871 exhaust valve noise

[bevans6]

I have no idea why the torque curve documents that lost showed what they did, I just remember what they said.  Don't blame me!

I went out and looked at my old 8V71N that was in my 1980 MCI MC-5C.  It's likely the same as yours.  The governor does not have a starting assist.  I do have this info:

"A properly adjusted governor gap will accomplish the following:

Provide sufficient weight travel in the idle range to prevent stalling during deceleration. A tight gap reduces weight travel in the idle range

Provide enough weight travel in the high speed Control range to prevent engine over-speed with light loads at full throttle. A loose gap reduces weight travel in the high speed range.

Prevent the force generated by the low speed weights (double weight governors) from depressing the high speed Springs If the gap is too tight, the force of the heavy idle weights operating on the high speed spring will cause the high speed spring to depress at too low a speed, resulting in low power"

http://transportation.centennialcollege.ca/oduffy/fuels/level%202%20fuels/DDC.pdf

Which implies that a tight gap will affect the ability of the engine to recover to idle after acceleration.  So between adjusting the idle speed, setting the gap and adjusting the buffer screw, you will probably get the beast running right.

[artvonne]

  Does B timing offer better fuel economy? Has to be some good reason to tune it down other than just to make less power. They could have done that with smaller injectors.

[luvrbus]

They stopped A timing on Detroits a long time ago the new injectors had the timing built into the injectors worth a set of injectors not to pull the back of the engine to me and the N series injectors were not something to be proud of lol

good luck

[wg4t50]

Paul,
Standard timing is not to lower horsepower, it is done to lower the rpm range of the engine.  Standard setting was the normal for mild running engines such that had the 4 speed gear box, due to the low rpm required before a down shift or Generator sets, pumps, compressors or steady rpm engines.
When you run the engine at the higher rpm range and do not need to drop below 1700 rpm for example, you can use the "A" marks, along with a large proper injector and timing tool setting, also if you want a good setting, use the dial indicator to set injectors. The bad part is with the Jake Brake setup, the dial indicator will not work, so your back to the standard selection of tools to pick from.
We have played many V-17 and V-92 engine games, for me, using different injectors, turbos timing height settings, you can make em smoke or not smoke, run for ever or burn em down, seize rings in top of pistons, oh what fun when your playing.
Still the best of the best is the 12V-71.
Many old guys who are most likely still hanging around know me with the old MCI-7 with the 12V-71 with the radiator hanging across the back, that includes Charlie Daniels and Fats Domino who enjoyed the encounter.
FWIW

[Larry B]

I found 8 new exhaust valve today in my spare parts, so made a tool and changed valves on front two holes . Noise sound to  be coming from front piston. Removed rest of parts on rear to to have a look down row of valves. held straight edge across top and and along side of valve stem ends. Both rows look nice and straight.  I have a buffer screw mounted, it is the electric jake switch and fast idle air cyinder that is not mounted on the buffer screw. At first glance it looks as if the center pin in the buffer screw is going to be too short to operate the electric switch. First I need to make the engine run smooth. My valve covers are off. I bent a piece of tin that sits around the inside of head. You could say I have 9" high valve cover with open top. no oil flying around with engine running.It will be running tomorrow.I will try increase idle rpm . This gov has internal start aid screw.

[luvrbus]

Maybe you lost a piston wrist pin retainer seal or the bolts are loose on the rod and piston

good luck

[Larry B]

  I had engine running today. Likely the best it has sounded in a while. I increased the rpm to 580. When the engine is coming down from being rev ed, it hunts for two or three sec and then smooths out. The clicking noise is not as loud as before. I may try a few small adjustment or recheck what is there but I can live with is there now. Thanks for all the help and good advice. My fishing buddy phoned, he wants to go ice fishing tomorrow