tappet clearances

[pennycar9]

Our main engine is a Cummins NA220 6 cylinder of unknown vintage. Over the weekend We did a full service on it and wanted to make sure the tappett clearances were OK but don't know what they are supposed to be.
Does any one know what they are? Exhaust,inlet and injector Tappets

 

[alan006]

My Cummins manual covers a 6BTA-220. If this is the same engine I can help you.
For Series B. Inlet clearance 0.010inch Exhaust clearance 0.020inch
For Series C. Inlet clearance 0.012inch. Exhaust clearance 0.024inch.
As I say I'm not sure if this is right for your engine.
Good luck.

 

[pennycar9]

Thanks for that Alan, I'll have a look next time I go down the 'hole'.

 

[tinkicker0]

N series Cummins 14 litre PT injector clearances should be done by a shop specialising in them. This is a critical adjustment.
I was a Cummins specialist many moons ago and there are so many variables and injector types that without the proper manual and injector service tools for the motor, you are going up an expensive blind alley.

eg. Some injectors were set at 5 in/lb. some at 7 in/lb, some you could set by feel and some gave trouble even with the correct timing fixtures and tools.

Never came across an NA before, mostly worked on NTE 400 Big Cams, B, C, K and L series, so can't advise further.

note that "clearance" is a misnomer, you are actually setting how hard the injector needle presses on the bottom of the cup. Too loose and you will get black smoke and rough running, too tight and you will get very rapid wear.

See your friendly Cummins man at your local diesel shop.

 

[PeteCooper]

But if they are asking about valve clearances surely that has nothing to do with the injectors?

 

[brianrunyard]

Re-read the original question;
You'll see he asked for valve clearances AND injector clearanes!

 

[PeteCooper]

Woops!

 

[Latestarter1]

Brigid Mary

Tinkicker has just given you darn good advice.

The Cummins 855 is just about the most durable diesel engine ever made, but doing the top end needs somebody who knows what they are doing, either with inch pound torque wrench or DTI gauge and fixture. Find a local Cummins specialist and say you want a 'top set'

The if you want to hear a naturally aspirated 855 set up right and you are down in Dartmouth. The Hauley tugs on the Lower Ferry have 855-195's which are beautifully maintained, in the summer they are thrashed all day long with just lovely bark and just a heat haze from the funnel. Fifteen years ago one of the tug engine had accumulated over 75,000 hours.

 

[pennycar9]

thank you all for your comments.
Our engine is a 220 hp naturally aspirated 6 cylinder in line, with 1 head serving a pair of cylinders. Each cylinder comprises 2 inlet and 2 exaust valves, now the rub is, there is no fuel pump supplying fuel to normal injectors, as is the norm with an engine such as a Volvo or a Detroit. The fuel is pumped directly from the tank to injector by a tappet driven by the cam shaft. So we have not only the usual inlet and exhaust valve tappet, but we have the fuel injector tappet as well.
Confused? not as much as I am!!!!!!!

 

[Latestarter1]

The Cummins PT (Pressure Time) fuel system is a low pressure common rail fuel system unique to Cummins;

The injector accomplishes all metering and injection functions. Very high (compared to conventional Bosch injection systems on say Volvo engines), pressures exceeding 20,000 psi. The pressure is developed in a gear-type pump which eliminates the need for high- pressure fuel lines running from the fuel pump to each injector.

A PT injector is provided at each engine cylinder to spray the fuel into the combustion chambers. PT injectors are of the unit type and are operated mechanically by a plunger return spring and a rocker arm mechanism operating off the camshaft.

There are four phases of injector operation, which are as follows;
Metering. The plunger is just beginning to move downward and the engine is on the beginning of the compression stroke. The fuel is trapped in the cup, the check ball stops the fuel flowing backwards, and fuel begins to be pressurized. The excess fuel flows around the lower annular ring, up the barrel, and is trapped there.

Pre-injection. The plunger is almost all the way down, the engine is almost at the end of the compression stroke, and the fuel is being pressurized by the plunger.

Injection. The plunger is almost all the way down, the fuel injected out the eight orifices, and the engine is on the end of the compression stroke.

Purging. The plunger is all the way down, injection is complete, and the fuel is flowing into the injector, around the lower annular groove, up a drilled passageway in the barrel, around the upper annular groove, and out through the fuel drain. The cylinder is on the power stroke. During the exhaust stroke, the plunger moves up and waits to begin the cycle all over again.

Injector adjustments are extremely important on the Cummins PT system because they perform the dual functions of metering and injecting. Also remember that this is an ‘open’ nozzle system unlike ‘closed’ nozzle on Bosch.

Find yourself a Cummins N/NT 855 Operation & Maintenance manual on EBay.

 

[Kawasaki]

Lateboater, "new user" it says.
Well, Welcome.
What a clear , concise and informative reply to brigid_mary's question.
Well done, glad to have You aboard.