Alex's stroker build

[Alex22]

Hello all,

I'll start off with some background.
The jeep:
1996 Cherokee Sport with 160K, 4.0, AX-15, Ford 8.8 (3.73 gears with posi and a Super88 kit) 4 inches of lift and 31" tires.
Me:
Just a kid with a lifted XJ. I spent the past few months on NAXJA looking up fixes for the priority jobs (D35 about to blow up) and have my sights set on my stroker now, and a new front axle. During the summer I'm an automotive machinist (2.5 years), weekends I'm a carpenter, and during the school year I'm an Electrical Engineering Technologies student at a community college and work part time as a machinist and a carpenter.

What I have so far:
The XJ
The engine out of a 98 Grand Cherokee with 90K miles on it
4.2 rods
4.2 crank (12 counterweight)
A cracked 0721 head donated by Chad Golen for me to cut up and check out wall thicknesses and a few test ports.
Mustang TB
Accesses to just about any part I want for a quick test fit
80+ years of combined engine building experience willing to help.

Progress:
4.0 engine disassembled
All 4.0 parts magnafluxed good
4.2 crank and rods magnafluxed good
4.2 crank ground .010 (low limit) and nitrided
0721 head cut in half with one intake and one exhaust sectioned.
Lots of ideas

The build:
The head will be ported to get maximum flow while keeping the ports as small as possible most likely chevy valves
Maybe a set of custom pistons
.020 or .030 over
zero deck
9 to 9.5:1 compression
heavily modify or build my own intake manifold and harmonic tune the runner lengths as best as possible.
balance the rotating assembly to race spec
polish, shot pen, install ARP rod bolts, resize and maybe nitride the rods. I have not made up my mind if I'm going to use the 4.0 or the 4.2 rods yet.
Borla exhaust
A'pexi map sensor or the AEM piggy back computer

Goal:
Reliable daily driver engine that will produce peak torque down low, I don't mind that it will run out of breath at higher RPM's.

This is all I can think of for now
~Alex

[John]

Welcome to the board. You have put some serious thoughts into your build. The 4.0 rods are going to improve a few things over the 4.2, dwell, wall pressure, and the skirt doesn't have to pull out of the bore slightly at BDC, but using them will complicate your piston selection.
Nitride treatment of crankshaft sounds good and I see you allowed for the dia. growth when grinding. Do you have the nitriding done locally? Nitriding the rods, are your thoughts to run floating pins?
Your comments on intake balancing brings me to ask the question about tuned exhaust. I find some HP after the header that most overlook. Too many consider only sound quality at this point.
If we can help.................
John

[Alex22]

I mentioned the floating pin idea in the KB944 thread, the 4.0 rod I grabbed today had the wrist pin bored off center and the side of the eye is not thick enough to support a pin bushing. The full floating piston is not necessary for my engine, redline and run out of breath close to stock RPMs. The main reason it is done in high performance applications is so that if the pin locks up in the piston from a lack of oil or its overheating the pin will still be loose in the rod and not cause it to break the piston and self destruct the entire engine. The reason it is done in some newer cars might be a production cost issue, probably easier to have a robot pop a clip in, drop a pin and put one more clip in than time the heat on the eye of the rod and get it in place quick enough.

~Alex

[Alex22]

Progress:
I've been scatterbrained on this build for long enough, too long. So yesterday after work I finally started working on it and here's what I have planed out.

I decked the block last night Deck Height: 9.4419. About .005 shorter than the low limit of a stock block
I measured the housing bore today. Housing Bores are +.0004 to +.0008 from the minimum spec. Max is +.001

The latest plan:
4.0 rods, stress relieved, shot peened and cryo'd (not nitrided) reamed out for bushings then honed to .927 (small block chevy)
Custom pistons, probably Diamond. Since I get them at cost a set won't be too much more than a set of KB944's. I'm going to use a narrower set of piston rings to reduce drag. The pistons will be cut to recieve cir-clips.

not sure about the cam/head and intake manifold yet.

~Alex

[Alex22]

Well the hardwood floors were being refinished at home so I had no place to go and ended up staying late at work every night and was able to make some more progress. but i forgot all my notes at work.
Measured the crank:
low limit give or take a tenth.
stroke: 3.891 to 9.906 I might offset bore the pin bushing on the two connecting rods that are on the shorter throws.
I need to check the balance on the crank and I might knife edge the counterweights and re-balance.
Cylinder head: (stock, as cast 0721)
Combustion chamber: 57.8cc's
Intake port: 116cc's
Exhaust port: 77cc's
I liked how flash opened up the pushrod holes for the lifters to fit and will be doing the majority of the milling on a Bridgeport.
Since the shop I work at will work on just about anyt engine that will fit in the door we have alot of parts for test fitting I got a handful of rocker arms, studs and fasteners and tried them out. As mentioned before the big block chevy rocker arms will work on the 4.0 head. The pedestals will have to be milled down about .250 to .350 to get the proper pushrod to rocker arm to valve geometry. A rocker stud with a 5/16 thread into the head and a 7/16 top will work, but the pedestal is large enough to drill it out for 3/8. If i do go down that road i will most likley have to modify an existing set of guide plates. If you don't want to spend the money on a set of BBC rocker arms then you can go with a set of 351 Cleveland stock stamped rocker arms. They look just like the stock jeep ones but they are a 1.7 ratio and have a different size fulcrum. They are meant to use a 7/16 stud and a lock nut so its not a simple bolt on, but they are cheaper than a set of BBC's.

A few days ago a customer wanted their 4.0 head ported. I only did 2 hours of work to the entire head (didn't) have a chance to flow it) but when I was done it
felt better than a vortec head with twice the time for porting.
Thats all I can remember at the moment.
~Alex

[Flash]

Glad to see some one, fallow in my foot steps (Not that I'm the only or the first one to do this, there has been many!!!!)

Spend a lot of "carefully" time on the first push rod hole and the hole will need to be offset ground by quit a bit.

Then on a couple of them, you will have a slight shelf, from the Block, that will need a slight bevel done too make lifter retrieval/install easier.

With a bridge port, it shouldn't take much time at all

If you do come up with a Cheaper way to put Roller Rocker on. A simple Write up would be grate to add to our fact section for others to fallow your example

Flash

[Alex22]

I would most likely plunge a 7/8 end mill through and use a carbide burr to get it to its final size. One helpful thing I do have is a sectioned 0721 head so I can see/feel how thick the head is around the pushrod hole.

Since I don't know if we have any BB Oldsmobile guide plates around at the shop, there aren't a lot of BB Oldsmobiles around here, does anybody know if the spacing between the rocker arm bosses is the same as the AMC I6
I've been using this website as a reference.
http://members.tripod.com/~Mojo_Page/Rokr1.htm

~Alex

[Alex22]

What would you know, the other day a set of Oldsmobile heads came in. After hours when I was working on my stuff I took a pair of 4.0 rocker arms and they screwed right into 5/16 holes in the Olds head. There weren't guide plates with the heads so I don't know if they will work yet, but its one step closer. One of the guys had a few different suggestions on what to use. The late model 5.0 fords used a piece of stamped steel C channel between the rocker arm and the pedestal to keep the stamped steel rocker arms from rotating off the tip of the valve. Those might be usable on a 4.0 head as well.

I got some flow testing done, but the screenshots of the reports and graphs were coming out blurry when I tried to link them in. I'm trying to figure out how to add them and still be clear enough to read.

~Alex

[Alex22]

I was able to figure out why the pictures weren't uploading nice. Webshots was part of the problem, i'm using imageshack now.

I used an as cast #0721 cylinder head cylinder#6 for 2 separate tests.
For the first I cut the seats using a 3 angle cuter and a radius cuter on the exhaust with the seating angle centered on the valve face.


The second test I used a radius cuter on the intake (seating angle in the same place) and moved the seating angle on the exhaust to the outer edge of the valve face. While testing I was able to hear a significant amount of turbulence in the exhaust port.


Here is a graph of the first test vs the second test.


This is a graph of the second #0721 test (radius intake seat) vs a stock, as cast #0331 head with a stock valve job with 7000 miles on it.
Even though this head did flow a little better from the factory I would not recommend porting a head that has a reputation for cracking.



And here is a stock #0721 head vs a Sonny's Brodix Aluminum Big Block Chevy head that I ported a few months ago.


~Alex

[Alex22]

The Oldsmobile guide plates look like they will need little to no modification to work on the 4.0 head. The stock jeep rocker arm bridge will bolt right onto an Oldsmobile head.

The correct .010 under bearings came in yesterday (accidentally ordered ones for a Renix block) and I was able to check the main oil clearance, .0023 to .0029.

As for the porting.... I was talking with Jim from CompetionCNC.com. sorry, he can't cut a inline 6 on his current machine. But as I mentioned I have a cylinder head that I cut in half. He is willing to digitize the ports for me so we can know the exact cross sectional areas of the ports and where the problem areas are. Since I'm trying to get maximum flow out of the smallest port possible this data will be very valuable. He is really busy right now so we are not sure when this will get done.

~Alex

[Alex22]

Some progress and more new plans.
Porting: Using stock valves I got the port to flow 260CFM @28 inches at 540 lift, but the velocity at the head bolt choke area was too high and it caused the flow to separate from the short side radius and the flow dropped to 235ish then slowly gained again. I have been opening up the choke but it is still separating and causing grief so it is not done yet.

New idea for crank and rods. As you might have noticed my crank may be for sale. That is because I'm looking at using a set of SCAT chevy inline 6 connecting rods which means the rod journals would have to be ground again and re-nitrided.

Cam/lifters and such. No cam ground yet, but I plan on using a Camcraft cam and standard lifters. All manufacturers of the tool is made to drag through a lifter bore to scratch it to increase flow around the lifter have stopped production so I will have to make my own tool. Or I might turn my lifters into camsaver lifters with either a cut off wheel or a surface grinder. It would be nice If I could get a belt drive setup to work in the stroker, It just might be a possibility.

This stroker is going to be built in true AMC fashion. All Miscellaneous Crap

~Alex

[Flash]

Whats the rod length compared to the 4.0L rod?
rod/crank journal is smaller on the chev rod?

Is it a floating pin on top...........Bigger or smaller pin, then the 4.0L

(In my best homer Simpson's voice)MMMmmmm Belt Drive


Flash.

[John]

Belt drive as in McCullough/Paxton/Eaton, I vote McCullough/Paxton supercharger.
John

[Alex22]

I would like to put a supercharger on this, but I'd rather not deal with that can of worms right now. The belt I was referring to would be a belt driven cam set. They are the best thing for reducing & isolating harmonics from the cam to the crank. The belt would also eliminate the chance of a harmonic in the timing chain its self.

The Scat rod is 6 inches center to center with a 2.000 standard size crank pin and the big end is .010 thinner than the stock 4.0 rod. The small end comes with a bronze bushing in it and should be the right size for the standard SB Chevy pin (.927) while the jeep pin is .931. The Scat rod is about 3x as strong as the stock cast rod, Do I really need the strength of a Scat rod, no, but since I don't want to buy a second set of 4.0 rods, sort through and pick the best 6, clean, Magnaflux, install ARP bolts, stress relieve, polish, cryo treat, ream and install bushing to run a .927 Chevy pin and weight match a set of rods the Scat rods are worth it to me. Thats ALOT of work to do to a stock cast rod.

This is the same style of rod I want to use in my stroker. I would rather use a forged I-beam rod, but they don't make it.


If I was to supercharge this monster from what I've seen a Whipple charger would take the least amount of power to spin.

~Alex

[Flash]

What about side to side clearance(big end of rod) The width of the two rods similar?(4.0L verses chev 6)
I'm sure you have evaluate all the obvious or popular rods but, how about the chry 340 rod......It has a 6.123? rod center to center, and came with the floating piston pin.

Vary interesting with the belt drive idea as well!


I know these 4.0L are far from a race motor.............but, it tickles the shit out of me, when some one build one as if it was!!!!!!!!!!

Flash