06 LJ Randy Rebuild

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akadeutsch
Movin on up ^
Movin on up ^
Posts: 312
Joined: February 22nd, 2014, 7:27 pm
Stroker Displacement: 4.6
Vehicle Year: 1981
Vehicle Make: Jeep
Vehicle Model: CJ8
Location: New Prague, MN

Re: 06 LJ Randy Rebuild

Post by akadeutsch »

Just great work. Using the older intake for equal size runners was a good idea. I'm just curious why there appears to be a step from the brick shaped manifold that you welded to the older intake where it meets the runners? The added manifold appears larger than the runners. Wouldn't you want them matching size to minimize drag and maximize velocity?
Everything in your build appears to be well thought out and I don't doubt there is a reason. I just don't see it yet. So, i'm only curious how/why you chose the volume of the manifold you joined to the old runners/manifold? Again absolutely astonishing work. I can't wait to read the data. Id like to know about the equipment you used to weld braze solder or whatever it took to get that result... cheers! Great work!
and thanks for all the pictures.
Randy Bobandi
I made it to triple digits!
I made it to triple digits!
Posts: 148
Joined: December 22nd, 2020, 8:50 am

Re: 06 LJ Randy Rebuild

Post by Randy Bobandi »

akadeutsch wrote: October 12th, 2023, 6:32 am I'm just curious why there appears to be a step from the brick shaped manifold that you welded to the older intake where it meets the runners? The added manifold appears larger than the runners. Wouldn't you want them matching size to minimize drag and maximize velocity?

So, i'm only curious how/why you chose the volume of the manifold you joined to the old runners/manifold?
This is a turbocharged engine. General rule of thumb for plenum volume is 1:1 (displacement:plenum) volume for NA engines, 1:1.5 for power adders.
Though there other factors involved, other than displacement, like max torque RPM range and especially space in the engine bay. The plenum volume I ended up with is 290 cubic inches, just over the engine displacement. There isn't much more room to go larger than that without mounting the engine on a slant. The dang steering shaft is just a couple inches from the intake plenum.

I'm not concerned at all about the "step". The step is the plenum flange from the OE manifold. Most all inline engine manifolds are constructed this way and it would be extremely difficult to weld the OE runners to a plenum without that flange. The OD of the runners for cylinders 1/2 and 5/6 are 1/4" from eachother. They would have to be welded to the plenum from the inside out if you remove the flange from the OE manifold. The other way to go is to just build a totally custom intake, which requires buying a $250 intake flange from Newcomer. That's more than I spent on this whole setup including the throttle bodies.
pzmanifold.jpg
ncmanifold.jpg
akadeutsch wrote: October 12th, 2023, 6:32 amId like to know about the equipment you used to weld braze solder or whatever it took to get that result.
I'm not using anything uncommon. I use the tried and true, YesWelder 205DS-B with a teflon liner in the traditional mig gun. 100% Argon. ER4043 wire which is preferable to 5356. 5356 is more likely to crack after several heat cycles.
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