OT: Any Jag or car-engine-sages here?

Catfish · 08-09-14, 04:13 PM

A bit OT here:

Not my car, but we have a problem: engine rebuilt, crankshaft in, oil pump and distributor shaft in, also primary chain at the front and the chain cover in place, no cylinder head, no camshafts yet.
All is well oiled and fitted with torque wrench -

Now when we turn the crankshaft, we need around 30 Newtonmeter to turn it (seems a bit much, but it's a 4,2 liter six cyl., pistons going up and down, primary chain with spanner mounted), however every 2nd revolution we have a "hard point", at which you need 40 Nm to overcome a sudden resistance.
A short resistance every 2nd turn - so my idea was it has something to do with an attached component that does 1/2 turn for every full crank revolution, right ? But the valve train is not fitted - no cylinder head.

My guess is it cannot be the crankshaft and main bearings itself, because it would then either happen once in a turn, or being a bit stiff during the whole revolution.

I also think that it should turn much easier than needing 30 Nm for turning, but i am not an expert with the 4.2 block.

Hmm

Anyone ?

Thanks and greetings,
Catfish

BrucePartington · 08-09-14, 05:43 PM

Model and year of vehicle, please, so I can look for engine layout.

Flying blind, I'd assume the said distributor shaft is the ignition distributor. If it is already in because it's driven directly by the crankshaft, that would be a "person of interest", since ignition distributors turn 1/2 per crankshaft complete turn - on a conventional four stroke reciprocating piston engine, that is.

Wolferz · 08-10-14, 05:36 AM

Quote:

Originally Posted by BrucePartington

Model and year of vehicle, please, so I can look for engine layout.

Flying blind, I'd assume the said distributor shaft is the ignition distributor. If it is already in because it's driven directly by the crankshaft, that would be a "person of interest", since ignition distributors turn 1/2 per crankshaft complete turn - on a conventional four stroke reciprocating piston engine, that is.

It may be different on a Jag six banger but, I think distributors are usually turned by a gear machined into the back end of the camshaft.
It could be the oil pump building up pressure as you turn the crank. If the crankcase is full of oil that is.

Can two blind mechanics land a repair safely, Bruce?

Edit: I reread the OP and I gather it's a DOHV setup? If that's the case, then the distributor is being driven by a gear on the crank. As is the oil pump. The most likely case of sudden resistance would be the oil pump building up pressure. Since most oil pumps are driven by a lay shaft attached to the distributor...
Try removing the distributor and the oil pump drive shaft and then see how things spin.

Catfish · 08-10-14, 12:31 PM

It is an early 2+2 4.2 litre 'E' from 1966. Engine also built in 1966, presumably original. DOHC engine with primary chain, and a second one driving the two camshafts.

Oil pump and distributor are being turned at the fore end of the crankshaft, the take-in nozzle
of the pump is in the rear, via this metal tube going from the pump to the rear part of the sump.

There is not enough oil in the oil pump to build up real pressure, it is just well oiled.

I agree it must be pump or distributor shaft, since the valves and camshafts and the whole cylinder head is not yet mounted.

Buddahaid · 08-10-14, 12:37 PM

Did the crankshaft spin easy after the main bearings were fitted and after the connecting rods were fitted?

Catfish · 08-10-14, 01:27 PM

That's the problem. He didn't check.

08-09-14, 04:13 PM	#1
Catfish Dipped Squirrel Operative Join Date: Sep 2001 Location: ..where the ocean meets the sky Posts: 17,802 Downloads: 38 Uploads: 0	OT: Any Jag or car-engine-sages here? A bit OT here: Not my car, but we have a problem: engine rebuilt, crankshaft in, oil pump and distributor shaft in, also primary chain at the front and the chain cover in place, no cylinder head, no camshafts yet. All is well oiled and fitted with torque wrench - Now when we turn the crankshaft, we need around 30 Newtonmeter to turn it (seems a bit much, but it's a 4,2 liter six cyl., pistons going up and down, primary chain with spanner mounted), however every 2nd revolution we have a "hard point", at which you need 40 Nm to overcome a sudden resistance. A short resistance every 2nd turn - so my idea was it has something to do with an attached component that does 1/2 turn for every full crank revolution, right ? But the valve train is not fitted - no cylinder head. My guess is it cannot be the crankshaft and main bearings itself, because it would then either happen once in a turn, or being a bit stiff during the whole revolution. I also think that it should turn much easier than needing 30 Nm for turning, but i am not an expert with the 4.2 block. Hmm Anyone ? Thanks and greetings, Catfish

08-09-14, 05:43 PM	#2
BrucePartington XO Join Date: May 2013 Location: KM AM99 Posts: 405 Downloads: 33 Uploads: 0	Model and year of vehicle, please, so I can look for engine layout. Flying blind, I'd assume the said distributor shaft is the ignition distributor. If it is already in because it's driven directly by the crankshaft, that would be a "person of interest", since ignition distributors turn 1/2 per crankshaft complete turn - on a conventional four stroke reciprocating piston engine, that is. __________________ "The bureaucracy is expanding, to meet the needs of the expanding bureaucracy." - Leonard Nimoy

08-10-14, 12:37 PM	#5
Buddahaid Shark above Space Chicken Join Date: Jun 2008 Posts: 9,332 Downloads: 162 Uploads: 0	Did the crankshaft spin easy after the main bearings were fitted and after the connecting rods were fitted? __________________ "However vast the darkness, we must provide our own light." Stanley Kubrick "Tomorrow belongs to those who can hear it coming." David Bowie

08-10-14, 12:31 PM	#4
Catfish Dipped Squirrel Operative Join Date: Sep 2001 Location: ..where the ocean meets the sky Posts: 17,802 Downloads: 38 Uploads: 0	It is an early 2+2 4.2 litre 'E' from 1966. Engine also built in 1966, presumably original. DOHC engine with primary chain, and a second one driving the two camshafts. Oil pump and distributor are being turned at the fore end of the crankshaft, the take-in nozzle of the pump is in the rear, via this metal tube going from the pump to the rear part of the sump. There is not enough oil in the oil pump to build up real pressure, it is just well oiled. I agree it must be pump or distributor shaft, since the valves and camshafts and the whole cylinder head is not yet mounted.

08-10-14, 01:27 PM	#6
Catfish Dipped Squirrel Operative Join Date: Sep 2001 Location: ..where the ocean meets the sky Posts: 17,802 Downloads: 38 Uploads: 0	That's the problem. He didn't check.