What's involved in a piston swap?

[KenH]

What\'s involved in a piston swap?

Considering upgrading my pistons from cast to forged if the amount of work and cost is not too extensive. The car has 27K miles on it and no known issues. What is involved in a piston swap with this many miles?

 

[dansauto]

Re: What\'s involved in a piston swap?

intake manifold and heads have to come off, pan has to come off. Pins off the crank and pull the pistons up thru the top. get new rod bearings and connecting rods too while you are doing it. Diamond pistons are the best value.

 

[XLR8]

Re: What\'s involved in a piston swap?

The most important thing to remember is that the conecting rods for the cast pistons are longer than the ones for the forged pistons. So if you are going to use Mopar pistons you will need to change the rods too. If you buy custom pistons you can just do the pistons if you tell the people making them what you are doing.

 

[KenH]

Re: What\'s involved in a piston swap?

If I did it, I was thinking about just going with the ones that Roe offers and keeping the stock connecting rods. Do the cylinders typically have to be hone/bored with this many miles or can you just drop in a fresh set of rings along with the pistons?

 

[Viper TT/10]

Re: What\'s involved in a piston swap?

the major cost for piston swap will be parts if you do the tear down and assembly yourself. i would machine hone the the cylinders,crankshaft journals and balance everything before reassembly, with new rod bearings and crankshaft bearings. you mind as well change the lifters since you'll have everything apart($300) for non bleed down type in our 01's. and again since everything is being done and apart a cam swap would be a good idea. only thing left after that is a nice set of ported heads.

sorry for adding so much more to the list, but that is what always happens to me when i think i'm just going to do a little simple modification.

 

[hemibeep]

Re: What\'s involved in a piston swap?

As far as what work to do.
I would definately atleast hone the cylinders. The hone pattern should match what the ring manufacturer recommends.

Changing from cast to forged will change the recip. mass and need a crank rebalance.

I had forged internals, but used new Ross pistons and file fit rings.

Also, the factory pistons have a .020 pin offset to preload the pistons, this keeps piston rattle down, the new pistons are no offset so you can just hear a little slap at idle.

My ross pisons where around 60 grams lighter, but not sure of the difference on cast.

 

[gotV10]

Re: What\'s involved in a piston swap?

i have been told by several that have done the swap that there is no need to rebalance.....anyone else hear the same thing? i am thinking of doing the same. i believe Chuck T. even confirmed this, i could be wrong though. Chuck please correct me if i am.

 

[hemibeep]

Re: What\'s involved in a piston swap?

gotv10,
I'm sure not the expert on these motors, but whenever I take an engine apart, I like to do anything I can to help it run better. Many, if not most, production engines are not balanced and run fine. I think the crank balance was around $200, as it did not need resized.

 

[carl B]

Re: What\'s involved in a piston swap?

I fitted a set of Roe pistons to my rods without any ballance issues

Carl

 

[Chuck 98 RT/10]

Re: What\'s involved in a piston swap?

I thought the piston-to-wall clearance was different between cast and forged pistons. Seems to me the cast pistons didn't expand as much so they has slightly closer tolerances.

Do your homework. Seems like an awful lot of trouble to do all that work for just a piston swap, particularly for the reasons you want to do it.

Call Levin or Heffner.

 

[Joseph Dell]

Re: What\'s involved in a piston swap?

You need to consider a different piston size (3.995" vs. 3.997") when doing a 96-99 vs an 00-02 block. 3.997" required for the creampuffs. Someone explained to me why once, but i forget the details. something about expansion of the cast vs. forged material.

you've got a PM, but there is NO reason to do a piston swap unless you broke something or want to change your set-up to run more power. These motors (even supercharged) will run for a loooooooooong time and do NOT need to be refreshed this soon.

my .02...

Joseph

 

[gotV10]

Re: What\'s involved in a piston swap?

i am wanting to do the swap so i can get blown. that is supercharged i mean. dell, how far are you from carroll co. ga? i will be moving there next friday.

 

[gotV10]

Re: What\'s involved in a piston swap?

can someone expand on what is needed ie piston size as touched on above, for a 2000 car. also are there options on "brand" of piston/rings, if so what is recomended?

 

[joe117]

Re: What\'s involved in a piston swap?

Ken,
It sounds like you never rebuilt an engine before this.

I don't think I'd make this my first rebuild.
Get someone to do it for you or at least get an experienced person to help you.

There are a few little things that must be done right.

 

[KenH]

Re: What\'s involved in a piston swap?

Joseph, thanks for the detailed PM, very informative.

Joe117, I have rebuilt a few motors a long time ago. Even took some college classes on engine machining. Skills are rusty and no one wants to mess up a Viper engine including myself, so I probably wouldn't tackle it on my own.

My primary reason for asking is that I am running 6.5lbs on the stock cast pistons. It is impossible to guarantee that the car will never have detonation. Air temp changes alone change the tune a lot and I have to tweak the tune occasionally to keep the car from detonation. I figured that if I popped a piston, it would take out a cylinder completely and I would be looking at a total rebuild for perhaps $6K when I could have just swapped the pistons for perhaps $2K and kicking myself the whole time. If that is not the case, then I'm not too worried about upgrading until I feel the need for more HP and if a piston pops in the mean-time, I'll deal with it then.

--- Ken

 

[ceieio]

Re: What\'s involved in a piston swap?

Ken - I wouldn't try to do it "in frame", I would pull the engine.

You will pretty much need a "full rebuild" gasket set since you will be pulling the top and the bottom of the engine apart. You will have unnecessary gaskets, but my experience with other engines has been that is often cheaper to get the full set.

With so few miles on it, you will likely not have to worry about a ridge at the top of the cylinder. The one thing to check is that the new piston's upper ring goes no higher in the bore than the old one did or you may need some light machining depending on how far the bore was originally machined.

When I put new rings in I like to give a light hone to make sure that the rings seal well. I haven't done this in a while so ring technology may have changed - talk to your supplier. A light hone is easy to do.

You could choose to replace the rod and main bearings; at a minimum, inspect them closely for wear. Since you run boost, I think it would be a good idea to pull the main caps and check the mains out. There is very likely nothing worn in the rotating assembly, but at that point it is so easy to check that you might as well do it.

With only 27K on the engine your oil pump should be fine. I don't know if you can see the pump gears on a Viper oil pump, but if you can, inspect them for unusual wear or foreign object damage and replace if necessary.

You might also consider putting in a new clutch disk while things are apart, again most of the work to access the disk is done, and the disk is cheap compared to pulling it later to replace.

Use plenty of assembly lube when you reassemble, and you should be off to the races, so to speak.

Craig

 

[Joseph Dell]

Re: What\'s involved in a piston swap?

I've done many a viper piston swap in the motor. I don't think (nor would i recommend) pulling the motor just to do it.

as for the issue of breakage, just b/c a piston goes, it does NOT mean that you toast the block. depends on how back it goes boom though. if you sense a problem and stop driving, then you are probably fine. if your piston knocks a valve and the valve comes off then it could be worse.

Maybe the best $$ would be spent on a good A/F gauge...

PM on the way shortly...

JD

 

[Dave T (BADVENM)]

Re: What\'s involved in a piston swap?

My '04 SRT Ram blew a rod out the block on a dyno run. I'm getting a slightly used '03 Viper motor and will be upgrading the pistons to better support the Paxton. From what I'm told the '03 had the strongest rods of any Gen III motor made.

Anyway, Woodhouse will be doing the work and from I was told they will need to true the big end and have a machine shop press on the pins. I will then get a ring set and all the bearings.

Not sure if this helps. I'm sure their are many avenues to go.

 

[KenH]

Re: What\'s involved in a piston swap?

Maybe the best $$ would be spent on a good A/F gauge...

PM on the way shortly...

JD

I have a Wideband Commander installed and wired into my VEC2 which I use for tuning.

Even when everything is tuned well (by well, I mean about 11.5-11.8 A/F and conservative ignition advance of no more than 3 degrees with my water/methanol) , every so often I will sometimes get a little detonation when I first get on the throttle, but I can't reproduce it on demand. Almost like there is some variable at play that is not consistent between runs even when the temperature is the same.

I assume it might be a slight variance in how the water/**** injection kicks on in relation to how quick the boost is kicking in. I have recently converted from windshield washer fluid to 50/50 mix to remove that as a possible variable. I do think the water/methanol injection does complicate the tuning considerably.

 

[Joseph Dell]

Re: What\'s involved in a piston swap?

Ahh... the initial detonation. This is a function of ALL of the W/M setups. When you get on it, the water doesn't come on instantaneously. and even then, it has a long path to travel before it gets to the motor. _every_ car I've ever tuned with water/**** has done this.

JD

 

[KenH]

Re: What\'s involved in a piston swap?

Yeah, there seems to be a fine line between stopping detonation when first hitting the gas and drowning the spark. Glad to hear I am not the only one. My hope is that the duration is short enough that it is not a significant stress on the engine.

 

[Dave T (BADVENM)]

Re: What\'s involved in a piston swap?

I remember something on my dyno charts where the air/fuel initially is in the 14 range (like 2000-2500 rpm) then by 3000 rpm drops to the 11-12 range. This initial richening could/does create problems? I believe Dan Cragin has a program to remove it in the lower rpm's.

 

[Joseph Dell]

Re: What\'s involved in a piston swap?

cruising on the street N/A, an A/F ratio should be about 14.7. so the dyno operator has some "input" into what the sheet looks like. it is perfectly normal for the dyno to reach lean when the run starts...

JD

 

[Viper TT/10]

Re: What\'s involved in a piston swap?

why not put a purge on the w/m system. that way you can spray a little w/m before goin full throttle? had on on my old set up.you can also sit in the staging lanes and purge before any 1/4 mile runs too.

 

[Boxer12]

Re: What\'s involved in a piston swap?

My '04 SRT Ram blew a rod out the block on a dyno run. I'm getting a slightly used '03 Viper motor and will be upgrading the pistons to better support the Paxton. From what I'm told the '03 had the strongest rods of any Gen III motor made.

Anyway, Woodhouse will be doing the work and from I was told they will need to true the big end and have a machine shop press on the pins. I will then get a ring set and all the bearings.

Not sure if this helps. I'm sure their are many avenues to go.

Man, that had to ****.

 

[Dave T (BADVENM)]

Re: What\'s involved in a piston swap?

Boxer, it really *****. Not sure if one person or persons are to blame. The truck had nitrous/propane on it then the Paxton. I bought it knowing it had the Paxton but didnt know it had nitrous/propane. I also cant find out who tuned it after the Paxton install and how much juice it was running.

Either way, part of it is my fault but I dont think all of it should be. Anyway, she'll be up and running in the next few weeks I hope...better then ever.

 

[ceieio]

Re: What\'s involved in a piston swap?

Ken - the reason I suggest you pull the block is that you have had either pre-ignition or detonation (they are different, but can be related). This can cause undue bearing wear in short order.

My supercharged engine experience is limited to a Keith Black Hemi in a AA rail, so I realize that the pressures and such in a street engine are less, but still elevated in your case. (OK, my Detroit Diesel toys are blown too but that's different!).

The first place you will likely notice wear damage from detonation is in the topside rod bearings. If you see unusual wear there, then pull the crank for sure and check the bearings. I suspect that will be easier with the engine out.

Saints be praised I never lost one this way on the KB, but the 335 Waterman Chevrolet was a different story. Bearings can go in a singe pass when the engine is out of tune (voice of experience).

I have never been so lucky as to have a piston failure that did not cause ruinous damage, although I know people that have been lucky. Even if you just get a couple of dents in the heads from a broken ring deck, those edges can become sources for hotspots which leads to pre-ignition, especially under boost.

As I said before you are probably OK to do as JD says, but it all depends on how you feel about this particular car and your knowledge of what stresses it has been subjected to. Under the right circumstances, I would just swap the pistons too.

Just an opinion for you to consider while you make up your mind on what to do with your car!

Craig

 

[Jack B]

Re: What\'s involved in a piston swap?

Joe:

just to chime in, a lot of people don't want to hear this, but, the dynojet a/f sensor/logic skews the a/f dramatically. When I first started dynoing, our operator was very proud of scraping the the Dynojet a/f setup because of its inaccurcy. At that time I thought it was marketing hype. In substanciation this dyno operator was also an assembler and developer for Dynojet. He has probably set up more dynojets than all the rest of the installers.

Since that time we have two cars that run in-car a/f setups. Our first dyno source has moved away an we now dyno at shops that have the Dynojet brand a/f setups. If you want to get as accurate as possible you must have them turn the smoothing all the way off. Secondly, they should start the run (graph-on) after the driver floors the car. This gets rid of some but not all of the smoothing. By doing the above you should see a difference from the normal pull where they turn on the graph prior to accelerating. You will still end about 1 point high at the start and about 1/2 point high at the end.

If you don't believe this have them kill the pull in the middle, the engine is now a pump and the a/f should be 21. On the dynojet it won't be 21 for several seconds, just indicating the error in there smoothing.

In ending, keep in mind that many dyno's have a/f data that contains drastic amounts of smoothing and this is nothing more than averaging in a prior time period. Since the prior time is a lean period this throws the whole curve high (lean).