Gannet

What's the minimum compression height that will allow a good ring pack and avoid the need for oil ring support rails?

briannutter

If you use a good dimpled oil support rail that can't rotate in the groove (due to the dimple facing down into the pin bore and effectively locking it in place), you will have no "extra" problems with oil consumption. Some piston companies use what amounts to a 3rd oil ring wiper (no dimple) that clamps against the back of the groove. These CAN rotate and "taco" if not designed correctly. These are the ones that give spacer rings a bad name. There are bazillions of engines out there running the good spacer with no problems. The problems sometimes associated with oiling with "short" pistons can often be attributed to other factors, including poor piston design/manufacturing.

All that being said, a 1.215 will work with the top land thickness needed with most 1/16 1/16 3/16 ring packages. Moving to the GFX 1.2, 1.2, 3mm ring package would get you 1.133 with the same land thicknesses as before (which I'd consider to be "no nitrous" land thicknesses).

Gannet

Thanks for the reply.

How much extra allowance for nitrous/boost ring lands?

briannutter

I'd like to see a top land thickness of .300, a 2nd land of .165 minimum, and a .080 3rd if you plan on running a 300+ shot. If you use those numbers, the compression hieghts would be come 1.346 for 1/16 rings and 1.242 for the gfx rings. You can save .050 worth of land for shots smaller than that. I'm ok with the thinner lands for boost as well because it's much easier on engine at any given horsepower than nitrous. -Brian Nutter-Wiseco

Gannet

Excellent info, thank you very much.

As you might have guessed, I'm running "what if" scenarios for the expected tall deck blocks. I'm trying to see what sort of stroke/rod/piston combos might make sense for a high-mileage street engine.

One combo that looks like it might work out would be a 9.7" deck LSx block, 4.25" stroke, 6.350" rod. With a 4.185" bore this nets 468 ci, but still gives you a rod ratio of 1.494, right in between the ratios for the factory 454 BBC and 400 SBC. Not ideal, but probably capable of long life given reasonable rpm limits. Compression height would be 1.225, leaving room for a decent ring package for moderate boost.

Going to a 6.450" rod gets the ratio to 1.518, but now you have to run a "short" piston with a 1.125" compression height.

The question is, if you wanted maximum durability, which would be better? I would think the slightly shorter rod and longer piston, but I am not an expert.

gun5l1ng3r

Would the longer shorter rod/long piston weight more than a short piston/long rod?

I think that weight is an important part of any rotating assembly, but in this case, I'll bet the difference is negligible.

The 4.25" stoke is kinda scary for 250K+ miles motor, but I am by no means an expert. It would probably be best to just listen to Brian

mike moore

iTrader: (19)

Typically, the shorter piston and longer rod will yeild a lighter assembly, if comparing i beam to i beam or h beam to h beam of course.

Gannet

For a big stroker street motor like this I would be figuring a redline of 6000-6200. I'm more concerned with ring seal, ring life, and bore life than I am about weight.

briannutter

If it wasn't for "rod ratio" there wouldn't be bench racers or internet forums. I haven't found much use for it elsewhere. The skirt profile is the real determiner of engine life. Again, I wouldn't worry about the spacer ring at all.

There's a few reasons I think you end up "settling" on the 1.115 "ish" c.h.

Adequate land thickness, enough reverse dome volume, and a skirt surface area that works.

The short piston is a light piston...it's the "rock on the sling" so cranks and rods can be lighter as well for any given level of stress.

The long rod allows the counterweights to be larger diameter and balancing won't cost you $800.

When I do a "really big" custom combination for someone, We add up the c.h., the skirt profile, the deck height, and the cylinder length; the allowable stroke is determined and lastly a rod length is settled upon. Rod ratio is what it is and the motor is as big and durable as it can be.

If the skirt is well designed and you go with a Zylan skirt coating, it will last a long long time. Anodized ring grooves are an option as well. The 1.2 1.2 3mm GFX ring is nitrided and has a napier 2nd. There's a really good chance it could be the first high performance ring to go 200k miles...we'll have to see.

mike moore

iTrader: (19)

The perfect rod/stroke ratio is 8:1. 8 rods to 1 crank. That's one of my favorite quotes.

NIIN20

X2~~

LSPerformance

iTrader: (23)

All this is well and good but what is the cylinder length in the block that you want to slap a stroker crank in? - just because you can stuff a crank and rods in it doesn't mean it's a good combination. I figure the minimum piston skirt length I need in the block @ BDC and fit a crank/rod to that. I talked to a block manufacturer last week and asked what the cylinder length was, the response was - "a 4.250" stroke crank will fit" - well I had to ask again and wait for him to go measure a block, the answer was 5.500". That being the case, I would never put that much stroke in a cylinder that short, I wonder how many just hang up the phone and start buying parts after getting the first answer?

Gannet

I ***-u-med the LSx block would have long sleeves. But I don't know, and the information would have to be favorable before I would ever go for it.

When/if the time comes (I'm still debating stroker vs FI) I would go to an experienced stroker shop, tell them my goals, and have them do the whole deal. Final displacement would just be whatever they think it should be.

For now, all I was trying to do was get an idea of what the largest sensible, high mile displacement would be for a tall deck engine. Something between 427 and 441 seems to be the answer for a standard deck block. Even there, i wish the pistons weren't so short. How much extra does the 9.7 get you?

I could just call one of the stroker shops and ask I guess, but they won't know for sure until they see the blocks and work with them a bit. Plus I hate taking up their time until I'm ready for money to change hands.

5.0stang

iTrader: (1)

Hello Brian,

I offer a bit different twist to your expertise. I am a 5.0L Mustang guy, but caught this thread thru a search and it got me thinking

What is the deal with the skirt coatings? Is it an aftermarket thing 'after' you buy a rotating assembly or piston, or do they come with it? Keeping in mind this is for 331 and 347 stroker kits

What is an anodized ring groove and what advantages does it have over a non-anodized ring groove?

I'm just looking for a long lasting (100k potential) 347. Just curious if I should run the 5.4" rod with the 1.090" piston (wrist pin intersects the oil ring land).

Thanks brian

briannutter

Coatings are great if the market supports the added cost. Quieter, longer lasting, and can reduce friction. Some parts we do are coated and some are not. If the added cost will drive away customers for cheaper competition, we leave it to coaters like Polydyn, Swain, and Calico. Some markets like Sport Compact parts, high-end 4-cycle motorcycle parts, and some marine accept the price increase better. We've now made skirt coatings standard on new production runs of LS1 parts, but I'll get to that in a bit.

There's many different types. Spray-on moly that we consider a break-in agent, prepping the skirts adds "tooth" for it to adhere to (and adds cost), but it turns moly from a break-in agent into something that stays around for a while. We offer one called Zylan, which is always done w/ skirt prep, adheres great, and actually does make power gains on our dyno, whereas standard moly does not. Polydyn, Swain, and Calico can all do some nice coatings and have various trade names for proprietary materials that come from Dupont and others.

The REAL technology is Wiseco's in-house new Screen printed coating. We use a new material, even better than Zylan, that actually reduces noise, and it's applied with a mechanized process so thickness is identical from piston to piston...versus the inevitable diameter changes that occur from hand sprayed parts. Because the screens are custom formed to the skirt shape, the coating doesn't wrap around the edge of the skirt (which can cause flaking). We've applied extra thick versions of it to some test pistons and have 2618 parts run at .0005 clearance (with what becomes an absolutely perfect skirt shape for a given engine).

If you're running 4032 material, the added silicon creates a hard surface that negates the need for Anodized grooves unless you're microwelding rings. The problem with 4032 is cracks start and they shoots from silicon particle to silicon particle like a bolt of lightning. You end up with shrapnel in the pan. High-end racing pistons are usually 2618 and the anodized grooves help groove life. That being said, we've had untreated 2618's undergo 50k WOT racing miles in racing driving school cars and power drop was within a couple percent of new.

There are a couple different ways to Anodize grooves and pin bores of pistons. Before final Lathe turning, dipping the whole piston is cheap, but it holds extra heat in and requires more clearance....In my mind not worth it because it causes more problems than it fixes. High level Cup parts undergo a masking process, which is many times more expensive, but then only the groove and the pin bores are anodized. Both types are offered by Wiseco, but the masked/anodized parts can double the cost of the pistons. Worth it to some, but not others.

As for your 347, as long as you have a dimpled Groove lock spacer, you'll be in great shape. Oil control comes from the correct skirt shape, but most importantly using rings that consistently work well without "issues". You'd be suprised at how many piston companies throw on a generic skirt shape that ***** in the bore at bdc and causes problems when short pistons are used. All I can tell you is to not judge spacers negatively because the problem can be coming from elsewhere.

Good Luck, Brian Nutter-Wiseco Piston

5.0stang

iTrader: (1)

Thank you so much Brian, that helps my comprehension even better

Now, I got a few basic questions for you, and I promise I will leave you alone

As I'm trying to learn the application for each ring.

What is the purpose of the top ring?

What is the purpose of the second ring?

Which ring typically will wear out faster stroker or poweradder, if that matters?

What is the purpose of the oil control ring and its two rings that go above and below it.

Finally, what EXACTLY does the oil support ring (when the pin intersects oil ringland) do to 'support' it?

I also see 'holes' in the oil ringland (bottom ringland) before rings are put on? How do those work?

Thanks very much Brian

David

briannutter

No problem. This is a bit oversimplistic, but here it goes: Top ring seals, 2nd ring is an oil scraper, top ring wears out first regardless. The expanders job is to load the top and bottom rails against the top and bottom surface of the groove and into the cylinder. Different oil ring expander designs do better and worse jobs of keeping them parallel. The spacer ring allows the oil groove to drop over the pin bore, freeing up anywhere from .128 to .197 worth of land material above it. If it's dimpled at 90 degrees to the gap, and the dimple hits the "4th land" when it tries to rotate-the end gap cannot rotate into the pin bore...which could cause the oil ring endgaps to do the same and "unspring". Some companies rely on the spring of the spacer to clamp on the back of the groove...this can work, but isn't quite as good as the dimpled spacer. Oil drainback holes are sometimes placed squarely in the back of the oil ring groove. I don't like this approach as much as dropping them into the skirt face below the groove- which allows oil a place to go when the bottom rail does it's work.