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lets talk cams and fuel injection

mudhog

mudhog

THEGAME
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ok my son has a 88 burb with stock motor in it right now. we have to pull the motor to replace the crank and main bearings. so when apart he wants to change the cam and maybe the pistons to get a little higher compression so he can have a little more horsepower. it has the stock throttle body fuel injection on it now. he has very little money so upgrading the throttle body isnt an option right now. so with the stock injection what would you guys suggest is the best cam to upgrade to and how much compression?
 
From what I've heard compression alone doesn't do alot for power. Don't quote me but I'm pretty sure 4x4high has said that, and I'll listen to anything he says motor wise...

Id do cam and heads before touching the pistons.


But with TBI, you will need a tune for the TBI with a cam upgrade IMO. They will run with lots of upgrades, but not efficient at all
 
Go mild. VERY mild. If you put too much cam in it or change the heads etc you'll have issues getting it to run without custom dyno tuning to get it dialed in. TBI doesn't like mods much.

I personally like Edelbrock's TBI cam. Adds plenty of grunt but still runs on a stock tune quite well.
 
Those TBI motors are uber finicky. You have to go very mild as stated. Or spend the rest of your days playing with custom chips trying to get it to run right... Depending on how much money you are planning on spending, a vortec motor swap could be a good option. THere is a complete 6.0 on craigslist in gresham for only $1300.

Short of that, i would read a good bit on this site. THe guy knows his stuff and has a good run down on making power with these motors.

http://www.tbichips.com/

Specifcally in this section. At the bottom he gives cam choices.

http://www.tbichips.com/truckmods.htm
 
If no money then you really have to be careful. I think a couple of cams actually come with a chip to install.

I, like most, used to think the TBI was severely limited but having a buddy that has started doing lots of tuning and he and I have talked a ton about the TBI system, he has gotten 383s with bigger cams then the motor should have to run awesome with a TBI, yes the injectors have to be right certainly but there is alot out there for the TBI system that just wasn't worth doing because better systems came along very quickly.

He has taken several motors with TBI that no one else could get to run properly and been able to smooth them out, make em idle good ( at stock idles so like 600 rpm) and make em pull to more rpms than before.

But it does cost money for a tune like that. It does take money to get a TBI to run that awesome. Sometimes not much but it does

So no money get a very TBI friendly cam
 
If he has no money, don't do it.

I've seen results of cam/exhaust swaps on TBI, fueling was off 20%, that's on the lean side. You can't add a cam and have it run right without retuning (open loop, to include WOT, will be lean because the O2 sensor isn't being "used") and it's only compounded when other components change.

There IS no such thing as a "computer friendly" camshaft. It's a lie, and should be prohibited as false advertising. The only people who can say something "runs right" after a swap are those who have datalogged after the swap, and see that fueling and timing is right. Seat of the pants does not tell you things like a lean condition under heavy throttle.

You may get away with it, because every application is different and how far off it is will always vary, but the FACT is that you can't know if it's right or not, if you don't take the time to datalog.
 
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I have an 88 K5. I bought a gm goodwrench stock 5.7 tbi for mine. It wasn't worth the hassle and expense of upgrading. A 5.3 or 6.0 would be far better than messing with a tbi engine. My pickup is a 79 and is carbed, so it was easy to upgrade.

Power is made with the right combo of parts. A better cam won't do a lot for crappy heads, intake, or the wrong CR. You may see small gains, with just upgrading some parts, but on tbi, it isn't worth the risk of it running like crap.

My pickup started with small upgrades to the 350, but now has a 406 with ported aluminum heads and intake, headers, 10:1 CR, flat top pistons, etc. It hauled butt.

I lost the thrust bearing so it is getting freshened up. We are going from a comp 270h flat tappet cam (224/224 and 470 lift) to a comp roller conversion with a 264h roller (212/218 and 487/495 lift). This cam should be better for low end torque and should be about the same for peak power. The Edelbrock heads are huge due to porting, so the new engine builder claims this cam will offset the head size. The guy that did the heads originally speced the 270 flat tappet cam.

Everyone has different ideas of what will work best. Finding the right combo of all the parts is the key.
 
take my word for it, start with a head upgrade. edelbrock has a set of heads that will work with the TBI intake. Only then would a cam change be worth anything.

I did a cam upgrade and it helped little if anything. Don't waste your money on anything unless you upgrade the heads.
 
Basically what everyone is saying here in this thread is this:

Go stock, or swap in a 5.3L / 6.0L. Like Dorian said, even if it runs alright after a cam swap it still isn't perfect unless you take the time to properly datalog it. That includings using a wideband O2 sensor btw, you shouldn't be using the stock narrow band O2 sensor for tuning beyond mild tweaking.
 
I have a 92 Roadmaster that had a crcked block when I got it. put another one in just stock. After about 2 months I installed a set of 1.6:1 Comp cams Roller rockers in it from a marine engine. Woke it right up. Even with the 2.96 gears in the G80 you have to be careful so it doesn't get loose. Only problem is it's alittle smelly at idle, but it doesn't set codes and runs smooth as glass any other time. I'm going to put a set in my 92 blazer and see what it does.
 
Correct if that's a wideband O2. Narrowband is worthless for anything but 14.7:1 unfortunately.

GM was pretty conservative on fueling in open loop, but as said before, every combination is going to react different. Which is where the wideband (coupled with datalogging preferably) comes into it's own.
 
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