up to date stroker info

[mountaineerjeff]

Well I've been on here for a while now, as I first decided I needed a stroker years ago. Well the RaceJeep is still running strong and it's 4.0 hasn't given up yet. So it has delayed my plan of building a stroker once this one gives up. Well I need to go faster, and I have to be at the limits of my pistons so I started looking into getting my build together. Well I've researched and read just about everything out there from a few years back, but haven't been up to date in recent times due to being busy setting up my new shop.

So I got some questions first off, has there been any success with our 5500 rpm redline? Has anyone found a reliable way of subduing the harmonics, or is the "rev through it" method still the only option?
This is the single biggest question that will steer the direction of my build. I've considered every displacement from 4.0-5.1 and if I'm restricted to a measly 5500rpm then I'm not gonna worry as much about rod/stroke or bore/stroke ratios.

Second question, has anyone come together on which blocks are the best? I know so many old school guys go with the pre95 but I've always heard the 96+ got extra material to make the block stronger. I've also heard the 02+ blocks are the strongest of all and are the only ones that support a reliable 4"+ bore. I'm wondering if these have just been over looked due to price and availability.

For those of you that don't know, RaceJeep is a street driven daily driver that is focused on street 1/8th and 1/4 mile drag racing. So the bump in rpm can really help me out, but being able to drive it to and from make the "rev through it" method not an option.

[Cheromaniac]

So I got some questions first off, has there been any success with our 5500 rpm redline?

Most of us haven't tried going that high 'cause the HP curve of our strokers has already started dropping off before 5000rpm

Has anyone found a reliable way of subduing the harmonics, or is the "rev through it" method still the only option?

The cam harmonic still exists at ~5600-5700rpm so you'd either have to stop short of it or rev through. Hesco have tried various tricks to eliminate the harmonic but without success.
You could minimize the risk of engine failure by nitriding the crank and having the rotating assembly lightened/balanced, but the longer stroke of the 258 crank increases the piston speed and effectively reduces the engine's "redline rpm".

[mountaineerjeff]

Thanks Dino.
Ok, so pretty much all my info is up to date. So now I need to consider what displacement to go with I'm thinking either 4.0/4.2/4.6 or their over bored counterparts 4.1/4.3/4.7

What are the power levels these parts can handle? I know boosted i6s have seen the 6-700+ mark, but where's the weak point? I know my 4.0 the weak point is in the pistons, but where do I hit the limits of the forged KB pistons?
Does anyone run forged rods, or are the 4.0 rods still the choice? If my limit is in the rod then I should be better off lowering rod stress by doing a 4.0/4.1
If the internals will hold up then I'm best with the rule of displacement and going with a 4.6/4.7

This brings me back to one of my original questions, the block. In what blocks is a 4.000" bore safe? And to what point is it "safe" obviously a bigger bore is safer in a shorter stroke motor. And is there a power level at which I need to worry about the block? This is the reason why the std size pistons are still on the table.

Don't mean to sound like I noob, I've obviously done tons of research, just wondering if anyone has up to date solid solutions to keep me from repeating other members mistakes.

[jsawduste]

JeepSpeed, a desert racing class that uses the 4.0 based engines in several classes is one example. These guys regularly spin 6500 for hours at a time. Many use strokers of the 4.5-4.7 displacement.

Harmonics are things not many understand.

Personally I like to use the 12cwt crank (heavier) not for the flywheel effect (minimal) but the extra mass changes the harmonic, frequency and rate. Saying that, Scat aftermarket cranks are 4 cwt and they seem to work just fine.

Saying that a camshaft has a harmonic rate at x amount of RPM is not taking into consideration the very factors that make a camshaft a rotating member. Drive type, blank material composition, lobe design, valve spring pressure(s) etc etc. All through the internet is this "cam harmonics" talk but I`ve yet to see factual prove of such. Yeah an extra journal would be nice and they are kinda long but there are simply to many variables to offer a blanket statement. I am sure harmonics play a part but at what rpm and how serious it is I cannot say. Opinion ? Build it, cam it and run it.

Surely I will be corrected on blocks but here is my take. I have run several 91-95 blocks at +.080 after being pinged for wall thickness. +.060 is a non consideration. Bore it and run it. Later model blocks have actually less meat but are made with a higher nickel content. They also offer a main cap girdle that up till then had never been used, hmmmm, why all of a sudden ??? These blocks I would be happy at +.060 but have never pinged one to see if the bore could be taken larger.

I like the extra bore as it helps to unshroud the valves a bit. Hey every little bit helps. Never have had any cooling or warpage issues.

You can run the fuel backwards, add extra cooling to the block as some options to think about.

Eagles if you can find them otherwise Scat`s rods are forged but stock rods with good bolts and prep are worthy of consideration.

Your obviously up on B/S ratio`s, Rod Length etc and how it effects parameters, scavenging etc. Run what you think is best matched to your needs. IMHO it is hard to beat a long rod if for no other reason your not pulling the piston out of the bore at BDC as far. Add in the dwell time and piston acceleration and it makes for a pretty good combo. YMMV depending on application.

Several venues for cam grinds to your specs so once you decide how you want the engine to run you can have a stick ground to your specs. Not that big of an expense and it offers several advantages not inherently available with "off the shelf" grinds.

Figure you plan on the ability to tune the ECM and do data acquisition. Ryan Hogan is who you want to talk to. Ryan has proven to me his abilities and familiarity of the I-6 family and JTEC protocol.

Not sure how much involvement with JeepSpeed Russ Pottenger has but he is in the neighborhood (So. Cal) and there is also JeepSpeed on Google to reference.

HTH`s

[jeepxj3]

Scat forged rods with ARP bolts are good to 600+HP.

Use +0.060" custom forged pistons, with necessary pin height for stroke used and dish for desired CR. Don't think 4.00" bore will work without sleeving it, IDK for sure.

The cam 'harmonics' was from awhile ago, several years ago. IIRC all were on pre'99 engines that used the pin/spring or bolt method to control cam walk. Cam harmonics or cam walk at the 5600 rpm IDK, or a combination of both. Maybe using the '99+ block and the cam retainer plate and this won't be an issue. No one has done it yet, 99+ block and over 5500rpm.

HIgher reving and over 5500 rpm is going to be limited by the head, cam, intake manifold and throttle body used. All this is compounded when using a stroker and bigger displacement and trying to flow 15% more air thru these parts. Ported big valve head, bigger cam than you would think, short runner bigger volume intake manifold (like clifford 4 barrel manifold), 70-90mm TB. And then you will need a custom tune to make all this run.

So 3.935" bore and stock 'short' stroke, 99+ block and more rpm/over 5500, more horsepower but less torque.
Or 3.935" bore and stroker, less rpm 5000-5200, less horsepower but more torque.

Then what compression? high CR N/A, mid CR and nitrous, lower CR and boost?
Do you stay EFI or go 4 barrel carb?

[mountaineerjeff]

Thanks for throwing in all the extra help, but the head/cam/intake/CR and such aren't of any issue, so that's why I didn't bring them up. I already have the boltons and make more power than almost all N/A i6 guys (may be one or two that I'm neck and neck with).
I'm currently running a port matched 99+ intake manifold with a bored 6X.Xmm throttle body...I think 64 maybe?
The stroker plan is a custom built multi throttle body manifold. Power goals are to legitimately push the max of whatever my internals will take. I'm thinking 300-400rwhp N/A and then double that on the bottle. So, despite the huge range...I'll be content with 6-800. But shooting for 700. If the motor will take it, then I'd hope for 400+600 on top and make 1,000rwhp but I like to set realistic goals so no one is disappointed.

So back on track...So there has been new development in the harmonics theory or what? I hate when there are mixed opinions on something that has a factual answer.

If I could have a 7k-8.5k rpm motor that I don't have to worry about breaking in half, then that would be worth about a small fraction of its weight in gold. (These things are heavy.) But if it's still uncharted territory then I'll stick with the 4.6. I don't think a 4.6 with forged pistons and rods will have an issue to 5500. Obviously I'd go long rod...but that just compounds my fear of the piston being the weak point. I'm considering which crank to run as well. My first thought is the 4wt 258 crank but I'd also consider knife edging and weight reduction on it...but then is it worth the coin to go aftermarket?

Here's one thing I don't get. I know the long rod KB 4.6 combo will hold 600hp. Are the forged rods really only rated at 600 as well? That seems low, but maybe it's just to cover themselves. Anyone know the strength of the pistons before failure? Obviously tune makes a difference, but I'm talking about ring landings and wrist pins height etc.

I'm starting to feel like my posts are too long and widespread.

[jsawduste]

Huh ?

[SilverXJ]

The cam 'harmonics' was from awhile ago, several years ago. IIRC all were on pre'99 engines that used the pin/spring or bolt method to control cam walk. Cam harmonics or cam walk at the 5600 rpm IDK, or a combination of both. Maybe using the '99+ block and the cam retainer plate and this won't be an issue. No one has done it yet, 99+ block and over 5500rpm.

The cam walk and the cam harmonic is two separate issues not related in anyway to each other.

[jsawduste]

The cam 'harmonics' was from awhile ago, several years ago. IIRC all were on pre'99 engines that used the pin/spring or bolt method to control cam walk. Cam harmonics or cam walk at the 5600 rpm IDK, or a combination of both. Maybe using the '99+ block and the cam retainer plate and this won't be an issue. No one has done it yet, 99+ block and over 5500rpm.

The cam walk and the cam harmonic is two separate issues not related in anyway to each other.

Thanks Chris, Jeff the "Huh" was not aimed at Chris aka Silver.

[Cheromaniac]

So back on track...So there has been new development in the harmonics theory or what? I hate when there are mixed opinions on something that has a factual answer.

The 5600-5700rpm cam harmonic is in an internally stock 4.0 engine and that hasn't changed, simply because there are only four cam journals and not even Hesco could find a fix for that. In the old days you could get around it by using a timing gear set instead of a chain but Mopar Performance gear sets have been out of the market for a few years now.
As long as the harmonic is only within a narrow rpm window, you can just accelerate through it without any issue. The stock 4.0L rods are plenty strong especially if "stress risers" are removed from the beams, the rods are shot peened, and ARP rod bolts are used.
I'd suggest a 12cwt 258 crank to minimize any harmonic (it'll be at a different rpm anyway) and if you also knife-edge the counterweights, nitride the journals, and balance the crank, you should be able to safely run rpm that most of us wouldn't even dare to try.

[jsawduste]

Jeff, ambitious goals but doable.

A call to Mike Knowles or Mike Panetta at Diamond Racing would clear up many of the questions on pistons. These are folks who do it for a living in the world of custom applications. They WILL know what the answers are.

A 600 hp rating ? Based on what ? Reciprocating weight, Generic comments relating to piston speed, thermal dynamics ? Just to throw an arbitrary number out is meaningless. I`ll bet if my piston weighed 1 gram I could rate the rod at 2,000 hp. On the flip side if it weighed a 10,000 grams it might break at 10 hp. Disclaimer.....Totally un speced numbers pulled from you know where.

I do not think you NA numbers are unreasonable at all. The spray numbers is where your obviously getting into uncharted territory. Here again I would tend to lean on folks like Diamond and Scat for hard information. Hell even Eagle and Callies might not be a bad idea. Very few, including myself can only offer opinion and conjecture at your upper limits.

Interesting that you bring up the twin metering devices. A recent conversation I had with a well recognized individual both on this venue and the I-6 community in general bought up this very topic. Due to the tremendous differences in runner length from a central point. Splitting the intake would be the better way to feed the chamber. There are folks doing sand drags whom are already following this path.

To add I suspect these guys know little/nothing about harmonics and also suspect there is little they could do about it anyways. Nonetheless they turn some pretty impressive numbers with there setups. Change one thing in the valvetrain and the harmonics change with it. A single roller vs a double. Harmonics from the crank having influence on the cam. Change the cam profile, lobe width the list goes on and on. To make a blanket statement is simply guesswork.


.

[mountaineerjeff]

So what we need is someone with some very good simulation software and a ton of free time.

The only reason I'm even worried about it at all is a higher red line would keep me out of third in the 1/8th and give me a safety net at the corner. I'm not hitting the top of third yet, but I def could with more power, and dont want to regear 10x.

Unfortunately I'm not, at least at this point in time, going to bite the bullet on a completely experimental engine.
I'm partial to the 4.0 and strongly considering just boring it, going with forged pistons and calling it a day. I think with the right cam I can make more HP on the 4.0 and all my issues are on the back half. I have enough torque to blow the wheels off as it is now.
If I just do a set of forged pistons, then I won't have as much invested in it, and wouldn't be terribly devastated if it cracks in half at 8krpm.

But I guess I really just need to do some pricing and make up my mind. Anyone know if the scat rods are lighter? I've always agreed with dino on just pamper the stock rods.

Also still no real info on the blocks...I though they were 91-95 96-01 and then 02+ are the 02+ any better or should I just stick with the 99 block that's in my jeep?

[jsawduste]

When I read your post my first thought was gearing......LOL

Diamond has always treated me well with forged pistons. Knowles and Panetta know there shit.

One thing that may or may not be a factor in block selection. The 99 up use the retainer plate for the cam. Which limits the cam selection. This may be a moot point as you may be considering a custom grind. But if you looking for an off the shelf stick the the older spring and pin has a far greater selection. Of course you could take a 99 + block and retro fit the spring and pin.

[jeepxj3]

I think that my point was missed. That 'harmonics' and 'everything' is all related.

The cam, with nothing inplace or attached, can probably be spun to 10,000rpm with it's 4 cam bearings, without any harmonics or cam walk/movement and therefor, no breakage.

-valve spring pressure
-flat tappet lifter face taper
-cam lobe taper
-cam distributor helical cut gear, distributor helical cut gear, oil pump, distributor
-single or double cam drive chain
All these, especially the helical cut distributor drive gear and distributor drive, all contribute to cam walk/movement, front to back.

This back and forth movement of the cam PLUS the rotation of the cam, sets up a harmonic frequency which depending on the above variables, valve spring tension, lifter face taper, cam lobe taper helical gears, on the 4.0 occuring around ?5600 rpm.

It is the cam walking/movement PLUS the spinning of the cam that causes the problem of harmonics.

Cam walk is controlled by-
pin and spring- weak at best when used with heavier valve springs, etc
measured pin or bolt- against the aluminum timing chain cover- weak as the aluminum cover flexes!
cam retainer plate- best and can be adjusted to tighter tolerances and keep the cam from walking

No cam walk, no problem harmonics. Remember, need cam walk and a spinning cam to produce the problem harmonics.

The old timers, HESCO, turbo tom, and others, were all NOT using the cam retention plate(CRP) as no cams were available for the CRP in the grinds that they desired. Lately, with companies like Jones Cams grinding CRP cams with more aggressive grinds, this can be a whole new world for the 4.0L performance.

[mountaineerjeff]

So you're saying 99+ blocks. I'd always heard 96+ as being the block difference. And I've also heard there was a 02+ change but that has yet to be verified in this thread.
So you're saying there are 91-95, 96-98, 99-01, 02-06 blocks? Or is it possible that the 02+ I've heard about is a chassis difference and is actually the same as the 99+ you are referring to?