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Finding TDC with distributor off car

SIVAllan

SIVAllan

Gold Level Sponsor
Google brings up a few ways. Does this one work?

Remove #1 plug.

Hand turn engine.

Verify #1 piston on downstroke, then on upstroke, using a pipe cleaner inserted carefully into the #1 plug hole to check direction.

Onec on upstroke, stop turning the engine when timing marks align.

Thanks.

Allan
 
R

RootesRacer

Donation Time
If you trust your pulley timing marks then #1 TDC is when you are pointing at the TDC point AND both your #1 valves are fully closed (not almost closed or beginning to open).

If you are looking to validate your pulley TDC timing mark, this must be done with the head off and with a dial indicator.
 
SIVAllan

SIVAllan

Gold Level Sponsor
Thanks.

Actually was aimed at the distributor. The WSM details how to set the oil pump, at a certain angle, so that the distributor can be adjusted to do its job.

The setting needs to be done while at TDC.

A distributor is adjustable, getting over my head here :) , but can it sync if the oil pump's drive is off a bit due to error in finding true TDE.

Allan
 
R

RootesRacer

Donation Time
Then go with the first part of what I wrote, and ignore the instruction you got from google.

You need to take the valves into account since you will be indexing the distributor to point at #1 when the ignition event occurs.
 
A

agmason54

Donation Time
#1tdc

Pull #1 spark plug and jam a wad of paper in the hole.Gently bump the motor until the wad shoots out like a pop gun.Now take the dip stick and put it down #1.Turn engine slowly by hand to feel the piston reach the top.Works everytime-all you need is paper and a plug wrench assuming the engine is in the car.
RedCarTWG
 
SIVAllan

SIVAllan

Gold Level Sponsor
Rootesracer thank you.

Am setting up a replacement engine (R.I.P. first engine) that runs, or did before a small accident that broke the oil pump to distributor drive, probably while dropping in the engine...

Had to replace the oil pump.

I'm not real clear on verification of TDC. I understand that both #1 valves need to be closed, and that they may not be totally closed just because the timing mark on the crank is dead on to the valve cover marker.

I need to figger out just how to make totally sure. Might be that I got lucky, and true TDC was at hand when I pulled the sump and replaced the oil pump.

Then again (damn the 'then agains)...:) but I'd rather be sure prior to dropping the sump again.

Thanks again.

Allan
 
husky drvr

husky drvr

Platinum Level Sponsor
Allan,

Keep in mind that the engine works on a four stroke cycle. You can have TDC between the exhaust - intake strokes ( exhaust valve closing and intake valve opening ) or TDC between compression - combustion strokes ( both valves closed ). The engine will not run if ignition is set to fire on the exhaust stroke.

If you have been looking at the service manual, then you have probably noted that the distributor drive slot in the oil pump gear is set off-center so that it will only allow the distributor to engage one way.

HTH,
 
husky drvr

husky drvr

Platinum Level Sponsor
SIVAllan said:
Rootesracer thank you.

Am setting up a replacement engine (R.I.P. first engine) that runs, or did before a small accident that broke the oil pump to distributor drive, probably while dropping in the engine...

Had to replace the oil pump.


Thanks again.

Allan
Click to expand...


Allan,

Not sure how the drive gear broke from your description. You need to be aware that a cam from an earlier three main engine is NOT compatible to use with a 1725 oil pump drive gear.

Just one more thing to check. :rolleyes:
 
A

agmason54

Donation Time
tdc etc

Allan,
What Don said is true but it will work if you swap the oil pump drive to mate with the cam.I run a 1592 cam in a 1725 engine with a 1592 oil pump driveon the 1725 oil pump-Confused?.You are lucky to have this told to you instead of finding it out like the old fashioned way....
Agm
 
SIVAllan

SIVAllan

Gold Level Sponsor
Don,

My Sunbeam education continues:) .

I made sure that #1 piston was rising then stopped turning the hand crank once the timing marks aligned.

Then the oil pump was installed, with the proper angle in the drive slot described in the WSM.

I've looked at that offset. It isn't offset very much to the naked eye. But I understand that aspect. The distributor drive will only hook up one way.

If a distributor is installed, then the rotor should point at #1 to indicate the correct stroke? And it would point 180 degrees the opposite on the wrong stroke...?

Allan
 
SIVAllan

SIVAllan

Gold Level Sponsor
husky drvr said:
Allan,

Not sure how the drive gear broke from your description. You need to be aware that a cam from an earlier three main engine is NOT compatible to use with a 1725 oil pump drive gear.

Just one more thing to check. :rolleyes:
Click to expand...

No problem with the cam. I don't know for sure what happened to the oil pump gear. It likely is a fluke. But I noticed it was missing a piece in the gear adjoinging the slots. I think the distributor turns in the direction opposite the break, so everything probably would have worked fine.
 
husky drvr

husky drvr

Platinum Level Sponsor
SIVAllan said:
Don,

My Sunbeam education continues:) .

I made sure that #1 piston was rising then stopped turning the hand crank once the timing marks aligned.

Then the oil pump was installed, with the proper angle in the drive slot described in the WSM.

I've looked at that offset. It isn't offset very much to the naked eye. But I understand that aspect. The distributor drive will only hook up one way.

If a distributor is installed, then the rotor should point at #1 to indicate the correct stroke? And it would point 180 degrees the opposite on the wrong stroke...?

Allan
Click to expand...


Allan,

It will depend on which side of the cam was up when you installed the oil pump. You have a 50-50 chance. If the cam was in the wrong position then the distributor rotor should be 180* out of position. If that is the case, all is not lost. You will just have to rearrange the plug wire positions in the distributor cap to match the correct cylinder firing positions ( unless of course you just really want to pull the pump again :eek: ).


HTH,
 
SIVAllan

SIVAllan

Gold Level Sponsor
Don,

I did a 180 on the distributor drive. Removed the pin, turned, reinstalled the pin (actually a machine shop did the work for 5$).

Chased side issues all day (leaking crossover tube hose at one fuel tank - fixed) (fuel pump not pulling from fuel tanks - still investigating - pump tested on car with remote gas source and is fine - maybe is drawing air somewhere).

I did sorta crank the engine. It "halfway" caught, spun itself a few times, oil pressure went up torwards 50.

I think two main issues remain for this engine to fire.

1--fuel delivery to carbs

2--distributor needs to be rotated a bit, but the steering assembly is in the way. The vacuum advance is already next to the assembly and still needs to be turned a little. Will have to lift up the distributor somehow, set it back down on the other side of the steering assembly. This will make the rotor point at #1 instead of #3ish.

Made some progress; rain headed in, won't be able to get back to it until Friday. Blast darn it.

Engine sounded great for the moment it ran. Nice deep British car sound.

Allan
 
SIVAllan

SIVAllan

Gold Level Sponsor
Bill Blue said:
With a slight Hoosier Hillbilly twang.

Bill
Click to expand...

Absolutely :) .

Will write/send an article to Andrew over the weekend, and will include the motor's odessy from Indiana to Atlanta :cool:. So far Air-pine has sent me to both Ohio (hardtop) and Indiana (motor), even though it hasn't left the driveway in Atlanta.

Tomorrow/Saturday weather permitting it will crank and idle Ok. I will need to replace the oil filter base gaskets. The ones I installed are leaking. Will look at gasket sealer this time.

Still a lot to do! but I look forward to resolving the myriad mass of details necessary for a runner.

Allan
 
T

Tom H

Platinum Level Sponsor
Allan,

I'm puzzled about all this rotating, shifting, and removing and installing pins to rotate the drive, etc. Why not just move the wires? Anytime you need to rotate near 90 Deg or more, just move the wires.

Tom
 
SIVAllan

SIVAllan

Gold Level Sponsor
Moving the wires will work; I know little of that, though. With the oil pump out, another method is to move the distributor drive accordingly, then install with a stock configuration, at least that's the goal.

Allan
 
tigretr

tigretr

Donation Time
I too was wondering how to find TDC with the head on until I started degreeing in my camshaft. The key is a $10 part from www.Summitracing.com called a piston stop. You screw this into your #1 plug hole (you will have to screw the adjustable stop all the way in so it can contact the piston) and gently rotate the motor until the piston hits the stop. Mark this spot on your balancer at the pointer. Then rotate the motor the other direction until it stops. Mark this point. TDC will be directly between these two points. You can put a piece of tape on your balancer and make your marks on the tape and the balancer so you can remove the tape, find the middle point between the two marks, then put the tape back on the balancer lining up the marks again. You will now have TDC.

Brian
 
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