Finding TDC

[bruceknoer2]

I'm trying to start my twin cam, several years since I assembled
it. By searching I've found several good posts on setting up the
ignition but the one thing that still insn't clear is how to find
TDC with the cam cover on. One suggested feeling the pressure of the
commpression stroke with your finger. This isn't going to work. So
I'm need a some tips to determine if I'm at the top of the
compression stroke. Any suggestions will be greatly appreciated.
Thanks, Bruce

[steveww]

Can't think how to do with the cam cover on. Why not just lift the cam
cover?

bruceknoer2 wrote:

[Elan45]

Surely one of us ought to be able to determine what position #4 exhaust lobe should be in when #1 is on the compression stroke and IIRC, you can see #4 ex lobe in the oil filler. Actual TDC needs to be determined on the crankpulley or watching the piston through the spark plug hole.

Roger


cover?

bruceknoer2 wrote:

[bruceknoer2]

Yes I wondered about seeing a cam lobe through the oil filler but as
you say, where would the lobe point.

--- In ***@***.***, "Roger Sieling" <rogsie@t...>
wrote:

IIRC, you can see #4 ex lobe in the oil filler. Actual TDC needs to
be determined on the crank pulley or watching the piston through the
spark plug hole.

[davidallen]

I've found putting a finger over the sparc plug hole always works!
Alteratively, screw the plug in very loosly and listen for the hiss.


David

-----Original Message-----
From: bruceknoer2 [mailto:***@***.***
Sent: 05 August 2004 15:38
To: ***@***.***
Subject: [LotusElan.net] Finding TDC


I'm trying to start my twin cam, several years since I assembled
it. By searching I've found several good posts on setting up the
ignition but the one thing that still insn't clear is how to find
TDC with the cam cover on. One suggested feeling the pressure of the
commpression stroke with your finger. This isn't going to work. So
I'm need a some tips to determine if I'm at the top of the
compression stroke. Any suggestions will be greatly appreciated.
Thanks, Bruce

[saarhus]

Since the #1 intake/exhaust will be oriented (looking at the front) 11 and 1 o'clock when at TDC firing position, the $4 exhaust will be pointing the reciprocal, or 5 and 7 o'clock, or pointing down. Easily determined from the oil filler. Line up the TDC on the crank pulley and you've got it. The caveat for this is that this is only a ballpark result, and not to be confused with "cam degreeing", etc.

Cheers!

Stan
Yes I wondered about seeing a cam lobe through the oil filler but as
you say, where would the lobe point.

--- In ***@***.***, "Roger Sieling" <rogsie@t...>
wrote:

IIRC, you can see #4 ex lobe in the oil filler. Actual TDC needs to
be determined on the crank pulley or watching the piston through the
spark plug hole.

[Fred Talmadge]

If you want to know "exactly" where TDC is you will need a dial
indicator with a probe down the spark plug hole. If you are just
setting the distributor; if you don't get #1 on the compression stroke
then the car won't fire up. Turn the engine over 360 and reset the
distributor.

Personally I'd remove the cam cover, it's not a big deal and it will
insure the engine will have the proper amount of oil leakage to
reinforce the tradition of British cars leaking oil.

Fred T. '65 S2

-----Original Message-----
From: ALLEN, David (Shipley) [mailto:***@***.***
Sent: Thursday, August 05, 2004 11:37 AM
To: ***@***.***
Subject: RE: [LotusElan.net] Finding TDC


I've found putting a finger over the sparc plug hole always works!
Alteratively, screw the plug in very loosly and listen for the hiss.


David

[schwartzd13]

In the old days we would put a 12" piece of brazing rod down the spark
plug hole, turn the engine by hand and watch for the rod's highest
position. (sh**t - if this isn't a wide open entrance for some sexual
innuendo...sorry)

Stan Aarhus wrote:

[Arno Church]

The exhaust lobe on #4 should be pointing towards the inlet cam and
downwards approx 45 deg
The inlet lobe on #4 should then be pointing towards the exhaust cam and
downwards approx 45 deg
If you then get pistons 1 and 4 at TDC , no 1 will be on firing , or
compression stroke
Watching the piston through the plug hole is very inaccurate for determining
tdc as you cant really see start and end of dwell of the piston at tdc

Another method of finding out if #1 is on comp stroke , is to put your
finger on the plug hole as you turn the engine towards tdc. You'll feel the
compression as on the exhaust stroke you'll wo'nt feel compression
Cheers
Arno


Surely one of us ought to be able to determine what position #4 exhaust
lobe should be in when #1 is on the compression stroke and IIRC, you can see
#4 ex lobe in the oil filler. Actual TDC needs to be determined on the crank
pulley or watching the piston through the spark plug hole.

Roger


cover?

bruceknoer2 wrote:

[Elan45]

Arno, I was trying to be politically correct when I said to watch the piston through the plug hole. I'd watch the piston come to the top with a screwdriver down the #1 plug hole, but someone went balistic last time someone else suggested putting anything down the plughole. As someone else has said today, this is not reallty an acurate way of determining TDC for valve timing etc, but close enough to doublecheck the timing mark on the crank pulley.But then, you still don't know whether #1 or 4 should be firing, and that is why you need some cam reference point or just guess and have a 50% chance of getting it right.

Roger


downwards approx 45 deg
The inlet lobe on #4 should then be pointing towards the exhaust cam and
downwards approx 45 deg
If you then get pistons 1 and 4 at TDC , no 1 will be on firing , or
compression stroke
Watching the piston through the plug hole is very inaccurate for determining
tdc as you cant really see start and end of dwell of the piston at tdc

Another method of finding out if #1 is on comp stroke , is to put your
finger on the plug hole as you turn the engine towards tdc. You'll feel the
compression as on the exhaust stroke you'll wo'nt feel compression
Cheers
Arno


Surely one of us ought to be able to determine what position #4 exhaust
lobe should be in when #1 is on the compression stroke and IIRC, you can see
#4 ex lobe in the oil filler. Actual TDC needs to be determined on the crank
pulley or watching the piston through the spark plug hole.

Roger


cover?

bruceknoer2 wrote:

[lotuselan2]

Fred
The motorcycle guys use a plug insert and dial indicators as you describe.
My son has one in his toolbox. It is quite accurate. You do not get a true
zero but you split the difference between say + and - 0.001". Having a
degree wheel on the crank also helps.

Just a side note, with the BDR we don't use the cam keys in the keyways.
They are taper fit and take the torque with cam bolt only hand tight, after
lapping the taper faces. So depending on the state of a rebuild, the cams
may not tell you much about timing.
Ken
'69 +2 with BDR

[lotuselan2]

David
They actually sell whistles to screw into the plug hole for this purpose.
Two-guys garage on Speed channel seem to think it is a good method. See my
other reply for the best method.
Ken
'69 +2 with BDR

[grat]

On Thu, Aug 05, 2004 at 01:39:24PM -0400, lotus wrote:

I too (horrors) stick a lightweight long shanked screwdriver through
hole to find top of the stoke/verify timing mark. Obviously you need
to go slow and not do anything stupid. To figure out compression
stroke I've always used a um, well a compression gauge... ?

fj..

[bruceknoer2]

I like the sound of that. If the #4 inlet lobe is pointing at the
exhaust and down, it probably is getting ready to open the #4 inlet
valve to pull in fuel as the #1 fires after compression. I think
I'll try that unless I see a post that is sure of another setting.
Thanks.

--- In ***@***.***, "Arno Church" <stuckect@i...>
wrote:

[Esprit2]

From: "bruceknoer2" <***@***.***>

Sent: Thursday, August 05, 2004 10:38 AM
Subject: [LotusElan.net] Finding TDC


Bruce,

You originally posted your question to both the Elan and Europa mailing
lists. Which do you have? I guess that really doesn't matter. The real
point is that the Elan has a timing park on the front pulley/block and the
Europa has a timing mark on the flywheel. Do you have the engine built to
the point that the pulley or flywheel is installed? If yes, then use
those marks to set the engine to TDC.

The next question is which cylinder is ready to fire... #1 or #4. Look
in the oil filler cap at the rear cam lobes. If the rear lobes are
pointing toward one another, #1 is ready to fire. If the rear lobes are
pointing away from one another, #4 is ready to fire.

If you have set the engine to TDC by the front pulley or flywheel markings,
then whether the cam lobes are horizontal or angled slightly is of no
importance. If, roughly speaking, +/- a lot, the rear cam lobes are
pointing toward one another, then the #1 cylinder is at TDC and ready to
fire. If the lobes are pointing away from one another, rotate the crank
one more revolution and back to TDC according to the timing marks.


Remove the distributor cap and observe which plug wire terminal the rotor is
pointing toward. If necessary, rotate the distributor body to align a
terminal with the rotor. That terminal is now #1. Install the #1 spark
plug wire there and the others in 1-3-4-2 order, counter-clockwise around
the cap as you look at the top of it. The ignition is now roughly timed to
TDC, +/- a bunch.

Rotate the crank around just short of a full revolution and stop with the
timing index pointing at the desired static timing mark... say, 12? BTDC.
Now use a test light or multimeter to set the distributor to the static
timing.

Rotate the distributor counter-clockwise just far enough to be certain the
breaker points are closed or the electronic ignition is "on". Then slowly
rotate the distributor body clockwise back toward the rotor position until
the points "just" open... or the electronic ignition just switches "off"
(the coil fires when the 12v primary voltage is switched off). The
ignition's static timing is now set to 12? BTDC... or whatever value you
chose to set the crank pulley/ flywheel marks to.

Good luck,
Tim Engel
Lotus Owners Oftha North
Minnesota, USA