Moparchat - Home of MOPAR enthusiasts worldwide!



Go Back   Moparchat - Home of MOPAR enthusiasts worldwide! > Technical Forums > Performance Talk

Click here to search for Mopar cars and parts for sale.


Reply
 
Thread Tools Display Modes
  #1  
Old 01-10-2012, 11:53 AM
bulldog426's Avatar
bulldog426 bulldog426 is offline
Registered User
 
Join Date: Apr 2008
Location: sippi
Age: 37
Posts: 868
Default approximate compression??

about what would the approximate compression be with a 69hp 340 with the stock high compression pistons with r/t magnum style heads that hAve beeen shaved .030 with 2.08 stainless steel valves??
Reply With Quote
  #2  
Old 01-10-2012, 06:42 PM
te.ringer te.ringer is offline
Inactive User
 
Join Date: Aug 2011
Location: glenn dale md.
Age: 69
Posts: 187
Default

would the pistons hit the head,without a much thicker head gasket.080/.100
I think the pistons are around .050 abouve the deck for open chamber heads,I could be wrong.
Reply With Quote
  #3  
Old 01-10-2012, 09:07 PM
coupe32's Avatar
coupe32 coupe32 is offline
Registered User
 
Join Date: Jan 2003
Location: newburgh in
Posts: 300
Default

I put closed chamber edelbrock 6077 heads on a 340 block but I could not use the stock 340 pistons. Not enough piston to head clearance. I think we finally wound up with 10.7 static compression using srp pistons after surfacing the block and heads. The pistons were either flush with the deck or slightly below deck. I don't remember. A friend once used stock pistons on a 71 340 with closed chamber heads and did not check the clearance and it was not pretty when he started the engine. The pistons were hitting the head slightly but it was enough to crack several pistons and break the skirts off of them. Check for Clearance!
Reply With Quote
  #4  
Old 01-10-2012, 09:10 PM
340_GTS 340_GTS is offline
Inactive User
 
Join Date: Sep 2009
Location: Torrington, CT
Posts: 687
Default

Yeah, stock 340 pistons have about .060" positive deck height. So, the heads must have this area machined into them for clearance. I do not believe there is any way you can use the modern Magnum heads on it.
Reply With Quote
  #5  
Old 01-12-2012, 02:40 AM
cageman's Avatar
cageman cageman is offline
Inactive User
 
Join Date: Dec 1999
Location: Bismarck ND
Age: 46
Posts: 5,544
Default

a 69 340 has a small dome across the whole piston, and it is designed to fill the stock x heads big open chamber. Wont work with magnum heads. They are closed chamber. Unless you run a really thick cometic gasket.
Reply With Quote
  #6  
Old 01-13-2012, 03:41 PM
mod4superstar mod4superstar is offline
Inactive User
 
Join Date: Jan 2012
Location: mn
Posts: 24
Default

I have a brand new set of cometic gaskets that are .1 or .12 thick i would have to check to be sure. Let me know if i should check. I bought them for a project and never used them
Reply With Quote
  #7  
Old 01-13-2012, 08:07 PM
te.ringer te.ringer is offline
Inactive User
 
Join Date: Aug 2011
Location: glenn dale md.
Age: 69
Posts: 187
Default

the problem with thicker head gaskets would be lifter pre load and possible longer pushrods unless you mill the heads a lot then compression could be to high for pump gas. sorry but in seems like a catch 22 again.
Reply With Quote
  #8  
Old 01-17-2012, 08:31 PM
Ray Bell's Avatar
Ray Bell Ray Bell is offline
Registered User
 
Join Date: May 2005
Location: Dalveen, Queensland
Posts: 3,236
Default

There is only ever one way to check compression ratios...

It involves careful measuring, using a pipette or syringe or similar to get the chamber volume (your chamber, not someone else's) and a lot of calculations. All re-checked over and over of course.
Reply With Quote
  #9  
Old 01-19-2012, 03:38 PM
bulldog426's Avatar
bulldog426 bulldog426 is offline
Registered User
 
Join Date: Apr 2008
Location: sippi
Age: 37
Posts: 868
Default

sounds too complicated so there goes that random idea lol
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Looking for the approximate resale value 1973cuda121 Vintage MOPAR chat 1 02-09-2010 08:01 PM
Anyone know the approximate CCs on my s/b "O" heads? 340727Dart Performance Talk 1 05-04-2002 09:27 PM
Horsepower Numbers (Approximate) SUN RA KAT Ram Truck Chat 14 04-21-2002 02:44 PM
LOW COMPRESSION + A BLOWER, OR HIGH COMPRESSION AND NO BLOWER. I HAVE A 440 moparman1971 Drag Racing Forum 2 02-18-2001 01:39 PM
compression ratio vs. compression BB 70gtx Performance Talk 3 10-11-2000 05:02 AM




All times are GMT -4. The time now is 03:02 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
. . . . .