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Is there a good forged alternative rod out there for a 250?

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mike1157
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Is there a good forged alternative rod out there for a 250?

Post #1 by mike1157 » Wed Sep 28, 2016 8:54 am

After looking at pictures of Does10's recip catastrophe when a rod broke in one of their engine combo's, and the carnage that ensued, I am starting to become concerned that I may be asking too much of my combination, and cannot afford to have it fail on me. So before I even start trying to lean on this combo,...I want to see if there may be a better idea and pay now instead of paying much more later.

I have stock, bushed, prepped (beams polished/resized/good bolts) rods presently. They are the ones that came in the engine The beam has a 1978 build code. (Guess that makes them cast)

Image

The engine is turbocharged, and could service whatever RPM I'd want it to, but it is a street driver, and right now, have no giant power aspirations although I've been told to expect it (350-400 hp/ 450-550 ft lb tq)

I also know that a rod tends to fail more because of excessive expansive loads (RPM) rather than excessive compressive loads, (boost),...and I just want to be safe.

My question is,.....what RPM would/should I consider "excessive"?

Right now,...I'm not planning anything more than 5500 RPM,..but really don't have any idea where this thing will want to go, and where it'll make power.

The limiting factor is that there are custom forged pistons already in this engine, with a pin height set to accommodate the stock rod length. I'd imagine that that also will force me to look at a set of custom rods if I cannot find an off the shelf solution that is close enough.
1978 Ford Fairmont Futura project: "The Gila Monster" Xflow'd Megasquirted, MPFI'd, DIS, T/C'd, A2WI/C'd 250, 4R70W shifted, and 8.8, 3.55 gear rearended.

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Re: Is there a good forged alternative rod out there for a 2

Post #2 by Does10s » Wed Sep 28, 2016 10:06 am

Just to be clear....our "carnage" wasn't caused by a failed connecting rod! It was caused by a cyl. wall that broke at around 4500rpm or so. The piston rings for that hole then got jammed and then the train wreck started to happen. Hence all of the broke or bend rods!

We spin Kelly's 250 to 6100rpm at the traps. We haven't used stock rods since that grenade engine, but that was more to do with getting the piston closer to a zero deck height.

We're using off the shelf aftermarket Manley H-Beam rods for a 4.6L Ford V8. They use a standard .912" wrist pin and are .088" longer than the 250 rod. (pretty sure that's the correct number!) The big end is a little smaller than the 250 rod, so you'll need to machine the rod journal to fit....or offset grind it to gain a few more cubic inches.
Because they're V8 rods, the big end width is less. I don't remember the exact numbers off hand, but it's something like .040" less. So the rod will "travel" fore and aft a bit within the rod journal. We haven't seen any issues with that at all! We've torn down the engine numerous times for other issues or just for maintenance, and have never had a problem with that extra rod room in the journal.

Later,
Will
Image
'86 Mustang, Turbocharged, Best ET: 10.70@132.
'69 Mustang Sportsroof, 351w, auto
'63 Falcon, Turbocharged 250, C4, 9", Best ET: 10.64@127mph 11/21/14

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cr_bobcat
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Re: Is there a good forged alternative rod out there for a 2

Post #3 by cr_bobcat » Wed Sep 28, 2016 10:12 am

hmmm...I've played the "what if" game for the 200 but haven't looked much at the 250. In my case though, I was trying to figure out how to increase the rod/stroke ratio instead of trying to match. I did get a quote some months ago of around $850 for custom made rods that would go with a GM piston of some sort. In your case, you might have to go custom on the rods.

I have these numbers for the stock 250 rod
Length: 5.880
Large Diameter: 2.1236
Small Diameter: 0.912 <- From specs on Summit for a stock piston
Width at Main: 0.994 <- Value I got from someone on here for the 200

I did find these AMC rods that that are close but not quite there.
https://www.summitracing.com/parts/sca-65885/overview/

They would need to be narrowed slightly and then you would need to bush the pin end but you still have about 0.084" to shore up on the main diameter. Your piston will also have to deal with the increased compression from the piston sitting 0.005" higher. Not sure what that would do to you there.
Block: Stock C8 Block/pistons, C9-M head, 1.75/1.5 valves, dual spring, 1.65 RAU Rockers, port divider, direct mount Holley 4412-500, HEI w/20* advance, manifold vac, dual-out Arvinode exhaust, Clay Smith 264/274 110* installed w/ 4* advance, adjustable dual chain timing, C4 w/ shift kit, 3.20 (TBC) rear ratio, 9.44 SCR / 7.97 DCR

Build that Six with parts from http://www.vintageinlines.com

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Re: Is there a good forged alternative rod out there for a 2

Post #4 by Econoline » Wed Sep 28, 2016 11:40 am

The earlier rods are forged. They can be found fairly cheap online, Rock auto used to have them, they may still have a set.
It ain't gonna fix itself

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cr_bobcat
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Re: Is there a good forged alternative rod out there for a 2

Post #5 by cr_bobcat » Wed Sep 28, 2016 11:48 am

Good call on the Rock. I see the C9DE-A rods listed there on closeout for $13.28/piece.
Block: Stock C8 Block/pistons, C9-M head, 1.75/1.5 valves, dual spring, 1.65 RAU Rockers, port divider, direct mount Holley 4412-500, HEI w/20* advance, manifold vac, dual-out Arvinode exhaust, Clay Smith 264/274 110* installed w/ 4* advance, adjustable dual chain timing, C4 w/ shift kit, 3.20 (TBC) rear ratio, 9.44 SCR / 7.97 DCR

Build that Six with parts from http://www.vintageinlines.com

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Re: Is there a good forged alternative rod out there for a 2

Post #6 by xctasy » Wed Sep 28, 2016 8:08 pm

The original 1969 to 1977 forged steel 250 L code rod was the original Ford engineering solution.

cr_bobcat wrote:Good call on the Rock. I see the C9DE-A rods listed there on closeout for $13.28/piece.


:thumbup: :beer: :mrgreen: :smash: :splat:

Find them, prep them, and run them!


The retrograde 1978 downgrade to cast iron rods was the problem. Just a great way to screw over anyone he|| bent on hoppin one of these bad boys up.


Well, they didn't count on you, Mike. Or Kelly and Wil, or Mike W, or Gene...


Gene gets high 14's on cast rods in his Mavrick 250.


Three generations of Ford have always kinda hated the I6. Shell moulding to reduce casting thickness to 120 thou in the cylinder bores, and a nominal (accroding to Ak Miller) 192 thou avergage for Ford six thinwall castings asside from the cylinders sure downgraded the potential strength and casting quality of all the 170, 200 and the new 250 blocks and heads in 1969. The final straw was the 1978 rod downgrade. These engines were truly the lamest Ford in line sixes, ever!

As was said once "he was born with a deep and abiding hatred for the inline six-cylinder engine. Despite its inherent balance, which made it the most common engine in the US for many decades, Henry saw it as the anti-engine, whose sign was 666."

This, offcourse, from a guy who raced the 999 based Arrow at almost 100 mph, and kept it from becoming a 666...

http://www.curbsideclassic.com/curbside ... 2-ford-v8/

or "the inline six: Ford's unloved red haired Red Headed Step Child"

http://www.hemmings.com/magazine/hcc/20 ... 35581.html




All Australian 1971-1992 Ford 250/4.1 ( IT 155 hp gross engine was 102 hp net to 164 hp net with the last EFI 4.1, the 170 hp 250 2v was 149 hp net. )

1988 -1992 SOHC 3.9 and most of the last 1993 -1998 SOHC Falcon 4.0 engines had the US 5.88" forged rod, and its okay to about 350 hp. They were 161 to about 220 hp.

Factory best was 220 hp in the SOHC 1992-1997 XR6's. Tickford (the Aston Matin and Subraru WRX modification company that did the Twin Cam, 347 stroker and Quad Cam Falcon engine developemenys, as well as the DB7 Supercharged Jag AJ6 six) found in 1991 when they did the first 4 valve engine tests, that the 3.9 and 250 small nose crank and 5.88 forged rods limited peak normally asirated power to 220hp naturally aspirated as the safe rpm was only 5000 rpm, but 270 hp normally aspirated was possiable without passing the 300 hour wide open throttle test. Ford Australias first long 6.06" rod 1998 to date Intech/Twin Cam rods was the result, okay to well over 400 hp. Then the upgraded Turbo F6 rod, for added reliabity

The US forged 5.88's are typical Windsor Cleveland plant rods, good metelurgy, but a little bit spindly of beam. With good US competition prep and replacement of the plasticine Ford standard bolts with ARP's, these things will take some really serious punishment.

Mike Vine (the biggest producer of turbo engine Falcons from 1984 to 1992) found 260 KW or 350 hp was the practical limit based on fatigue resistance and beam strength. Of the better forged rod.
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FAZER 6Bi (M112 & EEC5) or FAZER 6Ti (GT3582 & EEC5) 425 HP 4.1L/250 I-6
FAZER 6V0 3x2-BBL Holley 188 HP 3.3L/200 I-6 or 235 HP 4.1L/250 I-6
X-Flow Engine Components Ltd http://www.xecltd.info/?rd=10

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Re: Is there a good forged alternative rod out there for a 2

Post #7 by drag-200stang » Thu Sep 29, 2016 9:51 am

I would continue on your planed path, with the thought that for some unforeseen reason you may have to open the engine up then at that time you could up grade. this will give you time to get a cost effective forged rod on hand.
66 Mustang Coupe
200 turbo w/lenco 4-spd
stock adj. rockers, stock timing set, ARP studs
best 1/4 mile ET 9.85/best mph 139 on 8 lbs progressing to 15 lbs boost
Went 9's when 10's was fast.

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Re: Is there a good forged alternative rod out there for a 2

Post #8 by drag-200stang » Thu Sep 29, 2016 10:01 am

Does10s wrote:Just to be clear....our "carnage" wasn't caused by a failed connecting rod! It was caused by a cyl. wall that broke at around 4500rpm or so. The piston rings for that hole then got jammed and then the train wreck started to happen. Hence all of the broke or bend rods!

We spin Kelly's 250 to 6100rpm at the traps. We haven't used stock rods since that grenade engine, but that was more to do with getting the piston closer to a zero deck height.

We're using off the shelf aftermarket Manley H-Beam rods for a 4.6L Ford V8. They use a standard .912" wrist pin and are .088" longer than the 250 rod. (pretty sure that's the correct number!) The big end is a little smaller than the 250 rod, so you'll need to machine the rod journal to fit....or offset grind it to gain a few more cubic inches.
Because they're V8 rods, the big end width is less. I don't remember the exact numbers off hand, but it's something like .040" less. So the rod will "travel" fore and aft a bit within the rod journal. We haven't seen any issues with that at all! We've torn down the engine numerous times for other issues or just for maintenance, and have never had a problem with that extra rod room in the journal.
Later,
Will


Will, just to be clear you used stock forged rods or cast?
66 Mustang Coupe
200 turbo w/lenco 4-spd
stock adj. rockers, stock timing set, ARP studs
best 1/4 mile ET 9.85/best mph 139 on 8 lbs progressing to 15 lbs boost
Went 9's when 10's was fast.

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Re: Is there a good forged alternative rod out there for a 2

Post #9 by xctasy » Thu Sep 29, 2016 7:48 pm

Its cast due to the large formed font. Cast rods aren't bad, just a potentially nasty combination in a 250. Due to the cam to crank throw (stroke) centers, there isn't much space for a good batallion of alloy/aluminum SuperRods, so stock forged rods are the best solution.

Everything small I6 from about that mid 1977 year went to cast rods.

IIRC, Both Gene and Crosley use cast rods in there 250 and 200, respectively, stout 15 second cars that haven't blown up yet!


The forged rods have fine stamped in font. Aussie rods from 1961 to 1971 are just like US/ Canadian ones, including the 250, but have an AR prefix in the forgings, and then went to 72 DA codes after 1971.

Cast rods are like aluminimum rods, you just have to peridic test or log the amount of use they had. Difference is only they hate racing loads, and love slogging vibration loads from street driving. An aluminim ros, its the reverse, it hates street driving, and will fatigue and suffer cracking, but its great for racing, where periodic Zyglo testing is all you need.

Awesome cars like all the HO 455's, even the rare the Juge GTO Ram Air V, still just had cast rods like all 1963 to 1981 small and big blocks, 215-301, 4.9 to 455. In a long stroke 455 with huge piston speeds, that reved to 5800 rpm!

See http://www.hotrod.com/articles/hppp-120 ... ntiac-v8s/

Only the 455 uper Duty ever sought the need to have a proper forged 6.625" rod, and it was because of drag racing and endurance racing where it was planned to be dry sumped and beaten on or treated worse than any trashed 8000 rpm redline Lamborghini LP400.


NOTE WELL:-drag-200stang


As you'll know from your destroked 250 turbo aluminium rod experience in your Mustang, drag-200stang, forged alloy, aluminum built up or machined aluminum rods are actually really space consuming, but they can even explode and not take a block out!

The cast rods are a prone to fatigue failure. With an alloy/aluminum rod, in a turbo four or V8, it can only hack about 15,000 miles of mixed street/strip use on applications with high boost. As Mike Riechers from R&R Racing Products says:- The key is to replace the alloy rod before it fatigues, so it’s best to speak to your engine builder or search the internet forums for what other people are reporting.

See http://rrconnectingrods.com/aluminum-connecting-rods/

Cast rods are a little like that, but they are Not for Racing engines. Although Pontiac's have raced for years with cast con rods, but they are the exception.

Forged conrods, like the 1991 on wards Modular Ford 3.937" bore Romeo/Windsor/Cleveland plant OHC connecting rods (except 2003 Cobra) are of the powdered-metal Forged type with cracked caps. Same with the swap over from the stock Cleveland 302/ Windsor 351 con rods found in the 1982-1995 the 3.8 Essex V6...they replaced them with crack offs in 1996. So forged steel con ords have really gotten pretty good. Problem is, all the other really good Ford forged con rods are either a few thou too long, or custom. The 5.914" 3.8 con rod would be perfect, but its got a 302c/351c/351w 2.311" journal. B@$+@Rd!
Image
XEC Ltd ICBE's Inter Continental Ballistic Engines-
FAZER 6Bi (M112 & EEC5) or FAZER 6Ti (GT3582 & EEC5) 425 HP 4.1L/250 I-6
FAZER 6V0 3x2-BBL Holley 188 HP 3.3L/200 I-6 or 235 HP 4.1L/250 I-6
X-Flow Engine Components Ltd http://www.xecltd.info/?rd=10

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Re: Is there a good forged alternative rod out there for a 2

Post #10 by autoX65 » Mon Oct 03, 2016 11:42 pm

i cant find the site but I remember in the past i had saw a similar rod h beam style for the slant six that had comparable specs...not sure but good info an ya I wouldnt worry about it im sure its so tuned I cant imagine the rods would be any issue. sounds like they are a maintenance item now and who knows id imagine 15k miles is what 200 hard passes maybe say 100 hard accelerations on them and replace. tough call Mike.

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Re: Is there a good forged alternative rod out there for a 2

Post #11 by xctasy » Tue Oct 04, 2016 8:01 am

autoX65 wrote:i cant find the site but I remember in the past i had saw a similar rod h beam style for the slant six that had comparable specs...not sure but good info an ya I wouldnt worry about it im sure its so tuned I cant imagine the rods would be any issue. sounds like they are a maintenance item now and who knows id imagine 15k miles is what 200 hard passes maybe say 100 hard accelerations on them and replace. tough call Mike.


Slant six rods for the 225 are too long at 6.69, but the smaller 170's too short at 5.669 (LG)-5.705"" and 198's 7.005" are way to long.


Yeah, that's the 5.75" Chrysler Hemi in line six D series 215-245-265 conrod from the 1969-1982 Aussie Mopars, with Chevy wrist 0.927" pin and 2.0" small journal Chevy big end. Great, tough con rod. They are used often in Holdens, Chev's, Fords, but it'll need gudgeon bushing and an offset crank grind to fit Mikes Maurauder, um, Mercury, um, G'Monster.

Turbo Falcons in Oz use them to take them out to 266 cubic inches with almost 124 thou extra in the crank, and 60 thou in the pistons for 3.74 x 4.034". L/R or Lamda ratio drops below optimum to 1.424:1, but no one cares when you run 16 pounds of boost and make 500 hp...


I think Mike added 100 thou to the RaceTek piston deck for 1.634", and with a 9.649" deck, its gonna need a 4.17" offset ground stroke for it to gell with his components. 269 cubes sounds good but his rod ratio would be 1.378:1.

Then there are the Mitsubishi Silent Shaft Sirius 4g63 150mm/5.906" rods, but all the Jap stuff has a Holden sized 0.866 or near offer gudgeon pin. I use the Ford Corsair KA24 conrod, basically the 240SX Turbo rod, but its not a drop in...you have a lack of width to suit the stock crank, and the wrist pin is 0.866, not 0.912.

Image

see http://store.skunk2.com/media/catalog/p ... rods_1.jpg
Years ago, Lunati Chevy 5.85" stroker con rods were pretty good, a custom rod that can be dialed in to suit.

5.933" 4.6 rods are again 0.867" wrist pin

Chevy L6 6"rods can be bushed down

Jeep3.8/4.2/4.0 5.885" rods have big journals, 0.929" wrist. And are cast stock, but $43 for six.
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FAZER 6Bi (M112 & EEC5) or FAZER 6Ti (GT3582 & EEC5) 425 HP 4.1L/250 I-6
FAZER 6V0 3x2-BBL Holley 188 HP 3.3L/200 I-6 or 235 HP 4.1L/250 I-6
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Re: Is there a good forged alternative rod out there for a 2

Post #12 by MustangSix » Tue Oct 04, 2016 2:51 pm

Take a look at Scat H-Beam Connecting Rods 2-250-6000-2000. They're a bit wide on the big end, but that's a simple job to narrow them. Bush them for .912 pins or open the pistons for .927 Chevy pins.

The added length might make finding a piston to get the right deck height a bit easier.
Jack Collins

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Re: Is there a good forged alternative rod out there for a 2

Post #13 by xctasy » Tue Oct 04, 2016 4:15 pm

Those Jeep ones I noted were actually 43.68

https://www.summitracing.com/int/parts/ ... /overview/

Cast-a-away


MustangSix wrote:Take a look at Scat H-Beam Connecting Rods 2-250-6000-2000. They're a bit wide on the big end, but that's a simple job to narrow them. Bush them for .912 pins or open the pistons for .927 Chevy pins.

The added length might make finding a piston to get the right deck height a bit easier.


Page 10 or 10, saw it last night.


https://www.summitracing.com/int/parts/ ... /overview/

$467.97



Just like the Nismo 1000 hp, 1163 hp, then 1500 hp Falcon XR6 Turbo engine!

Image

No room for 6" rods, Mike had the block decked to suit the stock 5.845" rods (US rods seam to be 40 thou shorter than the 5.885 Aussie ones)

Mike1157 wrote:Well lets see.
Since my last post,..I've been waiting on the engine to get bored at the machine shop so that I could get it back home and mock up a couple of cylinders to determine how much additional decking was gonna be required to bring it to zero deck.
Friday I was able to get it back.
Image
Image
If you look closely, you can see the sleeve. The block has still got .008 that needs to be cut. That'll bring the epoxy that I had to use to widen the deck down to smooth as well.
Those pistons are Racetec 2618 forgings. Should net me a 9:1 CR.
Image
The fact that my name is laser etched on the bottom should be worth about 10HP per piston.:lol:
The rods are stock. Treated to the old school standard for prep: Beams polished, bushed for floating pistons, w/ ARP hardened bolts.
Image
After I determined where the deck needed to be cut, I put the block back on in my truck so that the machine shop can finish it.
Image
XEC Ltd ICBE's Inter Continental Ballistic Engines-
FAZER 6Bi (M112 & EEC5) or FAZER 6Ti (GT3582 & EEC5) 425 HP 4.1L/250 I-6
FAZER 6V0 3x2-BBL Holley 188 HP 3.3L/200 I-6 or 235 HP 4.1L/250 I-6
X-Flow Engine Components Ltd http://www.xecltd.info/?rd=10

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Re: Is there a good forged alternative rod out there for a 2

Post #14 by rocklord » Tue Oct 18, 2016 11:41 am

Check these out:

http://www.ebay.com/itm/PERFORMANCE-CON ... hg&vxp=mtr

International shipping.

From auction:

PERFORMANCE CONRODS TO SUIT FORD FALCON 4L 6 CYLINDER – EB ED EL EF XR6

These are 5.88 inch centre to centre and will fit other Ford 4.0L engines including some of the cross flow engines.

THESE CONRODS HAVE A SEMI FINISHED BRONZE BUSHED SMALL END

Bushes are finished at 21.98mm so can be used with the more popular 22mm pins and or OEM 23.17mm pins

These are a direct fit conrod for all Ford EB,ED,EL 4.0 Litre straight six cylinder engines.

These are rated to over 1200 horsepower, supporting modifications are necessary.

Features:

•High tensile 4340 forged steel
•2 Piece forging
•Hardness of HRC36-42
•Dowelled caps for precision alignment
•X-RAY & Sonic tested
•Quenching and heat treated
•Shot peened
•100% Magna-fluxed
•Weight Matched Sets + - 1 gram
•Vacuum degassed to remove impurities

All Connecting Rods come with ARP 2000 rod bolts fitted.
Dan

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Re: Is there a good forged alternative rod out there for a 2

Post #15 by CNC-Dude » Tue Oct 18, 2016 4:29 pm

There are very few options available now as an afterthought without significant teardown and added machining to both pistons and rods and of course, expense. But, for those looking ahead to build from scratch, I did look myself a while back and found many options in both H-beam and I-beam aftermarket rods that needed only a little tweaking to fit the small Ford 6 crank at a budget, leaving only the pistons as the real bigger dollar expense. But even then, the Racetec and others are pretty affordable for most people and you can then have a better bulletproof bottom end.
Image

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Re: Is there a good forged alternative rod out there for a 2

Post #16 by xctasy » Wed Oct 19, 2016 2:59 am

Scraping the bottom of the SBC camshaft! Ole!

Image

Even the 928/944/968 Porsche crowed use them on there 4.8" bore etch prime alloy V8 and slant four engines


Image

After a diet of 5.7 and 6 " SBF's, then came the 6.098" LS1.

Like a 5.565 for the sbc and the 6.135,6.200, 6.340, 6.385 for the BBC's, they all skipped the 5.85" rod. Olivers, Eagle and Lunati did them, and they were really common until the advent of the 1996 model year alloy Chev.


The Fall of Owe 08 (the October 2008 sub prime burst) forced a rethink on unused inventory, but it was the alloy Gen III /LS1 that was eating away theat burried the 5.85" rods in Gen1's and II'S.


Ok, Luntai first...

xctasy wrote:......Years ago, Lunati Chevy 5.85" stroker con rods were pretty good, a custom rod that can be dialed in to suit......



In just 10 years, the alloy GEN III has made people forget about odd ball Gen II LT1 stroker 30 thou over 3-7/8 th crank 396's...and its 5.85" rod!.

https://www.cantonracingproducts.com/Tr ... hunder.pdf

STREETTHUNDER|NOVEMBER/DECEMBER 2007

The Gen II family of V-8s includes the 5.7L LT1 and LT4, and the small-bore 4.3L L99. These engines were available in a variety of vehicles including Corvettes (Y-Bodies), Camaros/Firebirds (F-Bodies), and Caprices/Roadmasters/Fleetwoods (B-Bodies) between ’92-’97. Externally they all look the same, except for the cast iron heads on B-Body LT1s and L99s,and the powder coated red intake manifold on LT4

CONNECTINGRODS–LUNATI At 5.85 inches, these “Pro Mod” forged I-beam connecting rods are the minimum (and the only recommended) length for use in a 396



And the Eagle CRS5850S3D... now $527.99 from JEGS, when it was $475 then years ago....

http://www.jegs.com/i/Eagle/356/CRS5850S3D/10002/-1

old references

http://www.chevytalk.org/fusionbb/showt ... id/150334/


On ebay, see Image
Image

http://www.ebay.com/itm/Chevy-Eagle-I-B ... 1284466634


US $291.69


and this, the most important, differnt strokes for different folks

Image

http://www.strokerengine.com/rodstroke.html
Image
XEC Ltd ICBE's Inter Continental Ballistic Engines-
FAZER 6Bi (M112 & EEC5) or FAZER 6Ti (GT3582 & EEC5) 425 HP 4.1L/250 I-6
FAZER 6V0 3x2-BBL Holley 188 HP 3.3L/200 I-6 or 235 HP 4.1L/250 I-6
X-Flow Engine Components Ltd http://www.xecltd.info/?rd=10

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Re: Is there a good forged alternative rod out there for a 2

Post #17 by 65-coupe » Tue Apr 11, 2017 5:11 pm

Does10s wrote:Just to be clear....our "carnage" wasn't caused by a failed connecting rod! It was caused by a cyl. wall that broke at around 4500rpm or so. The piston rings for that hole then got jammed and then the train wreck started to happen. Hence all of the broke or bend rods!

We spin Kelly's 250 to 6100rpm at the traps. We haven't used stock rods since that grenade engine, but that was more to do with getting the piston closer to a zero deck height.

We're using off the shelf aftermarket Manley H-Beam rods for a 4.6L Ford V8. They use a standard .912" wrist pin and are .088" longer than the 250 rod. (pretty sure that's the correct number!) The big end is a little smaller than the 250 rod, so you'll need to machine the rod journal to fit....or offset grind it to gain a few more cubic inches.
Because they're V8 rods, the big end width is less. I don't remember the exact numbers off hand, but it's something like .040" less. So the rod will "travel" fore and aft a bit within the rod journal. We haven't seen any issues with that at all! We've torn down the engine numerous times for other issues or just for maintenance, and have never had a problem with that extra rod room in the journal.

Later,
Will


Do you have the part number for the rods you bought? What is the large diameter of the stock 250 rods. Also is the center to center length 5.88 for the 250 rods?
1965 Mustang coupe, SPI Orange with custom TMI interior, 250 DUI, CI alum head ported, 274/274 110 Clay Smith cam, 1.65 roller rockers, Holley 390 4bbl, Lokar pedals and throttle calbe. Street or track front coilovers suspension, CI headers stainless with Jet-Hot ceramic coating, CI Stainless 2" impostor dual exhaust, 17x8 Coys C-67 wheels,

oldsix
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Re: Is there a good forged alternative rod out there for a 250?

Post #18 by oldsix » Wed Apr 12, 2017 12:56 pm

The question was asked, what is the maximum RPM an engine should see? Based on a Gordon Jennings book Two stroke tuner's handbook, circa 1970, I seem to recall 4000fpm average piston speed was a good target for engines of that era, still a good value for aout al but the most highly strung motors. At 4000fpm in the 70's, rings would start to shift in their lands and chatter, loosing compression.

Coincidently, doing the math, 4000fpm works out to 12,000 rpm w/ a 2" stroke, 6000 rpm w/ a 4" stroke. Ring materials have improved, and thinner rings are now available, but 4000 fpm is just a good baseline number.

Also, having never failed a rod, my understanding is most ROD failures are due to overtightening rod bolts. I always assemble with a stretch gage to make sure I don't exceed the bolt maker's stretch requirement

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