longer rods in a 200?

[godheadcustoms]

I think this will work, but I don't if it would be worth all the hassle and money for negligible(?) gains. Does anyone has any data to support or refute this theory?
Here goes: The stock 200 bock has a .030 deck height, instead of milling the block to zero deck height for proper quench, stretch the rods .030. That in itself is nothing to get excited about, but if you run a tighter ring pack with 1/16", 1/16", 3/16" rings and run .160"-.180" down from the piston crown you could end up with a compression height of 1.214"-1.234" instead of the factory 1.5". Combine this with the .030" gained from the deck height and you end up with a 5.011"-5.031" rod, up from the O.E. 4.715". This now puts the rod ratio at 1.60-1.61:1 ,again, up from the O.E. 1.5:1 ratio.
Getting custom pistons made is fairly easy and relatively inexpensive, but what I see as the problem is finding con rods in close to perfect specs from another engine to keep costs realistic. I don't want to have to do this by calling Carillo! I haven't checked into any potential rods yet, wanted to gauge concsensus first. What kind of gains, emperical or theoretical, am I looking at going to a 1.6 rod ratio assuming all else equal, i.e.- a well sorted motor with 9.2ish C.R., ported head, big valves, decent exhaust, proper cam and carb for the application, etc ?

 

[xctasy]

The answer is simple. ACL make factory cast pistons able to take 500 hp. They are 1.163" deap, have any size from the OHC/DOHC 3.632-to 48 thou over (3.68"), and then the 200/250 3.68" to 3.71". The pistons are based on the XR6 Turbo design, and have excellent dimensional stability, so they won't slap and scuff bores like the forged ones can. All non forged pistons have a hotter operational temperature, but the ACL items are designed for rev ranges in the 4000 feet per second area. Stoke Falcon Turbo XR6's yield over 320 hp, and rev to 6000 rpm, about 3900 feet per second piston speed, still with unforged pistons.

Option one is grabing the Aussie or Argie 221 I6 rods, 5.14" long, and thick gasket with ACL or forged Ross/Cosworth or Mahle or Cima pistons.

Option two is a very thick gasket with 289 HP rods, 5.15", ACL or forged Ross/Cosworth or Mahle or Cima pistons. There are also the good Windor V8 5.09" 302 rods. Both the Windy rods need a crank either ground or down hand welded to locate the rod on the big ends correctly. The Windsor rods are narrower. The stock fillet raduis can be redone, and the crank is over engineered as it is.

These combos give a rod ratio of up to 1.65:1. In Aussie sixes, we have 202 Holdens with under weighted 1.9" big ends and 0.866" gudgeon pins, 5.25" rods and 3.25" stroke with a 3.625" bore. They rev to 7 grand all day with the right gear. The US 200 has a better block, stroke, better V8 rods to pick from, a crank with 226 thou more big end bearing, a 46 thou bigger gudgeon pin and a similar main bearing size.

It's just a matter of picking from the US inventory. I'd look at the Wiseco, Ross, KB, or whatever forged pistons you can get.

There is the option of offset grinds using the 5" Ford Pinto2.0 rods, about 2.047" at the big end pin. The Lima 2.3 rods are a better bet, and buying aftermarket pistons looks like the only option, as the Lima runs a stock bore size 100 thou over the stock 200 size. The stock 2.0 forged numbers don't come over 3.655" size, and some have the quirky 0.945" wrist pin

Lastly, DBzokale has found some 3.67" forged pistons with .900" pins from Buick, but they aren't low deck.

My 305 Chevy piston takes the bores out 56 thou, way too much for an older short deck US 200. There just isn't the wall thickness for safety's sake.

Happy hunting!

 

[twentyover]

Think Mike was working on forged pistons for us- weve discussed this a number of times.

First thing to do is to pick your ring set- might be wise to try to find a 94mm compression ring thats's 1/16" and Moly faced- or if you're in a dusty climate or not running air filters, Chrome rings (and there isn't such a thing as Chrom-Moly rings. These two alloying elements are added to steel to give high yield strength; Chrom rings are like standard CI rings except they are hard chrome plated- they're supposed to work goo in high wear siyuations. Moly rings have a band of Molybdenum on the face of the ring so the ring is sacrificial to let the cylinder bore live to see another day.)

Anyway, select bore based strictly on the ring pack you can get. For then look at high small a diameter pin you can run.

Like xtaxi's idea of negative deck height- just amke sure the rings are low enough on the piston for this.

I'm actually doing something similiar right now. i'm working on a 2.9l MGC 6 cylinder- Deck height is 10.25:, stock stroke is 3.5:, rods are 6.6", and compression height is almost 2". The head's at the porter, we're waiting for piston crowns to be developed that let me not need to notch the block for valve clearance while still gtting a respectable CR.

Right now it looks like the final mix with be 7.2" rod, 84mm piston running ,oly faced rings, abd about 6cc of dome to get 11.5:1. I thinking we mag be able to pull as much as 500 grams out of the piston/rod assembly

 

[godheadcustoms]

I know that this can be done, I just wasn't sure if the results could quantify the expenditure. My thinking was if there was a factory rod that could be modified to work, then the pistons could be made up to fit the specs of the rods. Getting custom pistons is pretty easy, and not really that pricey, all things being equal. I did some searching after the post and it looks like about a 3-5% improvement COULD be expected if the combo was dialed in. I'll have to mull this over a bit, decide if the money is worth the improvement. This is going to be a street motor, not a spec class race motor where every last bit counts. I'll probably go through with this as I think I'm going to have pistons made to my specs anyways, and V-8 rods are plentiful and cheap.
X, thanks for the info on the V-8 rods. Didn't even think about them
Decisions, decisions...