Need opinions: To EGR or not to EGR

[Daveo91Burb]

Trying to decide if I should keep EGR on my vortec 383. Vortecs make EGR a little harder since they don't have exhaust crossovers in the heads. Trucks from that era got their EGR input from the drivers side exhaust manifold. Emissions in my area are a rolling 25 years old, the Burb is a '91 so I don't have to worry about that part. I have all the parts needed to go with the EGR and the GMPP manifold I'm using has EGR provisions.

I know most will say dump it -- too much trouble, things to go wrong, and I have to go with custom chip anyway so will be easy to program out. But I think there could be an argument the other way: EGR lowers combustion chamber temp (that's the primary function) so presumably it would run cooler. Also, I'm wondering if there would be a benefit in cold weather since EGR has a heating effect on the intake manifold that is not present otherwise with vortec heads. (and it is present with my current TBI heads). I've also heard an argument that it theoretically could improve mpg since you're introducing an inert gas that would therefore need less fuel, but that seems to be a stretch.

This decision affects my exhaust manifold choice which is where I'm at with my build now.

Options:

1. Use original TBI manifolds - no EGR. Cheapest option because no immediate exhaust work required.
2. Use original TBI manifolds, drill and tap hole in drivers side for EGR (I've looked at this and I think it could be done)
3. Use Vortec manifolds that have EGR port. Was pretty sure I was going to go this route until I noticed the other day the drivers side is a Chinese aftermarket. Crap. Other problem is the driver's side outlet is located differently so I'll need to do some exhaust work, probably a custom y-pipe (I'm running a single 3", no cat, magnaflow muffler)
4. Something more radical, probably original GM rams horn manifolds. Seems like they're easy to get - $50 for a pair on CL. Definitely would require some exhaust work. I could run them without EGR or with if I drill and tap like in option 2. I'm a little nervous about fitment - looks like the alternator bracket might conflict with these manifolds. Anyone have any experience? Headers are a no - don't want the expense, hassle and heat. No need for them on this torque motor.

 

[4WDKC]

I dislike them because they clog and cause problems. In these old systems I dont think it uses the egr at idle, I know it is used at cruse to help with mileage.

1. Use the AIR tube from DS manifold for EGR, another option I have been looking at is 92-97 LT1 manifolds, they have all the emission ports.
2. See above
3. dont the vortec manifolds require modifying the frame?
4.Have read you can get them to work with Alt. bracket (perfect tiem for serp swap), my thoughts are now you have to move the O2 as ram horns dont have O2 bungs, they also dont have EGR unless you are talking about different manifolds.

 

[Daveo91Burb]

I dislike them because they clog and cause problems. In these old systems I dont think it uses the egr at idle, I know it is used at cruse to help with mileage.

1. Use the AIR tube from DS manifold for EGR, another option I have been looking at is 92-97 LT1 manifolds, they have all the emission ports.
2. See above
3. dont the vortec manifolds require modifying the frame?
4.Have read you can get them to work with Alt. bracket (perfect tiem for serp swap), my thoughts are now you have to move the O2 as ram horns dont have O2 bungs, they also dont have EGR unless you are talking about different manifolds.

Thanks some good ideas here. However I don't have an AIR system, I think that was only on early TBI trucks? So that won't work for an EGR feed. My existing manifolds also don't have any O2 ports, I think O2 is further downstream.

LT1 manifolds are intriguing. Kind of similar to rams horns. There are some on ebay, not too many though. I didn't see any on quick CL search.

Hadn't heard the vortecs need frame mods. They might stick out a little more than TBI manifolds on the front cylinders. There's also a heat shield that could get in the way. They definitely stick out more on the back cylinders, but the square's frame curves out there too. Here's a pic of DS manifold mocked up on my new block.

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Rams horn manifolds - still thinking about this. Sounds like it's much easier to do on 4x4s - good news for both of us. My truck already has serpentine, I thought they switched over to that in the mid 80s?? Rams horns have these weird casting bumps on top that interfere with center bolt valve covers for some reason. I had to grind those bumps off when I used the original manifolds with vortec heads on my Vette. This is the alternator bracket interference I'm concerned about - that bracket looks like it was made to just fit the original TBI manifold.

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[4WDKC]

The switched to a hybrid at first it was a 4 rib serp belt for alt, wp and crank, v belt for AC this is what I have and that same steel bracket oua re refering to is connected to my AC brackets. Because I didnt want to fight with that bracket, AC lines, and having to move the wiring around, I bought a 96-02 vortec 350 serp setup. This keeps the Alt and AC in original location, allows for use of newer more efficient compressor and I didnt have to look for cracks n locating one. Hmm guess I l have to keep my manifolds if I swap to headers then.

 

[yevgenievich]

Power steering bracket support can be relatively easily adopted to mount using spacer to just about any exhaust configuration.

 

[Daveo91Burb]

Cool, thanks guys. Still haven't quite decided what to do, but good that there are some options. Anyone have any experience with the vortec manifolds in a square? Will they fit without frame or other significant mods?

 

[Honky Kong jr]

I never felt the need to pump hot air in to the intake and put heat were you really don't want it.

 

[4WDKC]

I never felt the need to pump hot air in to the intake and put heat were you really don't want it.

The only benefit is the Vortec intake manifolds don't have heat crossovers so they can be finicky in cold weather at startup, if the EGR worked at cold start/idle it could help with this issue but, I don't believe it does.

 

[spanky55amg]

Coming from an auto tech... get rid of EGR. I completely understand why its there, but as stated:

a. clogs stuff, specifically the EGR valve itself. Which leads to a ton of drivability issues.
b. Why pump hot ass exhaust into a combustion chamber?
c. looks cleaner.

 

[Daveo91Burb]

The only benefit is the Vortec intake manifolds don't have heat crossovers so they can be finicky in cold weather at startup, if the EGR worked at cold start/idle it could help with this issue but, I don't believe it does.

I agree that the valve probably doesn’t open at cold start/idle but I think there would still be some heating effect - input into manifold is at front DS, but valve is at middle PS. But, as stated, this heating effect would be going on all the time, even when I don’t want it. I’ll probably leave EGR out and have it programmed out of chip burn, but I’d like to have ability to add it back if ever needed.

Same question as before: anyone have any experience with vortec exhaust manifolds in a square? Also, comparing them with my stockers it looks like they may flow a little better, but I have no data to support that.


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[twinturbo427]

I have an LT1 roller cam that I was going to do a roller conversion on my Suburban with someday. The thing has 117 degrees of sep because this model did not come with egr. Maybe somewhere in there lies your answer; no mechanical egr but add it to your cam specs.

 

[4WDKC]

I have an LT1 roller cam that I was going to do a roller conversion on my Suburban with someday. The thing has 117 degrees of sep because this model did not come with egr. Maybe somewhere in there lies your answer; no mechanical egr but add it to your cam specs.

It is my plan too but, I'm pretty sure the LT1s had and egr on them.

 

[twinturbo427]

I don't have the part number fro the camshaft with me but I barely recall something about that application having no egr. Take it with a grain of salt, I survived the 80s!

I will look when I have time.

 

[4WDKC]

I don't have the part number fro the camshaft with me but I barely recall something about that application having no egr. Take it with a grain of salt, I survived the 80s!

I will look when I have time.

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[MikeB]

Hadn't heard the vortecs need frame mods. They might stick out a little more than TBI manifolds on the front cylinders.

I'm not sure about your Suburban, but on my 82 C10 there was approx 1/2" to 3/4" clearance on the drivers side, and 1" or more on the pass side. I'd give you the exact numbers, but my truck now has headers.

I also took a die grinder to the ID of the manifold outlets, because they necked down to LESS than 1-5/8". According the to Walker Exhaust site, 1996-2000 C1500 5.7 liter headpipes were 2" from manifolds to dual catalysts. So, not exactly high performance stuff here, but along with the short duration camshaft, tuned for max torque at very low to mid RPMs. Enough torque down low to do burnouts by simply stomping on the gas!

On another note, make sure the exhaust manifold port openings are tall enough to not obstruct the top of the head ports. On later model 062 Vortec heads sold by GM Performance parts the exhaust ports are raised around .120", which apparently wasn't the case with the L31 906 and 062 production heads. I had to "raise" my manifold ports using a die grinder. Also, carefully select a gasket that doesn't cover up the very top of the exhaust ports.

I removed the heat shield, but I don't remember it hitting the frame. The two bosses are higher above the frame than they appear in the picture.

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