Inliners International Forums General Discussion AMC/JEEP Anyone De-stroked a six?

Almost all Amc/Jeep Six cranks from the 199-232 to the 4.0. and i thought that it might be interestng to destroke an AMC six, to get a higher winding mill to put in something like a dragster, because the cranks are similar in weight Im guessing torque would be affected but not radicaly. But top end power would get better due to the decrased stroke
Any thoughts?
anybody?

I don't know about the top part but the rpms will come up faster when it is destroked.If you are getting rpms faster I would beleive you would have better bottom end Not top end. Thats why the v8s guys would make the stroker 383 for more low end a faster rpm also destroking means less over all hp i think because you have taken away from the stock compression stroke.? only some food for thought here???? But by the same token destroking could let you run more of a pop piston to maybe compensate the destroking??
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NovaMan/Twisted6

Yeah, I was thinking ARIAS 12:1 Heads and a a Winder of a Mill hooked to a 904 Torqueflite With a Dana 20 and a magnesium (Lighter and stronger than Aluminum)Chassis would work out pretty well, But I woulnt be too upset to make a steel one. magnesium is hard to get a hold of, though, ad im only a college student so, fabbing a whole Dragster would be a stretch, I figured a De-stroked 258 running 12 to 1 heads and a pretty radical cam, some good headwork and an OFFY Universal/4bbl intake running a 390-500 cfm or a Holly 500 2bbl, would be pretty interesting. to say the least. If i ever so it, you guys will be the first to know.
Any of the Chevy guys ever tried to fit a 250 into a S-truck? Ive heard of 350s going in, but they are quite a bit shorter Right?

I'm not sure the L6 would fit The L4 is about the same lenght as the v8 so don't that is much easier then trying to put the L6 struck if you are meaning the s10.?}[oooooo]

Ps also by destrocking you are lossing cube in.

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NovaMan/Twisted6

[This message has been edited by Twisted6 (edited 02-10-2002).]

I am aware that Destroking a six would lead to smaller CID, but what im going after is a Mill that would wind up viciously, and be useless on the street, A drag motor. And remember that this idea is coming from the overactive Imagination of a college student.

I think what the problem here is, you aren't taking a heavy enough course load. I suggest a few more credit hours for the next semester; that oughta keep you mind off of cars! Just kidding...we need more guys your age to get interested.

Several years ago, I watched a very fast 258-powered Gremlin at the local drag strip. If I remember correctly, he was running in the low 13s! It was strong and consistant, noisy as a screaming demon and very radically cammed. I remember that he beat a very nice Mustang V8, easily! It'd be hard for me to believe that a de-stroked engine, of the same design, would be any faster. I believe the torque of the big ol' 258 would be hard to beat with a smaller, but higher-winding engine.

Hmm ok along the destroking line of thinking... shorter stroke with a longer rod or lower wrist pin location just shorten the crank throw. You could use the upper half of the cylinder to maintain the compression desired, make the effective stroke shorter but still be able to rev high would that be feasable?
Glenn

How 'bout a custom grind on the crank? Offset the journals and make them smaller by grinding the "TDC Part" and using custom rods to fit? Correct me if I'm wrong, but couldn't you get the lost compression back by decking the block and/or head? A lil off the head to "square it up" and the rest off the block might work...

Any other opinions?
:p

the two other options for re-gaining lost compression is to use longer rods (either custom, or ones from another engine modified to work with the ever fearless 258) or, if it aint to radical, custom pistons, (though this route can be quite pricey)

You're spending a lot of money to make the engine slower.

The 199 crank is the shortest-stroke AMC six crank, and is apparently made from a better steel alloy than 232 cranks. 199 rods are longer of course. There's some rumor that there were forged 199 cranks but there's no evidence for that.

Barney Navarro based his turbo indy motor on the 199, not the 232.

http://wps.com/AMC/Navarro-turbo-motor/index.html#CRANKSHAFT

But anyways the cranks are out there; and "no one wants them" because of the short stroke (everyone's building strokers it seems). There weren't too many 199's I think compared to 232's. Not sure how you'd tell what's in a sealed-up motor.

The will of course be the earlier crank pattern.

Are the 232 cranks breaking?
If not, why make less power? Less torque.

MBHD

I've never heard of any crank breakage issues with any AMC six.

I don't know Navarro's thinking, but seeing how it ran at insane boosts it must have been for revving. Clearly with the big pump cylinders were getting filled. One assumes Barney knew what he was doing.

550hp from the original single-turbo carbed motor, 750hp from the twin-turbo Hillborn injected motor. The motor was sleeved down to 181ci (0.44" thick cylinder walls).

In the '60s, Dodge built a "Hyper Six" in a 170cid, and a 225cid versions. The 170 wasn't any slower than the 225. They both used the same head, manifolds, and cam. The 225 had a higher HP rating, but didn't perform any better as the 170 revved like crazy, and you'd use a much shorter gear ratio. I just completed a 1500+ mile trip with 80-85 cars in the '08 Rods of Idaho and Oregon Cruise. There was a Dart wagon with a 170, built, that was getting 26mpg, and it was really quick, and a nasty yowl at WOT.

If it works in a Mopar, why not an AMC?

It should work on anything strong enough to rev without breaking. Assuming you can empty and fill the cylinders in time, more rpm equals more HP, since HP is torque x RPM.

The other route is the old fashioned one, big displacement, slow turning. It's really pleasant to drive cars like that; but it's not the way to make HP.

I figure ultimately I need two kinds of cars; old motors with no valve timing overlap, idle at 400rpm and highway cruise at 2100; smoooooth! Then some buzzy six that likes to hang out above 3000 rpm!

There was a magazine article about Barney Navarro's Rambler Indy car back in the 60s. Apparently he was inspired by 2 facts: #1 the Rambler six had the strongest most over engineered and over built bottom end of any engine he had ever seen #2 Indy rules allowed a bigger displacement if you used a stock block engine. I guess the 199 was the largest displacement allowed, the pure racing engines were what, 2 litres or 1.5 litres???

Navarro figured he could get the horsepower he needed by using high turbo boost and alcohol fuel, on a basically stock bottom end. I believe he was getting around 600HP. His car was very fast but I don't think he ever quite qualified.

Hey, I just posted this to the AMC-list. It directly answers "why destroke" ... I'm using SCDynoSim software for the numbers. It's not that the numbers are exact, but that they show trend and curves, and let you do what-ifs on valve size, turbo A/R, etc.


OK, I've been picking at this, I think I worked out the big chunks of how the Navarro six was set up. It's 5.95" bore by 3.00" stroke, for 182ci, from a worked-over 199ci.

I calculate 520hp at 5800 rpm, a broad flat torque peak of 500 ft/lbs from 3500 - 5500 rpm, with a Garrett turbo, .50 A/R, 3.1" turbine, 25 lbs boost. It's in the green for surge, overspeed and choke.

I have two TE-06 turbos with A/Rs around .47, plus a T04 same A/R. I plugged in small tube headers, open exhaust. And the factory stock cam! I kept getting crazy numbers when I tried the specs from the Winfield cam. I assumed that something like that was installed, but maybe that cam was in a box, on a shelf, for a reason. I really have no idea what was in the motor, but the software made sense when I used stock numbers (actually, a 195.6OHV cam as that's what I had entered and saved, but it's pretty much the same as the 199/232). I wasted a lot of time trying to fit that radical cam into the equation.

It's gotta ping the whole time though. Probably why the monster cylinder walls, crazy exhaust valve, double-O-ring head and block, etc. It looks like Navarro upped bottom end oil supply, but the valve junk in the head was totally stock.


OK so no one today would make a 500hp 199ci six (though it would be most cool at the track). But if you took a dead-stock 199 with .030 over pistons, ran 8 lbs of boost, and $$$ your way to 6000 rpm, you'd have 300 ft/lbs torque from 3500 - 5000, and 275hp around 5500 rpm. (It's the same shape curves as the stock 199, just taller :-)

That short stroke is the key -- the 232 gains a lot of torque, but loses 1000 rpm and 20 hp. The 258 is even worse, lots of torque, but HP peak moves down to 4000.

A hot 199 would be a fun, unique, and relatively cheap motor. Light too, and uses parts that no one wants (Rambler Mentality).



So I think this is what I'm gonna do with the fancy Navarro head.

I'm no race motor guy, but if you look at the bottom of those sixes they're crazily over-built. And it's not just some fat oversized casting with too much metal (like the older Nash-based six). Thinwall but lots of gussets and beams, and seven fat mains that ride on tall walls. Every cylinder section is boxed. It makes the block long, but not that heavy.

That guy Marino, that worked for Barney, said that the twin-turbo version had four bolts per cap, I don't know how that got those in there.

So #50 was run in 67, 68, 69 I think. The first year they had carb icing troubles on the single-turbo motor (that's the version shown in the Rambler ad), I think Gary Schraeder told me that. Not sure if they did the twin turbo 68 69 or what. Apparently they got the motor straightened out but what prevented it from qualifying in the last year was chassis issues, not motor issues, and I'm sure, ultimately, money.

How about destroking a 4.0 with the 199 crank. That would give a little more displacement with the larger bore of the 4.0 but the short stroke crank. Could use the long 199 rods and custom pistons. I myself prefer the largest longest stroke you can use for the torque. My .060 over 258 turne 6000 rpm when I used to drag race with no problems. Mike

The drop in peak HP-rpms is easily solved : bigger camshaft...

Been doing a bit of soul-searching with a dyno-program myself,saves some money to change cams and so on in the program instead if buying parts You think will be good for Your motor,bring it home put it in and find out that it's no good...

Go out by another one try again,that can be a money-pit big way.

But back to camshaft vs engine-size:I took the cam-card of a Crane camshaft and "built" 4 engines N/A with the same intake,carb and exhaust ,comp-ratio varied since a stroker was involved but none was a hi-comp engine(9.0-9.6).

A 4.0 liter with 9.0 comp peaked it's HP @ 6000 rpm,the 258 landed @ 5250 rpm and the stroker @ 4500,then I tried a destroked
258 0.060 overbore with a 4.0 crank/rods (around 226 cu in "baaad memory,and soon bedtime"...)the peak ended up @ almost 7000 something rpm of course it lost both hp and tq but on the other end it kept the HP up much longer "8500 rpm" The stroker fell flat on it's face @ 5000 and at 5500 it was absolutely dead.

This was with a Hyd. cam 216/228 @ .050 lift (112 deg lobe-separation angle) and to get the same peak rpm on the stroker You will probably have to get a camshaft with 15-20 more degrees duration,maybe even more than that,haven't tried that out yet.

Well enough for now it's time to go and take a talk with the pillow,up to work in 5 hours It's almost midnight here now but then it's Friday and a free weekend...

All the best : Speed Swede

You don't always need short strokes to rev high RPM! I've built many 292 Chevy's that turn 10,500 RPM at the starting line and were shifted at 9500-9700 RPM. They have over 4" of stroke! It just depends on how much $$$ you want to throw at it. The main premise for what Navarro did with his destroked engine was several reasons: First, in an inline 6, everyone here is familiar with harmonics im sure. With its 120 degree firing making different harmonic levels as RPM goes up, the shorter the stroke the less severe and destructive the harmonics are. Second, the shorter the stroke, the more rigid the crankshaft becomes, because it has more main to rod journal overlap making it flex less. Many modern BMW German Touring car racing 6 cylinder engines race at or beyond 9000 RPM for the same length of time many of our Nascar races last. Their strokes are also around 3", plus having fully counterweighted cranks helps also. He also was trying to make the cubic inch limit for the class to be legal for competition, and there probably weren't many engine combinations at that time that would have allowed him to devise the combo he chose. As someone has also stated, the blocks were very strong, so that coupled with the equally rigid and strong crankshaft made a good foundation for him to build upon.

Just wondering if you destroked your 292?
4.120" is the stock stroke.


Just to get a ball park figure,,,how much $$$$$ does it cost to be able to turn a 292 to 9500-10,500 RPM?
MBHD

Your're correct, I meant to say "over 4", instead of stating an actual stroke(it was getting late)! I haven't seen the book published by Leo, but he consulted with my mentors for much of his text and the techniques he uses today. Much of the procedures for attempting such a task, begins with the crankshaft. We would start by grinding the counterweights down to a predetermined height in a crankgrinder, and also knife-edging the leading and trailing edges of the counterweights.We also would weld up any factory balance holes that were left, to leave a smooth transition on the OD of the counterweights. Then to compensate for the material that was removed from there, we would scallop out the front and rear side of each rod throw, and then we would balance the crank. We would then grind the journals to fit our bearing clearances. Then send the crank out to be nitrided. The rotating assembly was made up of aluminum Super Rod brand connecting rods about a 1/2" longer than stock, and the pistons were Venolia. Total compression was around 15-1/2 to 1. The down side to all that work, was that you could only expect about 20 quarter mile passes before the crank would break. But competing and being at that top extreme level in Competition Eliminator is the high cost of it! Dollar figure wise the bulk of the cost was in the labor for the crank and head(lump port style), it was absorbed by the shop, because it was a family operation and "house car". I hope to be compiling my own account of this racing technology soon and reveiling more actual "speed secrets" for the 250 and 292 with photos and all based on my experience in that area.