Intake removal?

[Lloyd]

Before you start tearing things apart do a compression test. If any of the cylinders show bad, put a little motor oil down the spark plug hole - about a tablespoon then do the test again. If the results do not improve then you may well have worn valve guides - or seats...

 

To replace the guides I would suggest you take it to a machinist. They are very tight to remove, I beat 2 of mine to pieces before I gave up and brought it to a machinist. Also they will need to be reamed to a specific diameter. Make certain you do read the valve guide installation and orientation under Resources/Tech/Tech Tips like Don has suggested. You will need to pass this info onto your machinist. Might as well plan on reseating the valves as well.

[ol'skool]

Didn't you remove the manifolds because of a possible vacuum leak.  Your first post didn't say how it ran.  Did it run like this before you did all the work? 

[DodgeDan]

Yes, it has not been running right, and has just gotten worse. I have been trying to diagnose it for a while now.  My compression is actually good.  I figured maybe it was sucking air at the intake gasket, but even with the new gaskets it's still not right.  I couldn't get a vacuum gauge on it before as there was no where to put one, but when I had the manifolds off I was able to put a fitting in the intake, now with the vacuum gauge telling the story I see a very sad tale...  I'm thinking serious about calling it quits, cutting my losses and selling it, it's just getting to be more than I can handle.

 

Dan 

[Lloyd]

If you wrote the results of your compression test down please post them.

 

Also you said the vacuum gauge is fluctuating wildly. How far is it fluctuating? Is it a steady fluctuation? Doe it move quickly or slowly?

What does the needle do when you increase idle?

Do you have any smoke or vapor coming out the exhaust? If so what color is it.

Doe the engine run hot? Has the radiator over-flowed?

Did you ever check the timing with a timing light? Is the mark holding steady under the light?

 

Bear in mind that a vacuum gauge that is fluctuating wildly can be a number of things depends on what else is going on with the engine. It can be a blown head gasket in which case a compression check or just seeing water vapor coming from the exhaust and an overheating engine can help pin point. It can be a mis-fire in the distributor or across the coil or even a spark plug that is gapped wrong. I've pulled wires off the plugs one at a time just to see if the engine started idling rough. Primitive but it works. As far as valve guides go - where you were pointed - usually the needle will show quick but short fluctuations and will smooth out when you increase idle speed if its a valve guide problem. But if you see fluctuations in the gauge as you increase the idle it could be a valve or valve seat. Wider slower fluctuations usually mean a fuel/air problem which could be carburetor adjustment.

 

Don't give up just have to keep digging. Even if it turns into a matter of elimination. Believe me plenty of repairs have been accomplished just by eliminating possibilities. You've probably even paid other mechanics to do just that.

[DodgeDan]

I had posted the compression results in another post, so here they are again...

 

#1 100

#2 105

#3 95

#4 100

#5 105

#6 105

 

The vacuum gauge needle fluctuates wildly, I'd have to put it on again to see the exact numbers but I think it was bouncing from 10 to 20 inches, I'll get an exact reading for you and post it.  I'll check and see what it does on increased idle too.

No smoke or vapor, engine runs at temp, no overheating, no overflowing.

I have a timing light, but it's one I had bought back in the 1980's for 12v cars of the day, will it work with my 6v positive ground?

 

Dan

[_shel_ny]

Did you have a look at the valve springs when the manifolds were off.

 

The year after I got my 48 it developed a problem. I put a "for sale" sign on it, and it sold quickly. Well , it almost sold. Got a deposit. Then the next day when the buyer sobered up he had changed his mind. I ended up not selling it at that time.

 

I found 1 or 2 (at least 1, maybe 2) broken valve springs. I replace it, or them, and enjoyed the car for many more years before selling it last October. Also replaced the engine along the way, but that is another story.

[_shel_ny]

Timing light may work OK. Mine did. Can always use a 12V battery for a power source just for the light if needed

Edited September 27, 2014 by shel_ny

[soth122003]

The 12 volt timing light will work fine. just use a 12 volt battery or a jump pack for the battery source.

 

Joe Lee

[Lloyd]

Thanks for the compression test results. Sorry I didn't see the other post. #3 shows the lowest. Don't know what the expected compression psi is on a flathead, usually you will be looking for 120-135 and anything below 100 is low but honestly this is my first time working on one and the only thing I have done to one is rebuild it but right now its sitting on my bench. Haven't even got it in yet so perhaps some of these other guys can tell you what's good and what's bad.

 

But with later model engines a general rule of thumb is readings need to be within 10% of each other - or - lowest and highest need to be within 20psi.. Your lowest is not within those limits however you do show a low cylinder #3 and I would say its borderline as compared to the rest. Something you should take a look at.

 

Usually low compression on one cylinder is a valve spring or valve. You show the lowest on #3 and since the adjacent cylinders are good and you don't show any vapor from the exhaust and no over heating problems you can rule out a head gasket. 

I would start by pulling the valve covers and looking at the springs on #3. Look closely and pry them up and down to see if one is broke. Also if you can get someone to turn the engine over with the coil disconnected while you watch the valves moving may help to spot anything. See if one on #3 is moving a little sideways or is erratic. While you have the valve covers off it would be a good idea to adjust the valves as well.

 

There is also another test, a leak down test which will pin point any loss of compression. I've never done that test but I know it can be done. You will need a special tool that screws into the spark plug hole, make certain piston is at TDC on compression stroke, pressure the cylinder and see where the air is coming out is pretty much the gist of it.

[Don Coatney]

This might or might not help

 

 

[Lloyd]

Thanks Don, very informative. Ill be keeping this for myself.

What book is that?

[Don Coatney]

The compression test instructions are from a 1953 MoTors Manual. I do not recall where the milling chart came from.

[ptwothree]

While you are checking those valve springs, check the valve clearance on the #3 cylinder.  Tight clearances will cause a problem like you are having.  I'd check 'em all if it were mine.

[DodgeDan]

Here is a vid showing my vacuum.  How would you read these results?

 

http://vid171.photobucket.com/albums/u308/dahoude/WP_20140930_10_16_29_Pro.mp4

 

Dan

Edited September 30, 2014 by DodgeDan

[deathbound]

Check this out:http://www.secondchancegarage.com/public/186.cfm. Didn't see your exact issue, but still may be helpful.

Edited October 1, 2014 by deathbound

[DJ194950]

Slick video, could actually be that indicative of problem areas? Got to find my vacuum gauge!

 

Thanks for the post deathbound!

 

DJ

[Lloyd]

Thanks for the video of your vacuum gauge. Nice gauge. I see revving the engine up does not loose the shaking so I believe valve guides can be ruled out. First guess would be a valve or spring. I hear a knocking noise that corresponds to the needle movement? Have you tried unplugging your plug wires and putting them back on one at a time to see if the knocking noise goes away? Be curious.

[plymouthcranbrook]

In a related but personal question I am removing my intake and exhaust on my 52 Cranbrook due to a failure to idle. Holding the choke down cures the trouble and ignition seems to be still correct. I noticed that some of the nuts(but not all) were cone shaped on one end with slits cut in the. I assume that they go cone end into the washers that were on the exhaust manifold bolts. Some were cone end in and some out when taking them off. Should all the bolts be like this or is it just the exhaust ones?  I checked the manual and it said little about the procedure at all. Any information greatly appreciated. I expect that my driving the car more this year than ever might have been a party to this problem(Plus the short run to 70 MPH for a couple of miles)

[_shel_ny]

just two on each end for the exhaust, and yes, cone end into the tapered washers

[Don Coatney]

Attached as pictured

 

[_shel_ny]

----------------I assume that they go cone end into the washers that were on the exhaust manifold bolts. Some were cone end in and some out when taking them off. Should all the bolts be like this or is it just the exhaust ones?  I checked the manual and it said little about the procedure at all. Any information greatly appreciated.----------

 

In addition to the nut/washer positioning be sure to observe the proper reassembly tightening/torquing sequence to assure the best seating/sealing of the manifolds to the gaskets.

 

 

Edit: add second pic

Edited October 2, 2014 by shel_ny

[plymouthcranbrook]

Thanks all. I don't plan to disassemble the manifolds as there isn't any exhaust leak that I can locate. Just intake issues.

Edited October 11, 2014 by plymouthcranbrook