4a. Won’t start after full rebuild. Any ideas what to check next pse?

[BlueTR3A-5EKT]

1 minute ago, trchris said:

Steve

With number 1 at TDC both valves on number 4 should be rocking ie one just closing the other just opening

Chris

And to do that the engine needs a confirmed TDC mark somewhere visible

[Steven Whitaker]

So, is the consensus to pull the timing cover off and check the crank to cam relationship?

Should i test for compression with rocker shaft  assembly and pushrods out first, or not?  Will i send the cam followers through the garage roof?  Is it dodgy to do this.

[Rob Salisbury]

It would be meaningless to do this, first the engine has to suck air/petrol in to then compress, if the valves are closed nothings going in nothings going out!!

[trchris]

Steve

You don’t need to remove rocker assembly to check compressions, go back to the beginning get number 1 cylinder at true TDC mark bottom pulley only when your sure you have true TDC , then check valve timing ( 1 at TDC rocking valves at 4 ) if all correct then re check compressions ( if timing is out remove timing cover and adjust as necessary )

Chris

[Steven Whitaker]

7 minutes ago, Rob Salisbury said:

It would be meaningless to do this, first the engine has to suck air/petrol in to then compress, if the valves are closed nothings going in nothings going out!!

You mean removing the rocker assembly is pointless?  would it simply prove that the valves all close ok, if nothing else?  Would it rule out wrong pistons or wrong head / badly seated valves?  Am i clutching at straws?

[trchris]

Yes as long as the valve clearances are set it’s pointless 

Chris

[Steven Whitaker]

1 hour ago, BlueTR3A-5EKT said:

Having just looked through this post at no point do you say how you checked the crank and pistons are at top dead centre TDC.

The fact the valves are rocking or have no lift is immaterial if the pistons are half way up the bores.   The timing of the cam to the crank is the critical thing. That is done by getting the crank at TDC and fitting the cam timing chain and sprocket once the cam is correctly orientated with valves on “the rock.”  If using standard cam.

Did you mark the new crank pulley once it was assembled with the crank at TDC and mark mot to match the pointer on the timing cover?    You must not take the pulley off its hub once you have done 5at as there are 6 different bolt holes meaning 5 places to assemble it wrongly.

Can you turn the engine by hand with the plugs out?    If so yo can check the TDC with a piston stop screwed in to the plug hole.

With the stop screwed in.   BY HAND turn crank carefully and gently until the stop is felt. ( no1 piston crown is touching the stop)   Mark the periphery of the crank pulley next to the timing pointer.    Now turn the engine by hand in the opposite direction until the stop is felt.    Mark the pulley again.   Half the  distance between the two marks on the pulley is TDC.

Alternatively this sort of sliding gauge would give a good idea of where the piston/crank are.

https://www.feked.com/tdc-timing-tool.html

 

Remove stop once you have confirmed and marked the TDC position.   

This tool appears to be 14mm metric.  Is that correct as I expected an imperial thread on such an old car?

[Michel Higuet]

2 hours ago, Lebro said:

Worth a try, one cylinder only. be very carefull if you pull any pushrods out, you can often pull the cam follower out of it's hole at the same time.

Twist the rod as you pull it slightly up, and you should feel the follower drop down, it's then safe to remove.

Bob

Or better push a fine rod along the pushrod before removing it.

[Michel Higuet]

First step you need to find the true TDC, with the head off you need a micrometre but because your head is on you need the following tool ( and of course a degree wheel ).

When you have found the true TDC you mark it ( or checked ) on the crankshaft pulley. 

 

You will see with the tool in the sparkplug, turning the crankshaft clockwise and counter clockwise the degree wheel will stop at 2 different place, eg -10 and +20 so TDC is just at the middle +15, you remove the tool, set your degree at +15 and mark the pulley. 

 

The rotor need in the direction of cyl 1  it need to be the compression stroke  ( cyl 4 at this time is also at TDC but it's the exhaust stroke )

 

Start already with that.

 

 

https://www.amazon.com/Center-Locater-Screws-Bolt-Style-Spark/dp/B09NBL5TFV/ref=sr_1_21_sspa?keywords=TDC+tool&sr=8-21-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9idGY&psc=1

 

https://www.amazon.com/Motion-Pro-08-0092-Anodized-Degree/dp/B009D38L88/ref=sr_1_5?keywords=camshaft+degree+wheel&sr=8-5

Edited November 25, 2023 by Michel Higuet

[RobH]

1 hour ago, Steven Whitaker said:

This tool appears to be 14mm metric.

Yes that is correct. Standard spark plug thread.

[Michel Higuet]

If your camshaft adjustment is/was ok the high point of the inlet pushrod cyl 1 must be at 127°  

Interesting link, everything you need to know.

 

[Andy Moltu]

When checking TDC it doesn't matter if you have no1 or no4 firing or on the exhaust stroke. The crank is in the same position. 

It does matter for checking ignition timing as the cam rotates once for every 2 rotations of the crank.

[keith1948]

I think now you need to concentrate on why you only get 50psi compression. Start by making sure compression gauge isn't giving a faulty reading. Maybe check it on a modern car or a mates TR to see what reading it gives there.

Then did you grind/lap in the valve seats?

Rocker clearance is 0.010 inch (10 thou) on all valve stems once you have set up the timing. Check 1 with 8 open, 2 with 7 open etc. (numbers add up to 9 each time). Counting from the front of the engine if number eight valve is fully open, subtract eight from nine and the answer is one, so adjust the clearance on valve number one. If number six is open, then adjust number three and so on. Sorry if you know this already.

Keith

 

[Bfg]

Wow, I leave things for the weekend and come back to find so many cooks.  Can I order a Suffolk-ham mature-cheddar omelette please, with multigrain toast, fresh orange juice and a black coffee.

Table 3 in the corner.

 

[BlueTR3A-5EKT]

...and what torque was the cylinder head secured down to?

Book says 100-105  pounds per Foot.

I have heard of heads being torqued to pounds per inch, ie one twelfth of what they should be.

[Bfg]

p.s. yes I agree check the compression ratio gauge, and then recheck your TR engine's compression after adding a tablespoon of engine oil to each cylinder.  This will both lubricate the bores and help seal around the piston rings which have yet to be bedded in.  Do this with each of the spark plugs out and spinning the engine over on the starter with a fully charged battery.   The minimum compression my old sunbeam motorcycles will start on is about 100 psi, and they were designed to run at 6:1 compression on pool petrol.

Pete 

[Michel Higuet]

7 hours ago, Andy Moltu said:

When checking TDC it doesn't matter if you have no1 or no4 firing or on the exhaust stroke. The crank is in the same position. 

It does matter for checking ignition timing as the cam rotates once for every 2 rotations of the crank.

Yes except that with 50 psi on ALL cylinders he need to check the degreeing of the camshaft so which TDC here matter. 

Edited November 27, 2023 by Michel Higuet

[Michel Higuet]

5 hours ago, keith1948 said:

I think now you need to concentrate on why you only get 50psi compression. Start by making sure compression gauge isn't giving a faulty reading. Maybe check it on a modern car or a mates TR to see what reading it gives there.

Then did you grind/lap in the valve seats?

Rocker clearance is 0.010 inch (10 thou) on all valve stems once you have set up the timing. Check 1 with 8 open, 2 with 7 open etc. (numbers add up to 9 each time). Counting from the front of the engine if number eight valve is fully open, subtract eight from nine and the answer is one, so adjust the clearance on valve number one. If number six is open, then adjust number three and so on. Sorry if you know this already.

Keith

 

Why would you suspect a NEW compression gauge????  "did you grind/lap in the valve seats" SO on 8 valves ALL will be bad? He has 50 PSI on ALL cylinders before he will check if he had forget to put the rings on the pistons ( joke )  maybe checking the camshaft no?   

[Michel Higuet]

4 hours ago, Bfg said:

p.s. yes I agree check the compression ratio gauge, and then recheck your TR engine's compression after adding a tablespoon of engine oil to each cylinder.  This will both lubricate the bores and help seal around the piston rings which have yet to be bedded in.  Do this with each of the spark plugs out and spinning the engine over on the starter with a fully charged battery.   The minimum compression my old sunbeam motorcycles will start on is about 100 psi, and they were designed to run at 6:1 compression on pool petrol.

Pete 

Good idea but with 50 psi per cyl I would advice to put a half liter per cyl...

[John L]

Doesn't anybody live near Hebden Bridge to help??  We could fill pages and pages.....

John

[keith1948]

1 hour ago, Michel Higuet said:

Why would you suspect a NEW compression gauge????  "did you grind/lap in the valve seats" SO on 8 valves ALL will be bad? He has 50 PSI on ALL cylinders before he will check if he had forget to put the rings on the pistons ( joke )  maybe checking the camshaft no?   

Hi Michel

Earlier he had a multimeter giving wrong readings. Just because it is new doesn't mean it reads correctly and easy just to try on a different engine to make sure it is giving somewhere near accurate readings and not leading us down a route that is not relevant.  Just asking the question on valve seat lapping. Again eliminating something easy to cross off the list. As you say unlikely to affect all 4 cylinders but not impossible. And no I wasn't going to suggest piston rings missing.

You are probably right to suspect setting of TDC is wrong and valves opening and closing at wrong time.

Keith

[Motorsport Mickey]

 "And no I wasn't going to suggest piston rings missing."

Me neither, but I am suggesting they may have been put on upside down, that won't help any engine get compression.

Mick Richards 

[Rob Salisbury]

Dead easy way of checking if you are in the right valve timing ballpark  .... take all the plugs out and remove the rocker cover, find top dead center on the induction stroke,  (Cylinder no.1 inlet valve opening, exhaust valve closing) then turn the crank back 45' (assuming a standard cam 17/57/5717) the inlet valve should now be closed, adjust the valve gap to around 2 thou then put in place the thinnest feeler gauge you have, now wind the crank on towards top dead centre and where that thin feeler becomes tight is where the cam clearance ramp has been taken up and valve lift has begun, this obviously is quite inaccurate but if you can judge halfway between 45' and 0' then it's just over 20' and heading towards the point at which the valve should be opening and will give a clearer picture of where to go next.                                                                                       Cheers Rob 

[Andy Moltu]

Checking your cam timing is a relatively quick process (if it's incorrect, re setting it is a bit more complicated as you will have to remove the timing cover and set the timing).

A TR4 standard cam should have no1 inlet fully open on the mid point of the lobe 110degrees after TDC.

Check crank tdc. Attach a timing protractor to your crank when in this position. Rotate the crank 110 degs and no 1 inlet should be fully open. There is a good but quite long video here.

[SuzanneH]

Full circle……!!!