Using a DTI without removing heads?

[MPO]

Is it possible to use a DTI without removing heads?

Through the spark plug hole maybe?

Cheers

MPO

[bobfather]

I don't see why not, that was the standard method when I was doing it in the 80's

[MPO]

Any particular type?

I was looking at this but what would I use to extend it through the spark plug hole?

http://www.ebay.co.uk/itm/Dial-test-indicator-DTI-...

Cheers

MPO

[sheel]

Are you trying to determine TDC? if so, old spark plug, knock the insulation out of it drill it (if my memory serves me correctly!!) 10.5 mm and tap it to 12mm, screw in long bolt with lock nut on it, sparkplug body can screw into head, the long bolt can then carefully be pulled down to the top of the piston when at TDC, you will be able to feel the piston touch the bolt and carefully you can adjust the bolt in or out to match TDC

Hope this is of use

Rich

[MPO]

Yes, I am trying to determine the TDC :-), my engine is a pre serp so I need to be sure the TDC timing marks are correct before cam changes etc.

I'm hoping others have tried to use a DTI and how they managed to use it with the heads in place.

Cheers

MPO

[Pupp]

Finding TDC with a dial gauge on the piston crown is a PITA due to the dwell - use the plug gizmo Sheel describes and set it to lock the motor a bit before the piston goes over centre - mark the pulley where it locks in both directions, then divide the gap - precise TDC

[Boosted LS1]

^ This. It's called 'positive stop'. The spark plug extension will stop the piston reaching tdc on the clockwise up stroke at x crankshaft degrees. Next, reverse the crankshaft rotation and raise the piston towards tdc until it again hits the plug stop. TDC will be the crankshaft measurement in between the two readings.

[Sardonicus]

Agree with Pupp & Boosted wouldn't use any other method

[DangerousDerek]

I will be doing this today to see if my pulley shows true TDC. I set my cam with the heads etc off.

[MPO]

Thanks for the tips Guys :-) “You’s are the ‘Gurus’!”

Cheers

MPO

[phazed]

I have used a rod through the spark plug hole with a dial gauge and did the clockwise anticlockwise dance and found the timing marks spot on.

[gavgavgav]

I learned something today reading this!

[Steve_D]

I have a selection of modified spark plugs I have made for different engines over the years.
There is no better method than this. A DTI will not give a positive result and will just waste time.

Steve

[Twistygit]

Hi, I to am starting this job shortly and was wondering also on what tools and where to get them. Suppose eBay is ok for DTI's is it? Do you need 1 or 2? And what about protractor some say ordinary protractor is fine and drill a hole in it, is this what most do?

[phazed 11.83]

I got all my stuff from eBay apart from my home-made spot tool.

Use a special protractor for the job. The bigger, the better, approximately a minimum of 12 inches diameter is ideal but do have a look on timing engines on YouTube and you will see some monsters.

[Steve_D]

Twistygit said:

Hi, I to am starting this job shortly and was wondering also on what tools and where to get them. Suppose eBay is ok for DTI's is it? Do you need 1 or 2? And what about protractor some say ordinary protractor is fine and drill a hole in it, is this what most do?

I'm using a modified Kent Cams timing disc which is 170mm diameter.



The black bit in the middle is Glass fibre but could be any hard material. It has been turned so there is a lip for the disc to register on. The two screws hold the disc but allow it to rotate on the GF the thumb screw locks the disc.

The reason for this mod is that the disc has to be secured to the crank sufficiently that the crank bolt does not come undone when you try and wind the engine backwards. When you have used the deadstop to find TDC you want to realign the disc to TDC but without this modification it is almost impossible to undo the crank bolt without moving the crank and upsetting your carefully found true TDC.

You will also see the note on the disc about using a spacer. This spacer is smaller diameter than the end of the crank and holds the disc further away from the crank end so that during timing the cam you may want to slide the crank gear off the keyway and rotate it to a different keyway which you can do without disturbing the timing disc.

Be careful what you choose as your protractor as the amount you need to tighten the crank bolt will crush some plastics.

One DTI will do the job. get a plunger type not a lever type.

Steve

[m4tti]

Morosso sell a decent timing wheel

[Sardonicus]

Real Steel sell a 11" Moroso timing wheel for sensible money unless you want something like this nice bit of long lasting kit to see you out
https://www.summitracing.com/int/parts/cca-4791-1/...

[Steve_D]

A big disc is way better for accuracy but a pain in the butt if trying to time in a cam with the engine still in the car.
Even with the engine (RV8) on a stand it makes life difficult because the cam is so close to the crank so the marks on the cam pulley are hidden behind the disc.

Steve

[Twistygit]

Hi thanks for all the advice probably go with real steel have a 11", unless V8 development sell them, anyone know?