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Finding top dead center

M

mrpops

Regular Contributor
while cleanig up my twin 454&#

while cleanig up my twin 454's getting ready for spring i discovered my port motor has no timing arrow like the port motor. is there a way to locate tdc mechanicly without removeing the head .i have my ways of doing it but am looking for other opinions.these motors are remanufactured long blocks with only 200 hours.
 
"Ayuh,....

1 way is with a

"Ayuh,....

1 way is with a dial indicator thru the spark plug hole....."
 
You should be able to put some

You should be able to put something thru the spark plug hole and feel the point that the piston stops rising while rotating the crank in both directions and take the mean of that. You could also put a level on the timing cover and mark the zero degree point on the timing cover and do the same for the one with the pointer assuming the boat doesn't rock to one side when you do it. You could still do it that way by measuring the amount of tilt the boat takes when you go to the other engine.

I'm know as a finagler when it comes to doing things the unconventional way when the correct way doesn't work.
 
Sometimes the flywheel is mar

Sometimes the flywheel is marked with TDO and a corresponding mark on the bell housing. you can take the dust cover off and with the engine running shoot the flywheel with a timing light and if marked you will see the timing mark.
 
"The most accurate way is to i

"The most accurate way is to install a piston stop in #1 cylinder. Rotate the crankshaft manually until the piston contacts the tool and the crank will not rotate any farther. Using a reference point on the engine, mark the balancer at that reference. Then rotate the engine in the other direction until it stops again. Again mark the balancer at the reference point. Accurately measure and mark the exact center between the two marks on your balancer. Then when your new center mark aligns with your reference point, you are there, exactly there. This is also a good way to tell if your balancer has spun."
 
"thanks Rick that way i like i

"thanks Rick that way i like if i can get in under the manifold , i can make a stop out of an old plug"
 
"Hello Guys:

When I do what

"Hello Guys:

When I do what youall say the flywheel mark is at the same spot on the timing mark. I rotated until # 1 is at the top the balancer mark is at zero on the timing plate, rotata it opposite direction to #1 at the top and the balancer mark is at zero on the timing plate.

I guess I just don't understand.
Can someone further explain this to a shade tree mechanic?
thank
leonard"
 
"You don't rotate it until

"You don't rotate it until the marks align, you rotate it until the piston hits the piston stop and stops it from rotating any further.

If you have a piston stop installed the piston can not possibly achieve TDC and therefore the flywheel (I am assuming you mean balancer) marks can not possibly align with the timing plate (reference)on the engine block.

If you are using an adjustable piston stop, extend it until it stops the piston near the top of it's travel, then proceed as explained above.

Rick"
 
"Hello Rick:
Thanks for tryin

"Hello Rick:
Thanks for trying to help. First let me say that I have pulled the heads to have some work done on them, and I was just trying to understand tdc for the 2 strokes, compression and exhaust. When I get the piston for #1 at the top, the mark on the balancer is aligned with 0 on the timing marks then when I turn it in opposite direction until #1 is at the top the mark is aligned with 0 on the timing marks.
What am I missing?
thanks
leonard"
 
"Leonard,

Now it is a flywh

"Leonard,

Now it is a flywheel, not a balancer (you are in the Crusader forum so I assumed you were inquiring about an inboard).

So what's the question? Outboards have an index mark on the flywheel and a timing pointer on the block. When you align those marks you are at TDC.

I don't understand what you are asking?"
 
"Hi Rick:
It's a 270hp,35

"Hi Rick:
It's a 270hp,350cu crusader. Maby I have it all wrong. It's the front of the engine where you set the timing. The balancer(crankshaft damper) is on the flywheel with a slot cut in it to align with the timing marks on the plate that is attached to block. AM I righr so far? As I said the heads have been removed and I can see the pistons go up & down. Now when the #1 is at the top the slot in the crankshaft damper is aligned with 0 on the timing-cover-tab and if I rotate it in opposite directon to when #1 is at top the slot is again aligned with the 0 on the timing-cover-tab. IS THIS TDC?
Thankd.
Sorry if these are dumb questions just trying to understand.
leonard"
 
"Hello Rick.

I did not mean

"Hello Rick.

I did not mean to say 2 stroke, I was refering to the compression and exhaust stroke. TDC is when it's on the compression stroke, right?
leonard"
 
"Yes, TDC is when the #1 pisto

"Yes, TDC is when the #1 piston is at the top of the compression stroke. You can not determine what stroke it is with the heads removed unless you remove the timing cover and look for the timing gear alignment marks."
 
"Hey Rick thanks;
The solutio

"Hey Rick thanks;
The solution you gave on the Jan 25,9:57, was that for TDC? Have I got this all confused or what?
Leonard"
 
"Yes and yes.

First of all

"Yes and yes.

First of all you stated that when you check it like I described, the marks on the balancer line up with the timing marks. Well you're not doing it like I described. Not if the heads are off.

Exactly what are you trying to determine?"
 
Hey Rick:
I understand you ca

Hey Rick:
I understand you can't find TDC(compression stroke) with the heads off.
I just read the post and tried it to see for my self. I guess this is another stupid question. Why won't your post work if the heads are off.
thanks rick
 
"There is nothing to screw the

"There is nothing to screw the piston stop in to. I don't think you are grasping the whole concept. It screws in place of the spark plug to limit the travel of the piston. Does anyone else want to chime in here, I don't think we're connecting.

148436.jpg
Piston stop tool
 
Hey Rick:
I understand about

Hey Rick:
I understand about the piston stop. It screws into the plug hole and lets you know when the piston is at the top but with heads off I can see when it's at the top.
I'm sorry but I am just trying to understand
thanks
 
You can bolt a strap of 1/4 x2

You can bolt a strap of 1/4 x2 with a bolt through it on # 1 cylinder for a stop if the heads are off. Looking at it is way too sloppy.Turn the crank one direction until it hits the stop with the piston.Mark it on the vibration dampener.. Turn it the other direction until it hits the piston. Mark it. Half way in between the 2 marks is TDC on any stroke.
 
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