engine rebuild/ pistons

Slyclone

Slyclone

Well-known member
Just wondering everyones take on pistons. I sold my last set of forged to a guy in south america.

Thinking about a stock engine build. Should I be going back to the forged? Or is the OEM gm hyper stuff good.

I do have some OEM hyperutetics and I'm wondering for a stock truck No modifications would using OEM ones be alright?

My syclone them pistons did not hold up stock. I found #3 had grenaded in cylinder and was blown apart. A major detonation blew it into a few pieces and was still held together and functioning.

I remember the kB l1442 or what ever the number was a popular piston. Or the speed pro ? I forget. I have some stock hypers I was hoping will do the job.
 
Logan

Logan

Member
Re: engine rebuild/ pistons

I guess it would depend on your intent. If you are building a stock motor to sell then why not use what you have but if it is something you are keeping I would lean towards the forged. Plus, when you get the block worked at the machine shop there is a chance the stockers won't work for you if they have to do and boring on the cylinders.
 
Slyclone

Slyclone

Well-known member
Re: engine rebuild/ pistons

Well yea that's all pending compression tests and how I feel after that. Plan on just setting up a stock truck to drive everyday. Or daily.
 
autoaddictions

autoaddictions

Active member
Re: engine rebuild/ pistons

The rods are the bigger issue. If your using new rods in your build then get eagles. There cheap. At that point spend the extra money on forged pistons. SRPs from j&e are most common. If your using stock rods than ID use stock pistons. The rods will fail first.
 
It's just a six

It's just a six

Super Member
Re: engine rebuild/ pistons

On a stock engine, & if you detonate it enough, the pistons blow apart, then that takes out the rods.

The pistons are the first thing that goes when it detonates, the top of the pistons just comes apart.

Seen it & heard it time & time again.:2cents:
 
DaveP

DaveP

Active member
Re: engine rebuild/ pistons

I've pulled a bunch of stock bent rods out of SyTy engines that were still running just fine, including the pistons being OK. Jerry McCoy told me at the 99 Nats that he thought it was detonation that was bending the rods. This was way before many of us knew what we know now. But my experience is the rod can be bent without damaging the piston. So the piston does not "always" go before the rod.

You can't use stock pistons on Eagle rods, because stock pistons don't have circlip grooves for full-floating pins, which is what the Eagles are. Full floating. There's no way to retain the pin.

The last set of Speedpro 2441's I bought was 10 years ago. And it took a long time to find 6 of them then. Are they still available? Perhaps in .030 they might be. I needed Std, and they had to be found in 3 different warehouses around the country to make a set of 6 at the time.
 
Slyclone

Slyclone

Well-known member
Re: engine rebuild/ pistons

Well If something blew apart inside the cylinder walls wouldn't I want the walls to be freshened up and cut? I would not know anything untill I open it up. At this point in time I am just brainstorming and speculating my options. Like I mentioned I would be doing compression tests first to determine how healthy the block really is.

Yea, I had a spare set of SRP forged +.030 I sold. and I still do have some OEM GM pistons which are in fact .030 as well. I was not counting on a clean bill of health...

My syclone block that had a piston drop (prior to my ownership) I dont really think I had a option now that I look back. I had the forged SRP and used them. At that point in time I dont recall my engine guy saying your walls are in great shape lets use a std bore. Plus I remember buying the pistons and for a STD bore forged piston it was costed more than a .030 bore? :banghead: I guess a STD bore is sought after more.

I highly doubt I will be able to slyde with a std bore.
 
Logan

Logan

Member
Re: engine rebuild/ pistons

I don't think STD bore is more sought after. I would think the opposite. I have only built 2 engines so far but I was under the impression that most blocks get .030 unless they are in amazing shapes. I am sure there are guys with more experience in this that can confirm or deny it.
 
Slyclone

Slyclone

Well-known member
Re: engine rebuild/ pistons

I just remember buying the pistons. IT was MORE for a STD bore and Cheaper for the over bore.

Just double checked where I got them from and the prices are all the same now. UP $50 but all the piston sizes vs. price are same.

Being the price difference Than.. I thought that was the case.

DaveP were the SpeedPro 2441's Forged?



Just checked they are. 2441f is a forged part. And yes not really around. I could have Sworn a member here had a set...and claimed he found a few more sets..

So I guess the OEM gm hyperutetics are not worth the time as many newer replacements would be forged anyway.
 
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RealFastV6

RealFastV6

@jb_and_his_coffee
I have a set of coated std bore speed pros. Let me see if I can dig them up. I know I just had them in my hands recently because I got all pissed off that I had to buy a brand new set of +30s because the Ty block needed to be bored. They were lightly used but beautiful shape. Came from a Rockford Racecraft motor that they botched so it didn't live very long. Maybe 4k mi.
 
It's just a six

It's just a six

Super Member
Re: engine rebuild/ pistons

DaveP said:
I've pulled a bunch of stock bent rods out of SyTy engines that were still running just fine, including the pistons being OK. Jerry McCoy told me at the 99 Nats that he thought it was detonation that was bending the rods. This was way before many of us knew what we know now. But my experience is the rod can be bent without damaging the piston. So the piston does not "always" go before the rod.

.
Click to expand...

Just curious as to why were you pulling apart a bunch of Sy/Ty engines if there were running just fine?
 
DaveP

DaveP

Active member
Re: engine rebuild/ pistons

Slyclone said:
I don't recall my engine guy saying your walls are in great shape, let's use a std bore. Plus I remember a STD bore forged piston cost more than a .030 bore? I guess a STD bore is sought after more.

I highly doubt I will be able to stay with a std bore.
Click to expand...

I should have left the Std bore out of my post. I mentioned it in context of the SP's were hard to get 10 years ago, particularly the STD piston I used, where the .030 piston which is much more widely used may still be available. You're right, standard pistons are almost never used during a rebuild. For obvious reasons. The bores are usually not suitable for re-use.

In my case, I used a brand-new, never run 4.3 LB4 short block from GM service parts. I kept the brand new block and crank, and threw away the pistons and rods. It was $1,450 in 2003. Not inexpensive. But stronger than a .030 over bore. I also got the GM crankshaft which is stronger than a Scat, and being std/std it's stronger than a crank with undersize journals.
 
Slyclone

Slyclone

Well-known member
Re: engine rebuild/ pistons

Dave, I k now this is a weird question but how were you able to determine a rod being bent.

Was this something you knew was the problem? Like could you hear a rod knock or some sort of slap? Or some type of misfire and knock due to being unbalance? An audible noise Excuse my ignorance ..

I am not sure how you can identify a bent rod early on if the motor is still running and functioning. (Syclone had blown piston but I was never confronted about THE rod.)

Right now the engine on The other Truck sounded diesel so I'm Betting a wiped out cam lobe or lifter that's been worn to nothing.

In my eyes its a full rip down if a metallic part went up top. Any metal shavings would score the internals and require a cut. Maby all the rods are bent and it looks like a rib cage inside. Everything is still functioning..
 
It's just a six

It's just a six

Super Member
Re: engine rebuild/ pistons

When you have a bent rod, depends on how it bends.

Sometimes they compress, making the rod physically shorter, sometimes when this happens the bottom of the piston skirt will hit the counterweights on the crankshaft. Should be loud & very apparent.

I had this happen on my 65 Malibu SS, (when my friend owned it) It was loud for a little bit, but as the engine ran, it self machined/clearanced the bottom of the piston skirt then the noise when away.

You can have a bent rod & not hear anything also.:2cents:
 
Slyclone

Slyclone

Well-known member
Re: engine rebuild/ pistons

Anyone know the stock gm syclone/typhoon piston # or code.

I don't have my stock ones anymore to cross reference anything
 
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