Let me introduce myself and give some background info.
My name is Glenn Landrum and i'm one of several Directors in charge of the NASA road racing series Camaro/Mustang Challenge and i am responsible for the Texas Region along w/ another Regional Director.
for the last 10+ years the series has had in place a 230rwhp/300rwtq limit in place for the class. the class requires the use of stock parts and engine specs down to the exhaust manifolds. for the 3rd gen cars, the 305 is the only legal motor as it was the only factory option w/ the 5 speed. it can be raced w/ a spec carb/cam/intake package or w/ the OEM TPI motor.
in recent years there has been a push to allow the later model cars into the class (98-02 F-body and 05 to present Mustang). this required us to create a "sister class" to place these car into on a temp basis. eventually we want to move all the CMC legal platforms to CMC-2. the problem is w/ the 305 TPI cars. while they were suited perfect for the 230/300 power limits, CMC-2 has a slightly higher limit of 260rwhp/310rwtq. all the other legal platforms have been easy to get to those numbers. but for the last year we seem to not be able to easily get the 305TPI there. currently we are about to 240/305. this has involved an increase in rocker arm ratio, shorty headers and i think nothing else.
i assume you guys here have beat this 305 TPI deal to death. and while i'm sure you guys have always worked towards getting max power for the set-up w/ few limitations, i was hoping you guys could point us (the series) in the right direction w/ regards to what would be the path to 260/310 w/in the confines of the intent of the class.
the things we want to keep the same are:
OEM TPI, OEM heads, OEM displacement, OEM computer tune, close to OEM comp ratio.
my thinking is that there is a cam better then the LB9 cam out there that will net us the targeted 260/310 numbers, or close to it. a factory GM cam would be nice, but pretty much any manufacture will be fine as long as there is a easy supply path for them.

so, please feel free to offer suggestions, dyno info, ask questions relating to the topic at hand, and past experiences w/ gains seen from simple bolt-ons to cam upgrades.
any help will be most appreciated.

 

So let me get this straight. You are saying that you can now get 240RWHP from a stock 305 TPI with the only modifications being Headers and 1.6 ratio Rockers? That's about 275 FWHP on a 5 Speed car. That's really surprising.... And you are looking to find an additional 20RWHP with just a cam change?

Tough to do... The problem with this is that (without Porting) the stock heads don't flow well enough to provide that much power. You can use a cam that has a higher lift (up to about .480 max. with Stock Heads due to the Heads Lift limitations, and I suspect that they wouldn't flow any better with more Lift anyway) and a longer duration (up to 220 max. @ .050 112 LSA due to stock Computer tune limitations). Using a bigger cam than this will require modified Heads and Computer PROM changes in order to get it to run well.

The World Products S/R Torquer Heads that I am using are considered "Stock Replacement Heads" though they do have a slightly more modern design, better flowing Valves, and larger diameter Intake Valve, and they flow a little better than Stock Heads do right out of the box. The Cam that I am using is a California Smog Legal C.A.R.B. approved Cam (the Headers are C.A.R.B. approved as well). My point being that there may be a presedence implied here that you can use to help meet your rules book goals....

I have not put my car on a Dyno, but I suspect that with all my current modifications, I am close to your HP/TQ goals.

There is a fueling issue as well: To get that much power, you need to increase fuel by either raising the fuel pressure, or by using bigger fuel injectors. You can get away with about a 10% increase in fuel pressure without too much issue (I suspect that your guys are already doing this). If you do use bigger Fuel Injectors, you must modify the Computer PROM.

Most of us use a dual pattern cam due to the small size Exhaust Ports on these engines. I am using the following cam, and have had good success with my modified setup:

Crane Powermax 2032 452/465 214(270)/220(276) 112 deg., 1800 to 5800 RPM (2000 to 5500 RPM), P/N 104224
Lift (1.52 rockers): 0.458"/0.471"
Lift (1.6 rockers): 0.482"/0.496"
Duration @ 50: 214/220
LSA: 112 degrees

Crane Cams is no longer making Cams, but Comp Cams offers a very similar cam profile with a bit more lift and a faster ramp. Chevy makes a Cam that lots of us are using as well, I'm sure others will chime in about that.

I think you'll find that bottom line, it will take Exhaust, Cam, Heads, Fuel Injectors, and PROM upgrades to make the 305 TPI a competitive engine setup to run with the newer F-Body's and Mustangs. I'm sure that is not what you wanted to hear.....

 

This cam was designed specifically for the engine combination you are talking about using - 305TPI with stock heads & exhaust.
http://www.lingenfelter.com/mm5/merc...egory_Code=C30

Lingenfelter 74216 Camshaft L98, LT1, LT4 1987 - 96 TPI - Hyd Roller 213/219 .493/.502 HR112

It is best to upgrade the valvesprings for this cam. With straight springs you can get more clearance for the lift by using thinner retainers from a chevy vortec 4.3liter V6 engine. If you use beehive springs then COMP makes the retainers to make that work.

For a racing application where more power is needed, you should consider that TPI responds very well to modifications that will lower the temperature of the intake manifold pieces, and therefore the intake air.
All effective tricks apply such as running a valley pan/oil splash pan under the intake base, doubling the intake gaskets and/or using nylon sleeves in the intake base bolt-holes, blocking the EGR flow into the intake base, and routing the PCV so that it doesn't enter into the intake air.

If you are measuring any significant pressure drop (vacuum) at the intake plenum area when at WOT, then you might want to address the airflow restriction ahead of the plenum.

The TPI system uses a distributor to distribute spark, but applies the spark advance electronically by calcuating delay periods. This means that at WOT and full advance the rotor may be significantly out of alignment with the cap terminal that is to fire. You may want to consider rephasing your distributor cap or rotor to reduce this effect at WOT.

It is a shame that you can't modify the calibration of the ECM. There are ways to keep the stock calibration, but fool the ECM for times when you are racing. Two areas of possible interest would be the CTS coolant temp sensor, and the knock sensor. If you run a lower than stock coolant temp, then you should supply the ECM with a signal equivalent to the stock operating temp so the ECM will not assume cold operation. A simple resistor circuit and a two-pole toggle can accomplish this. Some people like to desensitize the knock sensor, or disable it so that spark advance will not be pulled while racing.

 

i dont want to restrict the options to just a cam change, but w/ the LB9 can as the "hot set-up" now, i'm sure there are gains to be made there. likely most of what we need. long tube headers are on the table as a possible option too. valve springs are open, so that isnt an issue. not sure about machine work required to fit them though.

the tune has to stay stock in the ECM. i'm not a big fan of that rule but its the rule i've had the most dificulty in getting changed over the last few years. that is to include no VATS or emissions related tuning either. we would be interested in any tuners who can provide input on this and the possible ways to provide a "spec" tune to those guys.
mnorton - do you have dyno numbers?

we wantto stay away from head porting. this series primary goal is cost containment. a top car can be built for well under $10K and be run on a season budget of $5K pretty easily.

also - just to be clear, these are in no way legal street cars. they are all purpose built racecars.

 

posted for your enjoyment:
http://www.vimeo.com/5924170
http://vimeo.com/5945413
http://www.vimeo.com/6019050
http://vimeo.com/6013713
http://www.youtube.com/watch?v=7dTLQCb0kgQ
http://www.vimeo.com/6025959
enjoy.

 

Nice video, looks really fun!

I watched the YouTube video and am wondering now what the top speed of this type of race is, and what gears they are running? In listening to the engine rev, I got the feeling that my car is faster rev’ing than the one that was in the video. I’m running 3.45 gears.

No I’ve never Dyno’d my car, but I can say that these modifications have made a big difference in power and in the way the car handles!

I think that you'll find that installing an after market Cam and using the Stock Un-ported Heads will not give you the gains that you are looking for.... at least not if you want to make these cars powerful enough to compete with a 2002 F-Body and 2009 Mustang.... My car would stand a chance, and maybe even beat the Mustang, but it's got Ported Heads, Bigger Cam, Bigger Fuel Injectors, Full On Exhaust, Custom PROM, and Several Suspension Improvements.

Since your guys are already using 1.6 Rockers, they are running 431/442 lifts 204/209 durations @ .050 with an LB9 Cam. Which isn't that bad when using the Stock Heads.... There's just not a lot left to gain. Certainly not 20 RWHP.

Since you don’t want to get into Head Porting, there is no reason to run a high lift Cam with the Stock Heads, .500 max,. (they will need some Springs and Head work for even that much lift) they won’t flow any better above that anyway.

If you are going to use after market Heads, Cam lifts can be higher to get more flow. The Heads are really what is going to determine your Cam lift selection.

There are several manufacturers that have good Cams for TPI cars. Comp Cams, Crane Cams, Lunati, Lingenfelter, and of course GM….. As a rule of thumb: All of the Cams you’ll want to consider have Exhaust Durations of 220 @ .050 or less. Intake durations of 215 @ .050 or less, and LSA’s of 112 to 115. If you go bigger than this, the Cam will not be Computer friendly.

Since you don’t want to get into PROM modifications, you may want to stay with Iron Heads in general (though the Aluminum Heads available for this engine are some really nice Heads). I say this because Aluminum Heads want about 5 degrees more timing than Iron Heads, and you won’t be modifying the timing curves. Maybe you could get away with physically moving the distributor a bit to increase the Base Timing, but then it would become an incorrect value in the Timing Table in the PROM…. so I’m not sure where the net gains would be. Also the higher cost of Aluminum is to be considered.

The only Stock TPI Intake compatible Iron choice that I am aware of, are the World Products S/R 305’s. (The Valve Springs and Seals on these Heads are JUNK so they would have to be replaced, or better yet, you can purchase just the Bare Heads Castings. These Heads are a bit rough in the Valve Pockets, so I’d think that everyone would really WANT to Pocket Port them, I know, No Porting!….) Max. Lift on these Heads is listed as .560. The combustion chambers are listed as 58cc, no value is given for static compression. I sent them an email asking them what the compression ratio would be, and they did not respond. I’m not very impressed with their customer service group…..

Like I stated in my previous post, to get more power, you’ll need more fuel, so an Adjustable Fuel Pressure Regulator will be needed. The Stock Fuel Injectors just won't flow enough to make close to 300 FWHP without 15% more fuel pressure.

 

that track is the fastest. the long banked front straight is just under 130. i run 3.42's and some run 3.73's. the fords like the 3.55's and 3.73's.

the dispartiy in performance between all platforms is kept in check w/ the power limits. LT1/LS1/and any other platforms that makeover the limit can use a restrictor plate to get power down. my 93 LT1 uses a plate w/ twin 33mm holes.
added to that is the minimum weight of each platform. LS1 4th gens and '05 up fords get the most. there is only like a 150lb swing from low to high. so far, we all seem to be very equal.

at best we could allow the GM aluminum heads, but not likely.

is the LT1 intake worth a look in this instance?

 

Oh, you hadn't mentioned that the LS engines have restrictor plates, that helps. I really don't know anything about the LT1 intake so maybe someone else here will chime in about that.