Changing cast to forged pistons

[BOTTLEFED]

I did a quick search on this and didn't find a definitive answer to my question.
So what I would like to discuss is:
What is needed to swap the pistons from cast to forged? - parts, machine work, etc.

I'll be doing all the tear down and reassembly myself so the labor cost will only include the machine work.

The problem I found in previous threads about this is everyone giving advice on what to do while you are in the motor.
I DO NOT need to know what I can or should do while the motor it apart. I have inspected the main and rod bearings and they look great. In fact this motor was out of a '98 and originally should have had forged pistons but looks like it was rebuilt and cast pistons were installed ( I seem to be running into this a lot ), thus it should be in pretty good shape since there were not many miles on the car (28k). The heads are from another motor.

I guess my main question is, Do I need to rebalance the assembly when changing the pistons?
It seems like when Arrow rebuilds these motors they like to replace the forged pistons with cast. So do they rebalance the crank when they do this or do they just swap them out?
Is there a large enough difference to throw off the crank?

My other dilemma is going with new rings or just using the old ones. Are the rings on the cast pistons the same as the ones for the forged pistons? I'm guessing a good hone on the cylinders will in order, but will rings be necessary?

I would like experienced answers, not "well I heard..." answers. I also DO NOT need to know about cast pistons and their advantages, or any questions why I want to change the pistons. I have a Roe S/C and I plan to run N2O. I'm tired of going through motors and I need to get this car on the road before winter comes. I'm not looking to send this motor out to get rebuilt; it doesn't need that. I just want to change the pistons.

Thanks you in advance for your knowledgeable help. I know I can count on you guys for advice

-Tim

 

[SquadX]

Well, I am going through the same thing right now. Just wanting to change the pistons from cast to forge for a little "insurance". I did speak with Chuck on this and was told if your running no more then 700 rwhp then just swapping the pistons would be ok but would need to rebalance the crank if the weight of the pistons differ. Chuck please chime in if I misunderstood your answer.

Also, I know that stock is 9.6:1 so anything lower would result in less power from NA but would be a must in your case since your running the ROE.

Tim I hope that helps some and I am looking for experienced replies as well so I am staying tooned and if I hear more on this, I 'll PM you Tim as I said, I am in the middle of doing this right now.

 

[2001 GTS]

I just put 11.5:1 compression JE pistons in my motor. It just had to be spec'd right. They are using floating wrist pins on the stock forged rods. Chuck told me that anything under 900rwhp is fine on the stock rods.

You will need to re-balance for sure, and why use the old rings??

 

[BOTTLEFED]

I'll be getting the rods and pistons so the rods are not an issue.

I would reuse the rings because this motor obviously has very few miles on a rebuild. I'll have them spec'd to make sure they are good.

It is just very difficult to find a local machine shop that can balance a V10 crank.

 

[SquadX]

Sorry to hackjack the thread but is there a weight or clearance or whatever issue with changing from Stock cast to stock forge? Does crank need to be rebalanced or any machine other machine work in doing this?

 

[BOTTLEFED]

I have the two in my hands and there is a considerable weight difference.
I'm trying to find a machine shop locally that can balance the assembly.

 

[1BADGTS]

Of coarse you have to rebalence since pistons are different weights.Why would you even consider using the same rings (how much are pistons tinds ,a few hundred bucks)Take it from a guy who has gone thru this quite a few times (my old GTS trapped 132 mph on motor alone and stock tires ) plain and simple if you tale the fast and CHEAP way in a rebuilt it will come back to haunt you.The correct way is to have ALL the tolerences checked( including cyl walls )and replace (NEW )rings,gaskets and bearings.If you dont have the money wait untill yo do because it will cost you more money in the long run.

 

[RTTTTed]

You want to phone a piston supplier (like Macedo Motorsports/M2) and ask Larry Macedo about this question. Some pistons are stock replacement weights and some are lighter for racing. Some pistons use lightweight wrist pins and some don't. Many can be "mix and match". Tough to find a machine shop that will help you "just do rods and pistons" without spending thousands on machine shop work (Most of it unneeded). But ... many people want a warranty.

Anyway, since the rings do most of the "wearing out" you MUST replace them. The rings (except cheapo junk) come with coatings to help break-in. The timing chain, rings and bearings are what gets replaced in a "rebuild" everytime. They're the cheapest parts in the engine. THEN the engine is rebuilt, crank. block, etc. don't matter if they're in good shape.

You can pull the engine, take it apart and check the bore for straightness with a bore guage. It should be straight enough so that it shouldn't need a bore. I would have the bores power honed straight. Order your pistons to fit the bore of your particlular block. Different alloys have different expansion rates and custom pistons can be ordered if need be. Call Larry at Macedo Motorsports (site sponsor) and ask him to sell you the parts you need. Tell him I sent ya/ Haha.

Larry used to build the racing engines for John Hennessey and is one of the most knowledgeable I know. Not just a "tech or mashinist", but also a researcher.

Ted

 

[plumcrazy]

this sounds like a recipe for another disaster.....

send this motor out and get it built right the first time..... TRUST ME ON THIS !!!

 

[1BADGTS]

this sounds like a recipe for another disaster.....

send this motor out and get it built right the first time..... TRUST ME ON THIS !!!

DEFINATELY i wouldnt put my lawn mower together the way the way hes talking about putting this engine together.I believe he also wants to use NX as well.

 

[1BADGTS]

I have the two in my hands and there is a considerable weight difference.
I'm trying to find a machine shop locally that can balance the assembly.

Your talking about GRAMS here.You put that together with an unbalenced rotating assembly you will be in a world of hurt and could lead to catostrophic problems.

 

[1BADGTS]

PS call Nick at Modern (732 )222-3679 if you ship him the rotating assembley he will balence it for you at a very fair price.Very experienced on Gen 2 Viper Motors as well.

 

[plumcrazy]

i dont know modern, so i cant speak for them (im sure theyre good)....but there are only TWO people on this earth i trust with MY engine....

Greg good 713-290-1103
and
Doug Levin 954-434-9356

BOTH have done me right and will ALWAYS have my business.

BOTH should be called and asked for an opinion if ya ask me

 

[BOTTLEFED]

this sounds like a recipe for another disaster.....

send this motor out and get it built right the first time..... TRUST ME ON THIS !!!

Phil,
I don't think you read my post at all. The motor needs to be rebuilt as much as the motor in your car. There is nothing wrong with it, except I want stock forged pistons.

I did not say I was going to do anything the wrong way. I was just asking opinions on how to do it.

I may call those guys for their opinions, thank you

 

[BOTTLEFED]

You want to phone a piston supplier (like Macedo Motorsports/M2) and ask Larry Macedo about this question. Some pistons are stock replacement weights and some are lighter for racing. Some pistons use lightweight wrist pins and some don't. Many can be "mix and match". Tough to find a machine shop that will help you "just do rods and pistons" without spending thousands on machine shop work (Most of it unneeded). But ... many people want a warranty.

Anyway, since the rings do most of the "wearing out" you MUST replace them. The rings (except cheapo junk) come with coatings to help break-in. The timing chain, rings and bearings are what gets replaced in a "rebuild" everytime. They're the cheapest parts in the engine. THEN the engine is rebuilt, crank. block, etc. don't matter if they're in good shape.

You can pull the engine, take it apart and check the bore for straightness with a bore guage. It should be straight enough so that it shouldn't need a bore. I would have the bores power honed straight. Order your pistons to fit the bore of your particlular block. Different alloys have different expansion rates and custom pistons can be ordered if need be. Call Larry at Macedo Motorsports (site sponsor) and ask him to sell you the parts you need. Tell him I sent ya/ Haha.

Larry used to build the racing engines for John Hennessey and is one of the most knowledgeable I know. Not just a "tech or mashinist", but also a researcher.

Ted

I don't want or need racing pistons or a racing motor for that matter. I just want a stock, forged piston engine.

 

[BOTTLEFED]

I seem to be finding the same mindless advice I found in my searching.
Let me repeat what I stated in the first post, "I DO NOT need to know what I can or should do while the motor it apart"

If I wanted to throw $$ away I'd send it to AIG.
I don't need a rebuild, just a piston swap.

Honestly, thank you guys for your opinions.
I don't hold it against you for regurgitating the info you have for any and all engine questions. I just wanted some answers that were specific to this question only, not how and where to get an engine rebuilt.

Chuck says the rings are reusable as long as they checked for clearance and are within spec. I will replace if not within spec have any defects. He does recommend balancing the crank for the forged pistons and rods.
The bearings look new and the journals are fine.
Timing chain has less than 30k miles on it, and that's if it wasn't replaced by Arrow. When was the last time you heard about a Viper timing chain breaking on a street car?
I have found a machine shop that can balance a V10 crank. They think the block will just need a light hone.

 

[RTTTTed]

One problem with not changing out rings or timing chain would be that the engine would then be called "reconditioned" ,meaning that one or some defective internal engine parts have been replaced. Rebuilt means that all high wear parts have been replaced (rings, bearings, timing chain and oil pump) and all parts were inspected and in excellent/new condition. Resale value of probably about $5,000 between the two.

As far as the bearings go, I was taught that after only a few thousand miles the molecules of the bearings were 'crushed' to that rod and rod cap and they were unusable a second time. They also will fall out of the rod cap whereas the new bearings will hold themselves in place once installed. When you torque the rod bolts down the bearings 'crush' into place and after the engine's been running for awhile the bearings lose their crush. Hopefully I've explained it correctly?

As far as using stock forged pistons I wouldn't. Aftermarket pistons come however you order them (9-1 compression) and are stronger than the old stockers. Aftermarket are usually also significantly cheaper.

Unless you're referring to USED stock pistons ... then I can't think of any reason you couldn't just throw a bunch of USED engine parts into an engine if you BLUEPRINTED the engine to stock specs. And checked the balance as well. I wouln't expect the best performance though.

Ted

Timing chains are probably the first thing needing replacement on these engines with rings being the second parts that would probably wear out. Changing the chain and rings for $350 should extend the engine life back to same as new instead of new - 30,000mi.

I've built engines like what you're wanting to build and raced as well as worn them out after the work. They worked great. I built many of my engines this way because I wore out a lot of cars and put on a lot of miles. Also didn't want to be throwing away good parts.

My engine was completely rebuilt at 10,000mi. when the forged pistons were installed. If you've got the money this is the way to go, no doubt.

 

[plumcrazy]

Im pretty sure DLM told me whay back when, he can get you pistons or point you in a direction of a set thats similar weight to OEM and i think ROE can too....

but without a doubt id change the rings and bearings too. theyre too cheap NOT to

 

[1BADGTS]

I seem to be finding the same mindless advice I found in my searching.
Let me repeat what I stated in the first post, "I DO NOT need to know what I can or should do while the motor it apart"

If I wanted to throw $$ away I'd send it to AIG.
I don't need a rebuild, just a piston swap.

Honestly, thank you guys for your opinions.
I don't hold it against you for regurgitating the info you have for any and all engine questions. I just wanted some answers that were specific to this question only, not how and where to get an engine rebuilt.

Chuck says the rings are reusable as long as they checked for clearance and are within spec. I will replace if not within spec have any defects. He does recommend balancing the crank for the forged pistons and rods.
The bearings look new and the journals are fine.
Timing chain has less than 30k miles on it, and that's if it wasn't replaced by Arrow. When was the last time you heard about a Viper timing chain breaking on a street car?
I have found a machine shop that can balance a V10 crank. They think the block will just need a light hone.

No one has the right to tell someone else how to spend their money BUT you have to realize we are trying to help you here as we are all fellow Viper owners and this is one of the purposes of these forums.(Judging by the facts that you want to resuse rings ,bearings and timing chain from an engine with 30000 miles that SHOULD? make over 800hp you need all the help you can get .Your rebuilding the engine yourself and dont know if you need to rebalence the rotating assembly if you change piston weights ?The persons doing the machine work THINKS the block just needs a light hone .(Did he actually look at the block or mike the walls or more likley you described the condition to him over the phone.)Either all of the above is a very bad joke or someone is giving you very bad info that in all liklehood will result in massive future spending )

 

[Simms]

but without a doubt id change the rings and bearings too. theyre too cheap NOT to

Agree 100%. Not a place to cut corners.

 

[BOTTLEFED]

(Judging by the facts that you want to resuse rings ,bearings and timing chain from an engine with 30000 miles that SHOULD? make over 800hp you need all the help you can get .

the motor was rebuilt, it does not have 30k miles on it

Your rebuilding the engine yourself and dont know if you need to rebalence the rotating assembly if you change piston weights ?

I'm a certified auto tech and I know what I'm doing. I was asking this because Arrow apparently throws cast pistons in forge piston motors so I wondered if the pistons were interchangeable and the assembly balanced out to the same.

The persons doing the machine work THINKS the block just needs a light hone .(Did he actually look at the block or mike the walls or more likley you described the condition to him over the phone.)

Yes I called them on the phone. I did not drag my engine around town asking opinions. Just like if I call DLM or your Modern guys, I will get an opinion of what needs to be done. Obviously the shop will not know until they get the block. And no, the block has not been mic'd.

Either all of the above is a very bad joke or someone is giving you very bad info that in all liklehood will result in massive future spending

I don't think Chuck Tator's info is bad. I will take his word over your opinion on any and all advice, from rebuilding Viper motors to which shampoo to use because I know and trust him.

 

[BOTTLEFED]

Im pretty sure DLM told me whay back when, he can get you pistons or point you in a direction of a set thats similar weight to OEM and i think ROE can too....

but without a doubt id change the rings and bearings too. theyre too cheap NOT to

sorry Phil but bearings are not cheap (at least for me).
They have to be special ordered and fitted for each main cap. I was quoted $80 per set (ea. cap). Then I will have to pay the machinist to mic the caps and journals and find the correct bearing size for each one. At $85/hr for the machinist this will be a huge bill for the bearings alone.

 

[1BADGTS]

the motor was rebuilt, it does not have 30k miles on it



I'm a certified auto tech and I know what I'm doing. I was asking this because Arrow apparently throws cast pistons in forge piston motors so I wondered if the pistons were interchangeable and the assembly balanced out to the same.



Yes I called them on the phone. I did not drag my engine around town asking opinions. Just like if I call DLM or your Modern guys, I will get an opinion of what needs to be done. Obviously the shop will not know until they get the block. And no, the block has not been mic'd.



I don't think Chuck Tator's info is bad. I will take his word over your opinion on any and all advice, from rebuilding Viper motors to which shampoo to use because I know and trust him.

Maybe i am missing something but if your certifyed you should know (without having to ask )about forged piston verses cast gram weights.No competant engine builder will comment or have an opinion as to whats needed in a rebuild over a phone description from a customer WITHOUT having actually seen and miked out the motor in person. Your trying to cut corners on a 800 hp engine if you want it to LAST for any period of time you really should take it to someone that will tell you the truth instead of what you want to hear.All the apove posts from are from people who g=have been there before.

 

[1BADGTS]

PS i really would like to know how your going to get used bearings and piston rings to SEAT properly after they have been removed .(products are not made to be reinstalled after already used).One failure as a result of a bearing not seating properly (metal on metal )=catostrophic engine failure.

 

[RTTTTed]

sorry Phil but bearings are not cheap (at least for me).
They have to be special ordered and fitted for each main cap. I was quoted $80 per set (ea. cap). Then I will have to pay the machinist to mic the caps and journals and find the correct bearing size for each one. At $85/hr for the machinist this will be a huge bill for the bearings alone.

"Fitted to each main cap"? Then the block is warped and needs an alignbore???

Of the thousands of engines I've rebuilt the only "bearing fitting" is either .001, .002" undersized or standard, .010", .020" and 1 engine the customer uinsisted on .030" bearings according to availablilty and crankshaft size. I blueprinted every engine I ever built and never had a "machinist" custom fit (grind? bend? taper? pin?) any of my bearings. Is this a new proceedure that I've never heard of? What tools are necessary? I've always blueprinted using Plastiguage.

Ted

 

[BOTTLEFED]

Maybe i am missing something but if your certifyed you should know (without having to ask )about forged piston verses cast gram weights.No competant engine builder will comment or have an opinion as to whats needed in a rebuild over a phone description from a customer WITHOUT having actually seen and miked out the motor in person. Your trying to cut corners on a 800 hp engine if you want it to LAST for any period of time you really should take it to someone that will tell you the truth instead of what you want to hear.All the apove posts from are from people who g=have been there before.

OK, if you think no competent engine builder will give an opinion on what to do then I will call your Modern shop and see what they have to say. I'm sure they will give me some advice and a quote on pricing.

So you are saying that everyone giving advice on this thread has had a Viper block torn down to the crank and pistons? and they have rebuilt the engines in their Vipers?
I think not

 

[BOTTLEFED]

PS i really would like to know how your going to get used bearings and piston rings to SEAT properly after they have been removed .(products are not made to be reinstalled after already used).One failure as a result of a bearing not seating properly (metal on metal )=catostrophic engine failure.

Yes the bearings seat just fine after being removed, ask your Modern shop
How else do you think an auto tech is supposed to check if it is within specs during an inspection?
Have you ever heard of plastigauge?

You're going to have to try a lot harder to make yourself look smart; your spelling sure isn't helping
BTW, the term is MIC not MIKE

 

[BOTTLEFED]

"Fitted to each main cap"? Then the block is warped and needs an alignbore???

Of the thousands of engines I've rebuilt the only "bearing fitting" is either .001, .002" undersized or standard, .010", .020" and 1 engine the customer uinsisted on .030" bearings according to availablilty and crankshaft size. I blueprinted every engine I ever built and never had a "machinist" custom fit (grind? bend? taper? pin?) any of my bearings. Is this a new proceedure that I've never heard of? What tools are necessary? I've always blueprinted using Plastiguage.

Ted

Ted,
yes, I think it is a modern technique for tighter clearances. I'm only relaying the info I got from my machinist when he called Sealed Power to order new bearings. I guess there are certain measurements for the journals and bearing surfaces that correspond to letters (A-H) when you order the main bearings. It is done this way from Arrow.
This was confirmed by Chuck when I ask him about ordering bearings.
I'm not a professional engine builder so I did not understand the exact details. You could probably call Doug Levin for a more specific description.

 

[BOTTLEFED]

To end this discussion,
on Phil's recommendation I talked to Doug Levin today. He's a great guy and we discussed my options.
I've decided to just install this motor with the cast pistons the way it is. I'll run only a 5# pulley for now with a conservative tune.
Meanwhile, I'll start collecting parts and $$ for a nice, forged motor that will be freshly built.

Thanks again for all your opinions. When I started this thread I was hoping for input from engine builders, or at least guys that have dealt with this situation before. Good or bad, I guess there just aren't a lot of Viper owners that tear down their motors.

 

[RTTTTed]

As far as Viper owners working on their cars, I seldom meet any owners that do any of the work or understand their cars. It seems that Viper techs don't make enough money to purchase their own Vipers. Of the techs I've talked to one owned a Dart race car and another owned a Nova. Sean Roe, Larry Macedo and J. Hennessey all own Vipers though.

I don't trust anyone to do work on any of my cars so I do it all myself(except rear end gear changes), including paint, body mechanical and electrical. Ported my heads before VOI X when I changed my headgaskets.

I will be looking for a tuner that's smarter than me to help fix the tune on my car in a week or two though.