4.0 header

[sandsgg]

I have an edelbrock header from my 95, I was wondering how much of a benefit will I get if I swap it and a late model intake into my renix? I know from searching I'll have to change the downpipe out but what other problems might I run into as well?

 

[cruiser54]

Intake isn't worth it.

Header is. You will have no O2 sensor bung or EGR bung in the 95 header. It will fit fine but you may have to file the intake manifold a bit. No biggie.

Done this numerous times.

 

[O-Gauge Steamer]

The "horse shoe" intake manifold makes it's difference on the highway. At low engine speeds, it provides very little over the old style "log" manifold.

As to actually feeling the highway improvement, hard to say. I installed on on both the 87 I had and the 98 I have. Until I replaced it with a Supercharger....

Then, as if by magic, the performance increased indeed.....

I can say that on both the XJs I fitted the new style manifold onto, the highway mileage went up. IMO, the better bang for the buck is a combination of a larger throttle body couples with a free flowing air cleaner.

There is a very simple vacuum test that can be ran to see if the existing intake system is at all compromised.

 

[streetxj]

I installed a 62 mm throttle body when I had the log intake in my 96' XJ and I also already had the modified stock intake system. It made a slight difference. When I swapped in the 2003 horseshoe intake manifold, it made a nice difference. It felt like I upgraded the rear differential gears. The rpms climb up a lot smoother when I'm accelerating and it has more low-end/mid range power. That made a bigger difference than the 62 mm throttlebody alone on the log intake. I already had the modified exhaust system at the time too. It seems that the swap is worth it if you have a high-flow exhaust system and intake system. I also lightly grinded down the injector bosses of the intake manifold before installing it and applied a thermotec heat wrap under the intake manifold. The thing is that you have a renix and an HO intake, whether it's the horseshoe or the log type, will not align with the lower intake ports correctly. So I think it will be better if you keep the Renix intake manifold. You can clean whatever sludge that is in the intake, carefully clean the intake ports, and add a heat wrap underneath the intake manifold to keep the intake temps lower. You have to clean the intake really well for the wrap to really stick to the intake.

 

[O-Gauge Steamer]

IMO.... The "smooth" runners of the late model manifold will flow the air charge faster than the old style manifold. If you were to grab an Engineering Handbook and look up the properties of a fluid traveling through a pipe, you will find that the sharper the turn in the pipe, the more turbulence is setup at that point. Turbulence impedes flow.
There are formulas to calculate the turbulence...........

A fluid in a pipe will want to form a vortex running the length of the pipe. This puts the majority of the flow in the center of the pipe. You can see how it is that this mass of working fluid would strike the side of the pipe at the hard 90 turn. This is what generates the turbulence. The working fluid flow will "stall" at this point.

Well, then, you ask... Why did the original designers build the log manifold in the first place? That answer is simple. At the beginning of automobiles, intake manifolds were assembled using standard pipe fittings like you would run water in. Later on, they went to castings but, the basic design had been set as "it works". Yup, it works all right. Not well but, it works. And rather than spend the monies to build better, the inertia of the thing just forced it forward. Look at the early intake manifold and compare it to a manifold from the AMC I-6 that had a carburetor on it. Very nearly the same.

Not good, functional...

It worked so they left it alone.

So then, you have to ask which offers the least amount of resistance. Multiple hard 90 degree turns or, gently continuous bends. I vote for the gentle bends....

There is one other, easy to install, modification that will make a difference. That modification is a Header Blanket. If you have the intake manifold off anyway, then that is the time to install a blanket. The blanket will reduce the operating temperature of the intake manifold.

In my case, it made a 20 (C) degree drop.

There is much said about "cold air" intakes. Truth be told.... As long as the air is drawn from under the hood rather than directly from the atmosphere, the air will be heated. I am a fan of drawing in outside air through an insulated pipe.

 

[streetxj]

I agree. But will a header blanket cause the header to deteriorate a lot quicker and crack easier like it does with header wraps? The thing is that the header itself will get even hotter and create even more structural stress. Not sure if the same thing applies to header blankets though.

 

[SolarBell]

No. The blankets redirect the heat rather than trapping it. Since they are looser they don't create hot spots. And since they allow air movement against the exhaust they don't trap moisture to accelerate corrosion.

 

[streetxj]

No. The blankets redirect the heat rather than trapping it. Since they are looser they don't create hot spots. And since they allow air movement against the exhaust they don't trap moisture to accelerate corrosion.

Cool. I'll do more research on it.

 

[O-Gauge Steamer]

This is where it gets interesting. Every Header Manufacturer out there (that I am aware of...) will void the warranty if Header Wrap is used.

Not so with the Header Blanket. The reasoning is as follows:
Header Wrap creates hot spots at the end of each portion of the wrap. A blanket just lays on the header shielding the intake manifold from the heat. No hot spots generated at all.

Fair warning here: Until the blanket finishes "cooking" in place, there will be some peculiar aromas emanating from under the hood....

When I replaced the stock TB with a 68mm TB I not only installed a blanket but I also installed self adhesive insulation to the underside of he intake manifold as well as the Supercharger's intake manifold.

Heat is the enemy. On this, there are no arguments at all. The cooler you can keep the air charge the better. And up here where I live, heat is very hard to control owing to the lack of density as compared to sea level.

My version of heat control is:
1) Header Blanket
2) Self adhesive insulation to the intake manifolds.
3) Aluminium radiator.
4) Electric water pump.
5) 3 each 10" electric fans.
6) Large external transmission cooler (eliminating the loop in the radiator)
7) A second, fan forced transmission cooler (out of the air stream, fan is T-Stat controlled)
8) Power Steering cooler from an F350.

The Heep operates at or about 90 (C) degrees. That is 194 (F) degrees. It does tend to rise a bit when making full boost (8 pounds of boost) accelerations but, it promptly returns when the throttle is lifted.

Works for me......

Excessive? Maybe. But the rig is Supercharged and I tend to err on the side of caution.

If, that is, you can use "caution" and Supercharged in the same sentence....

 

[Root Moose]

Header blanket, got link?

 

[O-Gauge Steamer]

The exact part both SolarBell and I are running.

http://www.jegs.com/i/Thermo+Tec/893/14004/10002/-1

 

[SolarBell]

Mine looked like I had an engine fire the first time I ran it from my greasy fingers installing it. Was smelly but fine for a few weeks afterward.

 

[O-Gauge Steamer]

Well....
Can't say you were not warned...

But yes indeed, clean hands are sort of required less grease get on the exhaust.

I was surprised at just how long it took to cook in. The results are instantaneous though...

 

[Root Moose]

The exact part both SolarBell and I are running.

http://www.jegs.com/i/Thermo+Tec/893/14004/10002/-1

Thanks, ordered from Summit with some other odds-n-sods.

Too bad the intake and exhaust share the same bolts for connecting to the head. There's no way to add a phenolic spacer to the intake short of modifying the intake. Proximity to the exhaust probably meets it wouldn't make any difference but if we are nerding out anyway.