Fab EGR Tube for header or go back to 258 head & manifold?

[MattandOrange]

I've got a 4.0 head w/header on my AMC 258 i6 / 4.2l block with Howell TBI. I'm still kicking too much NOx and realized that I don't have a line to my intake to get the EGR functioning.

I already went to the referee. He passed my EGR but put N/A for EGR function. He might have overlooked that high NOx came from a non-connected EGR(and maybe a bad catalytic converter). Or maybe he wanted me to figure it out myself.

Q. Is it worth attempting to fab an EGR tube from the header's flange? Will I get enough back pressure to activate the EGR?

Q. Should I just go back to a AMC 258 i6 / 4.2l head & exhaust manifold?

Thanks in advance!

 

[IOPort51]

I vote for the EGR tube in the header. I would re do mine if I had half an excuse to pull the header off to weld the bung. Even carbed motors run smother with an EGR valve.

 

[Scooter402]

I'd say fab the tube and be done with it. Nothing but welding in a bung and bending some tube to fit.

 

[MattandOrange]

IO & Scooter,

Q. Where would you put the bung on the header?

-Will there be enough back pressure to engage the EGR if I put the tube just above the flange? The exhaust would essentially go down the pipes and back up over a further distance.

-Should I do a Y pipe higher on the header so that the air is escaping 2 chambers?

I remember the stock exhaust manifold had the EGR tube around the #2 cylinder. The pipe curved down then went up into the intake. Wouldn't that mean that the EGR was only collecting exhaust from the #1 & #2 cylinders?

That being the case, an old school hot rod guy/Smog technician told me that since headers are better avenues for air than exhaust manifolds, I may not even get enough back pressure.

I picked up a couple of bungs from a specialty performance shop in town already.

Thoughts?

 

[IOPort51]

you may not have as much pressure in the exhaust but you still have vacuum in the intake. It does not take a lot of the exhaust gas. I would put it on the nearest and/or most convenient exhaust tube.

I would hit the grave yard and pick up two or three of the tubes. bending steel tubing can be a bit of a problem so doing a little creative cutting and splicing may be in order.

 

[MattandOrange]

@IO

The pipe for 4, 5 & 6 are the closest to the intake. You think that'll be alright?

 

[Scooter402]

I may not be directly answering your question here, but my understanding of the EGR valve is that it is opened under engine load. While the engine is under load, it is creating more exhaust gasses, increasing exhaust back pressure. True, one tube of a header may not produce enough back pressure to feed exhaust out (I would think only if it were open -- if a full exhaust system is in place, I don't think it would be the case), but as IO had already pointed out, there is vacuum from the engine. Also true, while the engine is under load, the vacuum signal drops, but I would still think that the increased exhaust gas output would still let the EGR function as it should.

 

[MattandOrange]

True. Thanks guys!

I forgot about the vacuum from the dual CTO which is present. Hopefully, the position of the EGR tube and the vacuum will be enough to engage the EGR.

I found the fittings this afternoon. I'm off to the industrial metal shop tomorrow, the muffler shop, the smog station and hopefully AAA to get my tags.

Applicable to California:
The referee called me back about my inquiry about the EGR passing. It's only a visual inspection of the EGR, not for function. Since I'm in Burbank, I needed an ASM(Acceleration Simulation Mode) test. The ASM test is 15 mph & 25 mph under load to measure NOx. EGR functionality is only actually tested in a TSI(Two Speed Idle) test, which doesn't make sense because EGR non-function leads to NOx fumes which aren't even tested anyway.

I'm probably missing something, but it seems like they're intentionally confusing people so that they give up their old cars.

 

[IOPort51]

someone help me out here, is the egr on ported or manifold vacuum ?? I had thought that it was open at idle with warm engine.

 

[Scooter402]

someone help me out here, is the egr on ported or manifold vacuum ?? I had thought that it was open at idle with warm engine.

I believe you are correct.

 

[IOPort51]

so the vacuum should come from a manifold vacuum through a normaly closed port on the CT switch.??

I believe you are correct.

 

[Scooter402]

so the vacuum should come from a manifold vacuum through a normaly closed port on the CT switch.??

I think technically, yes, it is from a NC port on the CT switch...but essentially, it is from ported vacuum.

 

[jdarg]

I think some of the responses led you the wrong way - EGR should not be diverting exhaust gasses back to the intake at idle. This means use of a ported vac source, not manifold. Otherwise it dilutes the intake charge way too much at idle - where there is a VERY strong vacuum - and causes stalling or poor idle.

 

[hagar]

someone help me out here, is the egr on ported or manifold vacuum ?? I had thought that it was open at idle with warm engine.

It only opens as throttle increases with a warm engine.
The engine will idle very poorly with an open EGR, assuming it will even idle.
If you were to reach in/under the head of the valve and depress the diaphram, the engine will die.

 

[MattandOrange]

When I pressed the diaphragm of the EGR at idle, I would actually rev higher. With the EGR removed completely(no blockplate), the engine would immediately rev to 4000 when I start it. Probably a really dumb question but, why is this happening?

I presume that since I'm essentially varying the restriction of air into the motor, the motor is going to running wildly because the combustion cycle has no way to control itself.

I'm going to get the tube installed tomorrow. Wish me luck.

 

[yellow85cj]

Might be a little late on this. Here is how I did mine. Pulled a tube from an early 4.0, and a bung from Borla. Bolted the manifolds to the head and took it all to a welding shop. After putting on the bung, they cut the tube and fit it together. One of these days when the CJ gets back together I'll find out if it works.

 

[MattandOrange]

That looks fantastic, yellow! I have a similar set of pipes.

After a 1 day delay, I just picked up my CJ the shop and they ended up welding a tube of their own into the bottom of the intake. I have mine coming from a little bit south of the #4 cylinder. It was a slightly straighter shot into the intake. When I got back to work, I pressed the EGR diaphragm slightly and the RPM dropped as it was supposed to. It's a brand new EGR so maybe it's a little tighter. Anyways, off to the smog shop tomorrow AM.

VF Sales(Vincente) - bung/fitting
Morse Muffler(Ron & Tim) - muffler shop

 

[IOPort51]

Are they still selling the one with the selection of orifice sizes?? which one did you use, what number?

That looks fantastic, yellow! I have a similar set of pipes.

After a 1 day delay, I just picked up my CJ the shop and they ended up welding a tube of their own into the bottom of the intake. I have mine coming from a little bit south of the #4 cylinder. It was a slightly straighter shot into the intake. When I got back to work, I pressed the EGR diaphragm slightly and the RPM dropped as it was supposed to. It's a brand new EGR so maybe it's a little tighter. Anyways, off to the smog shop tomorrow AM.

VF Sales(Vincente) - bung/fitting
Morse Muffler(Ron & Tim) - muffler shop

 

[MattandOrange]

@IO Not quite sure I understand your Q.

It didn't work. The EGR would drop the RPMs when I pressed the diaphragm, but it didn't move when I pressed the throttle. I don't know if I'm not getting enough back pressure or if the location of the EGR tube was too low. My HC and NOx numbers were almost the same as when I failed with the referee.

What else could it be?

I have a AMC 258 i6 / 4.2l head & exhaust manifold lined up for $AMC 150 . I really don't want to go that route but it might be my only option. Any thoughts?

 

[MattandOrange]

OOOooo!

Could it be that since the head from the 4.0 & header flows a lot better than the AMC 258 i6 / 4.2l 's and the exhaust manifold, there's inherently not enough back pressure to engage the EGR on the stock intake?