Measuring pistons

Paul Merolla · 01-06-2010, 04:27 PM

Can anyone tell me where on the piston to measure? It's a Lunati pn 327. Thanks

Chad E532 · 01-06-2010, 04:49 PM

I typically measure the diameter about a half inch below the oil ring groove perpendicular to the wrist pin on the skirt. This is for a standard cast or forged piston, not sure if this applies to pistons with inserted or coated skirts.
Thanks,
Chad

BillK · 01-06-2010, 07:28 PM

Paul,
You really need to call Lunati and ask them. Most piston manufacturers measure about 1/2" up from the bottom of the skirt like Chad said, but there are also some that measure half way up the skirt and at least one that I know of that wants you to measure right below the oil ring groove. You really need to find out from the manufacturer.

Alan Roehrich · 01-06-2010, 07:53 PM

Bill is right, call Lunati and ask them where to measure their piston, and also tel them everything about your engine and how you run it. If it is a BowTie block, they need to know. If it is poured, they need to know that too. Tell them what temperature you run it at as well. A little exchange of information could save you a lot of time, trouble, and money.

Paul Merolla · 01-06-2010, 08:42 PM

Thanks guys, I'll call 'em. I thought maybe there was a standard answer, like, "Lunati says here, JE says there, etc." I've assembled 2 small blocks for my street car, but never have done it accurately...just had the machine work done and put it together. I want the stocker to be right and lay the foundation for learning to make it go faster.

Alan Roehrich · 01-06-2010, 09:16 PM

Even more bad news here Paul. I thought I'd drag out a Lunati catalog and see if I could find the information you needed. Lunati was sold a couple of years ago. The major owner of Comp and a couple of other people bought it from Holley. Where the rub comes in is that the new catalog (2008/2009) does not even show ANY of the old pistons, all they show are the new pistons Wiseco makes for them. A bunch of people at Lunati were let go both before and after the company sold. There may not be any information to be had about those pistons from Lunati. I hope you have a lot better luck than I think you will. Let me know what you find out, and if you need help I'll try to find you some.

01-06-2010, 04:27 PM	#1
Paul Merolla Senior Member Join Date: Dec 2001 Location: Papillion, NE Posts: 609 Likes: 238 Liked 293 Times in 65 Posts	Measuring pistons Can anyone tell me where on the piston to measure? It's a Lunati pn 327. Thanks

01-06-2010, 04:49 PM	#2
Chad E532 Member Join Date: Jul 2008 Location: Lindstrom MN Posts: 156 Likes: 7 Liked 54 Times in 7 Posts	Re: Measuring pistons I typically measure the diameter about a half inch below the oil ring groove perpendicular to the wrist pin on the skirt. This is for a standard cast or forged piston, not sure if this applies to pistons with inserted or coated skirts. Thanks, Chad

01-06-2010, 07:28 PM	#3
BillK Member Join Date: Nov 2005 Location: Waldorf Md Posts: 230 Likes: 12 Liked 30 Times in 17 Posts	Re: Measuring pistons Paul, You really need to call Lunati and ask them. Most piston manufacturers measure about 1/2" up from the bottom of the skirt like Chad said, but there are also some that measure half way up the skirt and at least one that I know of that wants you to measure right below the oil ring groove. You really need to find out from the manufacturer. __________________ Bill Koustenis

01-06-2010, 07:53 PM	#4
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,097 Likes: 1,544 Liked 1,775 Times in 404 Posts	Re: Measuring pistons Bill is right, call Lunati and ask them where to measure their piston, and also tel them everything about your engine and how you run it. If it is a BowTie block, they need to know. If it is poured, they need to know that too. Tell them what temperature you run it at as well. A little exchange of information could save you a lot of time, trouble, and money. __________________ Alan Roehrich 212A G/S

01-06-2010, 08:42 PM	#5
Paul Merolla Senior Member Join Date: Dec 2001 Location: Papillion, NE Posts: 609 Likes: 238 Liked 293 Times in 65 Posts	Re: Measuring pistons Thanks guys, I'll call 'em. I thought maybe there was a standard answer, like, "Lunati says here, JE says there, etc." I've assembled 2 small blocks for my street car, but never have done it accurately...just had the machine work done and put it together. I want the stocker to be right and lay the foundation for learning to make it go faster.

01-06-2010, 09:16 PM	#6
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,097 Likes: 1,544 Liked 1,775 Times in 404 Posts	Re: Measuring pistons Even more bad news here Paul. I thought I'd drag out a Lunati catalog and see if I could find the information you needed. Lunati was sold a couple of years ago. The major owner of Comp and a couple of other people bought it from Holley. Where the rub comes in is that the new catalog (2008/2009) does not even show ANY of the old pistons, all they show are the new pistons Wiseco makes for them. A bunch of people at Lunati were let go both before and after the company sold. There may not be any information to be had about those pistons from Lunati. I hope you have a lot better luck than I think you will. Let me know what you find out, and if you need help I'll try to find you some. __________________ Alan Roehrich 212A G/S