My son wants to make modifications to his TPI engine, at what point do you discard the TPI in favor of a higher flow intake system? His target hp is around 475. Opinions?

 

The stock TPI isn't going to go 475 HP. Try a super ram, miniram, LT1 intake, etc.

 

 

Check out the March 07 Super Chevy magazine. They did a "stealthy" TPI mod (383 stroker), using TPIS large runners, Extrude Honed stock manifolds, and ported factory heads and got up in the 500 mark. Almost looks "stock"


Tim

 

Was it an L98??? stock L98 heads don't flow very well.... they are going to top out around 410hp unported... while it's cool that they got 'em to flow... unless you can port your own heads into the 240 to 260 cfm range you'd be money ahead to go ahead and buy some heads that will flow well enough to make the hp you want. You'll spend $1000 in porting charges making them flow less cfm than brand new heads that flow better.
L98's only flow
189cfm @ .400
199cfm @ .500
199cfm @ .600 in stock configuration.... pretty weak...


I think 475hp would be much easier to reach with a less restrictive heads and less expensive induction system....
A pair of Iron Eagle Platinum 200 cc ports flow 270 cfm... you can
get em brand new for $650...
Ad a Demon carb on and Edelbrock Air Gap or Victor with a roller cam
in the heads lift/cfm sweet spot and you'll walk all over 475hp and higher.

 

 

Yes, it's an L98, aluminum heads. I don't have the issue with me right now, so I don't know which year the block/heads were from. I think they said they got the heads to flow 230 or 260. Again, I don't have it in front of me so don't know for sure.

It's someting I might like to do myself, as the TPI just looks...cool, but I'll still opt for set of better heads. My only real problem with any performance mod is I need to pass a sniff-test so I'll need to keep the cam "fairly" mild. I know it will reduce it's potential, but it will still be a helluva lot better than the 250-ish as it is bone-stock.


Tim

 

The general rule of thumb is that you can make 2hp for every 1 cfm
of flow your heads make.... But... the cubic inch displacement of your engine will play a large determining factor at what RPM the 2hp/1cfm is
made.... larger ci motors(383 for expample) by vitrue of their size are going to be drawing a greater amount of air down the intake tract at lower engine speeds....
A 350 can match this draw.... but it will need to be spinning faster to
do it... at higher RPM..
Tuned manifolds... which Tuned Port Injection manifolds are... are
great for torque within a certain RPM band... but their effectiveness is pretty much limited to use within that band.
The Chrysler Sonoramic cross rams of the early 60's were the original factory equipment "Tuned" manifold. While Chrysler was researchiing the effect of tuned manifolds and runner lenghth...they made a manifold runner that slid like a trombone slide... they were able to see the effect
of different runner lengths on the hp and torque curves immediately
by moving the slide in and out. The Sonoramic Commando Crossram
had a runner length of 30 inches... and a torque sweet spot of
2800 rpm ( made for a heavy car).... the Max Wedge Crossram had a
runner length of 15 inches which moved the torque sweet spot to
3600rpms.
What you will need to do if you are dead set on using a TPI Manifold is match the torque/rpm limitations of the Tuned manifold
with the RPM needs of the engine given it's displacement and the Rpms
it will need to draw 500hp worth of Air down the intake tract....
If these 2 factors contradict each other ..... you're not going to make
it happen....gotta match...

 

There are large tube TPI set ups if you like the look. Get a larger base, port it, same for the runners. Then heads and cam to match!

 

the stock d113's are good to about 350chp, max.

homeporting? that's a terrible idea. unless you know exactly what you're doing and understand shaping to maintain/increase cross-sectional velocity, you'll trash the heads and they'll be less than worthless.

by the way, i would never go from efi to carb either. that's going backwards in time.

475chp is out of line unless he's going larger cubes.