Alessandra

Hey guys,

I need some help! I'm looking to change the cam in my 89 Iroc-Z but I really don't know too much about them. I know I have bigger injectors in there so at the moment it's basically dumping fuel with no added performance. I'm also changing the gears at the back to 3.73 but I'm not sure if that makes any difference when buying a cam. I need help on basically everything...intake and exhaust duration, lift, etc. Thanks.

JekyllandHyde

iTrader: (3)

Camshaft selection is a topic that will take pages and pages of discussion to fully understand. What exactly are you looking for in terms of performance increases and what else do you plan to do to the car?

What exactly has been done already? A larger camshaft coupled with bigger fuel injectors may not necessarily help you with running rich. In fact, a larger cam may just make it run worse. In order to properly account for the larger injectors, you would need chip work for the car's computer to get it to run right.

JekyllandHyde

iTrader: (3)

Oh, as a primer on cams, here's a good general beginner's article:

http://www.lunatipower.com/Tech/Cams/CamSpecTerms.aspx

Keep in mind that you will need to take into account other considerations such as the lift limitations of your heads, piston to valve clearance, etc.

When I chose qa cam for my car, I studied everything for a good 3 months before settling on the one I have in there now. I am extremely happy with it.

Sojer

Stock heads a mild cam. What size injectors do u have. A tune is a must but I am going with a zz4 cam, but a zz3 if they make them still. Call comp cam. U will need a adj fpr to turn down the fuel. But if u not doing other mods like intake headers its not worth doing jst do a tune and u will be better than most 305s. The tpi base will not let u make much power.

Alessandra

So far only the exhaust has been changed. I have a Jet chip which I think is for the cams so I kind of did things backwards because of some bad advice. The car is running a bit rich right now and I'm only getting 200KM to a tank; I'm not sure if that's normal for these cars.

Right now in terms of performance the car really lags and I was told that changing the gears in the rear end will help with a quicker take-off. So the plan for this year was to change the cam and the gearing. If what I read was right only changing the gears won't give it much of a powetr increase.

JekyllandHyde

iTrader: (3)

The lag in performance is more than likely the fact that the car is running so rich. All that extra fuel isn't being burned completely so it actually will rob you of power. Do you know what injectors you have in there exactly? A 305 should have 19lb injectors, at most 22lb, but you would need chip work and an adjustable fuel pressure regulator. Unfortunately, a cam won't help you much in this case and may just add to your problems until you can get the car running right as a good baseline. My best advice would be to give the car a full tune up, change out the plugs as they'll most likely be fouled from the car running rich all this time, and either change out your injectors to the proper size or get a chip burned for them.

JekyllandHyde

iTrader: (3)

Oh and in all honesty, the JET chips don't really do much of anything other than play with your timing a little bit and change your fan settings to make them come on sooner. You may "feel" a difference but that's mostly from the car running colder than it used to. They are off the shelf chips which do not take into consideration parts that you have in your car. That is why I burn my own chips. You could get one custom made from some mail-order companies if you wish.

Alessandra

Apparently I have 45 lb Accel injectors so they definitely have to be changed.

I will definitely change the chip then and get a custom one made

JekyllandHyde

iTrader: (3)

If you have 45lb injectors, it would be better for you to change the injectors to something smaller instead. Injectors run on duty cycles. Typically, you would want to run injectors at a 70-80% duty cycle meaning thay are at 70-80% of their capacity based on rated flow. It is very possible to have TOO LOW of a duty cycle at which point the fuel would not get proper atomization as the larger injector is opening much less than it was designed to do.

Get the 19lb injectors and put them in. Or if you plan to mod the car some more, get the 22lb injectors in there and get an adjustable fuel pressure regulator to tune them. Getting 45lb injectors to work for your mild bolt-on application will be extremely difficult if not impossible. Are you sure nothing else was done to your motor? 42lb and up usually means you're running forced induction or a really hot normally aspirated setup. To give you an idea. I run 39lb injectors in my car. It's a 350 with a large cam and Trickflow 195 heads. They are TOO BIG for my motor. I need to actually step down to 36lb injectors to get the desired 75% duty cycle to get my car to run right.

If you need a good recommendation for where to get fuel injectors, I am getting mine from www.southbayfuelinjectors.com. They have always gotten me what I need and are always willing to help. Frank over there is very knowledgeable and can get you exactly what you need. Tell him Al sent you.

Alessandra

I'll definitely check that out, thank you. If I swap the injectors to 22lbs is it in my best interest to still get a cam or should I leave that stock? And will that have any affect on the gear changes?

JekyllandHyde

iTrader: (3)

If you go to 22lbs, it would be a good idea to get an adjustable fuel pressure regulator to be able to turn your fuel pressure up or down to tune the car. As far as the cam, it's entirely up to you. I would read more on proper cam selection as getting a cam is a lot more than simply ordering one and putting it in. I bet you just getting the new injectors and leaving the cam stock you will notice a very good bump in power because the car will finally be running right.

ninetyone

iTrader: (2)

The deal is this on tpi cams. You wanna keep the duration below 220/220 degrees @.50 and keep the lift below 470/470. That is if you plan on keeping the stock springs. The LSA should also be at least 112. Now, this will keep your car drivable with little to no drivability issues. Of course, custom tuning of your car's computer chip always helps and can improve performance as well. As for gears , if you have an auto i would stick to a 342 ratio at the max. IMO, a 373 is too much for a 700r4 transmission.

ninetyone

iTrader: (2)

Remember the closer you get to 220 on duration , the less low end torque you will experience. A cam with lots of duration will make more of its power up high in the rpms. How exactly do you want your car to perform? Street car? Track only car?

Alessandra

Street car for sure. Should I also stick with hydraulic flat tappet or roller?

Alessandra

Thanks for all the advice. I'm definitely going to look into that. I do have an automatic so for the gears I will go with the 3.42

Alessandra

I'm going to put change the injectors to 22lbs. Hopefully the car will start to run right again

JekyllandHyde

iTrader: (3)

If you have the 89 stock 305, then you have a hydraulic roller cam. Just stay with a hydraulic roller. If you go with the 22lb Injectors, remember to add that adjustable fuel pressure regulator since you will need to play with the fuel pressure to get it to run perfectly. Stock injectors on 305s were 19s. Even 22s might run a tad rich but at least the computer will be able to better correct for it.

Alessandra

Thanks for all the help guys