What's the benefit of 200 rods in a 250?

[eattsie9 350]

Sorry if it's been asked before in sure I've read it here somewhere but don't remember and can't find it. I saw the spool rod n piston set for 250 xflow. It comes with 200 rods, just curious what is the benefit of 200 rods in a 250?

 

Cheers

 

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[Nath 1,975]

Buy it... Then send me the link so I can buy one too.

 

Lets you rev the 250 higher but the pistons to suit are stupid hard to come by.

[eattsie9 350]

http://www.spoolimports.com/spool-conrod-piston-packages/ford/ford-200-conrod-and-piston-package

 

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[Nath 1,975]

Oooh. Yeah maybe not hey.

[Thom 6,650]

It gives a longer rod to stroke ratio, meaning the pistons move faster in the middle of the stroke but slow down towards the ends of the stroke so it takes less effort for the pistons to change direction, it's supposed to free up torque in the sub 7k rpm range, ford themselves did it with the boss 302 (by using 289 length rods) and many have done it to 351 clevos (by using a 302 length rod)

[eattsie9 350]

Thanks

 

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[wagoon 2,429]

There is absolutely no denying the benefit of a 200 rod setup in a crossflow, BUT does it suit what you want to use the engine for. A 200 rod combo is useful when you are trying to extract the last 2% of power out of a crossflow AND revving the engine to 7500RPM all the time. So if the car is for drag racing where you are trying to win a championship or set the fastest time ever by a NA crossflow, your car is for burnout comps where the engine will be sitting above 7000rpm for 3 minutes at a time or your the new drift king where the limiter is used to show how strong your car is go the 200 rod setup. Unless you are doing these events or an event just like it you DON'T need 200 rod combo. The only other time you will need a 200 rod combo is if your building a car for street machine and so they can fill out the story they can say you have a 200 rod combo.

 

Now to the links you provided.

The cheaper set has flat top pistons, which will limit the cylinder head you can run if you want to use petrol instead of race fuel. You will find it hard to keep the CR down with flat tops and still get zero deck height ( zero deck height is better for performance)

The more expensive set have custom compression ratio but at $2200 is stupid expensive unless you need forged pistons or desperate for 200 rod combo. As an example my solid roller cam crossflow has 10.5:1 CR, will have a rev limit around the 6200-6500rpm, will run on pump fuel and I'm hoping for at least 350fwhp. I am using standard hypetec pistons with hastings rings and it cost me less than $300.

 

So if you win lotto, have money to burn, want the wank factor of forged setup or are trying to set records go for the 200 rod setup. Otherwise save yourself a stupid amount of money and use standard pistons, spend the rest on better parts and go just as fast.

[slydog 7,873]

Well said Thom & Ryan...Longer dwell time @ TDC for a more complete burn and piston speed.But all this ONLY works if the cyl head is up to it and it has enough compression and camshaft to match.

 

So if you NEED to go the 200 rod the CP kit is for you or a Wiesco/Scatt combo but you spend the same amount either way.That said the Wiseco piston is the best (ask Mossy what they can take year after year) of the lot and the Scatt rod comes with a 2000 series 7/16th bolt that take ALOT more than the 5/16th units.   

[gerg 10,871]

I'll add that shorter skirt piston gives slightly less friction and a lot less weight. The ACL version is about 130 grams lighter than its 250 rod equivalent, which is heaps. This puts a lot less strain on the rod, especially at TDC when the piston is trying to pull the rod apart. This along with the slower acceleration at TDC and BDC allow high rpm with better peace of mind. Best to balance the crank when changing the weight of anything though.

 

Rod/stroke ratio: here's a visual..... imagine a short kid (with little legs) trying to pedal a big bicycle. Lots of effort, especially when going fast. Get a taller kid of the same build (but with longer legs) on that same bike and effort is much reduced, the motion is more natural.

[eattsie9 350]

Bloody good info thanks. So the long an curly of it is I don't need 200 rods as I suspected and I thought that kit was pretty bloody expensive too thanks for the help all

 

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[wagoon 2,429]

I will add that if you want a really good setup put ARP rod bolts on standard rods and use the piston that best suits your head, camshaft and compression ratio

[ando76 4,354]

If you want to build a strong, torque monster and have a non individual runner intake - go short rod

 

If you want to build a strong, torque monster that RPM's to 7200 comfortably, have individual runner intake and a cylinder head that flows over 225cfm- go long rod.

 

If you want to build a long rod motor to impress your mates - do it. 

 

Trust me - the short rod motor with a four barrel intake (or restrictor class racing 2 barrel intake ) is a formidable thing. 

 

Yes I know all the stuff about bore stroke ratio and all the long held beliefs of the benefits of the long rod.  I have built enough of these as competition engine to know what works and what doesn't.  Brenton's new race motor is a short rod - big solid cam beast and it is stupid fast.

 

As always the choice is yours. 

[Nath 1,975]

 your the new drift king

 

Pretty sure that sounds like me.

 

...

 

Guys?

[CHESTNUTXE 7,311]

What about how the longer rod weigh's more than the shorter rod ?

[ando76 4,354]

Most of the aftermarket long rods are actually lighter.  also there is a good weight saving in the lighter (shorter skirt) piston when fitted to the long rod.

 

I've never actually weighed a stock 200 rod and a stock early short rod.  Be interesting actually.

[CHESTNUTXE 7,311]

yeah hard to find those acl short skirt pistons,no way am i gunna pay 2 grand for a aftermarket set up,im sticking with my normal crank and rod set up,and add other goodies to it.

[PRO250 1,506]

I have been down this road and been 250 rod and 200 rod combos with my engine there was no real gain that we could see on the dyno or in the car for that matter with 262@50 cam and 4 barrel I never tyred it with webers

I just sold 2 200 rod engines people think its better and in something like rob has it is, on a engine that does not turn past 6200 theres no need the 250 rod will put up with it and love you long time

can you but the rings for the 200 rod pistons again? I have a set of new 200 rod pistons  in the shed ive never done anything with cause you cant seem to get the ring sets for them anymore so I bought these to nick the ring set for the my engine that I killed a piston ring

 

[Nath 1,975]

I kinda feel like unfamilia needs to chime in here about rod stroke or something.

[ando76 4,354]

Yeah the old ACL thin ring 200 rod pistons were hard to get rings for.  I ended up using some - cough cough - buick oil control rings in mine.  I had to screw around a bit to get them to fit but it worked. 

 

I have not had do one for awhile so I am not sure if it is still a pain.  Even more reason to go to the short rod.  lol.

 

My Ross 200 rod pistons use the thick rings like the short rod pistons.  Now there are other forged pistons available at a reasonable price that I would use instead of the Ross units.  My roller cam engine - that I am actually starting to build - is using Ross units.  Only cause I have them - not cause they are better than the motorbike Wiseco units.

[broken-wheel 659]

actually the longer rods reduces piston speed which allows the engine to rev better, the xflow is already a long stroke motor with high piston speed at 7k, having a longer rod reduces piston speed in the critical upper and lower position (TDC/BDC)

 

Effects of a longer Rod

* Less rod angularity reduces wear.
* Lower piston velocity and acceleration reduces tensile loading of the rods.
* Less ignition timing is required which resist detonation.
* Compression can be increased slightly before detonation is a problem.
* Less intake runner volume is required and high rpm breathing is improved.
* Reduces scavenging at low rpm (weaker low RPM power).
* Longer TDC dwell time. (high RPM efficency).

 

The  difference between 5.7 and 6.2 rods is not as big as people make it out to be, with some good forged rods and ARP2000 bolts the shorter rod will be ok and sing every day at 7k but if you want that little extra insurance then go for the long rod

[FORD_MAN 1,026]

PPM also sell a forged piston & H beam set but not sure if 250 rod or 200 rod,

https://www.pureperformancemotorsport.com/index.php/ford-xe-xf-4-1l-forged-pistons-and-h-beam-connecting-rods.html

[ando76 4,354]

Yep I have a set of those rods that came in a damaged engine I bought.  They are an awesome piece of kit - similar looking to my spool rods.  The ones I have are a short rod.

[FORD_MAN 1,026]

Cool been wondering what they were like, I've seen my neighbor has used them in a SOHC speedway engine,

looks like 250 rod would suit my next crossflow