I am thinking of putting some headers on my motor. It has the stock ported TPI unit with a 406 bottom end that is getting choked by the stock exhaust manifolds. The motor makes all of it's power under 5000 rpm so should i go with the longtubes or shorties?? What headers are you other TPI guys running and what would you suggest?? What kind of improvements did you see??

 

I think the stock TPI is choking you a lot worse than the manifolds.

Long tubes would probably allow that big motor to breathe better, but ground clearance and cat placement will be a huge issue. 1 3/4" headers with an aftermarket y-pipe, along with a high flow cat and 3" or larger exhaust will probably be a bit easier to deal with.

But for God's sake, get a stealth ram on that motor!

 

i heard that long tubes will give ya a little bit more power and tourqe but the problem with long tubes in the clearance problems

 

Agreed, the TPI is hurting you big time.

Also agreed on the headers, LTs will give you more power (actually more mid and low end power) but will cost you clearance. If this is a drag only car or very limited street use car, go for the LTs... If not, your only option is the SLP 1 3/4" shorties.... Don't mess with any other shorties as the smaller header's primaries will hurt your 406.....

Hmmmm......

http://www.thirdgen.org/techbb2/show...hreadid=160038

 

Lets get to the root of your problem then we'll talk headers

First off, TPI induction was designed for the 305. It has sufficient flow to supply enough air for a 350 but thats about its limit.
Have you ported any of the stock TPI components? What injectors are you running? Is the TPI MAF or MAP? What EPROM are you using?

After addressing all of those issues then you can move on to trying to make more power. If you put headers on the engine you will only run leaner and probably won't be able to compensate for the added airflow.

What I would do is get a hi-flow base, SLP or edelbrock runners, and port the plenum. As for injectors you will need a minimum 24lb. run at about 50PSI (hose off). You also need to have an EPROM burned for the combo you are running.

As for headers I would run something with a 1 3/4 primary tube to a 3" collector. Long tubes will work but ground clearance will suffer. I have a few friends that run a custom header shop here near Detroit and they can make you custom headers/exhaust that fits your needs and your undercarriage.

PM me if you want more help or info on getting a set of headers made.

 

A stealth ram costs less than just these 2 parts, and flows a TON more. A high flow base and new runners is definately a step in the right direction, but when you compare the minimal gains to what you'd get with the stealth ram, the differences become staggering.

The stealth ram can flow 300cfm per runner in 100% stock, unported condition. Even with my accel base and SLP runners, my 350 is choking by 5500 rpm. Imagine how badly a 400 will choke with that same equipment.

Long runners are great on 305s and mild 350s because they give you so much torque. With a 400, torque will not be a concern. Actually, with a little less torque at low rpms, you'll find that you get considerably better traction, and when you combine that with massive upper rpm breathing potential, you wind up with a rocket ship.

 

The stock TPI components have been ported, and i am running the injectors that were on my 305 TPI which i believe are 19lb/hr, it is MAF (1989), and i am using the stock PROM. I run my AFPR at 50 lbs hose off. I use my car only during the summer and for racing but i need to pass a sniffer test so if you could get me a quote on 1 3/4" headers that have the A.I.R tube that would be great!

 

The stealth ram sounds like a great idea but at how high of RPM's will the intake make power? Also what would be everything that i would have to buy to convert to the Stealth Ram?? Thanks!

 

I think it was just under 700 for 1 3/4 coated with air and the install kit. Thats the price with the discount. You have till tuesday the 18th to get in on it.

http://www.thirdgen.org/techbb2/show...hreadid=160038

 

Jump in on this GP with us, I can't wait to get mine!!! I'm getting uncoated 1 3/4"s and sending them to Jet Hot to coat 'em, y-pipe and all.




Ed

 

You should at the very least get that car on a dyno with some bigger injectors and get a chip burned. I know you are going lean which at this point could be very dangerous.

 

19lb injectors are way to small for a 400. you need a set of 30# and a chip change. then for headers id look at a set of hooker supercomps. they are long tubes, 1 3/4 primaries, with 3 inch collectors

 

I have a A/F guage and i don't get a lean reading NA, i get what i am supposed to have, but on the spray it is really rich.

 

DON'T SPRAY IT YET! I'm telling you, either your O2 sensor is giving false readings or your a/f gauge is out of whack. You should be running very lean and nitrous will break things with that setup. You need to get it on a dyno with a wideband O2 and see what its really doing. Get a set of injectors and have a chip burned for it.

 

FULL STOP!!!!

You are running 19lb injectors along with a stock MAF sensor and chip on a warmed over 400???? Nuh uh.

You are DEFINITELY running lean on the top end. For two reasons:

1. You are POSSIBLY maxing out the stock MAF. Once it hits 255 g/s you get NO more injector pulsewidth becuase the ECM can't understand flow rates higher than that. Your engine might still be increasing it's air flow well beyond 255 g/s but the ECM will only inject enough fuel to feed 255 g/s of air. Lean out on the top end is the result.

2. Stock 19lb injectors are ALMOST CERTAINLY pushing 100% duty cycle just trying to keep up with only 255 g/s worth of airflow anyway!! You can only increase the fuel flow by increasing the injectyor pulsewidth (open time). At a certain point there isn't enough time for the small injector to be open to match the airflow. That's where the injector would theoretically be open 100% of the time (100% duty cycle). In reality you don't want to ever be over 80% duty cycle or rish damaging the injector and driver circuitry. I think this is by far the more dangerous of the 2 issues facing you. If you're running mid-low 13s you ARE pushing a set of 19 lb injectors beyond their limits.

On the cheap you can do 2 simple changes that will get you past much of this (not all):

1. Bigger injectors. You know you need them no matter what, might as well get them. A set of Ford SVO 24lb injectors should work fine (they equate to 26lb injectors using GM's calibration scale).

2. Get your chip reburned with only ONE change- the injector constant. Change it to 26 (or whatever size injectors you are using). MAF systems HATE mismatches between the injector constant and the actual injector flow rate. Don't JUST change the injectors, you must do BOTH. THis is a simple enough change you cna probably find somebody local who can do it for you for cheap- it's changing one number, not remapping an entire fuel curve. 5 minutes of work, with the proper chip burning equipment.

This gets you past the injector limitation at least. The MAF sensor limitation shouldn't hit you unless you are running significantly faster than about 110 MPH trap speed for the 1/4 mile (on motor only, not with the nitrous flowing). To verify simply make a full throttle run with a scan tool and see if you ever get up over 250 g/s reading on the MAF. If you are, you're maxing it out. If not, you're still safe on that issue.

I suspect you'll be borderline but still safe. The MAF itself might still be a restriction, but as long as you aren't maxing it out at least you know it's not causing you to run lean. Just removing the screens can help it's flow some, too.

NOW you can go about the issue of pumping up your 5000+ RPM performance and do so reasonably SAFELY. The above changes might make some slight improvement in high RPM performance but you are still limited by the intake and exhaust system's breathing capabilities.