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 10-03-2012, 03:16 PM
78 VOLARE 78 VOLARE is offline
Inactive User
 
Join Date: Oct 2012
Location: prince edward island, Canada
Posts: 3
Default misfiring 340

I have a 72 340 that seems to be acting up. When it idles, it sounds rough and when i unplug wire number 1 or 4 it don't change the idle, just like the cylinders were dead. Wires are firing and pulled plug out of hole and it is firing. Thought it may be vaccum leak, pulled off intake and put new gaskets, still the same. Now pulled heads off and there was a film of oil and antifreeze between gasket and head and block. Is this normal? Also was a trace of antifreeze in cylinder 4. Anyone ever run into this? Just looking for advice.
Reply With Quote
  #2  
Old 10-03-2012, 08:40 PM
mopar29mod mopar29mod is offline
Inactive User
 
Join Date: Aug 2008
Location: Killeen, TX
Posts: 606
Default

a compression test is one of the best ways of finding a bad cylinder
Reply With Quote
  #3  
Old 10-04-2012, 06:30 AM
chirorod chirorod is offline
Inactive User
 
Join Date: Nov 2007
Location: Florence, MA
Age: 84
Posts: 724
Default

I think your system of diagnosis leaves a little to be desired. As just suggested, a compression test should have been done when your dynamic test gave you a positive. Just making a quick judgment about what the problem is usually doesn't work.
The oil and coolant you noticed after pulling the heads might be normal drip for head removal. You didn't say anything about the condition of the gaskets. Since you had the heads off, did you do a quick check for valve sealing?
1 and 4 are on opposite sides, so a vacuum leak would not be the first choice for diagnosis. Anyway, vacuum leaks are more often at hoses and fittings than at the manifold gaskets.
Did you check the distributor cap for cracks, the wires for cross-firing?
Reply With Quote
  #4  
Old 10-04-2012, 12:08 PM
aarracer aarracer is offline
Inactive User
 
Join Date: Mar 2007
Location: British Columbia
Posts: 891
Default

Good time to look for cam or lifter damage?
Reply With Quote
  #5  
Old 10-15-2012, 03:33 PM
78 VOLARE 78 VOLARE is offline
Inactive User
 
Join Date: Oct 2012
Location: prince edward island, Canada
Posts: 3
Default

I had done a compression test before disasembling. everything seemed fine. The head gaskets looked normal, no visible rips or holes. Verified the operation of camshaft before removing heads. I will have to get my heads checked by a reliable shop, as far as I can see valves seem all good. As for wires, plugs and distributor cap; changed them all in the spring and motor worked fine then. Thanks for the comments, in the future i'll have to make better judgement calls.
Reply With Quote
  #6  
Old 10-16-2012, 01:55 AM
Rich Kinsley Rich Kinsley is offline
Inactive User
 
Join Date: Jan 2005
Location: Omaha/Ne
Age: 80
Posts: 760
Default

The water and oil could just be leakage from pulling the heads. If the plugs and cyl's looked really clean in the suspect cylinders then you probably have a crack or head gasket issue. Been there. Done that.
Reply With Quote
  #7  
Old 10-16-2012, 06:38 AM
chirorod chirorod is offline
Inactive User
 
Join Date: Nov 2007
Location: Florence, MA
Age: 84
Posts: 724
Default

But he said he had 1 and 4 not working. Usually, head gasket problem will get adjacent holes.
Reply With Quote
  #8  
Old 10-16-2012, 01:26 PM
te.ringer te.ringer is offline
Inactive User
 
Join Date: Aug 2011
Location: glenn dale md.
Age: 69
Posts: 187
Default

If you had a duel plane intake #1and #4 same runner ,was carb mounting bolts tight? also did engine shake while it was idleing? If it did pull wire off #1and #4 did shake go away?If so problem is in that cylinder.A shake is a intake valve not sealing right.cracked dist cap,wiped exhaust lobe in that cylinder .If no shake it is a lean condition.carb adjustment,intake runner gasket,vacuum port running off runner for 1#and#4 also a rare but did happen pcv valve came apart. I hope this helps .
Reply With Quote
  #9  
Old 10-17-2012, 12:03 AM
Rich Kinsley Rich Kinsley is offline
Inactive User
 
Join Date: Jan 2005
Location: Omaha/Ne
Age: 80
Posts: 760
Default

Quote:
Originally Posted by chirorod View Post
But he said he had 1 and 4 not working. Usually, head gasket problem will get adjacent holes.
You are right. Sorry.
Reply With Quote
  #10  
Old 10-17-2012, 02:37 PM
78 VOLARE 78 VOLARE is offline
Inactive User
 
Join Date: Oct 2012
Location: prince edward island, Canada
Posts: 3
Default

Thanks for all the info guys, and upon futher inspecting the cylinders I found large crack in number 4. None visible in 1 but al least i now know what the problem is. Again thanks for all your info it will be knowledge for the future.
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
still misfiring captsamuel Ram Truck Chat 6 06-23-2004 03:54 PM
misfiring on boost brian phillips Performance Talk 11 06-14-2004 08:41 PM
Misfiring ramsstboy Ram Truck Chat 8 08-12-2001 09:24 PM
Misfiring gthomas Ram Truck Chat 4 07-16-2001 11:04 AM
V10 Misfiring....Badly gthomas Ram Truck Chat 0 07-04-2001 01:49 AM




All times are GMT -4. The time now is 08:24 PM.


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