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post #1 of 45 Old 11-11-2019, 02:11 PM Thread Starter
Vernors
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Stroker Build - Outline & Parts...suggestions?

Hi,

Got a 4.2 with a problem so am probably going to swap in a 4.0 bored 60 over and wanted to ask for constructive opinions/suggestions

Already installed on 4.2.

HESCO MPFI, 1994 ECU
7120 Head
New Timing Chain

Considering a 4.0 swap as follows:

4.2 Crank
4.0 connecting rods
4.0 Block from 1996+
Keith Black Silvolite +0.060" bore pistons, compression height 1.380", dish volume 15cc
CompCams 68-235-4 210/218 degree camshaft
Mopar 0.043" head gasket
0.043" quench height
Meling High Flow Oil Pump
Bosch 0280155784 injectors
Adjustable Pressure Fuel Regulator
New piston rings
New bearings

Block to be dipped, decked and bored 60 over.
May grind out some of the chamber area of the 7120 to lower compression

I've never done this before, so a couple questions...and my apologies if they are newbie ones.

First, is this a good piston/cam combo for daily driving as well as offroad use?

How significant of an increase would there be over just swapping in the 4.0 with stock pistons, the 4.2 crank (budget stroker) and connecting rods?

Are the fuel regulator, injectors and high flow oil pump going to also be needed if just going budget stroker?

Got to keep the price down on this build, but since Black Friday is coming up I'd like to have the plans done before to benefit from any sales.

Thanks for the advice.....

Verns

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post #2 of 45 Old 11-12-2019, 07:54 AM
KARamsay
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It is a bit off your discussion - and Extra $$$
I am very happy with the Yella Terra Roller rockers I installed.
https://www.quadratec.com/products/51103_500.htm

With building the engine I would suggest that it is NOT the head head or the block you are using - but the prep that goes into each of them:
Port/polish
valve angles on the heads - mine are radius
Balance
Intake and Exhaust
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post #3 of 45 Old 11-12-2019, 10:56 AM
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No I haven’t looked recently; but to my recollection the keith black silvolight pistons with the right pin to crown height are discontinued and no longer available? But there’s other sources for pistons that are as good or better. There hypereutectic pistons on places like Clegg for $300 but I don’t know if those are the right pin-to-piston top; you’d have to find the specs and look up the old jsawduste posts here where he discusses this. I don’t have a link available off the top of my head are saved in my phone I’m sorry.

Anyway it looks like you’ve done a good amount of reading and you’ve picked up some great information. Unfortunately a key component - the pistons - maybe changes the recipe slightly. (It is true you can build a stroker with a stock piston, but I couldn’t make myself do it knowing there’s good options with the right engineering)

And a brief thought I think the cam would be good because it appears that the duration and lift is minimal; for wheeling a nearly stock cam profile gives you the best torque and horsepower at a lower RPM. But I have not recently studied the options nor that cam - I could wrong. Dunno.

Some thoughts:
-SCAT (and rumor was maybe crower or holley but not in catalogues?) makes a 4.0 stroker crank that’s not crazy expensive. Should be under a week’s paycheck ($450?) and it’s $100-$200 for a machine shop to check, touch up, and perfect your used crank. I have one of the ‘heavy’ 1977/78 12-counterweight 258 cranks and I will probably use that because I like heavy cranks.
-The right pistons shouldn’t require modifying the combustion chamber to keep compression down to where you can run 87 octane. The shape of the chamber and the piston height is what makes a nice burn in a nearly stock or stock head. The poor man’s stroker stock-type piston option doesn’t have an optimal TDC shape and flame travel characteristics want super (91) to make it safe and happy.
- I’m not dissing karamsay by saying this but if a big six is your goal you don’t have to do rollers and stuff. If a basic long-mile big six is your goal stock stuff is fine. If you desire ultimate and trick, by all means go roller rocker, porting, three-angle valve job, etc. just saying; in my case I wouldn’t be after ‘ultimate’ anyways but even if I were I’d have to say “when!” to the budget at some point.

Keep posting- looking forward to and would love to read and hear your journey, expense, experience, and progress.

[size=3]Shackles & D-rings are different things.
Cranking IS turning over
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post #4 of 45 Old 11-12-2019, 12:08 PM Thread Starter
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Thanks for the feedback folks, I've been reading more about this and there seems to be a lot of discussion over using an aftermarket cam vs stock in a stroker set up. It sounds like an aftermarket cam could smooth out the engine performance, but may not boost power or torque that much over stock. I'm guessing, that a cam can shift hp/torque to different areas of the RPM range, but doesn't necessarily increase HP and Torque by a significant amount? 25 - 35 hp?

The piston/cam selection is what is throwing me off....and to add more information I'm running an AX15, 4.10 gears, 33" tires.....so am trying to figure out how to match everything and have a weekend driver that can go on trips while also doing well offroad. Not looking for just a rockcrawler.
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post #5 of 45 Old 11-12-2019, 12:55 PM Thread Starter
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Ok, a follow up. I just called a well known cam company and it sounds like they suggest only a mild cam upgrade over stock. Details:


Basic Operating RPM Range:1,000-5,200
Intake Duration at 050 inch Lift:210
Exhaust Duration at 050 inch Lift:218
Duration at 050 inch Lift:210 int./218 exh.
Advertised Intake Duration:254
Advertised Exhaust Duration:262
Advertised Duration:254 int./262 exh.
Intake Valve Lift with Factory Rocker Arm Ratio:0.477 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio:0.493 in.
Valve Lift with Factory Rocker Arm Ratio:0.477 int./0.493 exh.
Lobe Separation (degrees):111

They said it would make sense to custom grind the camshaft, basically close to the numbers above.

if there will be not much difference in performance, I'd rather use the stock cam and put the cash towards better pistons if I'm not getting at least 15 to 20 hp difference. Any power gain estimates?

Either way, I'll have to pull the stock cam and see if it's worn.
Attached Thumbnails
Cam Specs 4.0 and 4.2.jpg  
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post #6 of 45 Old 11-12-2019, 03:00 PM
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Vernors sent me a PM.


Fish` your absolutely correct in that the piston/rod combo has a lot to do with the success, or lack thereof. The industry has changed a bit and like you said some parts are no longer available.


This message is what was my reply to Vernors. It contains contact info that might be helpful for others.


Hi Vernors,
I`ve been out of the engine building business for a few years now. However I do keep up with the industry.


Russ Pottenger of Bishop Buell race engines has done a wonderful job of supporting todays stroker builds. Russ has "packages" that would fit your needs perfectly. He also has VERY fair pricing and a wonderful record of after the sale support.


He will be able to offer you several options and advise the advantages/disadvantages of each.


Russ and myself speak fairly often and have been friends for a number of years. Please mention John referred you when you contact him.


626 673-2203 is his number


https://www.facebook.com/Bishop-Bueh...8948051907539/ His business page


https://www.facebook.com/russell.pottenger His profile


I know you will be happy with your stroker. Still running mine that was built back in 2006. 75 cruise is no problem.


Feel free to contact me if you have any other questions.



Thanks for allowing me the opportunity to help out.
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post #7 of 45 Old 11-13-2019, 12:58 AM Thread Starter
Vernors
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Thanks for the suggestion Jsawdust I spoke with Russ today and he was very helpful. Clearly knows his stuff. I'm looking at options since black friday is quickly approaching, but I'm 100% confident that Bishop Buehl Racing can handle a solid setup. He's been in it for many years.

We'll see what he suggests and his price, he was very up front and clear which made things understandable. I'm either going to have him build a bottom end of a 4.0 that he has in stock, and then swap out my core block, 258 crank and 4.0 connecting rods, or work with him for parts and do it myself. My goal for this jeep has always been to learn, so I do almost everything...which has mostly worked out.
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post #8 of 45 Old 11-13-2019, 07:20 AM
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Hey, if you’ve got the cash- having an outfit like that assemble the long block is perfectly acceptable.

I, too, am VERY diy. Granted, I’ve successfully rebuilt and put together a number of engines. Not dozens or hundreds, but I feel pretty comfortable and competent.

But getting older has matured me somewhat. Building things myself has almost been a matter of pride and in my younger years I’ve envisioned paying other people to do ‘my work’ as beneath me like it would make me a lesser man if I didn’t do it myself.

The other side of the coin is that I have had many financial ups and downs in my... career...? and if I didn’t do a lot of things I’d not have had the funds to keep a vehicle running. So I’m thankful for the skills and innate mechanical sensibilities I’ve been fortunate to have- Vermont is mostly rural and NOT having reliable transportation isn’t tenable unless you’re a welfare...person.

So I’d be supportive of having them build a motor for you.

I’m no guru but imho a very basic improved grind on an aftermarket cam is ok, but I’m feeling like for your purposes a stock cam would be ok. Either way- have them supply the cam with lifters from the cam maker; you’re in that deep that imho even a good used cam isn’t a good place to save money. But go with their recommendations on aftermarket vs stock. IIRC edelbrock has an improved cam that’s essentially stock? But has a shade of improvement 1500-2700rpm without dumping the 1000-1800 torque. I think it was Edelbrock; it sticks in my mind cuz they’re not a “cam company” but it could have been another old-line company like Crower? Ask Bishop Buell...

I think you’re headed in a good direction.

Side thoughts:
While there’s a number of places you can buy a jeep stroker, I’ve read enough to be concerned about most of them. There’s a couple I’d trust, then there’s Bishop-Buell which seems to be doing nice, clean, informed work without requiring a second mortgage.

(Weird side note cuz I talk stuff up a lot and hear stuff from guys who spend way too much on their jeeps:
There’s more than a handful of shops around the country that “could” build a blue-printed motor. Their core market is usually regional circle track race-series motors and/or drag or pulling motors. The market at that level appears to start at $20,000+.

And as my not-so-local machine shop reports...there’s plenty of other machine shops around New England that can build awesome motors that only last a few hours if that before boom. He’s got quite a selection of junk on display from these race engines that came to him like the week after they were put in service- that’s not what you’re after, either! I think he’s around $4500? if he supplies the parts but not the 4.0 motor core though I haven’t asked him recent. He doesn’t do head or chamber mods, either. Just clean, precise assembly of parts with clearances checked.)

Keep the thread going- I want to follow this getting in motion and into service!

[size=3]Shackles & D-rings are different things.
Cranking IS turning over
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post #9 of 45 Old 11-13-2019, 07:48 AM
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I run the cam you specced (Comp Cam). I also happen to run the Roller valve train. Bling, but it is quieter, and probably worth 2-3 hp.

Only thing I would suggest is NOT to cut your head chambers to drop CR. Blueprint your chambers to equalize to the largest one, and stop.
Calculate your CR based on your proposed deck height, piston dish, and the actual cc's of the equalized chambers. Try calculating based on .017/.043/.053 head gaskets before you make any permanent machining changes. The available gaskets will be good for a .8 CR change...once you cut the metal you can't get it back.
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post #10 of 45 Old 11-13-2019, 12:07 PM Thread Starter
Vernors
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Thanks for the advice everyone, I'll definitely post updates as this goes along. I'd actually prefer building the block myself as I've never done it and need to start somewhere. I've started on a parts list which includes plastigauge to make sure tolerances are within spec....

Found an early edition (1990) complete 4.0 engine which I'm picking up on Monday. I'll tear it down next weekend and dye test the connecting rods and block, probably won't bother with the head as the 7120 I've got is better.

Good advice on blueprinting the head to match the chamber size. I think I saw that done once with water, a flat piece of plastic and measuring syringe.

Prior to this debacle, the MPFI with 7120 on the 4.2 was definitely better than stock, but still not good enough. Looking forward to building the stroker and really do appreciate all your help and advice. Thank you all.

KYP

Vernors
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post #11 of 45 Old 11-13-2019, 08:49 PM
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Piston choice (or lack of choice) is the reason I sold my '77 258. I considered a stroker but after realizing the commonly available pistons were either too expensive or needed additional machining, I rethought the engine build. A good engine builder will help you understand how quench height, chamber and bowl shape, compression ratio, and valve timing affect detonation.

Getting correct fuel and spark to the engine is a critical task. Please don't just assume increasing fuel pressure is enough. Look into a standalone fuel controller or an OE controller that can be tuned. There are tools and software available for the Jeep ecm but I believe the learning curve will be steep. I've been tuning GM computers since the mid '90s but I'm a long way from understanding the tools available for the early Chrysler / Jeep ecm's let alone doing tuning.

One consideration about changing the cam: Most current oils use reduced levels of ZDDP and attempt to make up for this with alternative EP lubricants. There are discussions on almost every old car forum about camshaft durability and oil formulation. Solutions include buying more expensive oils, adding oil supplements, or changing to roller lifters. There are a number of Jeep forum discussions around failed 4.0 cams and while some may be due to improper break-in, I can attest to at least one engine that lost two cams despite being broken in properly both times. I was asked to help and after looking at the situation my solution was to select a different valve spring that would produce slightly higher open pressure than stock with a mildly higher rate. Ultimately I chose a set of springs from a 4.6 Mustang engine combined with retainers from a 2.2 Cavalier engine. The LN2 retainers allowed the engine to use stock 7mm stems while the springs allowed full cam lift without requiring high seat pressure. I wish I could report on the success of the combination but the engine is still on an engine stand. Still, I'm confident the combination will be fine.
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post #12 of 45 Old 11-14-2019, 08:27 AM
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Checked back to see how this thread was progressing.
Random thoughts in no particular order.


There are several "name" tuners that have plenty of stroker experience. As Fish mentions engines have been spotty. One tuner in particular wont touch engines built by companies X/Y and Z simply because the quality of the end product has been so poor. Good parts but not put together well. One company in particular is very poor, however they are an asset to the good builders..........for rebuilding the screw-ups.


OBD1 SBEC (91-95) doesn't allow you to change the ECM programming. However with the proper injectors and fuel pressure it has proven to work fairly well. There are a few tricks if you want to "fool" the ECM but in most cases it works ok as is.


OBD2 JTEC on the other hand opens up a wide range of tuning capability. Personally I use Chris Jensen to tune my OBD2 converted YJ. Chris has changed a number of "values" in the ECM and it runs better than the OBD1 but more important it cant hurt itself with things like trim delay.


In all the engines built I have never lost a cam. Used ONLY GM EOS assembly lube and Brad Penn 10w-30 in the crankcase. Couple other tricks were to put a slight chamfer on the cam bearings and also delete the oil filter adapter on the side of the block. A Bosch oil filter mates perfectly where the adapter once mounted. Engle was the supplier of the valve springs and we kept the seat and open pressures conservative. On the OBD2 engines sometimes the rev limiter would be removed. Could still spin well over the 52/5300 redline with no valve float with those springs. Russ has Comp Cams grind cams to his spec. Typically he has them change the lobe separation to 113*. That 113* keeps the MAP sensor happy at idle with enough vacuum. Russ also offer a nitriding option that can help with lobe wear.


Always purchased my pistons from Diamond racing. They would build to spec. They were not the cheapest but you could order whatever pin height, ring combination, dish volume you wanted. Another options was to bush the rods for SBC full floating pins. A must IMHO. Russ buys his from a respected company, again to his specs set for locks and floating pins. A win win situation.


Tight quench, reasonable spring pressure and floating pins were the keys to a good stroker. Please, be nice to your tuner and don't be set on running 87 in it. 91 is fine but your leaving way to much on the table to run 87.


Typically over cammed my engines. Especially when using the 12cwt crank. Advancing the cam a few degrees bought the low end torque back but still allowed for higher RPM runout. Recall deleting the rev limiter ? Also the inertia of the "heavy" crank helped the low end. While at higher RPM it tended to dampen harmonic vibration due to its added mass. The cam I run in my YJ and what Mike Johnson ran in his 4500 rig. A 274 (224 @ .050) .480 with stock 1.6 rockers. I run HS 1.7`s with raise the lift to ~ .510. Which is a helluva lot more cam than a stock grind but works very well down low. Around 2700 it really kicks in and you can feel the and hear the powerband.


Anyways, I have snow to shovel and need to get going. Just some random thrown out for folks to consider.


You know, I have a couple 12cwt cranks, an NVH block and a couple clyi............No, down boy, down...........
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post #13 of 45 Old 11-14-2019, 10:42 AM
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Quote:
Originally Posted by 1project2many View Post

One consideration about changing the cam: Most current oils use reduced levels of ZDDP and attempt to make up for this with alternative EP lubricants. There are discussions on almost every old car forum about camshaft durability and oil formulation.
One consideration for 'cam life': Have the supplier NITRIDE the cam before shipping. Cost will run from $100 -175 depending on whether it's done in-house or subbed out. Using a 'break-in' oil (Brad Penn/Joe Gibbs/etc.) instead of off-the-shelf current grades (although you may have fussy cats after that) will eliminate cam worry until the Jeep falls apart from rust.

There are better and worse zinc formulas out there The high mileage ones have often contained elevated zinc levels, but it's still way down from the 'good ole days. Of course, you'll have to contend with inspections and any other 'legal' (but not always smart) regulations as they pertain.
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post #14 of 45 Old 11-19-2019, 05:34 PM Thread Starter
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Update: Picked up a donor motor and disassembled it last weekend. There is a bit of a lip on each of the cylinders (150k on engine) at what appears to be the top of the stroke. I'll need to find out if it still can be bored.

Piston walls are smooth, the crankshaft bearings are smooth, no burn marks or wear. Since I see no damage to the piston walls I'm assuming the connecting rods are straight, but will need to check. Hmmmm, it just occurred to me that I should probably check the piston rings to see if they are worn evenly...clearly making some assumptions here.

One thing I noticed was that the engine didn't come with a journal girdle. The block casting number is 8933002665 which I think makes it a 1990 or earlier.

Was this an upgrade for later years and does anyone know if they are retrofit compatible? I assume that they increase the rigidity of the system.

....{update} Just read up on this and it looks like the journal was added in 1996+ years and that it can retrofitted, but that the bearing cap bolts from a 1996+ need to be used.

Opinions on whether this should be done?

Thanks.
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post #15 of 45 Old 11-19-2019, 06:29 PM
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8933002665 is a 87-90 RENIX block. There is suggestion that the RENIX blocks have a different deck height than the later 4.0 HO blocks.


1989 4.0 Engine
Deck height = 9.429 - 9.435 inch


1991+ 4.0 engine
Deck height = 9.450 - 9.456 inch


Did it have 7/16th or 1/2 head bolts ? If 7/16ths you might consider using a different block. They should be 1/2 but just asking.


I've never built a RENIX blocked stroker but if it has 1/2 head bolts you should be fine. Just be aware that to get the quench numbers you may have to deck the block a bit more.


RENIX or HO will take +.060 all day with many HO`s being able to take +.080. Can`t say for certain about a RENIX and more than .060.


Mine is +.080. It was pinged prior to being bored and still has plenty of meat in the walls. YMMV but odds are in your favor.


The 96 up blocks (NVH) are stiffer in the casting with additional webbing and the additional main girdle. For what we are doing, again I wouldn`t worry about it. Now if you were going to spin it hard or have forced induction the later block would be nice to have.


Side note .....look at the 4.2 main caps and you will see they are much beefier than the 4.0`s. I liked to use 4.2 caps with ARP studs with everything line honed. Including the cam journals.


The OEM rods are notorious for being twisted, unequal lengths and the big ends are not the roundest. Get the rods rebuilt by a shop that knows what they are doing. Use ARP bolts and convert to FF pins.
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