work much better on a much more radical motor with a much higher lift cam, single plane intake etc. Then it would start to make more top end HP then the smaller heads.
The smaller head would still likely be better on the low rpms(more torque) on this more radical motor.
Its all a matter of matching up the right head for the job.
Flow and volocity have to be careully balanced.

 

My 3 top priorities, and they must be appropriately MATCHED, are:

1. Heads
2. Cam
3. Compression

You can screw up a bunch of stuff if you get these 3 right and it'll still run like a raped ape. Too big a carb, too big an exhaust, etc. All that is fixable. However, trying to tune around a combination that has even one of those 3 things above wrong is misery. Get 2 of them wrong and it's a dog for sure.

If I could add a 4th thing to the list, non-engine related, it would be a properly matched torque converter (if running an automatic) so you can actually get to the meaty part of the torque curve, wherever that might be for the combination you've built.

 

Well said, thats exactly it. And its also in that order,

Heads make or break an engines power capabilities.
Camshaft determines the power band
Compression makes the process more efficiant, to a point, then detination makes compression bad(assuming pump gas).


Heads only flow to a certain point, so you dont want a cam that has lift that goes past the heads. You dont want so much duration the car wont idle, or not make power till 4500+(street driven typically) The cam has overlap so you can have a little more compression, but not too much. And material of the heads also helps determine compression limits.

Its just a matching game