jk3 or jp3 and spill rail timing

[londonron]

Have changed my piston rings. Done the valves and hard to start still. I will do the rest of the engine but needed it back for the summer. So was thinking check the timing is OK. Wouldn't mind a bit of help or advice.

 

Also what's the difference between a jk and jp. How do I tell which I have? I did clean a plate and it's a jk though was told it's a jp. As the manuals match I wondered whats the difference

[by'eck]

JK's don't have compression change over valves - the big black knobs on water rail side of engine - instead they have the compression ratio fixed midway at 17.5:1.

 

Other differences are that the rockers are lubricated with external pressure oil feed rather than the screw in grease cups on JP's, and safely rev to 1500 rpm courtesy of copper/lead thin wall bearings, so developing more power than the earlier JP's they replaced .

 

I think it's spill timing BTW, performed on injection pump and described on page 39 of manual downloadable here. Spill rail collects leak off from injectors.

Edited May 13, 2015 by by'eck

[londonron]

if youre correct then i have a Jp with a jk indentity issue as it says jk but has changeover valves. and yes spill timing. Have read the manual and what shall i do with the statement that it depends on which make i have. With my engines indentity issue how do i tell it i have a 1200rpm or 1500 version ? as i also have rockers with grease points i guess i have the jp and therefore a 1200 version.

[by'eck]

if youre correct then i have a Jp with a jk indentity issue as it says jk but has changeover valves. and yes spill timing. Have read the manual and what shall i do with the statement that it depends on which make i have. With my engines indentity issue how do i tell it i have a 1200rpm or 1500 version ? as i also have rockers with grease points i guess i have the jp and therefore a 1200 version.

 

Your call but everything you mention suggests it's a JP, so I would time injection pump accordingly. The timing mark should be on the flywheel, check out my post here for data.

 

JP's were supplied governed to 1000 rpm (most industrial versions) and 1200 rpm (most marine, JPM versions).

[Giant]

Sounds like you have a set of JP heads that have been put on a JK block. Or it might be as simple as the crankcase door (with the serial number on it) being a replacement that came off a JK.

[frangar]

My JP2 was fitted with a JP3 flywheel at some stage in its life...I guess to get a starter ring. However someone then timed it on the timing marks.....amazing it ran but was smoky and knocked a big end out.

 

The moral is that old engines have bits changed over the years...best to double and triple check where possible and don't trust anything on face value.

 

Cheers

 

Gareth

[by'eck]

Interesting that the parts manual quotes same numbers for flywheels on JP2 and JP3, even JK's. There was a different part number for electric start models but it was still common to two and three cylinder models. Can't remember if timing marks for both two and three cylinder models were stamped on all flywheels, but worth checking yourself once TDC on firing stroke of appropriate cylinder is found. This is probably why timing reference is quoted as distance from TDC on flywheel circumference for both 23" and 26" flywheels as well as degrees BTDC.

[martyn 1]

if youre correct then i have a Jp with a jk indentity issue as it says jk but has changeover valves. and yes spill timing. Have read the manual and what shall i do with the statement that it depends on which make i have. With my engines indentity issue how do i tell it i have a 1200rpm or 1500 version ? as i also have rockers with grease points i guess i have the jp and therefore a 1200 version.

Not sure what the confusion is here as it makes no difference with spill timing if its JP, JS or JK as for over 1000rpm engines its 26 Deg and the JP's that top out at 1000rpm will happily run without issues at this as well so assuming yours is a JPM or a JK it would still be 26 Deg.

 

When we looked at your cylinder heads they are definitely JP not JK and as for the bottom end of the engine the only difference is the bearings and governor weights so I would check what engine number is stamped on the flywheel and although that could have been changed as well at least if it matches the side door you know with a certain level of confidence that you have a JK bottom end with JP heads.

 

Interesting that the parts manual quotes same numbers for flywheels on JP2 and JP3, even JK's. There was a different part number for electric start models but it was still common to two and three cylinder models. Can't remember if timing marks for both two and three cylinder models were stamped on all flywheels, but worth checking yourself once TDC on firing stroke of appropriate cylinder is found. This is probably why timing reference is quoted as distance from TDC on flywheel circumference for both 23" and 26" flywheels as well as degrees BTDC.

The flywheels are the same in a very loose term (23" 26" diameters and then 4.5 wide and 5 wide on the larger 26" but essentially they are marked on a per engine basis hence the same part numbers. As Gareth has mentioned the problem arises when a 3 cylinder marked flywheel is fitted to a 2. Although the cylinder 1 marks will be in the same place unfortunately as you know the 2's are usefully timed on cylinder 2 which means you would need to add those marks to the flywheel or carry out the spill timing on cylinder 1 but the position of the coupling adjustment bolts is fun to get at hence lister stating cylinder 2........

[frangar]

Interesting that the parts manual quotes same numbers for flywheels on JP2 and JP3, even JK's. There was a different part number for electric start models but it was still common to two and three cylinder models. Can't remember if timing marks for both two and three cylinder models were stamped on all flywheels, but worth checking yourself once TDC on firing stroke of appropriate cylinder is found. This is probably why timing reference is quoted as distance from TDC on flywheel circumference for both 23" and 26" flywheels as well as degrees BTDC.

 

The diameters etc are the same….the timing marks aren't! Only when a new pump was trying to be timed shortly after I brought the boat was this found out!

 

The give way was the serial number on the flywheel which was for a JP3.

 

It now has new timing marks!!….all this was a long time ago but goes to show that with old engines nothing should be taken for granted.

 

Cheers

 

Gareth

 

edited to add:

 

Sorry Martyn... should have read to end of thread before posting!

Edited May 15, 2015 by frangar

[londonron]

story of my life martyn. I couldnt just have a jp could i

was hoping that if i was a mix and match that maybe it was set up for the wrong one etc . by the sound of it that isnt going to be the case. Great advice with the flyweel. are they always stamped in the same place? not the most room at that end so a clue could save a sore back and all that

[martyn 1]

story of my life martyn. I couldnt just have a jp could i

was hoping that if i was a mix and match that maybe it was set up for the wrong one etc . by the sound of it that isnt going to be the case. Great advice with the flyweel. are they always stamped in the same place? not the most room at that end so a clue could save a sore back and all that

The engine number, well at least the engine number the flywheel was originally fitted to will be stamped on the outer face of the flywheel, same one as the timing marks. the only other possibility if that doesn't match that on the door is to check the crank as on Lloyds checked marine units the engine number will be stamped on that as well.

[londonron]

damn, cant find the timing marks on the flywheel. found a stamp but that was very worn and couldnt make out the serial number. All after the first hour of use which was fine, a bit smokey but as you told me i thought fine, it will settle.

started it today and its smoking very badly. Considering my issue was bad starting but no smoke the engine is now worse after an oil change, head and valve refurn and new rings.

[RLWP]

High or low compression?

 

Richard

[by'eck]

damn, cant find the timing marks on the flywheel. found a stamp but that was very worn and couldnt make out the serial number. All after the first hour of use which was fine, a bit smokey but as you told me i thought fine, it will settle.

started it today and its smoking very badly. Considering my issue was bad starting but no smoke the engine is now worse after an oil change, head and valve refurn and new rings.

 

If you can find TDC firing stroke on No.1 cylinder (for JP3), even if it means taking off crankcase door, this can be marked on the flywheel. According to flywheel diameter, you can then measure back to spill timing point according to data here and mark that as well.

[londonron]

I think its a job for test match special once the cricket starts .