ive been thinking of retiring the tired old 305 in my bird. ive been looking into a tpi setup using vortech heads on a 350. my only thought is i know the tpi has great lower end torque but id also like a little more on the top end. does anyone know what i could do to a tpi setup that wouldnt sacrifice alot of the lower end torque for a little on the top?

 

port the livin **** out of it and u could pull to 5500 easy. but unda 2000-2500 you will be a lil soggy.

 

unda?



Tpi drops off at 4500rpm periond because of the physics of the runner length. You build a TPI car for torque. If you want top end get a RAM setup. That will give you a tad less torque, but you can pull to 6k+ easy.

After 3 years of researching and learning TPI that's that.

 

True. But If you're making alot of power opening things up does some good.

 

It is my understanding that it is the design of the stock base itself that limits the TPI system to 4500 RPM max power. If you are going with vortec heads, you will need the aftermarket baseplate to go with it. Thus solving your 4500 RPM limit for max. HP. However, the base is actually made by Edelbrock and the ones I have seen could benefit more with a good porting job.

 

If you want the car to pull past 5500 rpm, then I'm with Twilightoptics. Swap the TPI for a 'Ram' Intake (SuperRam, MiniRam, StealthRam) or a LT1 Intake. TPI is just not a good top end design.

If you want to keep your TPI, then there are some things you can do for better flow (aka more power). You can try porting your TPI but there is really only so much you can do with the stock pieces. Port the plennum, port match and Siamese the runners, port the base if you can. Other than that your biggest TPI gains will be aftermarket, Bigger Throttle Body, Bigger Plennum, Bigger Runners, Bigger Base. Other ways to gain power could be a cam suited for the TPI powerband, better flowing heads and a custom burned chip. The main thing to remember is that the best output will come with a good combo. Doing random mods wont get you alot of power, you need to have the parts compliment eachother. I recommend you decide what your goal is as far as power and powerband and plan from there.

 

It is not the base itself that limits to 4500 its the runner length. Hense TUNED port injection. The runners from plenum, through the long tubes, through the intake base and head are a certain length and no matter what sound waves can only travel so fast through them. Once you get to that high an RPM it just wont go any faster to give you increased power. People say it can be streched with a bigger base/runners but no one has posted the dyno sheets that i've seen.

When I put my Pro Topline heads on, I'm going to have my base ported and soon to have new runners, and it will be dynoed then and we'll see where the power *tappers off*

 

I think you might need to research TPI for another three years...
So you are saying I could just throw my Superram plenum and runner kit on a stock ported base and it will continue to make power past 4500 RPMS, I really doubt it!!

 

Let's put it this way, when I dynoed my car with a 383, ZZ9 cam, AFR heads, accel base and stock runners/plenum/TB my HP peak was at 4400RPMs. I was having some ignition troubles at the time but I haven't dynoed it since so I can't throw any real numbers out there.
My best guess is that had it been running right it would have peaked around 4500-4600 RPMs (and that is with LOTS of mods). Consider that the stock HP peak is at 4400 RPMs and you can determine that the stock runners/plenum/TB severely restrict top end HP.
After I added the SuperRam plenum and runners it pulls much harder and is much better suited to my combo. I now shift around 5700-5800 RPMs instead of 4800 with the stock setup. I will dyno the car again this summer, hopefully after I burn a chip for the new mods.

 

Then why does the Miniram pull to 6k? Experiance shows me it does on an l98 w/ hotcam.

Yeah do some searches

 

I assume that was a reply to 85TPI400

The miniram doesn't use the stock intake manifold though. I agree with your argument but that was a bad example.

Basically the stock base does limit power but not RPMs. The stock runners/plenum are what restrict the top end the most.
You will benefit from an aftermarket base but you'll still peak at about 4400 RPMs

 

My point exactly. It all has to do with runner length when you are talking about TPI.