Q about TMI pistons

Reply Subscribe

Thread Tools

Search this Thread

Jul 25, 2008 | 06:42 PM

ctubutis

Thread Starter

Moderator

Joined: Nov 2007

Posts: 22,415

Likes: 92

From: Denver Metro Area, CO

Q about TMI pistons

OK, so, I think I want Tim's pistons. I was reading his Web site to be saying that they will
yield 9.5:1 compression ***when you have a 76cc chamber.***

And it just occurred to me - is this site in fact saying I'll end up with a 76cc chamber and
9.5:1 if I use his pistons?

1978 D7TE ABB (3rd char is hard to read for certain) block
1978 D5AE A2A heads

-ct

Jul 25, 2008 | 06:49 PM

80broncoman

Laughing Gas

Joined: Nov 2003

Posts: 898

Likes: 1

From: southeren Oh

The 76 cc is just the cubic volume of the combustion chamber. This can be made slightly smaller with machining. if you mill some of the gasket surface off the chamber gets smaller.
Chamber size has nothing to do with piston configuration.

Jul 25, 2008 | 10:00 PM

ctubutis

Thread Starter

Moderator

Joined: Nov 2007

Posts: 22,415

Likes: 92

From: Denver Metro Area, CO

Yes, I see now; the original cc volume is 78.4, Tim's pistons reduce it to 76.

Jul 25, 2008 | 10:17 PM

80broncoman

Laughing Gas

Joined: Nov 2003

Posts: 898

Likes: 1

From: southeren Oh

Quote:

Originally Posted by ctubutis

Yes, I see now; the original cc volume is 78.4, Tim's pistons reduce it to 76.

No the pistons do NOT change the volume of the chamber at all.
Chamber volume is somthing you can measure.

How the pistons can change the compression ratio is that it changes the
volume from the top of the piston to the top combustion chamber.
(thinner head gaskets can do this also)

Jul 26, 2008 | 02:56 AM

mustang81

Laughing Gas

Joined: Jan 2006

Posts: 883

Likes: 7

From: New-brunswick,Canada

you have a certain volume between head gasket or "head" and top of piston due to a dish piston wish is a positive in cc,s. When you have a dome piston you still have cc,s but in negative. All depend in pistons and head combination to achieve the desirer compression ratio.He have 2 kinds of compression, the dynamic and the static. You should do some reading at bubba's it will be more helpfull than me.