David Brown 990 almost done, valve adjustment?

I had put a message out there a couple times about my DB 990 having problems. If you search "David Brown 990 don't run good" or "David Brown 990 Injection pump" you can read all about it. Dieseltech suggested a blown head gasket and he was correct. I took the head off a couple days ago and there it was, a piece missing between two cylinders. I am very thankful for his input and everyone else that provided information.

Right now I am hung up on adjusting the valves. The manual talks about some timing peg in the flywheel for TDC, I have no idea how to access my flywheel without splitting the tractor. Right now I have the head on, the lift rods in and the rocker arm assembly bolted back in with the valve cover off. I am watching the valves move and I have my manual there, but I don't really know for sure when that first cylinder is at TDC like the manual mentions. I feel like skipping this step since all I did was take the head off and let it hang there for a few minutes while I took the old gasket out and put the new one in. I feel like I might do more harm than good.

Any advice on when I am at TDC on cylinder number one with the situation I have would be appreciated.

Thanks again.

Hello Up Oliver,
Do not start the engine! You NEED to adjust the valves. I am not familiar with that engine, but usually there is a pipe plug in the bell housing facing the front of the engine, there would be were the flywheel TDC mark is. Some engine have a hole in the flywheel that a bolt would go into to stop the engine at TDC. Other have a pointer that you line up at the proper timing mark. You can also take #1 injector and feel the top of the piston travel. TO BE ON #1 you have to turn the engine until the intake valve goes first down and the up. When the valve is closed you then feel the piston come up to TDC. I do not have the valve lash for you, but if the firing order is 153624, I can give you a short cut to adjust the valves. Let me know if you want it and I'll post it for you. I usually hang out at ToolTalk,


Guido.

If you want to get #1 at TDC compression stroke, watch the rear most cylinder rocker arms. When they are in "overlap" (the exhaust is just going closed, the intake is just beginning to open), the #1 will be on TDC compression.

You don't want to skip setting the valves! Very important! In fact, you need to do it twice. Once before starting it, then again after it has run and the head has been retorqued.

Thank you sir. I will get it done and I appreciate the information. I am about 99% sure I did not retorque my head bolts when I rebuilt this engine 8 years ago. I probably only have 300-400 hours on it since then. Would that be the reason my head gasket blew?

Anyway, I saw that part in the manual this time, about running it for a half hour and resetting the valves and going through the head bolts again.

And what you said about watching the rear cylinder rocker arms jogged my memory a little and makes the one little note I have on it make more sense.

Thanks again.

Thanks Guido. I will look for those things you mentioned with regard to knowing when I am at TDC. I have my injectors out and did not think of using that hole to determine when that piston is at the top. Thanks for that information. I watched the intake valve open and close but exactly when that piston is at the top was something I had no way of knowing.

With your response and Steve's I should be able to get it done.

Thanks again.

Like Steve says below,#1 is on TDC when it's companion cylinder's valves rock/overlap,then #1 valves can be adjusted.Your firing order determines the progression:1,3,4,2 should be yours,so adjust 1 when 4 rocks,3 when 2 rocks,4 when 1 rocks,and 2 when 3 rocks.Just bar the engine around slowly in direction of rotation as you observe the valve train.
One thing-I would have checked and cleaned the block for more than a few minutes.And maybe use some copper-kote gasket sealer,or checked the block with a straight edge.Also clean out each of the head bolt holes' threads with a full tap,and clean and blow them out.Then,clean with a wire wheel,and LIGHTLY lube the bolts and washers.This assures a good,even torque down,following the torque pattern in your manual,or starting from center out.Mark

Thanks Mark.

I am usually very particular about what I do, but I was in a old shed with lots of gaps in the boards with 40 MPH gusts outside. I did clean off the block as best I could, but I wanted to get that head back on before the perfect gust came through and blew a bunch of crap in my engine.

But I appreciate the information, I am working on a pole barn that will have a shop section so the next time I will be in a nicer environment and will be able to work without worry. If this happens again, or maybe I should say when this happens again (considering I have a few older engines around) I will use your procedure. Sounds thorough. One question I have is about the copper-kote, is that for any gasket? Or just ones with copper in them?

Thanks again.

Make your life simple and ignore the instructions about which valves to set with engine at TDC, turn x degree set etc.

Look at the valves, lets say exhaust valve on cyl # 2 is down.
You know beyond doubt the intake valve on cyl #2 is at rest, and visa versa when an intake valve is travelling down.
Set it and mark it with a piece of tape, wax crayon whatever.
Continue to set and mark any others that you know are at rest using the above method.
Give the engine a half turn and set and mark some more.
Quarter turn, repeat etc until they are all set.
Does not take long and removes any chance of incorrectly setting a valve when it was not at rest.

You can do this on almost any engine and be done in less time than it would take you to find the manual, instructions and TDC.