Engine won't turn...

Hi,
Rebuilt 1500 cc engine. I adjusted the valves then I'm trying to put back the timing belt. Since it have a shaved housing, I put a 1300 cc belt and tensioner bearing. But this is not the problem. Problem is I can't rotate the engine so the cam mark and the crank mark (5 BTDC, this is carbed engine) align. When they are close, the engine won't rotate anymore, even when applying a lot of force, In fact, instead of turning, the cam or the crank nuts are turning, applying more and more torque without the engine turning. I stopped before doing something foolish. I wonder if there is interference between the valves and the pistons. This is a 1500cc but there were many modifications.

Any suggestions?

Daniel Forest
Montreal, Canada

Who built the engine?

Is it in the car or out of the car?

Was the head shaved, if so by how much?

Stock valves or big valves?

Cam specs (lift specifically)? Stock springs?

If it's out of the car, pull the head and verify the bottom end rotates without catching on anything. Then verify the top end rotates freely.

If you have a big cam (sounds like you do, shaved cam housing would indicate a reground cam) then you may be in spring bind. Did you upgrade the springs or re-use stock?

If it's in the car and/or you don't feel like pulling the head, you could check for p/v clearance with one of these:

http://www.harborfreight.com/digital-inspection-camera-67979.html

Pete

You're pushing the pistons into the valves.

Hopefully you haven't done any real damage to the valves since you say you used a lot of force.

I'm not sure the best way to get things back into alignment other than pulling the cam box to make sure the valves are all up out of the way and then re-installing with everything aligned to TDC.

You say this happened after you adjusted the valves?

Take the cambox cover back off and look for a shim that's gone walkabout or failed to seat properly in its bucket.

If everything looks good, move the crankshaft back to 90 degrees off of TDC, all four pistons safely out of the way at midstroke, and try rotating the camshaft. If it won't turn a complete revolution, you've got either spring bind or a serious problem in whichever valve cannot be fully depressed before the cam lobe binds.

Any chance

that the Aux shaft got out of alignment while the timing belt was off and the lobe for the fuel pump is interfearing with the #2 connecting rod?

catterar said:

that the Aux shaft got out of alignment while the timing belt was off and the lobe for the fuel pump is interfering with the #2 connecting rod?

Click to expand...

That's a DOHC problem - shouldn't happen with our SOHC motors.

ooops

guess I've been spending too much time on Mirafiori.com.:tomato:

+1

If this does not resolve the stuck crank problem, the cylinder head will need to come off to have a look-see.

The crank should turn with not much more than 20ft/lb at the crank on a new engine and significantly less for a run-in engine.


Bernice

EricH said:

You say this happened after you adjusted the valves?

Take the cambox cover back off and look for a shim that's gone walkabout or failed to seat properly in its bucket.

If everything looks good, move the crankshaft back to 90 degrees off of TDC, all four pistons safely out of the way at midstroke, and try rotating the camshaft. If it won't turn a complete revolution, you've got either spring bind or a serious problem in whichever valve cannot be fully depressed before the cam lobe binds.

Click to expand...

What to do.

Turn the crank shaft so that the timing mark is either 90 degrees before top dead centre or 90 degrees after top dead centre. Then rotate the cam shaft to the timing mark as all of the pistons will be halve way down the bores. Then turn the Crank shaft back to TDC. I doubt you have bent a valve unless you have really put some torque multiplier on the crank shaft nut. Put the timing belt on, put some oil in the cylinders and do a compression test to check for a leaking valve.


TonyK.

Grimsby Ontario Canada.

What I did...

Ok
I recheck the valves clearance. All is ok. If I move the crank 90 degrees from TDC, then I can turn the cam. If move the cam 90 degrees from TDC then I can rotate the crank all the way.

I loosened the cam housing while at TDC. Then I turned the crank at 5 BDTC (it's a carbed engine). Then I torqued the cam housing bolts. While torquing the cam turned 2 notches out of alignment with TDC. I tried twice, and same thing happened.

Then I looked at the adjustable cam timing wheel. I thrusted my friend but it is adjustable via 3 nuts. So the holes may be wrong. The TDC mark maybe 120 degrees off! I wanted to compare, but I'm short on 1500 cc stock cam wheels. I only got 1300 cc... I will find one to test with a stock cam wheel. That may be the problem. But If my friend did it's job right, then I got a big problem... Next step maybe to try with a stock cam just to see if everything works right. But then, I will need to find another cam to get the power out of the build engine.

Daniel Forest, Montreal, Canada
1980 X1/9
1987 X1/9

DanielForest said:

Ok
I loosened the cam housing while at TDC. Then I turned the crank at 5 BDTC (it's a carbed engine). Then I torqued the cam housing bolts. While torquing the cam turned 2 notches out of alignment with TDC. I tried twice, and same thing happened.

Click to expand...

ok, you have valve/piston interference. The good news is that if your valve clearances are still good, you haven't bent a valve.

Then I looked at the adjustable cam timing wheel. I trusted my friend but it is adjustable via 3 nuts. So the holes may be wrong. The TDC mark maybe 120 degrees off!

Click to expand...

120 degrees out is easy to check for. With the crank pulley timing mark lined up at TDC, the cam will be holding the valves for cylinder #1 both open while allowing #4 valves to both be closed. That's not exactly a precision measurement, but 120 degrees out will be obviously wrong.

I wanted to compare, but I'm short on 1500 cc stock cam wheels. I only got 1300 cc... I will find one to test with a stock cam wheel

Click to expand...

You can line a 1300 cam wheel timing mark up against the little cast finger on the snail mount. Again, 120 degrees won't be subtle.

My "1300 vs 1500" issue with an adjustable gear

I bought an adjustable cam gear from one of our vendors for my "stuff a 1500 with performance head into a 78" project. I noticed pretty quickly that the timing mark on the adjustable gear did not match the timing mark on my stock 1500 gear. If I had tried to install the belt and rotate the engine using the vendor's mark, I am sure I would have run into trouble.

I lined up the key holes on the vendor's gear and the stock 1500 gear to show the difference. Then sent the vendor this picture with a description of my dilemma and asking if there was a 1500 version of the gear.


The vendor responded with this picture showing me that, in their view, the marks lined up perfectly and I had the proper adjustable gear.


Of course their picture compared a stock 1300 gear to their adjustable gear. I tried to explain that they were not looking at a stock 1500 gear, but I don't think I ever convinced them I had a legitimate issue.

After much measuring and test fitting, I got the adjustable gear all lined up the way I wanted it. I could see that the mark on vendor's gear face would most likely line up perfectly with the snail mount pointer on a 1300. Sadly, I am not working with a 1300.


In the end I made my own marks on the adjustable gear to match the 1500's pointer on the cam guard. I did use a drill to carefully make them more permanent at a later date.

Somewhere down in my boneyard I have the piece of paper on which I carefully noted the number of teeth between the index hole and the timing mark on a 1300 and a 1500 pulley... Will dig that out tomorrow.

DanielForest said:

I loosened the cam housing while at TDC. Then I turned the crank at 5 BDTC (it's a carbed engine). Then I torqued the cam housing bolts. While torquing the cam turned 2 notches out of alignment with TDC. I tried twice, and same thing happened.

Click to expand...

Are you setting the belt up with the cam at TDC and the crank at 5 BTDC?

I ask because you took the trouble to mention "it's a carbed engine", suggesting you think the cam should be set up with crank at 5 BTDC.

Cheers R

TDC

Heu.... Yes?

I was assuming the 1500 cc engine should be set at 5 degrees BTDC at crank while the FI should be at 10 degrees BTDC. Maybe I'm confusing with the distributor adjustment?

Anyway, that wouldn't change much thing since while turning the crank I couldn't reach 5 BTDC, even less 0 BTDC..

I had to change one shim, but I think it was because I took the measure with the lobe not exactly up. I had to INCREASE the shim height by .020. I hope I didn't get a a bent valve.

Thanks for the info about which cam lobes should be up or close. I will also check on my 1500 cc running engine the angle between the TDC mark on the wheel cam and the pilot hole.

And also, BTW, I didn't answer all the question about the modifications because I bought the engine already modified and didn't get most specs. I had the engine rebuilt keeping the hi-perf. items and changing the pistons, rings, seals, etc.

Thanks all for your help.

Daniel Forest
1980 X1/9
1987 X 1/9

Yep, all engines must be set up with cam and crank at TDC. The other timing marks are purely for ignition timing. It may not fix your piston-valve clearance issue but it will certainly help when you get it running!

Cheers R

DanielForest said:

I was assuming the 1500 cc engine should be set at 5 degrees BTDC at crank while the FI should be at 10 degrees BTDC. Maybe I'm confusing with the distributor adjustment?

Click to expand...

yep... Valve timing is set with crank at TDC, and then when you have the engine running and you're rotating the distributor to get the ignition timing just right, you dial in a few degrees of ignition advance.

I got it, but...

It was the adjustable cam that was 120 degrees out. I aligned the cam with the piston #1 lobes open (timing belt side) and the #4 piston (tranny side) closed, then I easily moved the crank to TDC. I then refitted the outside part of the cam wheel and bingo, there was one position where the timing mark was exactly where it supposed to be.

Now, my fear is about the possibility of a bent valve. After I applied some force on the ratchet with an extension (while trying to turn the cam to tdc while the crank was already at tdc), I had to change the shim on the exhaust on the #4 piston. The previously measured clearance was .017 then after it was .025. So I changed the shim and everything seems to be working fine, but should I opend the head to check before I refit the engine in the car? Is there another way to check?

Sorry for some poor sentences, I'm much better in French! ;-)

Daniel Forest
1980 X1/9
1987 X1/9

could you pressurize #4 cylinder through the spark plug hole (both valves closed of course) and see if it holds pressure?

Compression test will tell the story...

DanielForest said:

Now, my fear is about the possibility of a bent valve. After I applied some force on the ratchet with an extension (while trying to turn the cam to tdc while the crank was already at tdc), I had to change the shim on the exhaust on the #4 piston. The previously measured clearance was .017 then after it was .025. So I changed the shim and everything seems to be working fine, but should I opend the head to check before I refit the engine in the car? Is there another way to check?

Click to expand...

If the #4 cylinder is down on cranking pressure, that would indicate a problem with cylinder sealing.

A cranking compression test is the easiest to perform, do it across all 4 cylinders (one at a time of course) with the throttle plates open.

A leak-down compression test (basically what Jeff is suggesting above) would be a better test but requires more equipment (leak-down tester and air compressor).

Pete