06 LJ Randy Rebuild

[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'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.

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Id 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.

[Randy Bobandi]

I am currently in the middle of the development of Jeep/AMC straight 6 Roller Camshafts. The first grind is only a couple weeks out.

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There are important things to keep in mind when converting this engine to a roller cam. This is a public service announcement.

1- This will be expensive. None of the major camshaft grinders have ever wanted to jump on board. I had to go to the guys that machine custom Tool Steel NHRA Top Fuel camshafts. Jesel and Militia Racing Products are the only two companies that found this project interesting and doable. The camshaft itself will cost $1,700.00. No refunds, but they can obviously be reground several times if necessary. Considering the cost, this conversion is not well suited toward a mild or stock grind. Flat tappet cams work great for that. This project is geared towards aftermarket EFI, turbochargers and goals of 1000+ HP.

2- Getting roller lifters with an anti-rotation mechanism into the lifter bores of these blocks is not simple. Roller lifters are typically 3" tall so you can't snake connected tie bar lifters into the bores. Dog bones could work but there isn't a great way to fasten dog bones into the block. They would call for an experienced machinist to come up with a good dog bone solution. Keyway lifters would work great but they're only available as a solid lifter, also installing the keyed bushings is very expensive and not really a project for the home garage. What we'll end up with is a custom tie bar solution. Well, it's really a modified tie bar. The tie bars will be riveted to one lifter and slotted on one end so you can snap them onto the other lifter while they're in their bores.

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3- The camshafts are the same material that they use in top fuel engines. The manufacturer doesn't want any other material but bronze used for distributor gears. Guess what? Nobody makes a 4.0L distributor gear in bronze, they're all iron. We have found bronze gears that will work however. Turns out, the Mopar R5 engine uses the same gear as the Jeep engine. Although, the Jeep distributor shaft is about .040" larger than the R5's. So you'll have to drill and hone the R5 bronze gear to .5285" and it will work just fine. You may want to have some spares and keep an eye on wear because you'll now have a bronze gear driving the oil pump. Or you can always go to an external pump.

4- The distributor gear may only sync up with the late model 99-06 EFI systems. It may not work with an actual distributor, The gear on the iron cast cores is indexed to a specific degree and getting the gear indexed properly presents a whole set of problems for the machinist. However, the gear is indexed due to the distributor not being able to turn 360 degrees. The fastening tab is cast into housing of those early model distributors. I think if you grind that tab off, it can then be clocked freely and fastened with an external tab.

If you guys have any thoughts on this project let me know. Especially with the lifter anti-rotation mechanism.

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