Stroker worth the "trouble" ?

[Alex22]

I'm not familiar with the older AMC stuff. That being said, are those slots around the mains a stock piece or were they cut/ground into the cranks. I don't really like the idea of grinding the crank like that. If it is not done with a radius cutter then it will make the crank more likely to crack there. Also, the upper bearing for the 4.0 already has a slot in the upper bearing shell and a smooth lower. That is done so the oil is forced to cover the entire lower bearing shell and the oil will prevent the bearing from touching the crank and it will absorb some of the shock from ignition. At work we have been cross drilling Porsche crank shafts because the center main does not have any holes to start with and we want more oil to be forced in from the block to oil the rods. I don't see the point in cross drilling the mains of a jeep crankshaft. If you were to cross drill the center main of a jeep crank then less oil would make it to the thrust surface and could cause premature wear on the thrust bearing and the crankshaft.
Navarro's crank also appears to be a cast nodular iron crank (higher nickel content iron) which is a stronger material than the standard cast iron 4 counterweight 4.2 cranks. The crank has 8 counterweights so I would assume it weighs close to a stock 4.0 crank, about 50 pounds. The heavier the crank the harder it will be to start a harmonic in, from what I have seen most people on the forum prefer the 4 counterweight crank because it is lighter and will rev up slightly higher than the 12 counterweight.

Kris,
Thanks for the info on the AX-15, Is there any way to make the 3rd gear syncro stronger or is an after market one available?

~Alex

[John]

The 199's used a cast pearlitic malleable iron crankshaft. Mr. Navarro knew what he was doing in specifications for cutting techniques. That cut works as a hydraulic lift to more rapidly float the bearings from the crankshaft as well as providing a reservoir to insure a good planing film.IE on start up the crankshaft is sitting on the bearings with a minimum amount of oil film. The oil pressure is directed to work on the reduced area and lifts/centers the crankshaft to its running clearance and now provides for increased oil flow across the entire bearing surface. This galley will now be a mini sump to increase lubricant film feed.
John

[Alex22]

Ok, Now I see what they were intended for. I mentioned the cutter radius part in case someone was reading this and thought a hacksaw/file/cut off wheel would accomplish the same job.
John, can you post the link to Navarro's info, if there is a website?

~Alex

[John]

I will put a few links together and get back to ya. Yes there is a reasonable amount of info out there. But as always, never enough.
John

[John]

http://www.racn.net/index.php?option=co ... &Itemid=88
http://www.fixrambler.com/art63.html
http://hooptyrides.blogspot.com/2005/08 ... ction.html
http://www.geocities.com/mmbb444/page32.html
http://www.oldracingcars.com/results/re ... 71B#note10
http://www.forum.route66rambler.com/ind ... temId=1555
http://ahraf.com/pioneer.php?pioneer=barney_navarro
http://www.forum.route66rambler.com/ind ... ,35.0.html
http://www.hotrod.com/newsstand/hrdp_08 ... index.html

Alex22 here is a good start re some of Barney's accomplishments, some of these have links within links. Glad you are interested. He was one of the great minds of hot rodding's history.
John

[Alex22]

Another reason for either cross drilling or cutting the groove around the mains of the crank is to put more oil to the rods. Half of the time the oil hole that leads to the rod is on the underside of the bearing with the oil passage cut off from the supply. By cutting the crank you can allow the rods to be fed constantly. Another way to do this is to install two sets of upper bearings, you may have to modify where the tang fits on the caps. You will have lower oil pressure at an idle with that setup, so it might be the case where a HV pump is required.

~Alex

[John]

The oil pressure is directed to work on the reduced area and lifts/centers the crankshaft to its running clearance and now provides for increased oil flow across the entire bearing surface. This galley will now be a mini sump to increase lubricant film feed...... Yeah more oil, yes we are on our way to needing increased flow and pressure. But all else the same you really won't see much change in idle oil pressure. When you spin this crank up to speed you will actually draw the extra oil from the new galleys. Think about how a gear pump works, This may be closer to the wankel though. Have a good day.
John

[Alex22]

There will be a noticable difference in idle oil pressure because you are feeding the rods twice as much oil as you were before. At an idle the pump is spinning at about 1500-2000 rpm and cannot pump the same volume through the passages. There is still enough oil pressure for adequate oiling because you barley need any pressure at an idle. The shop has built a few "dual upper" engines and every one of them has had lower oil pressure idle but it will pick up to standard pressure once you rev it up.
Using two upper bearings and cross drilling the crank accomplish the same thing so you can use one or the other, contradictory to what Leee at Hesco says. (for those who don't know he says that you need to cross drill the crank if you want to use it at higher rpms.)
I've inspected and repaired/replaced enough oil pumps, I know exactly how they work. Almost like a roots style supercharger.

~Alex

[John]

Yeah, thats how they work.
John

[Alex22]

Here is what Scat thinks of cross drilling a crankshaft
http://scatcrankshafts.com/PDFs/ScatCrank07.pdf
Check out Page 24.

~Alex

[4.whoa]

I have a question about the "dual upper" mod. Since a lot of these cranks come with 4.2 bearings can those uppers be used along with 4.0 uppers it'd be good- beats wasting them.

[lafrad]

I used a set of 4.2 "upper" bearings in the maincaps on my build. I cut the main cap tangs wide enough to accept the new location of the bearing, then squished a dab of JB Weld in the gap of the tang just for good measure. If you do this, be sure to check the bearing opening for roundness, as the JB can actually harden "larger" than it was when it flowed into position... forcing the bearing out of round. Oh, and don't worry about the #4 maincap... (the center one)... there is no rod oiling that is going from there....

I realize its not the BEST way to make up for the tang, but once everything is compressed and in place, the alignment tangs don't really see any side to side force...
With a High Volume oil pump, I get 25 psi at HOT idle, 50 psi-ish at 2500 rpm HOT. when cold (32F), I get about 60 psi solid... so... when cold, the oil pump is a little strong, but its perfect after everyhting has been running for a bit.

[gonridnu]

Ummmm....cross drilling cranks has been found by all reputable crankshaft builders to NOT work.

It sounds good in theory but unless you run 90 lbs of oil pressure it doesn't work. Even then it still doesn't but you may not burn up rod bearings . Grooved mains good....cross drilling bad. Read up on it a little or call a crankshaft manufacturer. It's one of those things from days gone by that everybody thought worked but when the data came in it was just the opposite.

If you feel the need to increase rod lubrication check into teardrop oil holes on the mains that actually scoop oil off the bearing.

[4.whoa]

Is that better than chamfering the holes What way do you "aim" the teardrop and how large/deep should it be?
everyone talks of doing things to the main journals, what about the rod journals? to chamfer or not to chamfer

[SilverXJ]

The 4.0L doesn't really have a history of eating rod and main bearings. I say leave it alone.