It is currently Tue Nov 20, 2018 3:23 pm

All times are UTC - 5 hours [ DST ]


Forum rules


Please click here to view the forum rules



Post new topic Reply to topic  [ 31 posts ]  Go to page Previous  1, 2, 3  Next
Author Message
PostPosted: Sun Aug 19, 2018 9:46 pm 
356 Fan

Joined: Sun Apr 20, 2008 12:54 am
Posts: 2894
It shouldn't, but viewing the cylinder ends and their seats in the heads, they look like their sealing may be the
problem or from weak rings, oil ring gap not @ the top, and head torque--they should be torqued alternately @ 7-lb increments to final 28 lb; If not, the 1st head being fully torqued won't be correct after the 2nd head is torqued.
This was causing some case stress found by RIP Ray Litz back in the early days!


Top
 Profile  
Reply with quote  
PostPosted: Sun Aug 19, 2018 10:11 pm 
356 Fan

Joined: Wed Nov 23, 2011 10:52 am
Posts: 3391
Location: Cleveland, Ohio
Dick, what cylinder ends and ring gaps are you viewing here? The only picture here shows a pair of intake ports.

_________________


Top
 Profile  
Reply with quote  
PostPosted: Mon Aug 20, 2018 12:09 am 
356 Fan
User avatar

Joined: Wed Mar 26, 2008 11:45 am
Posts: 6043
Location: San Francisco
C J Murray wrote:
How does a carb make exhaust come up the intake port?

Cliff, suffice to say I can see it as (complexly) possible and also easily ruled-out, so why not try an easy test to confirm it is not that?
I have spent way too much time examining what must *clearly* be the cause of the problem, only to find out it was that thing which it 'can't be', and often in concert with another issue.
I now try to remove every single possible cause as soon as early as I can, especially when it is an easy 'fix'.

_________________
Ron LaDow
www.precisionmatters.biz


Top
 Profile  
Reply with quote  
PostPosted: Mon Aug 20, 2018 12:37 am 
356 Fan

Joined: Thu May 08, 2008 9:20 pm
Posts: 17
Hello,
Thanks again for all your replies. I really appreciate your help. I want to express the symptoms better than I did in my first post. My impression is that ALL the cylinders are backfiring. When it is happening, it is really wild looking into the engine compartment. These are not normal deceleration pops, it's like loud popcorn everywhere with huge bangs mixed in, and sometimes flames come up into an air cleaner. The bangs are on both sides and seem like all 4 cylinders. When this first started two or three years ago, it would come on only after driving a few miles. More recently, it begins as soon as the engine starts. Which at this point I only do for diagnosis--the car can propel itself, but I don't consider it driveable--it could hurt itself or someone else.

This weekend when I found the soot in #3 intake, I seized onto it. I know the picture I posted is dramatic, and makes the impression that #3 is THE backfiring cylinder. But please forgive me--I think I created a red herring with that photo. I know you must be weary of amateurs like me who can't describe their problems accurately. I'm guilty I guess. I really don't think #3 is making all that noise, or that I would have failed to notice it was all coming from one cylinder. (Of course the soot needs to be addressed too.)

For a couple of years I've been trying to find what could make all the cylinders backfire at once. Any "in-common" ignition components: distributor, coil, plug wires. or ??? I heard low float level can cause backfiring--so maybe fuel pump, dirty gas tank, or partly clogged lines. But at onset of this problem, the car ran perfectly well until warmed up.

Every running problem this car has had in the 29 years I've owned it has been ignition. So I still expect an ignition answer. My 022 is pretty worn but I've swapped it for an 050 I had around and that didn't fix it. I swapped coils w/no luck. I have replaced the plug wires in the last 8 years, but maybe they didn't last--should try it again. I replaced the fuel filter and the fabric hoses. I just got a fuel pressure gauge to check the pump, although the car has run so well at times--could the pump be intermittent?

So I'll check the fuel pressure, maybe rebuild pump
observe float levels
watch the new clear fuel filter
maybe replace plug leads again
get the 022 rebuilt
finish switching to Zeniths

What else could cause the backfiring? Erratic sparking, lack of fuel? I'd be grateful to know anything that comes to mind.
Thanks--
John


Top
 Profile  
Reply with quote  
PostPosted: Mon Aug 20, 2018 6:03 am 
356 Fan
User avatar

Joined: Tue Mar 25, 2008 6:32 pm
Posts: 3297
Location: Harrodsburg, Kentucky
Tag: I wish I knew as much as I think I know.
John, I suspect the Solex carbs have the normal Solex problem in that the bases are warped and you have a big air leak. Switch to the Zeniths and I am sure the problem will go away. Get the solex carbs rebuilt.

_________________
If I had known I would live this long I would have pushed the envelope a little harder.
Cymru am byth
David Jones #9715


Top
 Profile  
Reply with quote  
PostPosted: Mon Aug 20, 2018 6:35 am 
356 Fan
User avatar

Joined: Fri Oct 23, 2009 7:24 pm
Posts: 7012
Location: 30MI WEST OF PHILA
John Berners wrote:
What else could cause the backfiring?
Badly worn camshaft.

_________________
'57 Speedster - very real
'59 Sunroof - mostly real
'60 Devin D Race Car-in process - fake chassis - real body
'63 GS 2133 coupe - very real
'67 S Original Owner - ultra real


Top
 Profile  
Reply with quote  
PostPosted: Mon Aug 20, 2018 8:12 am 
356 Fan
User avatar

Joined: Mon Jul 08, 2013 3:18 pm
Posts: 345
Location: Lyme, CT
Tag: What?
John: I don't see any mention of a leak-down test. Do it. Last year I had similar symptoms with good compression readings but popcorn noises and backfiring from the exhaust. I was convince it was a burned exhaust valve on #1. Did the leak-down and immediately ID'd the leaking intake valve on #2 when the compressed air blew out the carb. Pulled the head and found years of carbon build up on the pistons and valves. See Pix. Took heads to my local race-prep machine shop where they found seats and guides good but a few valves out of spec and a few close, along with tons of crud. I replaced all the valves along with the old, cracked pushrod tubes, gaskets, etc. and cleaned up the pistons. Buttoned it up and all is good now. Recommend the simple leak down test before you fiddle with fuel pump, etc. Good luck.


Attachments:
#2 Piston.JPG
#2 Piston.JPG [ 1.66 MiB | Viewed 296 times ]
#2 Valves in Head.JPG
#2 Valves in Head.JPG [ 1.54 MiB | Viewed 296 times ]

_________________
Paul Ahnell
'60 Normal Coupe
Top
 Profile  
Reply with quote  
PostPosted: Mon Aug 20, 2018 9:44 am 
356 Fan
User avatar

Joined: Thu Mar 27, 2008 9:14 am
Posts: 1995
Location: near Ft Collins
Tag: Official curmudgeon
Here's a long shot I've seen only once.
The combustion is leaking around the plug heli-coil and due to a crack has entered the intake port.
Possibly a valve seat also.

_________________
 


Top
 Profile  
Reply with quote  
PostPosted: Mon Aug 20, 2018 9:59 am 
356 Fan
User avatar

Joined: Thu Dec 15, 2011 9:01 pm
Posts: 814
Location: Laguna Beach/Traunkirchen
Leak-down test was always my go-to. Not very sophisticated, just hooked each cylinder up to the old air compressor and listened for air leaks. But when drag racing or hill climbing, certain problems are not very likely (like flat camshafts). I just wanted to verify if any exhaust valves were bent or pistons broken from over-revving. Still a very easy and informative test for street motor problems.

_________________
 


Top
 Profile  
Reply with quote  
PostPosted: Wed Aug 22, 2018 10:03 am 
356 Fan

Joined: Thu May 08, 2008 9:20 pm
Posts: 17
Hello, Thanks for all these ideas--I really appreciate all the experience and generosity with your knowledge.
I borrowed a compressor from my neighbor and am getting the adapter I need. The Zeniths are on for now. I'll keep you posted!
John


Top
 Profile  
Reply with quote  
PostPosted: Wed Aug 22, 2018 10:47 am 
356 Fan
User avatar

Joined: Fri Oct 23, 2009 7:24 pm
Posts: 7012
Location: 30MI WEST OF PHILA
John, are you saying that the backfires happen with both Solex and Zenith carbs?

_________________
'57 Speedster - very real
'59 Sunroof - mostly real
'60 Devin D Race Car-in process - fake chassis - real body
'63 GS 2133 coupe - very real
'67 S Original Owner - ultra real


Top
 Profile  
Reply with quote  
PostPosted: Wed Aug 22, 2018 2:52 pm 
356 Fan

Joined: Thu May 08, 2008 9:20 pm
Posts: 17
Hi C J,
No, only with the Solexes. The Zeniths haven't been run since 1991! My current project is to get the Zeniths driving. I was hoping that would fix the backfiring, but there are so many other possible causes that I am not counting on it now.

Today I found it's not so easy to get a supply of compressed air quiet enough to hear to do the leakdown test! The setup I have here makes so much noise leaking from its own fittings I can't hear if there is leakage from the valves...
Thanks!
John


Last edited by John Berners on Wed Aug 22, 2018 3:28 pm, edited 2 times in total.

Top
 Profile  
Reply with quote  
PostPosted: Wed Aug 22, 2018 3:11 pm 
356 Fan

Joined: Thu May 08, 2008 9:20 pm
Posts: 17
That is to say, the Zeniths are now sitting on top of the manifolds for the first time in years, but they haven't been run and the car is nowhere near ready to try starting. If it were to "pass" the leakdown test, can I run it for a bit with all the shrouding off?
John


Top
 Profile  
Reply with quote  
PostPosted: Wed Aug 22, 2018 3:13 pm 
356 Fan
User avatar

Joined: Wed Aug 27, 2008 10:54 am
Posts: 2105
Location: Alpine AZ, Green Valley AZ
Only for a bit...... Your cooling air isn't doing anything good for you.

_________________
Some days it just isn’t worth the hassle of chewing through the restraints......


Top
 Profile  
Reply with quote  
PostPosted: Wed Aug 22, 2018 3:43 pm 
356 Fan
User avatar

Joined: Fri Oct 23, 2009 7:24 pm
Posts: 7012
Location: 30MI WEST OF PHILA
You can run it for awhile without cooling if it is stationary and under no load. You can use a house fan to cool a little if you want. If the engine was in the airflow instead of in an engine compartment it wouldn't need a fan and sheetmetal at all.

_________________
'57 Speedster - very real
'59 Sunroof - mostly real
'60 Devin D Race Car-in process - fake chassis - real body
'63 GS 2133 coupe - very real
'67 S Original Owner - ultra real


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 31 posts ]  Go to page Previous  1, 2, 3  Next

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: Google [Bot], jule block, Paul Hatfield, Richard Holler


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
Powered by phpBB® Forum Software © phpBB Group