piston height tolerances

[340rt]

I am building a 340 short block using TRW L2316 forged pistons with the tops milled .018 for zero deck.I will be using eddies with .039 felpro gaskets

I measured piston height using just one piston/rod assembly in all holes to reduce variables and almost all of them are within + - .001 of 0 deck Except for cylinder number 2 that is .005 above deck.
I know there are some tolerances Can anybody tell me what they are? Thanks in advance.

[dust]

heh, I'm keeping an eye on this thread....

[rumblefish360]

If you used the same piston and rod assembly with the bearings installed, and that one is positive, the crank is off. You can;

Mill that one piston to desired height and rebalance the assembly. (Possible cutting of the valve relief, check with clay)

Or

You can have the crank fixed via a crank master/grinder to correct the throw of that journal. Actually, all the crank gets checked.

You do not/should not have the space to run it .005 positive deck with the .039 gasket..

[340rt]

Originally Posted by rumblefish360

If you used the same piston and rod assembly with the bearings installed, and that one is positive, the crank is off. You can;

Mill that one piston to desired height and rebalance the assembly. (Possible cutting of the valve relief, check with clay)

Or

You can have the crank fixed via a crank master/grinder to correct the throw of that journal. Actually, all the crank gets checked.

You do not/should not have the space to run it .005 positive deck with the .039 gasket..

Rumble thanks for your reply , The engine has not been rebalanced yet so milling .005 off the piston top and then rebalancing the assembly looks like a good proposition.
Correct me if I am wrong,but milling one piston will make it lighter than the others .Do the other pistons need some kind of machining to equalize their weights and only then go ahead and rebalance the engine?
Regarding the valve reliefs I will be using a CC268 cam .480 lift and 1.5 to 1 rockers .I'll check for interference anyway.

Some information that I did not give is that cyl#1 gave me a 0 deck reading and cyl#2 a.005 positive reading .Both pistons share the same journal Is it possible that a throw that is off will affect one cylinder only?

[dwc43]

Yes, the pistons should be rematched to the lightest psitons of your set. They must be ball milled on the pads under the piston to set there weights. I like to get mine within plus or minus 2 when it comes to there weights.The closer the better.

[maxwedge413]

i would definately varify stroke before creating an oddball set of pistons ive seen decks out by 005 or more also connecting rods out by more than that espesially after recon.

[rumblefish360]

Some information that I did not give is that cyl#1 gave me a 0 deck reading and cyl#2 a.005 positive reading .Both pistons share the same journal Is it possible that a throw that is off will affect one cylinder only?

Thats odd.
4,6,8 are not positive just 2? And 1 reads zero.
Just double check that #2 hole again before you do anything. Just to make sure that the rod went around the crank right.

[340rt]

I decided to double check all of my measurements . Originally I only used a dial indicator with a magnetic stand.This time around I used a straight edge on the pin area ,some feeler gauges and the dial indicator to check for TDC only. The results make more sense now : cyl#2 .007 above deck ,cyl#4 .005 above deck ,cyl#6 .004 above deck and cyl#8 .002 above deck .
That deck surface is clearly tapered. The left bank isn't too good either :cyl#1 .002 above deck cyl#3 .002 above deck cyl#5, 0 deck and cyl#7 .002 below deck.

So what is the next step now,to basically get the machine shop mill the top of both decks so that all of the pistons stick out .007 and then cut the top of the pistons an equal amount (.007) for 0 deck ?

[dust]

Originally Posted by 340rt

So what is the next step now,to basically get the machine shop mill the top of both decks so that all of the pistons stick out .007 and then cut the top of the pistons an equal amount (.007) for 0 deck ?

Your machine shop isn't SpeedOMotive, is it?

[maxwedge413]

that sounds very normal rember they werw mass produced

[340rt]

Hey dst ,call it a coinsidence or whatever but you posted a thread on May 19 telling us about how "good" SpedOmotive is. Just 2 days earlier ,May 17 ,I posted a thread titled " reliable machine shop" in a popular forum ' Moparts...' where I was asking specifically about SpeedOmotive Why? because I thought that if they are well known for their stroker kits there machine shop should be top of the line ... I got two replies to my post on the very same day and one said that he had not personally delt with them but he thought that they were good . I called them to get some prices and this JERK answered the phone giving me a big attitude... he acted as if he was doing me a favor.... That pissed me off and I got very frustrated to say the least! Then I read your post and I said, Thank God I did'nt deal with those guys. I do have a machine shop close by ; Superior in Anaheim but they are a little pricey ,that's why I called speeOmotive because their prices are more reasonable ... For those of you that think otherwise I got to admit that I am not badmouthing the quality of their work for the simple reason that I did not deal with them .But dst's experience speaks for itself. The biggest frustration when I work on my engines is having to deal with machine shops. I am used to doing my own engines and I can only blame myself for my mistakes. But when I have to rely on somebody else working on my engine ...It gets really scary .So for those of you that deal with reliable machine shops you are very lucky!!! .dst ,my advise is that you try talking to the general manager directly some times you'll be surprised how good results you get because the good name of the company is THE most important thing to them, I've been there. Hope you resolve your problem.

[B1owner]

Originally Posted by 340rt

; Superior in Anaheim but they are a little pricey ,that's why I called speeOmotive because their prices are more reasonable ... .

Cheap machinist are like cheap doctors.....you really cant afford one.

[dust]

Originally Posted by 340rt

I called them to get some prices and this JERK answered the phone giving me a big attitude... he acted as if he was doing me a favor....

.....................

.dst ,my advise is that you try talking to the general manager directly some times you'll be surprised how good results you get because the good name of the company is THE most important thing to them, I've been there. Hope you resolve your problem.

Do you remember the SOM person you spoke to? Thanks for the advise, I'm currently waiting for replies from Edelbrock and Probe before I go back to SOM.

I also post on Moparts but I did not see your post. I posted almost the same thread that I posted here on May 19th on Moparts to get more advise and also to share my SOM experiances with others.

The dealership I work for uses Johnson machine. Good rep from what I hear. I'll probably use them on my next engine. I can get more information if you want it.

[340rt]

Originally Posted by dst

Do you remember the SOM person you spoke to? Thanks for the advise, I'm currently waiting for replies from Edelbrock and Probe before I go back to SOM.

The dealership I work for uses Johnson machine. Good rep from what I hear. I'll probably use them on my next engine. I can get more information if you want it.

Sorry I didn't get his name.I was so upset that I just hung up on him.

Johnson machine .Just give me their phone # and I'll give them a call. Thanks

[rumblefish360]

Originally Posted by 340rt

I decided to double check all of my measurements . Originally I only used a dial indicator with a magnetic stand.This time around I used a straight edge on the pin area ,some feeler gauges and the dial indicator to check for TDC only. The results make more sense now : cyl#2 .007 above deck ,cyl#4 .005 above deck ,cyl#6 .004 above deck and cyl#8 .002 above deck .
That deck surface is clearly tapered. The left bank isn't too good either :cyl#1 .002 above deck cyl#3 .002 above deck cyl#5, 0 deck and cyl#7 .002 below deck.

So what is the next step now,to basically get the machine shop mill the top of both decks so that all of the pistons stick out .007 and then cut the top of the pistons an equal amount (.007) for 0 deck ?

Sounds about right. Go to the expensive doctor to have it looked at. Let them double check your findings. It shouldn't be to hard to straighten this out.

[340rt]

I want to thank each and everyone of you for your replies.

[340rt]

I want to thank each and everyone of you for your replies.

[mrbill426]

Are the heads you are using open or closed chambered?
Thanks.

[340rt]

Hi, I will be using the closed chambered Eddies (6077)

[mrbill426]

Okay, thanks.

I'm still learning all this machine shop terminology. "Zero deck" I guess means the tops of the pistons are flush with the block surface. I have a pair of the 60179 heads that are open. They allow for the pistons to stick up a bit. What I don't quite get is the difference between positive and negative deck height, and whether or not it is measured at the highest point of a (domed) piston, or the flat top of a piston.