Daves03

Is it possible to have a 305 TBI in a 1991 chevrolet camaro RS with a .630 lift cam and still be able to drive it down the road, if so how can this be accomplished, i want that crazy nasty exhaust lope something fierce and am trying to figure it out, tpi systems can do it par say the videos why cant a tbi, I have heard that the fuel injectors will have to be upgraded, the fuel pump will need to be upgraded and the knock sensor will have to be disabled(was also wanting to install a noisy gear drive) and would have to install a fuel pressure regulator, help me out guys. I know it could easily be done with a carburetor but the fuel injection im new to this, in case you are wondering i also just rebuilt the 700r4 and upgraded the torque convertor to a 2400 series stall from B&M.

Ronny

iTrader: (1)

problematic to say the least. You need to run ECU open loop and need to install a wide band. Plus upgrade fueling needs and airflow in/out needs. Support is here.

Daves03

now when you say open loop is that using a burning software and ability to burn the prom and disable the closed loop process and the wide band is that the power band of the cam shaft like say from 2500-5000? I just didnt know if it was possible on a fuel injection car without messing up the fuel injection, i knowed that the fuel system and air system would have to be upgraded thats a must, Thanks for the reply.

I read somewhere on here about a summit wideband o2 sensor control module or something similar is that what i need for the wideband, basically something to read and control the fuel mixture for the upgraded cam.

Ronny

iTrader: (1)

Open loop is not using the NB02 to allow stoich(14.3/1) during cruise. Closed loop is disabled by setting the enable coolant temp very high in chip. Issue is reversion where the overlap fools the NB(or WB for that matter) and sees unburned 02 and adds copious amounts of fuel typically lower in the RPM band. You basically run off predetermined(by you) fueling tables(VE). The WB may help at WOT and say above 2500rpms to correct tables. Under 2500 you pretty much are on your own and could do plug checks to check fueling.

Yes you will burn a series of chips. WB datalogs will be reviewed after each burn. Definately not a mail order purchase.

I will suggest that cam is not for one that is new to EFI. A better thought is to run a computer cam in middle of chart with a wide LSA of 113-114.

Saabster

iTrader: (2)

What heads are you going to run that are compatible with .630" of lift? If you want the lope I think you want overlap anyway, not necessarily lift.

Ronny

iTrader: (1)

These will work. http://www.edelbrock.com/automotive_...ictor_jr.shtml

Saabster

iTrader: (2)

Aside from the valves smashing into the top of the 3.736" bore, yeah, those will work great.

Ronny

iTrader: (1)

another argument for a 350 cid!

Daves03

thats another thing ive been contemplating the valves lightly kissing the pistons and high compression ratios. But i do believe you are right i think that its not the lift im looking for as much as the duration to get that nasty erratic rough idle. Ive got a lot of work to do and numbers to crunch but im trying to see what everyone else has dont and figure out what works for them and what didnt work for them so i dont waste a lot of money on something thats not going to work when someone say like ron can tell me what he knows will work and im happy with that.

But at the same time i do appreciate everyones info and help with this project.

Now at the same time a guy at work told me about a cam called a thumper he said that may give me the sound that im looking for without the massive lift, I guess its like saab said not actually the lift im looking for but the duration.

dimented24x7

iTrader: (2)

There are some considerations to running a cam with SD and TBI. First, obviously your stock computer will become completely useless, even with a chip. Need to go to a TBI PCM or EBL to have a chance of it running right.

Second is scavanging. Unlike a carb, EFI systems deliver the fuel in descrete pulses. With cam overlap, you can run into a situation where the exhaust pulses pull the fuel straight through the cylinder and out into the exhaust. This can cause a lean condition which gets worse as teh RPMs drop and the manifold pressure rises. In its worst form, it leads to stumbling, low RPM bucking, and surging idle/stalls. Theres also no easy answer to it. Ive been experimenting with firing my injectors after the exhaust valve has touched down, but this results in drivability issues from the fuel not having sufficient time to mix with the air. The easy answer is to watch how much overlap you have. Its not the duration that causes the loping idle, its the overlap. If you want the lope without some of the other issues, than a lower duration cam with a tight LSA will do the trick.

The last consideration is with the vacuum and SD. Cams with overlap cause cylinder bleed down and cross-talk between the intake and exhaust. This not only reduces low RPM power, but causes the engine to pull poor vacuum. This makes fueling hard with SD because at idle and low RPMs, you only have a small portion of your VE table to use for fueling. Depending on the size of the VE table, this can result in very little ability to properly fuel the motor.

Another thing about overlap is that once you have a cam with overlap, kiss your emmissions good bye. The overlap means that closed loop is impossible due to all the air in the exhaust. The computer will drown the motor in fuel if you try to use closed loop at low RPMs/idle. Been there and done that... Some computers like the TBI PCM allow for open loop idle, but this may still make it hard to pass emmissions.

Now, performance wise, a good cam to use with TBI would be something like the comp cams 262HR-12. It will pull good vacuum, have decent lift+duration, and offer good, emmissions compliant performance. You will need to at the very least get a good intake + exhaust, and rework the heads for the increased lift. Ideally aftermarket or modded vortecs would be best. I would not recommend getting a cam just for the sound effects. If your not experienced with how to deal with tuning with such cams, the end result will be an engine thats slow and runs like complete crap, if it even runs at all.

Daves03

The cam that i want in the car is just for the sound, i dont really care if the car is fast, i have a car thats fast, i just want something that looks good, sounds good and runs pretty good.

As far as the emissions go my 2003 chevy s10( i love it but i hate it) they are so strict as far as emissions and obd2 on my truck north carolina can suck it on my camaro, we used to have the emissions test old probe up the tail pipe but they did away with that, all we have now on vehicles 95 and down are safety only to some year like 1976 and then you dont have to have it inspected anymore.

Basically im just looking for a cam to give the car the heavy raspy rough idle sound that im badly looking for, i have though about it just pulling the tbi and dropping a good intake and carb on it, i know that a rough cam can be done by carb

the whole time im sitting here thinking if a man with a 2004 pontiac gto can have a rough idle and a man with a 2000 camaro ss can have a rough idle why cant I? then comes the answer the LS series motors(endless possibilites) But at the same time I would like to keep my fuel injection because on my old cars i hate pumping the gas pedal cranking the engine over pumping some more cranking, my car fires right up even in the dead of winter. I may never be able to accomplish what i want the engine to sound like and not sacrifice my fuel injection but im trying to look at this problem from all angles. but with it being a 91 and so many repairs to be made ive got a long road ahead of me.

now also i was looking at a couple of videos on youtube and one recommends a lunati bracket master II cam it has a pretty nice sound to it and a little less lift i speced some on summitracing.com, but the catch is there either mechanical flat tappet or hydraulic flat tappet which means i would have to give up my roller style setup.

dimented24x7

iTrader: (2)

With that said, if your still hell bent on getting a lopey idle, then a single pattern cam with a tight LSA will work if you know what your doing. After my failed retro-roller conversion, I decided to try a single pattern isky flat tappet (221/221 .465/.465 108 LSA). If you've seen some of my other posts, you will know that this was a rather enlightening experience with EFI. When I first started (or tried to start) the car it would not even run due to the overlap. So, expect to be buying EBL or a PCM and doing some tuning.

However, with tuning, it runs very well, and still has a slightly noticable idle. One nice thing about single patterns is that they have very strong midrange torque, so you can still have good drivability. The cam I have also pulls very good vacuum during cruising, so it drives nicely and still has enough low end to cope with the 2.77's out back. The video below shows realistically what you could expect when trying to get a lopey idle while still having a chance of the car running OK. It wont sound like a cammed up motor, but it will sound better than the usual stock V8 idle.

http://www.youtube.com/watch?v=wc2kaqXTh-M

Edit: didnt see your reply, but this is still applicable.

dimented24x7

iTrader: (2)

If you really want to get a big, nasty cam, then you can expect to have to run MAF. SD can work, but usually doesnt cope as well with all the overlap. At the risk of sounding like a shameless self promoter, one way to do this is with MAF TBI. Other options are to convert to SFI like the systems used on the GTO and 4th gen camaros. I did it, and I can say that its VERY EXPENSIVE, and requires a decent ammount of knowhow to do. But, they are adaptable to your 305 (or 350 if you choose to swap it out), and will allow you to get the idle you want. Expect this to be a serious endevour, though. Requires massive changes to the car as well as diving into late model EFI tuning.

Daves03

http://www.summitracing.com/parts/HRS-110305-08/

I just wonder if this one would be close
108LSA
.480/.480 lift
306/306 Duration

I would think that would give a pretty nice rough idle and not be too much lift least not as much as the .630 i started after.

dimented24x7

iTrader: (2)

Wrong application (retro roller), but it should definitely lope, if not chop. It has a lot of advertised duration, so there is probably a considerable ammount of overlap. Dont know if it would be a good performance choice as its a semi-lazy lobe profile. The smaller the ratio of the duration @ .05" vs. the advertised duration, the slower the ramping rates are. Cams with less advertised duration for a given duration @ .05" will build better cylinder pressures down low and take better advantage of the mid-lift flow of heads like vortecs.

Daves03

okay ima get some sleep tonight ill have to continue my quest for the perfect camshaft tomorrow.