will the edelbrock P/N #5002 cam work with the 305 TBI engine? the car is a 1992 firebird.

here are the specs on the cam:


i just got this cam but now that i have read into it i'm not sure its going to work. i got new edelbrock valve springs (part # 5703) and a new set of high energy pushrods to go along with everything the cam also came with a new set of lifters.

 

That cam has WAY too much duration for a 305 TBI. Even if you could tune the chip properly (which I doubt, because you won't have enough manifold vacuum), it would put your powerband too high in the RPM band - you'd need a forged crank and rods to support the kind of RPM that this cam will make the 305 rev to in order to make power. That cam is good to 7000 RPM in a 305 - way too much for your stock crankshaft, main bolts, etc. Even if your engine could tolerate such RPM, your heads and intake would be useless for it.

Also, your motor is designed for hydraulic roller lifters. This is a hydraulic flat cam.

----> You need a hydraulic roller cam with less duration.

All in all, this is a very poor to impossible choice for a 305 TBI.

 

oh well........i jumped into buying it lol i'll just take it back to the store tomorrow.........any suggestions on a cam that will give the car a nice rumble? preferably crane,comp, or edelbrock because i can get them pretty cheap where i work. i'm running a 3 inch flowmaster exhaust and i have a manual trans. everything on the car is pretty much stock.

 

Unless you learn to burn your own chips any kind of a cam with a lumpy idle is not a possibility.

 

Well, as I said, the L03 (your 305 TBI) has hydraulic roller lifters. Hydraulic lifters are generally safely limited to around 6000 RPM (though you can get "rev kits" that will allow a few hundred more RPM). Also, your crankshaft is nodular cast iron and your block is a two-bolt ...both of which can handle 6000 RPM but you don't want to push past that often. As well, your computer has entries to adjust fuel and spark only to around 6000 RPM.
Your stock heads have pressed-in rocker studs. If you put in a high lift cam (which will require stiffer valve springs to rev properly) and you rev too high, too often, you'll eventually pull one of your rocker studs out of the head (not good). Again, your RPM are limited to about 6000 RPM.

On your stock cylinder heads, your spring retainers will hit the valve seals (on the intake valve guide bosses) at around 0.47" to 0.48" of lift. So your cam will be lift-limited by this.

Your computer uses a signal from the MAP (manifold absolute pressure) sensor, along with other sensors, to control the fuel injectors. If you use a cam with too much duration there won't be a high enough or stable enough manifold pressure for the computer to control the injectors properly.

The "biggest" cam that will function properly with your computer will also run out of steam at around 6000 RPM.

So....

1) For many reasons, you should select a cam that will make peak horsepower at around 5500 RPM with a redline at around 6000 RPM.

2) Your lift will be limited to less than 0.470" because of cylinder head construction. Your duration will be limited to less than 215 degrees @ 0.05" lift, with slightly longer duration on the exhaust. With this duration you'll need a lobe separation of around 112-116 degrees for the computer to be able to control the injectors properly. With 215 degrees of duration you'll need extensive computer programming (though it's "easily" done). Try to select a cam with less than 210 degrees duration to make chip tuning possible and your car might even run "decently" without tuning (but tuning will be required to get the full benefit of the cam).

I suggest you find a cam with around 0.450" lift (on intake and exhaust) and 200-210 degrees duration and a lobe separation of about 112-114. Such a cam should be able to make peak torque at around 3500-4000 RPM and peak power at around 5000-5500 RPM with a 6000 RPM redline. It should at least run decently with your computer and should be fine with your stock heads (but you should get stiffer valve springs).

But, keep in mind, your intake, heads and exhaust manifolds will be limiting factors. This cam probably won't be able to make its peak power at 5000-5500 RPM because those components will run out of "air" before then. You'll probably end up with a power peak around 4500 RPM.

And you WILL require chip programming to get the full benefit of this cam swap.

 

I would add headers before doing a cam change. I did not see anything but 3" exhaust mentioned. Headers and tuning (Prom) will gain alot.

 

post of the year goes to you!

 

Well, sorta kinda not really. It's not that a big cam won't have enough vacume for the ecm, it's the fact that the cam will cause your car to idle in a different area of your VE table with a different vacume reading. You have to retune the VE table in order to match up with the new cam. The bouncy MAP readings are also hard to tune around, but not impossible. Rbob's new EBL has an Alpha-N mode that fixes this. So a big cam will work fine with your ECM, but not without tuning.

With that said, you need to match the rest of the engine to the cam you use. Swirl port heads and stock exhaust won't work well with that cam.

 

I was referring to the fact that the big cam will put the idle MAP readings "further up" in the tables, leaving less entries between idle and wide-open throttle - precision is lost because you have fewer blocks in the table to work with ...probably not catastrophic, but not desirable. I don't know Jack about Rbob's EBL ...but it sounds like something else to drain away my pay check. On the other hand, the other "limitations" of the L03 make a big 'ole cam impractical anyway (unless the rotating assembly is replaced with forged parts, which I wouldn't do on a street-driven 305).

Where can I get some info on EBL? Is there a webpage or thread around here anywhere?

 

Check out the DIY prom board for EBL info, your correct that your Idle MAP pressure is much higher, but as soon as your rpm's increase your MAP values come back down to something a little more reasonable. A stock LO3 idles in the 30 to 40 map range. My 218/226 cam in a 350 idled in the 45-50 map range, and Fast has ran a cam slightly bigger in a 305 that idled in th 80 map range. As soon as your rpm's get up a little your map values drop back down into the 30-50 range, so it's not like your entire VE table will never be used below 80 map any where in the RPM range, it's just idles at a higher MAP value. Alpha-N uses a table to simulate a MAP value based off of RPM and TPS, this calculated MAP value is much more stable and tends to smooth out a big ole nasty cam.

Alas, as we both said a cam this big is completely mismatched to a stock or even mildly modified LO3. Just wanted to be clear as to exactly why the ECM is going to go nuts on a stock tune.

 

Now that I never realized. I've never tried to tune in a "big" cam with the look-up tables simply because they put the L03's powerband in an area where I don't want it.

That sounds like a very logical idea. I've toyed with the idea of using an artificial neural network (ANN) to control fueling and spark in these cars. I've never gotten deep enough into the capacity of the ECM to do calculations fast enough to work with a simple neural network, but the sampling rate on these things is fairly low so it would probably be able to handle it. I've implemented similar ANNs for controlling permanent magnet motors like in hybrid vehicles - my research "associates" include some Engineers working with the Toyota Prius' hybrid system ...they don't know about my love of the Chev V-8 . The ANN works wonderfully and adapts very quickly to disturbances.

It would be a beautiful thing to get working with TBI, because it would potentially erase the need for tuning the computer regardless of what cam, heads, exhaust, etc. you used - the ECM would tune itself. I don't see a reason why some sort of artificial intelligence can't be used in these machines to replace the labour-intensive drive-around-and-tweak-the-tables-until-it-works-best method. Perhaps I'll have to consult your expertise on these ECMs when and if I ever get the hankering to get into it. Do you know much about the assembly code of these ECMs and how to modify it?

 

I'm what you call an intermediate tuner, I pretty much have the tuning aspect understood pretty well. I can also take a look at a hack and see how the code works. It helps to better understand what's going on in the background. What I can't do is rewrite and assymble the base code. I've done some basic C++ but nothing close to this. Rbob is who you want to talk to, as well as Demented247. You also can't forget the old timers like Grumpy and traxion. If your serious about developing source code you need to get involved on the DIY prom board. It's been started a few times but never really gone anywhere. Rbob's EBL system and Grumpy's $60 code is pretty much the only custom source code offerings out there.