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View Full Version : Welding forged pistons for higher compression.


JackM
August 1st, 2009, 02:08 PM
Has anyone in here done this? I want to try it as I want 13:1 or more on my 2.4L 4G64 engine I'm working on and it doesn't appear that those are available. If someone does make them, so I don't have to try to weld these, please let me know!

A friend of mine does it to his GM which is a meth 1500+hp car. He is always welding and cutting his pistons to fit into the chamber differently to allow for as much compression as possible. It doesn't seem to hurt them and he has been using the same pistons for a very long time. I would ask him, but he is not the one that does the welding so he doesn't know how to do it.

I was thinking of using 4047 TIG rod as that is going to have the highest silicon you can find for welding. I'll try to weld it the same way I weld center diffs which shouldn't hurt the piston too bad due to the heat as I should be able to keep the heat away from it.

I have a couple of dead forged pistons here that I was going to practice on and see if I ruin them from the heat. I'll measure them before and after, and I may cut them into pieces when I'm done to see if the heat was too much for them also. Any tips you have would be great! The fear I have is they may show no damage when I'm done welding them, but once heat cycled in the car they may change...

What I was going to do was add a little too much weld to the piston to make a dome to fit into the head and then use the milling machine to cut it down so I can have all 4 pistons perfectly the same.

We are getting hooked on high compression here. High compression on a boosted engine with E85 seems to work very well. My brother had 12:1 on his 2.4L and ran a touch over 40PSI of boost with it. If the car is setup right, you can run high compression with high boost pressure and the gains are pretty amazing!

Any thoughts or tips on welding a forged piston would be much appreciated! I would really like to try this and hope it works, lol!

On a welding forum, I found this on a topic where they were welding cast pistons:

I did try to build up a scrap piston crown a while back, but at that time was still having a hard time with aluminum welding in general. Quite a few hours practice and a couple hundred bucks of argon later and I think I am ready to give it another try.

I used 4043 filler here in the fist attempt a couple months back and got too much heat. it did hold up to destructive testing of the cross section pretty well but fractured along an inclusion.

Will do a better job controlling heat next time.

Welding piston domes? No problems there, especially for that little toy engine, 4047 should fit the bill as stated above. Might be wise to stress relieve the casting however, or else it will relieve itself the first time you run the engine and may warp to a shape that invites mr. stick.

They have not welded forged pistons, they are talking about welding cast, so I do not know if what they say will also apply to the forged units or not...

Thanks!

Jack

XakEp
August 1st, 2009, 02:29 PM
I want 13:1 or more on my 2.4L 4G64 engine

o shi

You're insane. I dig it.

JackM
August 1st, 2009, 02:36 PM
If the piston manufacturers were not such a-holes I would love to just have them make what I want, but I have determined that it's impossible. I will have to make my own I guess...

Jack

matthewdesigns
August 1st, 2009, 02:38 PM
If you need to heat cycle/stress relieve the pistons I can put them in my oven here at work to do that. It's computer controlled and I can raise/lower temps at custom rates and intervals to about a 10*F tolerance, up to ~2000*F.

Have you looked into having custom pistons machined to your specs? I know you can CAD the thing up at work.

JackM
August 1st, 2009, 03:31 PM
Yeah, but the piston manufacturers don't give me the time of day. I would love to just have a set made to what I want instead of hacking others, but I just don't have a choice.

Jack

JackM
August 1st, 2009, 04:01 PM
I got some contact info from a person on the Link forums. I'll give a custom made set another shot. If I can't get them to do anything for me which won't be a surprise I'll start hacking a regular set I guess.

Jack

6-Bolt
August 27th, 2009, 11:12 AM
I know Magnus will make a high compression piston (12.5:1). However, it would cost $729 or possibly more.

http://www.magnusmotorsports.com/engines/dsm.htm

Josh Warriner
August 27th, 2009, 12:21 PM
Yeah, but the piston manufacturers don't give me the time of day. I would love to just have a set made to what I want instead of hacking others, but I just don't have a choice.

Jack

Have you tried Ross? I was under the impression they'd do a single set of custom pistons. But it's going to cost you. Probably not more than a grand but I'd expect around $600-800.

Overkill
August 27th, 2009, 12:45 PM
I don't think Jack does business with Magnus anymore

Jack dislikes Ross due to their wristpin design I believe. Not sure if he knows he can upgrade the wrist pins to tool steel.

I know I can get the Ross pistons in the configuration he wants as we just had a custom hi compression set made for my buddies 3.5L stealth motor.

BlueVelocity
August 27th, 2009, 01:20 PM
I know I can get the Ross pistons in the configuration he wants as we just had a custom hi compression set made for my buddies 3.5L stealth motor.


Jasons? If so, yes, those were really nice.

JackM
August 27th, 2009, 01:27 PM
I finally got a hold of a guy at Wiseco (my favorite piston manufacturer) thanks to a couple of people on DSMlink. They are making them now for me. Little brother is going to have serious compression in his EVO and I went stupid with the compression for my 2.4L winter project. I guess we will see which works best.

Ross requires a piston to bore clearance at a minumum of 6 thou. Might be okay for a real race car but that's just way too much for a street car.

Jack

Overkill
August 27th, 2009, 01:35 PM
That is correct Erron and I look forward to hearing and seeing that motor run.

I thought you were the king of piston slap Jack? Wiseco says .004, but if 2618 alloy .005 and then add another .001 for a forced inducted piston. Are you planning on using a different alloy then 2618? If not it sounds like the clearance would be the same as Ross.

JackM
August 27th, 2009, 02:48 PM
Nope, Ross pistons are different and expand more than most of the other manufacturers. I am no piston expert, but due to this the Ross pistons are supposed to be stronger for it, but everyone that I see with serious power seem to use JE or Wiseco HDs.

I really like the Wisecos as they are near perfect out of the box with little to no need to file the rings down, the pin clips snap in easily, and they require a smaller piston to bore clearance. Less work on the assemblers part means there is less of a chance of a mistake. I have also seen them in cars with more HP than I would ever have an live so that's good enough for me.

After you're done with filing the rings down and getting those PITA spiral locks in a set of Ross pistons you might understand.

Jack

6-Bolt
August 27th, 2009, 05:38 PM
I finally got a hold of a guy at Wiseco (my favorite piston manufacturer) thanks to a couple of people on DSMlink. They are making them now for me. Little brother is going to have serious compression in his EVO and I went stupid with the compression for my 2.4L winter project. I guess we will see which works best.

Ross requires a piston to bore clearance at a minumum of 6 thou. Might be okay for a real race car but that's just way too much for a street car.

Jack

Are you still going 13:1 compression ratio? Also how much are the pistons costing you, if you don't mind me asking? Interested to see how much more it cost for custom Wiseco.

JackM
August 27th, 2009, 05:42 PM
I'd have to look at my emails with them but I believe it was just shy of $700 per set and they were the HDs. Takes 1 month or more to make.

Jack

Gimpin
August 27th, 2009, 05:51 PM
wow ... sounds like an interesting build. Hopefully the starter is heafty enough to crank it over. I have heard of the starter struggling on the expo 2.4 motor with the 4g63 head and that nets around 12.5:1

JackM
August 27th, 2009, 09:28 PM
My brother has built a few 12:1 4G64s and no issues with the starters.

Jack

Gimpin
August 27th, 2009, 10:15 PM
My brother has built a few 12:1 4G64s and no issues with the starters.

Jack

cool ... could have been a battery issue too

JackM
August 27th, 2009, 10:41 PM
Could have been. My brother got 220PSI out of a compression test from an old stock junkyard untouched 4G64 bottom end with a 4G64 head bolted on top of two MLS head gaskets, lol! I'm sure if the system isn't in good shape it would be pissed off. He ran 40PSI of boost on E85 with a T04R and no knock with 12:1. E85 man, it freaking rocks!

Jack

t_jolt
August 28th, 2009, 08:03 AM
The thought of going 13.5/14:1 has really crossed my head a lot lately. Yeah its super high compression but if you take your time. do things right, i believe the gains would be crazy.

Mirage
August 28th, 2009, 02:37 PM
What's crazy is that years ago people questioned why I wanted higher compression when I built my original block for my '90.

Only a few years ago a lot of people thought it impossible to run crazy amounts of boost on anything higher than 9:1.
Next new engine I build will be in the neighborhood of 11:1 on E85 in a stroker for the twistys.

Biggest issue I can see with a domed piston is simply getting the proper valve/piston clearances set up with the particular cam profile that's going to be used.

Marcus

JayRolla
August 28th, 2009, 06:08 PM
What's crazy is that years ago people questioned why I wanted higher compression when I built my original block for my '90.

Only a few years ago a lot of people thought it impossible to run crazy amounts of boost on anything higher than 9:1.
Next new engine I build will be in the neighborhood of 11:1 on E85 in a stroker for the twistys.

Biggest issue I can see with a domed piston is simply getting the proper valve/piston clearances set up with the particular cam profile that's going to be used.

Marcus

Maybe when pump gas was in mind.

6-Bolt
August 28th, 2009, 07:09 PM
After reading this, I am really tempted to get higher CR pistons for my rebuild. Thinking about 11.5:1.

Having the benefits of the higher CR would be great, like faster spool. Plus I built my fuel system for E-85 :)

iamtall77
August 30th, 2009, 04:05 PM
Jack, glad to see you guys going this route. I was always a fan of high compression motors, but using pump gas never made that possible. Now with Link and E85, you can do amazing things.

Also, it's probably a good thing you guys are in the transmission business, because the power you're going to be making is sure to break a few transmissions. Any plans to make a pure race car to promote your business?