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Hello Fellow Chrysler friends,

I've started having problems with my 1948 Windsor, and can't seem to track down the issues, and make the car reliable for driving and touring.

When I start the car, it runs and idles beautifully.  But as I get out of the driveway and things start to warm up,(not even a 1/4 mile down the road) it loses power, backfires through the carb, and generally can't get out of it's own way.  

 If I let up on the gas, it will run and idle really well.  Put my "foot in it" and it starts backfiring and seems to "bog down".

I also know... I have either a burned intake valve or it needs to be adjusted in the number 6 cylinder...  there is about 40 lbs of pressure in that cylinder... while the other 5 have anywhere from 95 to 100 lbs of pressure.  And, when I'm accelerating, I can hear the tell tale "popping" sound through the carb, of the pressure in #6 going up through the intake manifold and carb.

 

 I'm thinking, I should do what the "old timers" used to call a "Ring and Valve Job" to deal with the weak #6 cylinder.  

 But I still have the lose of power/ backfiring issue.

I've put new tune up parts in, and cleaned the plugs.  I also checked to see that fuel deliver isn't the issue.  

 

Has anyone in here had a similar problem?  

How difficult is it to do a "top end" rebuild?  Can I order up gaskets, parts, and just take things apart and then put it back together again with new valves and rings... or is there more to it than that?

 If this is more than a "I can do my own maintenance" on my cars... oil changes, brake jobs, tune ups, type work... should I ask someone else to get into the engine?  I'm afraid, if I take everything apart, and have a deeper problem, or the usual broken bolts in the head or the manifolds... I'll be sunk for trying to deal with them.

 General maintenance I'm good with...   an engine rebuild I've never done before.

 

Local people I've talked with, and my 90 year old godfather have said... the Spitfire 6 is "bullet proof" and easy to work on....  I'm not so sure..   :-)

 

Anyone with any advice for me, would be greatly appreciated 

 

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Benefits of AACA Membership.

If you're lucky the problem is only the small wire inside the distributer with worn insulation grounding out when the vacuum advance kicks in.

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Posted (edited)

My understanding is, exhaust valves burn. Not intake valves.  Every time the cylinder draws in fresh cool air over the intake valve it cools the valve down. The exhaust valve does not get that luxury.  The teeny amount of time that the exhaust valves are closed on their seats, is the most cooling they get. Super heated air moves across the exhaust valve when it is open and allowing exhaust gasses through, keeping it hot. As valves wear, the seat area doesn't line up well any more. The seats can't transfer heat from the valve into the cooler valve seat. Their contact area becomes smaller and smaller as they wear.  Additionally as the valve wears down into the seat deeper, valve lash becomes tighter and tighter. The valve lash setting is very important to maintain for this very reason. As valve lash decreases, the time that the valve remains on its seat, able to cool, becomes less and less. The valve gets so hot eventually that yes, parts of the metal valve flute will burn away.  If you hear popping noise up through the carb, you more likely have an intake valve problem. And I doubt an intake valve is burnt.  Additional to all this, #6 cylinder runs hotter than all the others. It is the furthest away from the cooler water from the water pump. The water from the water pump must travel through the entire length of the cylinder head, getting hotter each inch it passes. Finally reaching #6 cylinder.  Another important factor contributing to proper valve lash maintenance. All this is pretty preventable, with good valve last maintenance.

 

I have indeed done a valve grind, by hand in my 1953 flat head 265 CI engine.  It can be done. I sourced a hand cutter for the valve seats. I leaned over the fenders and hand cut every seat. I purchased all new valves and lapped them in. I checked sealing with both visual clues after lapping, and I used kerosene to look for leaks. I had 2 dead cylinders. #5 and #6 when I bought my car. All was brought back to proper compression and the car has run great ever since. The only complaint is, I was under a time crunch,  and I did not replace all the valve guides. I should have. 1 and 2 cylinder had a little excessive guide wear. Now descending a long hill, they pull in a little oil and it will blow some blue smoke out the exhaust. Only on a long down hill.

 

A ring job can be a can of worms. The oil pan must come off. Rod caps removed. Pistons, with rods pushed up through the top and out of the cylinders. De-carbon, clean pistons. Hone cylinder walls. Assemble with new rings and button all back up. You may very well find cylinder wall scoring or a ridge at the top edge of your cylinder. Then that will need to be addressed. 

 

Here are a few pics of my valve grind. It was worth the effort and very rewarding.

 

2 dead cylinders seen here in the pic, #5 and #6. . See dark worn exhaust valve pic. Very poor contact sealing area here. Silver new valve with duller center strip area after lapping, showing good even seat contact. My seat cutting tool is seen. The stellite exhaust valve inserts are very hard, but can be cleaned up with determination and stubborn efforts.  Last pic of copper head gasket is when I am ready to button it up. All compression back up between 95 and 100 psi.

 

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Edited by keithb7 (see edit history)
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Last pic. ready to go...

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Forgot to mention that if you have a valve that is not sealing, a couple of things can happen.  If intake, when on compression stroke the spark plug fires. Explosive burning gases can enter back into the intake manifold and sound like a back fire, however up through the carb intake.

 

Additionally, assume an exhaust valve is not sealing properly. On compression stroke the raw unburned air/fuel mixture can be pushed into your exhaust manifold and exhaust pipe. Then at TDC the spark plug fires, creating an explosion in the cylinder. It is not a controlled explosion and volatile fuel is also in the exhaust system and the exhaust valve is not closing properly. The fire travels into the exhaust and explodes in their shooting an explosion out through the tail pipe.

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In reading your initial post two things came into my head.

Valves (already discussed)

And condenser (possibly coil).

Of coarse there could be a simple fuel starvation. Running lean could cause these symptoms.

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4 hours ago, 53 New Yorker said:

I also know... I have either a burned intake valve or it needs to be adjusted in the number 6 cylinder...  there is about 40 lbs of pressure in that cylinder...

 

If there is any doubt, adjust your valves. make sure none are too tight. 40 pounds it probably a burned exhaust valve, but never assume.... A leakdown test would tell for sure. Also make sure you don't just have a valve stuck/sticking open. If you do, the clearance will be huge.

 

4 hours ago, 53 New Yorker said:

I can hear the tell tale "popping" sound through the carb, of the pressure in #6 going up through the intake manifold and carb.

 

There are no absolutes, but a rhythmic snapping back through the carb usually indicates a flat exhaust lobe on the camshaft. Adjust your valves. While the covers are off,  have someone crank the car (with the spark plugs removed) while you watch the valves moving. One that moves less or not at all should stick out like a sore thumb.

 

4 hours ago, 53 New Yorker said:

If I let up on the gas, it will run and idle really well.  Put my "foot in it" and it starts backfiring and seems to "bog down".

 

Could the exhaust be plugged? How long since the car ran properly?

 

4 hours ago, 53 New Yorker said:

I also checked to see that fuel deliver isn't the issue.  

 

Are you really, really sure of that? Cars with a restriction in the fuel system (plugged tank vent, plugged fuel pickup, plugged sediment bowl screen/stone etc.) usually run fine in the shop and then screw up a few feet down the road.

 

4 hours ago, 53 New Yorker said:

Can I order up gaskets, parts, and just take things apart and then put it back together again with new valves and rings... or is there more to it than that?

 

There's more to it. It is still a very doable thing. Lots of good info in Keithb7's post. Do whatever it takes to to get the compression back in that cylinder before you deal with the other problem.

 

2 hours ago, keithb7 said:

My understanding is, exhaust valves burn. Not intake valves.

 

99.9999999 percent of the time that is true. I am a former drivability/tune-up/smog tech, and I have seen exactly 3 burned intake valves in my life. Every time I chased my tail for hours thinking it was something else. It is more likely that you will win the Irish Sweepstakes than ever see this. The symptoms vary depending on whether the car has a carb or fuel injection, but in general they tend to run rough on transition (a change in engine speed), and occasionally backfire, either at random, or when cracking the throttle. Again, you will never see this. If I had just done the leakdown test in the first place, it would have been obvious.

 

 

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keith, I got the brake tool. thanks. I am having my power brake booster rebuilt and when I install it I will at least pull the front drums and check my adjustments. hope I can use the tool correctly. beautiful valve job. you do nice work and have become very knowledgeable. I may tap you for some help in the near future.  thanks again. 53 ny"er may get lucky and find the head gasket is the issue. every one of these old Chryslers I have bought have needed new head gasket. the ones I replaced always blew between 2 cylinders, and sucked water out of the water jacket. lots of smoke.   dennis

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Posted (edited)

Low 40 lbs compression on #6 cylinder .

Popping up through the carb is a serious problem that needs to be fixed...most likely a intake valve sealing problem.

There could be a broken or weak intake valve spring ...causing the popping through the intake.

I have seen one split intake valve on a 47 Chrysler convert I did for a customer.

.

Edited by c49er (see edit history)

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@skyler no problem. Contact me any time. I do enjoy helping others with these old Mopars. 
 

When you get in to adjust your brakes, definitely let me know how you’re doing. I got mine dialed in really good. 

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If there were no other extenuating causes generally "back firing" which is through the carb is caused by a lean mixture, "after firing" which is in the muffler is caused by a too rich mixture.  Many people use the term backfire when they really are describing after fire.  Two different things, with at least two different causes neither of which is interchangeable.

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If there were no other extenuating causes generally "back firing" which is through the carb is caused by a lean mixture, "after firing" which is in the muffler is caused by a too rich mixture.  Many people use the term backfire when they really are describing after fire.  Two different things, with at least two different causes neither of which is interchangeable.

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I agree with Tinindian 100%.

The first things I would look for is fuel starvation. Improperly vented gas tank, kinked fuel line or weak fuel pump. All of these could be an inexpensive fix. 

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Hello Everyone,

 You've given me some easy things to look for...  And I will try to get through them, to see if it turns out being something easy and an "inexpensive fix" and will let you know how it goes.

 On the other hand,  with regard to the #6 valve not closing...  and perhaps a weak or broken spring,  or perhaps, it just needs to be adjusted properly... I looked at the engine, and I can see there is a sort of "wing nut" hidden behind the manifolds that holds the cover in place...  This looks like you have to be a very flexible contortionist to get in there and work on setting the valves behind the manifolds.  Can you really get in there, with tools and a gauge without taking the manifolds off ?

 

 Cheers, and thank you for all your incredibly useful feedback 

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17 minutes ago, 53 New Yorker said:

Hello Everyone,

 You've given me some easy things to look for...  And I will try to get through them, to see if it turns out being something easy and an "inexpensive fix" and will let you know how it goes.

 On the other hand,  with regard to the #6 valve not closing...  and perhaps a weak or broken spring,  or perhaps, it just needs to be adjusted properly... I looked at the engine, and I can see there is a sort of "wing nut" hidden behind the manifolds that holds the cover in place...  This looks like you have to be a very flexible contortionist to get in there and work on setting the valves behind the manifolds.  Can you really get in there, with tools and a gauge without taking the manifolds off ?

 

 Cheers, and thank you for all your incredibly useful feedback 

Yes and yes; doable but difficult with the manifold (s) in the way.  You may well find better access by taking the wheel off on the manifold side and seeing if there's a removable inner guard panel, many vehicles of this period were fitted like this for that reason. Obviously safe jacking and supporting the car is paramount!!

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12 hours ago, 53 New Yorker said:

Can you really get in there, with tools and a gauge without taking the manifolds off ?

Yes you can and it should be done with the engine at operating temperature and idling.  Be thankful you have a WPC engine and not a Pontiac engine.  You only need two wrenches and a feeler gauge (preferably a go/no go feeler).  My engine needed three wrenches and a feeler gauge until I replaced my tappet adjusters with WPC ones.

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Hello Keithb7....  Thank you for posting the video of adjusting the valves!  That was/is awesome!

I was reading the shop manual today and was confused when it said to adjust the valves with the engine warm and while it is running!  I thought they must have made a mistake in the manual...  But, you just expertly showed how it is done!  thank you.

 

The manual for the 48 also mentions taking an inner panel out in the wheel well area.

 

 Cheers,

  Wm.

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Posted (edited)
16 minutes ago, 53 New Yorker said:

Hello Keithb7....  

I was reading the shop manual today and was confused when it said to adjust the valves with the engine warm and while it is running!  I thought they must have made a mistake in the manual...  But, you just expertly showed how it is done!  thank you.

 

 

 

 Cheers,

  Wm.

 

I did find it is challenging, and not necessary to actually turn the tappet nuts to adjust while the engine is running. It's difficult as wrenches bounce up and down with the tappet opening and closing.

Get the car good and hot. Get your feeler gauge in there while it is running. Make note of which ones are out. Too tight or too loose. Then turn off the engine. Make a few quick adjustment as needed, using your feeler gauge. Fire up the engine again and see if you can get your feeler gauge back in there. Too tight, it will not go in while the engine is running. Too loose you will hear ticking when you slide it back out. A good, proper setting will want to pull in the feeler gauge just a little bit, nicely each time the tappet rises, as the engine is running. My understanding is this is because the tappets are shaped so they want to twist and turn on the cam lobe each and every time they lift. This helps with good even tappet wear. This twisting, torsional force will want to pull in the feeler gauge. You'll feel it when you have it right. It'll go in easily when the engine is running and start tugging the feeler gauge inward. With the hot running engine, the properly set tappet will remain quiet when your feeler is pulled out, and you'll have it bang on.

Edited by keithb7 (see edit history)

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