Cyl sidewall wear with a 416

[airwoofer]

I have the heads off the stroker I bought here:
http://www.forabodiesonly.com/mopar/showthread.php?t=154286
To get the springs checked to be sure their tension has not dropped and to get them flowed. So looking into the cylinders I find a bunch of wear where the piston skirt would rub. There is the nice light crosshatch except wherethe skirts rubbed about 1/2 way up the stroke travel (2 - 2 1/2 inches from the deck) which are worn smooth. Also the pistons rock on the pin a lot more than I would expect and at TDC they also slide side to side on the pin more than I would figure. The pistons are KB forged 745.070.3 and per the build sheet I got with the motor have 0.005 clearance with the freshly bored cylinders.

Is this kind of side wear on the cylinders normal with 4" strokers? Should I pull these and either get them coated or put in a new set which has the skirts coated? Man I hate the thought of having to pull it back apart cause then I would probably end up doing stuff like putting in a Hughes girdle which will require align boring the mains again (maybe). Plus then I would probably put in a bigger cam and different higher compression pistone... in other words a rebuild.

The story was this engine was built, dyno'd, then pickled and sat for the last 3 years. Who knows, maybe it was run hard and put up worn out. BTW, the nitrided cam looks about new with all the lobe tips still black. the flat hyd lifters have a circle in the center, about 1/2 the diameter of the rocker, that is kinda yellowish brown. When 2 lifters are put flat to flat they still rock a tad.

 

[64 SRT8 Dart]

Hmm, could be the machine shop who did the bore went a little too much??
Also when putting more stroke in the engine the rod/stroke ratio is affected and sometimes this puts alot more pressure on the cylinder walls than if were stock. The rod is actually forcing the piston into the side of the cylinder causing the early wear. Replacing stock length rods with longer rods help but then you have to go with custom pistons with a different pin heighth to move the pin closer to the top of the piston.
I've heard that if you have bored the block out quite a bit and put a stroker crank in you can actually push the piston right through the side of the cylinder, prob at high rpms though.

 

[RustyRatRod]

Judging from the lifter wear, the story you got on the engine is probably spot on. Also, without pictures, the cylinder wear is tough to comment on. Most any build you can rock the pistons around in the bore on. I wouldn't sweat that. Often times if an engine is overheated, that can translate into premature piston/cylinder wear. But, without pictures, it's a tough call.

 

[dodge freak]

Also when putting more stroke in the engine the rod/stroke ratio is affected and sometimes this puts alot more pressure on the cylinder walls than if were stock. The rod is actually forcing the piston into the side of the cylinder causing the early wear. Replacing stock length rods with longer rods help but then you have to go with custom pistons with a different pin heighth to move the pin closer to the top of the piston.
I've heard that if you have bored the block out quite a bit and put a stroker crank in you can actually push the piston right through the side of the cylinder, prob at high rpms though.

Not sometimes but ALL the time.

The factory was not wasting time and money by having a big block with a higher deck for a longer stroke. They did it so the pistons could have a longer skirt and the engine would last a nice long time even under hard use and 3.75 inch stroke

In the 70's for circle track racing Mopar sold a crank that gave the 340's , 3.55 CI, I forgot the ex spec, think it was a 3.58 stroke crankshaft. Heck that isn't even close to 4 inches. Its now 35 years later but are engine parts or motor oil that much better today ? Maybe machining is and there are proven 4 inch strokers out there, still seems like too much stroke for my taste. Why stink money it to something that might not withstand much abuse--why not just get a stock stroke BBM-be cheaper and last longer--yeah takes up too much space in the engine bay--only negative about the big blocks

 

[340sFastback]

The small block mopar deck height is plenty tall for a 4" stroke crank. I would check out that bore diameter and compare it to the specs of that piston. I believe my bore was .0045" bigger then the pistons. I also run the KB 745s.

You don't need a main girdle. If you got main studs that is all you need.

 

[moper]

Yes, the 4" arm with the rod ratio of 1.55 will wear a hell of a lot faster than 1.85 which is the 340 rod ratio. I'm not familiar with that shop, but that's not real telling. There's more I dont know than more I do. The things that will affect the wall stability are stroke, rod, piston, wall thickness, wall finish, and cleanliness. The only things we have full control over are the last two, and we can check for the third. If the wall finish is rough, they will wear faster adn wear the pistons faster. I would say pull a couple rods and actually measure the piston and the bore. Short pistons rocka lot at TDC, and .005 is a lot of side clearance. But, if it's all right, the wall clearance tightens up when it's at operating temp. I'll also note ring seal also goes away a lot faster. My life expectancy for them is 25-30K miles before they will need attention. Most vehicles are not driven daily or tremendous distances, so that's not an issue. I have seen one or two go twice that, but a lot depends on the machining and parts used.
Off topic, but this is why I'm not for strokes longer than 3.915 in B wedges.

 

[airwoofer]

Great discussion - and yet another reason FABO is such a great resource. I have talked with the builder who thinks the indications on the cyl wall are no big deal. I think the bores are finished properly and the engine did have quite a few dyno hours.he I just wish it had coated skirts, I think.

This brings up the topic of coatings on the skirts and coatings on piston faces and the combustion chambers on aluminum heads. Do thermal coatings make the supposed 1 point of compression with alum heads go away - ie bump compression with thermal treatments?

I am on the road up near Carlilse picking up body parts for da fish. Saw a few cool Mopars at the dude's house. Life is g.ood

 

[Guitar Jones]

Why stink money it to something that might not withstand much abuse--why not just get a stock stroke BBM-be cheaper and last longer--yeah takes up too much space in the engine bay--only negative about the big blocks

Well actually there are other negatives about big blocks, they are also heavy and the stock blocks aren't any better than a small block when it comes to handling horsepower.

Some of us would rather do something different as well. I had a very nice 550 horse 440 I was planning to stick in my Duster when I got it but after looking at it and the 340 that was already in it I was really on the fence about what to do. Then some bozo told me I couldn't run 10's with a 340 in a street car so that settled that problem, it had to be done and the 440 was sold at Garlits' show that year. lol

 

[moper]

Honestly, the rod ratios are low in the B/RB strokers too. Do you think the end result is any different? They wear just as fast.
On the coatings... I think they would help on the friction part. I know for a fact they do. But it's a temperary thing. It's not forever. On the temp coatings.. Yes, they work well. But in terms of detonation resistance... I dont think they would help too much. Possibly make a situation worse depending on the cause of the detonation.

 

[Fingers]

Then some bozo told me I couldn't run 10's with a 340 in a street car so that settled that problem, it had to be done and the 440 was sold at Garlits' show that year. lol

I just love the way people say something can't be done, because they haven't been able to.
Then I really love the looks on their faces when someone shows them it can be done.

 

[RustyRatRod]

Sorry, I'm callin bullshit. The small block chebbies all have rod ratios in the 1.5s and they are some very good engines......regardless of the hooha and jokin around we do about them. The 400 small block has a 3.75 stroke and a 5.65 rod which makes it have a 1.493 rod ratio. They don't wear the cylinders any worse than anything else. I've torn down lots of them with well over 100K that still had cross hatch in the walls. Find something else to argue about. This ain't it.

 

[TXDart]

Great discussion - and yet another reason FABO is such a great resource. I have talked with the builder who thinks the indications on the cyl wall are no big deal. I think the bores are finished properly and the engine did have quite a few dyno hours.he I just wish it had coated skirts, I think.

This brings up the topic of coatings on the skirts and coatings on piston faces and the combustion chambers on aluminum heads. Do thermal coatings make the supposed 1 point of compression with alum heads go away - ie bump compression with thermal treatments?

I am on the road up near Carlilse picking up body parts for da fish. Saw a few cool Mopars at the dude's house. Life is g.ood

I have the same question,I purchased some used Ross pistons for a 416 build and they have minor wear on the skirts...

 

[1wild&crazyguy]

bore gauge, check for taper.

.005 isnt bad with a forged piston, they will maybe burn a lil oil sooner with the piston able to move/rock more....but thats life and typical when clearancing a forged piston for strip use. back in the day u'd see .008 skirt clearance..

bore gauge, and pics would help.