Are Sierra Pistons Forged?

[CLAYC]

Are Merc replacement pistons made by Sierra forged? Can you mix Sierra with Wiseco Forged Pistons?

Thanks

 

[slasmith1]

Re: Are Sierra Pistons Forged?

I don't know if this will give you the exact info you are looking for but here goes. The pistons in a motor need to have these common characteristics.

1) Same piston surface design.
2) Same bore on all cylinders.
3) Same weight on each piston/connecting rod.
4) same height of each piston and connecting rod.

If I left anything out I'm sure someone will chime in.

 

[CLAYC]

Re: Are Sierra Pistons Forged?

Yeah, I know all of that from V-8 hotrods. I'll be more specific..

Have a 200 EFI that needs new pistons... the bore is standard 3.500 + hone for final 3.501 on 5 holes. The other was bored to 3.020..final 3.021..

Do I put Wiseco pistons (forged), Sierra ( unk if forged or cast) or Vertex cast pistons. Problem being is finding a Sierra or Vertex in .020. I have been told there are problems with cold seize when using Wiseco in standard bore. Was also told the bore needed to be .003 over standard for Wiseco... Now, another trip to the machine shop is going to get expensive. I have no problem allowing the engine to warm up in cold water to avoid cold seize. But we all know if the tolerances are not correct warm-up will not avoid a failure.

Also been told by various engine builders I can mix Wiseco and Sierra Pistons with no problem..

Just got off phone a performance shop who said to stay away from Sierra and Wiseco and go with Vertex (cast) in a standard bore (to include +.015-.030) stock application. Said he's seen lot of problems with the other two pistons.

Any suggestions?

 

[newtong_ware]

Re: Are Sierra Pistons Forged?

Seems like a large difference in the final bore from the 5 cylinders to the 1 cylinder. 3.5 to 3.02 seems huge.

I can't speak for anything other than my experience because I am no expert, but I did a full rebuild on a Johnson 115 4 cylinder last year. I had to bore to .020 over to remove surface damage. I used properly sized Wiseco forged pistons and matching rings and I have had no problems whatsoever. I love the way the motor runs out, and it is a 1976 model.

I used various gaskets and seals and bearings, some OEM and some Sierra. I personally have no problem with Sierra. I did one carb with OEM and one with Sierra rebuild kits just to see and have found no differences.

My gut tells me that I would want the same piston in every cylinder. If that is a problem to do, then dimensions and top surface contours would have to be a perfect match along with weight.

Best of luck to you.

 

[Faztbullet]

Re: Are Sierra Pistons Forged?

Serria,Dolphin,Vertex,Pro,Mallory,Redline,Redrhino and WSM pistons are a cast piston and most are by same maker just one of the above labels slapped on box. Only Wiseco and Wizard ($270 per piston) are forged to my knowledge. All pistons either forged or cast will weigh the same. That is why you can run standard and oversizes and different brands together without upsetting balance.

 

[sb220]

Re: Are Sierra Pistons Forged?

Just for useless knowledge, what are the benefits of a forged piston?

I dont imagine it being much of a cost or ease of manufacturing difference.

Resistance to shattering?

 

[Faztbullet]

Re: Are Sierra Pistons Forged?

Here is a answer from ACL piston manufacturer..

CAST VERSES FORGED


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This is an age-old problem for engine designers. At what sort of power level is it necessary to change from a conventional cast Eutectic/Hypereutectic piston to a forged item? According to ACL's chief piston engineer, the only real disadvantage of a cast piston (in high output situations) is in the case of a piston failure, a cast items is more likely to shatter and damage the engine, as a whole, more than a forged piston.

A big advantage with forged pistons is they generally result in a more ductile material, with the effect being the piston can take a higher level of detonation before failing. This is not such a huge bonus as your engine should be tuned not to detonate in the first place. In extremely high rpm/high horsepower applications, the great strength of the forged piston can add reliability.
In the instance if building of a normally aspirated engine, the is probable little advantage in investing large sums of money in forged pistons, when a correctly-tuned engine with either standard Eutectic items or modern design Hypereutectic (ACL Race Series or similar) pistons will give the same power output and reliability levels.

 

[CLAYC]

Re: Are Sierra Pistons Forged?

Seems like a large difference in the final bore from the 5 cylinders to the 1 cylinder. 3.5 to 3.02 seems huge.

I miss typed the size.. it's 3.5 on 5 cylinders and 3.520 on the other..


Faztbullet... thanks for sharing you knowledge and insight. You've answered many questions others couldn't.

 

[newtong_ware]

Re: Are Sierra Pistons Forged?

I figured you missed the size, I was just checking. I like the forged pistons. My rings seized, the rings shattered and the pistons took a beating too. That is why I bored out .020 over. I did not know the reason for them being better, but after reading other posts, I am glad I got them. I got the Wisecos' for a lot less than $270 per piston, trust me.

"My momma told me...you better shop around!"

>>>>Newt

 

[Frank Acampora]

Re: Are Sierra Pistons Forged?

I just rebuilt an Evinrude V4 looper for a fellow where the stock cast piston shattered the skirt for no known reason. I have also seen stock cast pistons where the wrist pin holes were worn and beat into egg shape. That won't happen with the forged piston unless you forget to run oil.

On my own engines I prefer Wiseco pistons and if I rebuild for someone else, I recommend them. They are well made and balanced to factory weight even in oversizes so you can replace only one.

I did rebuild an 4 cylinder engine where I inadvertantly set the timing to 42 degrees advanced instead of 32--Good thing it was my own engine. The Wiseco pistons melted the crowns a bit but maintained their integrity. I only needed to replace the pistons because they "offended me esthetically" --no cylinder scoring and no overbore necessary. The only reason I knew I had a problem was because aluminum throw-off shorted two plugs. There's the advantage in forged pistons.

I have heard the stories that Wiseco are "crap" but I have probably used 30 or 40 of them with no problems. As far as cold seizing, I have my machine shop hone my cylinders to exact overbore size and I have not yet had any problems.