blown7

Hey guys. I just finished dynoing my 13B-PP. It made 215 at the wheels. I want more after this race season and have thought of a few parts i will need.

Right now the ports are 50mm wide in the housings. I'm running a weber 48IDA with 46mm venturies. 240 fuel and 130 air netted a 12.9 a/f, that sits atop of a MFR PP intake. The car has a dual 2" exhaust all the way back to the axle where it joins into 2.5 over the axle then splits into dual 2" again.

The rotors are stock GSL-SE with 3mm carbon apex seals. The ports are D shape on the inside.


I know I'm going to buy a 62mm terminator II weber style carb this year. I'm wondering what i should do with the exhaust and how long the primary pipes on the header should be before being collected. and what size pipe the rest of the system should be.

I've ran this setup for a few years and i think this is the last year with it. I'm not against taking the keg apart to install different rotors, but i'm not sure what to run.

The car is nothing more than a drag car and only is driven to the race track.

Shainiac

iTrader: (7)

What rpm are you making 215 at?

blown7

8500rpm. it goes flat from there, stops climbing.

j9fd3s

iTrader: (3)

it seems like 215RWHP is like 255-260flywheel? seems like it could make a little more?

couple ideas:

have you tried with the air filter off? i know any taller hits the hood, but it seems small.

ignition: MSD? stock? timing? plugs? there is a fellow on NP who made something like 18hp by putting in the race style plugs and an MSD on a 280ish rwhp PP

exhaust: all the PP's ive seen run 2" pipe and collect it into 3". have a look around for header lengths, old school is about 90" the shorter ones are in the 24-26" range. in a street car GTOrx7, runs a 50something incher, it peaks once at low rpm, and then again up top. might be worth checking exhaust backpressure.

it would be nice to have lighter rotors, and the 9.7 compression, but they made 300+ hp with the 12lbs rotors way back when

Shainiac

iTrader: (7)

I was also wondering about the 2.5" back to dual 2". Why not collect to 2.5" and expand to 3 for the rest of the system? Would be lighter too. Not that its worth all that much, but do you have velocity stacks in the filter box?

blown7

Right now I'm running stock ignition but I'm looking at getting a microtech ignition only computer with a 2nd gen CAS. I need to redo the exhaust system with 3" but i'm not sure how long the header tubes should be before i collect it. I really want this engine to make close to 300rwhp. If you guys can help out the some exhaust ideas it would be great.


I also dont run a air filter, just open volocity stacks.

84stock

iTrader: (5)

Here's an exhaust idea for you..........

http://s222.photobucket.com/albums/d...ortexhaust.flv

JZG

Your intake port is upside down, and doesn't appear to have the duration it needs for 300 hp. At least square up the bottom corners.... (if your engine is apart)
Exhaust port looks ok though.

From the pics it appears you have enough room for a 4.5in K&N which wouldn't hurt. You can use the same base and lid, just buy a new element.

If you're going to buy an ignition only ecu (which I don't think Microtech make anymore), you may as well go the whole hog and get fuel injection. By the time you buy a 62 Terminator you could almost have a 62 TWM t/body and 4x injectors.

rotarygod

iTrader: (1)

Don't even think about an exhaust cutout!!! Besides the fact that it is ungodly loud and horrible sounding, you won't make anymore power. I had mine on for a grand total of 1 day!

A D shaped port is fine but yours are upside down. There is more to flow than just open area. On the intake side the D shape should face up and on the exhaust it should face down. This alone is costing you some power.

215 rwhp is quite frankly pretty bad for a peripheral port. Especially considering that you can get that much from a very good streetport. Exhaust changes can get you some more power. A peripheral port needs to collect to larger than 2-1/2". Your ignition is definitely holding you back. Convert it to direct fire. You'll notice a difference. A bit larger carb will help too. Not much point going larger than 51mm. On a high overlap engine like a peripheral port, intake and exhaust changes can make huge differences so make your changes there. You may still find another 30 hp locked in there somewhere.

DriveFast7

iTrader: (1)

Work on the exhaust, peripheral ports are very sensative to exhaust tuning. Your collection point to long and like everyone else here says, collect it into a 3" pipe.

j9fd3s

iTrader: (3)

crispeed once mentioned that they found something like 50hp just by playing with the intake/exhaust/heat management on the same PP engine without touching the ports. i don't think he posted exact figures either, but i think they started around 320flywheel hp

BLUE TII

iTrader: (9)

I second the intake and exhaust port D shapes being upside down.

Also on the exhaust port especially it will see a huge increase in flow with the proper radius bevel on the sides and top of the port. I wish the old Yawpower site was up still as they had a great write up on it with flow bench numbers and pics.

You are looking for something like these turbo ports in shape but A LOT bigger.

JZG

^^ Those ex ports are plenty large enough for a PP, it's just that they're upside down, particularly the one on the left.

Liborek

+1

In other thread, there is picture of MFR housing and exhaust port is relatively small, but with lots of duration.

Intake port on this engine is really upside down and just by looking it seems it closes very early... but its not bottleneck of this combination, exhaust is...