I'm trying to figure out what cam to run in my 383 tbi engine. I was told that the cam in it right now (comp cams xtreme 4x4 hydraulic cam 122352) Doesnt have enough lobe separation at 111*. The engine is a pre 87 4 bolt main block that has a scat 383 kit and World sportman heads. I dont want to put a roller cam in because of cost and its going into my blazer that doesnt see much over 4000rpms. I plan on upgrading to a larger tbi, injectors, chip, etc. and smog is not an issue. Can anyone tell me if I can make this cam work or is there a better cam to run?

 

Look for a emissions cam for tbi injection, the largest one for your injection system will work great as im told, it will make tons of torque, i believe crane makes it.

 

There is NOTHING wrong with a 111* LSA on a cam.

I have run TBI engines on 107* LSA cams and they run fine. It is the overlap you need to look at. Pretty simple really. The more overlap you have the less vacuum you get. The MAP sensor needs a steady vacuum signal. Doesn't really matter what it is if you are tuning your own chips.

The RAMJET/HT383 ROLLER cam is a TORQUE monster.

 

So can you tell me what the overlap is of this cam and will it be possible to have someone else burn me a chip to make it work? I'm not ready to start burning my own chips and its my daily driver so down time is an issue. I was planning on having turbo city burn mine for me because its where I got my bored tbi at.
http://store.summitracing.com/partde...5&autoview=sku

 

You really should have done some more research before you dove into a stroker project.

TBI is a speed density setup which means that it bases fueling mainly off of manifold vacume and rpm. Any thing you do that effects vacume will effect the way your ecm works. That means exhaust, intake, heads, cam, and most importantly the size of your motor. What happens when you change these things is the motor now moves a different quantity of air at a particular vaccume reading. This is not a bad thing, and is the whole idea of modifying your engine. The problem is that you HAVE to retune the ECM for the changes. The other problem is that every engine is different and every combo of parts is different and some one on the other side of the country isn't going to be able to tune your car out thin air.

Your going to have a heck of a time even getting your motor to move your car when you first start it up. If you lucky it will start and idle without flooding the engine. The bigger the cam you go with the worse it will be on the stock tune, but it realy won't matter what cam you go with because even with the smallest cam your tune is going to be off by a mile.

With all that negatism said, properly tuned your combo should be a monster and make a ton of power. You just have to make a decision to do one of 3 things. I'll list them from hardest to easiest.

1. Find a shop that knows TBI well enough to tune your car in hand, and preferably on a dyno. The down side is this will cost a small fortune and if you ever change any parts you'll need to get it re-tuned.

2. Learn to tune yourself. There are stickies at the top of the page that will walk you through the beginning steps. It's not easy, but it's not that hard either. I HIGHLY suggest getting started on a stock motor to learn the ropes. Learning on a new combo is a real pain and you could potentially hurt your motor if you really screw something up. On the flip side of that comment, you WILL hurt your motor if you don't tune it.

3. Of course the easiest option is to just go carb. 9 times out of 10 the factory jetting will be close enough and tuning them is very easy. The down side is worse than FI gas mileage and you'll never get the drivability out of a carb like you will with FI. Also this may not be an option depending on emissions in your area, then again a big cammed 383 might be hard to pass even with FI.

 

I'am aware of the effect this engine will have on a tbi setup but I got the engine for free because my buddy went to tpi. The engine was carbed before and only had about 10,000 miles on it. I drive an offroad truck so carb is out of the question (stalls way to much) and I understand that I will have to learn to burn my own chips. I really just want someone else to burn the first chip so I can break the motor in and get it moving. My only real concern is cam selection because I want to make sure that its going to work with the engine and have enough vacuum to run smoothly with a tbi setup.

 

With the EBL you can run ANY cam made with TBI. I even was able to run a wild cam with a well tuned stock ECM just fine. It idled at just 10 in/hg @ 750 rpm in my 305. With the transmission in gear and the A/C on it was lucky to make 7-8 in/hg @ 800 rpm.

 

Is that enough vacuum for power brakes? I've always thought you needed a minimum of 12" vacuum at idle.

 

My power brakes are not Vacuum run. Mine are hydroboost. They always have been.

 

Do you think it would be worth the money converting my block to run a roller cam just to have a better cam section?

 

but, what about in an f-body?

 

Add an electric auxiliary vacuum pump. GM produced many of them in the mid 80s.

 

ummm ... when i think about auxiliary vacuum pumps, i think about those things that are supposed to make your dingie bigger