1956 420C suction on exhaust manifold

td14addict · Post by **td14addict** » Sat Aug 15, 2015 8:21 pm

I know this sounds pretty simple. Exhaust valve must be open. But I just cleaned the head and lapped the valves and they all looked really good. We set the valves but now when cranking over the engine there is suction on the exhaust manifold. It seems to be on #2 right before the exhaust valve opens. Is there anything else that could cause this issue? I am hoping that there is a piece of dirt in the valve and when I try to start it tomorrow it will blow the valve clean. I have 70 pounds on #1 (was 90 last night) and 45 on #2 (was 75 last night) the engine has not yet run. It was stuck and the cylinders are badly pitted but I am hoping to get it to run enough to make sure the rest of the machine will function properly before I spend the money getting new sleeves put in. Any other thoughts would be greatly appreciated.

gregjo1948 · Post by **gregjo1948** » Sun Aug 16, 2015 4:38 am

Lapping valves is not a cure for bad seating valves. It is done to see if the valves are seating properly. When lapping, don't spin the valve around and around. Mark the valve and head and use the mark as a reference and turn the valve back&forth with short twists using the mark to see that you're not rotating too far.I'm thinking your valves and seats need to be refaced by grinding. Also, you should always install a new head gasket after removing the head. gregjo1948

td14addict · Post by **td14addict** » Sun Aug 16, 2015 9:38 am

Thanks for the reply. This is not the first head I've done. I ground the valves on my td14. And I realize what lapping is for and to only spin back and forth. They looked really good. Nice dark ring on both the valve and the seat. Not trying to be rude just trying to explain better. This is also not the first headgasket I have reused so I am plenty confident in the headgasket. I am mostly wondering if there is something else in these engines that could have gotten in wrong that would through off the timing between the crank and the camshaft. The guy I got the dozer from told me the "took the engine down and checked everything and it all looked good" I am not sure how far in he got and from the looks of the steering clutches he put together he doesn't know much about working on these.

Thanks again.

gregjo1948 · Post by **gregjo1948** » Sun Aug 16, 2015 10:22 am

I don't know your knowledge on engines is why I posted the way I did.
I'm thinking you may have a head gasket problem. If #2 is preparing to exhaust would that mean #1 is preparing to compress? If the gasket is faulty, the intake vacuum from #1 may be drawing thru the exhaust of #2. Does that make any sense? gregjo1948

td14addict · Post by **td14addict** » Sun Aug 16, 2015 10:41 am

I appriciate both your responses. As far the head gasket if that was the case would it not have suction on number one when number 2 is on compression? I'm just not sure how it would work one way but not the other. I'm going to attempt to start it shortly. If it runs hopefully it will clear up and issues. If not I will be pulling the head off again. Always open to hearing ideas from others! Thanks!

gregjo1948 · Post by **gregjo1948** » Sun Aug 16, 2015 11:17 am

You're making my head hurt!!!! I think, maybe, it's a bad exhaust valve on#2 or may be clearance problem on it. If it's drawing in on the manifold just before the exhaust valve opens, the #2 piston is going down on the power stroke. Therefore, if the #2 valve is not sealed, there will be a suction on the exhaust manifold. How's that sound? gregjo1948

ddaxe · Post by **ddaxe** » Sun Aug 16, 2015 2:20 pm

I have seen.. not on dozers engines per say.. but I have seen where the camshaft and or lifter have, from years of service.. get a "push" of material.. meaning a bump develops on a lobe or lifter... and does kind of what you describe... so.. as the engine or offending cyl goes through it's cycle.. the bump opens the valve just enough for a second to release pressure or draw in.. depending on where the bump or build up is in relation to where the engine (cyl) is in its cycle... this one engine I was looking over baffled the heck out of me... so as I was scratching my head.. I was slowly turning the motor over by hand.. and then I seen it..(finally) the exhaust valve popped up n down.... In all the years working on engines I have only ever seen this once... it may not be whats going on with yours... just offering a suggestion.. something else to consider checking out...

ddaxe · Post by **ddaxe** » Sun Aug 16, 2015 2:29 pm

another thing to check.. or to test the seal of the valves or to see if there's a crack somewhere.. is to set up the head... in working order... turn it upside down and pour some light solvent (varisol) in the combustion chambers... and let it sit over night... if it holds the liquid... the sealing it good...

gregjo1948 · Post by **gregjo1948** » Sun Aug 16, 2015 4:28 pm

ddaxe wrote:I have seen.. not on dozers engines per say.. but I have seen where the camshaft and or lifter have, from years of service.. get a "push" of material.. meaning a bump develops on a lobe or lifter... and does kind of what you describe... so.. as the engine or offending cyl goes through it's cycle.. the bump opens the valve just enough for a second to release pressure or draw in.. depending on where the bump or build up is in relation to where the engine (cyl) is in its cycle... this one engine I was looking over baffled the heck out of me... so as I was scratching my head.. I was slowly turning the motor over by hand.. and then I seen it..(finally) the exhaust valve popped up n down.... In all the years working on engines I have only ever seen this once... it may not be whats going on with yours... just offering a suggestion.. something else to consider checking out.
..

ddaxe---I believe smaller air cooled engines (lawn mowers, wood splitters, etc.) have that extra lobe on the cam to relieve compression while starting.

td14addict · Post by **td14addict** » Sun Aug 16, 2015 8:10 pm

Thank you for the great ideas. I had heard about that trick for checking the valves before but completely forgot about it until reading your reply.

My biggest trouble with trying to figure this out was that i couldnt turn the motor over by hand anymore. Once the rad was on I was unable to get enough leverage on the fan blades to turn the engine over even with the plugs out.

We did fire it up today, After attempting to start it on 6 volts (bought a new 6 volt battery and new 6 volt coil) with no luck after 20 minutes we decided to put the 12 volt coil back on and see if it will go. well it cranked for about half a second and it was running. It actually sounded pretty good. I took a short video of it running and I will try to post it here, If what I try doesnt work I will upload it to youtube and put the link in after. The video was taken before we fine tuned the distributer and set the idle.

Thanks for the help!

https://video.fyhz1-1.fna.fbcdn.net/hvi ... e=55D160EC

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1956 420C suction on exhaust manifold

1956 420C suction on exhaust manifold

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