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Cam Options With TBI

vtblazer

vtblazer

1/2 ton status
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Just picked up what is said to be a 383 motor and it has TBI.

Seems to be, it looks like an older block with new style heads.
Also has the external balanced crank so this much I believe to be true.

What are my cam options to run with my current set up?
(thinking ahead just in case :wink1: )

It's in my 71 K5 that is built and used for 99% wheeling and 1% surface street runs.
Basic drive train specs: 383/th-400/203/205 w/5:13's and 40's.

The motor hates to be @ zero and if much more timing is put in manually, it will start spark knocking.
My current plug wires are junk, installed em only to get it running.
Waiting for the ones I ordered to show up. (armored for heat)

So I'm hoping the the crappy plug wires are causing some issue's here. :dunno:

I'm willing to swap out the cam to make the computer happy, so give me some input PLEASE. :D
 
With an unknown cam, pretty hard to tell if whats there is even a problem.

This has gotten to be cliche, but what really needs done is to datalog the motor, or get it to a dyno shop that can tune.

A 383 is an entirely different animal, and if that TBI setup has not been changed in a few ways from the stock 350, disaster is right around the corner. (look for post re: burnt pistons and 383 TBI)

Minimum needed for a CID/engine component change is (likely) injectors and ECM tuning. There is no way around this. No one will argue that every motor is different in timing and fueling requirements, datalogging and tuning is the only way to correctly fix this.

Can't stress enough that a 350 and 383 aren't even close to the same thing as far as EFI is concerned.
 
dyeager535 said:
With an unknown cam, pretty hard to tell if whats there is even a problem.

This has gotten to be cliche, but what really needs done is to datalog the motor, or get it to a dyno shop that can tune.

A 383 is an entirely different animal, and if that TBI setup has not been changed in a few ways from the stock 350, disaster is right around the corner. (look for post re: burnt pistons and 383 TBI)

Minimum needed for a CID/engine component change is (likely) injectors and ECM tuning. There is no way around this. No one will argue that every motor is different in timing and fueling requirements, datalogging and tuning is the only way to correctly fix this.

Can't stress enough that a 350 and 383 aren't even close to the same thing as far as EFI is concerned.
Click to expand...

So just changing the cam won't cure the disease? :(

I may as well just swap my other 350 back in and reuse these heads I guess.
 
So what did the setup come off of? Was it tuned previous?

On any of these EFI engines, changing components affects how it runs. Heads, transmission, displacement, cam, TBI, injectors, exhaust, intake, all of it. So if ANY of it is different than what the ECM was originally running, it will be less than optimum. Sometimes less than optimum works, sometimes it results in bad driveability or engine damage. Way too many variables to know for sure unless you can narrow down what all the components are, or how it is running now. :(

You can try plug wires, but I'd be a jerk not to caution that the motor could be running very lean and trying to run it as-is could result in it's destruction.
 
If you take some time and do a little research, you will be able to make that 383 work. Generally, for TBI you want low duration and lots of lobe separation. For the extra cubes you WILL have to PROM tune and play with FP, etc. Basically, anytime you put TBI on a motor that has been changed compared to stock in anyway you are going to have to do some real tuning. On a really mild engine you may be able to get away with more fuel pressure, but you're going to want to check the A/F just to be safe.
 
Wow, I'm floored here...:crazy:

I had a really sweet running carbed crate 350 that I just took out hoping to really improve things by installing this 383/TBI motor.

It came from a running driving truck so I figured it was okay but the "assume" thing struck again.

I'm willing to spend more time and money to tune it if possible but I don't want to waist either.

Any/all help or advice you guys may have, I'm open to finding the best way out here.
This is my wheeler and I need to to run correctly through whatever I throw at it.

Thanks :bow:
 
Kurt, saw your PM, figure we might as well keep it public, this stuff is good reference for people later on!

First off, you probably need to figure out what kind of TBI it is. If it's an aftermarket or 454, you might be all right injector wise, and on top of that, if it's a higher CFM model, all the better for the 383.

What system are we dealing with here? I assume GM setup, but if not, what? If GM what ECM is it running, and if it has a sticker on the outside of the ECM case, should be a 4 letter code (like "APYP") on the sticker. That might help as well, to determine original application if all the parts appear stock. Won't hurt to pull the cover off of the ECM (plate held on the top with two screws on either side) and look at the piece in the blue plastic there...the 4 letter code if not on the outside of the ECM, should be here if stock. If it's aftermarket, you'll probably see something indicating such. You can remove the PROM by depressing the lever on either side of the blue thing, like you do RAM in a desktop computer if you've dealt with those. :) All the GM PROM's I've looked at had the "BCC" (BroadCast Code, the 4 letter code) printed on them such that the PROM did not need removed to read it.

Finding this info out might help some. But datalogging would be your friend. If you've got a laptop, search "winALDL", and building a cable for it. That will tell you straight away if your system is running lean, knock is being sensed, etc.

As to the send away chip burners (like TBIchips.com) I think they can typically get close, because they have experience, but it's still not as good as trial and error, which takes a lot of to get perfect. Southernspeed will jump on and take about EBL I'm sure, but that might be putting the cart before the horse. Need to figure out what you are dealing with before attempting to set it right.
 
dyeager535 said:
Kurt, saw your PM, figure we might as well keep it public, this stuff is good reference for people later on!
Click to expand...

Good thinkin' . :waytogo:

The TBI is factory GM from a 90 blazer w/an auto tranny.
Was a 700r/241 truck, had A/C and power everything.
I'm using the computer from it with a Painless wiring harness.

The motor is an old style block that has been stroked.
When swapping motors is was apparent when looking at the externally balanced crank etc.
So I'd say they used the original heads/intake when the change to the 383 was done.

I'll get the #'s your talking about and go from there.
I do have lap top availability.
I also have two other GM computers, one from an 86 vette and the other from an 87 iroc if they could help in any way but their for TPI so maybe not.
 
Yeah TPI ones won't help.

Hopefully from the BCC we can figure out which displacement it is.
 
Well....at the risk of sounding like a stuck record ....EBL. An EBL set up with IAT and WBo2 will allow you to run any set up. Once you've determined what injectors and FP you have your set. If you have have stock 350 injectors you would benefit from Turbo City's high flow 350 units. 454 ones may be overkill.
I know I keep banging on about this EBL stuff but it really is worth the money. Easy to use and has datalogging built in plus many 'extras'.
 
southernspeed said:
Well....at the risk of sounding like a stuck record ....EBL. An EBL set up with IAT and WBo2 will allow you to run any set up. Once you've determined what injectors and FP you have your set. If you have have stock 350 injectors you would benefit from Turbo City's high flow 350 units. 454 ones may be overkill.
I know I keep banging on about this EBL stuff but it really is worth the money. Easy to use and has datalogging built in plus many 'extras'.
Click to expand...

Is there a link or something where we can view, read up on and buy this stuff?
Thanks for the info.
 
So good news on the plug wires. :)

The EFI engines certainly don't run a whole lot worse with one or two dead cylinders do they?

You shouldn't have to remove the ECM case top to read the BCC. Does anything on the case or PROM indicate that it's a reman unit? I haven't dealt with many remanned units, but it's typical in other remanufacturing processes to not indicate what the exact piece is. And remanned ECM's are far too common. :(

Anyways, you can remove the PROM like I mentioned before, and the blue cover is removable as well, if you need to try and find the BCC. Not sure if there are any pictures floating around of what it NORMALLY looks like to help you. I'm sure there are, just not sure where to point you for photos.

I can't recall who had the 383 TBI horror story on here, but I believe it was burt4x4 (or burts4x4?) that had his 454 dyno tuned. Very eye opening post, as he showed the before/after Air/Fuel Ratio.
 
I think it was Burt, remember hearing about it.

My case does say "remanufactured for GM" on it.

Wouldn't the plugs 'tell all' if it was running lean?
The plugs I pulled out of it looked beat but not lean.
 
They certainly can. The setup will compensate for fueling at light/moderate throttle, the problem is that at WOT, or close to it, the O2 sensor input is ignored, and programmed fuel tables take over. Problem is, they are programmed for a 350, not a 383. So you may end up running quite lean up high, but ok at lower RPM's. Obviously not good to run lean at high RPM's/loads.

You'd see that with a scan, as the ECM compensates more than it normally would.
 
Still on it. :D

Aquired a lap top. (free)

Now I can do the 'look see' thang.

Thanks for all the info/links, mucho appreciated.
 
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