Engine rebuild, turning the short block by hand

[kav]

I'm in the process of rebuilding my 1969 911T engine an the short block is back together (no P&C's). When I turn the engine by hand with my digital torque wrench on the crank pulley I get a reading of 6.7 ft lbs, does this seem in the ball park?

The crank was polished, the mag case was align bored back to standard, all new bearings etc. The flywheel is attached on the back of the engine. I know the assembly lube is more viscous than the oil that will replace it but I thought the crank would turn more freely than that?


Cheers.

-Kav.

[MBruns]

Yes, with assembly lube thats a good value, I look for less that 10 to get it to move and around 6 to keep it moving and thats with a low tension ring set and the bottom end.
Mike Bruns

[kav]

Originally Posted by MBruns

Yes, with assembly lube thats a good value, I look for less that 10 to get it to move and around 6 to keep it moving and thats with a low tension ring set and the bottom end.
Mike Bruns

Thanks Mike, just to clarify I have no pistons and cylinders attached to the rods. I'm confused by the 'tension ring set and the bottom end' comment?

Cheers.

-Kav

[MBruns]

Kav, the bottom end (crank/rods) is what you have, adding the drag of 6 pistons/cyls will change the value a bit depending on what style of rings you use, certain custom rings can have less tension/drag for race applications vs. stock street versions, I always check the effort it takes as the engine goes together all the way through the valve train.
Good luck with your project, Mike

[kav]

Originally Posted by MBruns

Kav, the bottom end (crank/rods) is what you have, adding the drag of 6 pistons/cyls will change the value a bit depending on what style of rings you use, certain custom rings can have less tension/drag for race applications vs. stock street versions, I always check the effort it takes as the engine goes together all the way through the valve train.
Good luck with your project, Mike

Great thanks Mike! It means I've done something right ...ish!

Cheers.

-Kav.

[kav]

Originally Posted by MBruns

Kav, the bottom end (crank/rods) is what you have, adding the drag of 6 pistons/cyls will change the value a bit depending on what style of rings you use, certain custom rings can have less tension/drag for race applications vs. stock street versions, I always check the effort it takes as the engine goes together all the way through the valve train.
Good luck with your project, Mike

Actually Mike do you mind giving us your thoughts on what effort it takes the engine to turn as it goes through it's build up stages?

-Kav.

[MBruns]

Kav, there are alot of variables once you get past the short block and even with that depending on what you use for assembly lube, but I have seen mag cases that will hardly turn over with new bearings or are so stiff you need a pull bar to get it to move, not so much with the 3.0 based cases but I always check. beyond the bottom end piston ring drag, cyl wall finish,cam lift and valve spring pressures etc... I can share one from a 3.8 TT that the file is still on the table and a 3.0 that is going together now, both have heavier springs and agressive cams but it will give you an idea.
Mike Bruns

[lvporschepilot]

This is a helpful thread to many. Quantifiable numbers are great. Once heads and cams with heavy valve springs are on is when it gets difficult simply due to the valve spring adding so much more parasitic drag. Regardless , great thread.

Not to detail much here, but does anyone leakdown each cylinder before running the engine or is it seen as pointless until the rings seat a bit? Mahle or JE differences due to Mahle 4032 pistons running slightly tighter clearances? Lots here I know. Highly controversial subject I would think as many don’t believe rings ‘seat’ all that much. Would love to know thoughts from those who have done many.

[MBruns]

I always leak test after I get the valve train together not so much for the value but for consistency.
Mike Bruns

[Catorce]

Unfortunately you are not going to get quantifiable values throughout the process. If there was a defined numeric torque value it would have been listed in a Porsche manual.

After building more engines than I can remember, you learn to work by feel. You turn the crank and you can just feel whether it is right or not.

Of course this comes after experiencing self made mistakes like bad bearings, wrong clearances, and even cams installed 180 degrees out, all of which can be felt when rotating the motor. Just takes experience.

In the OP's case, turning the motor with just the crank in it should have just a touch of the slightest drag and be ridiculously easy to spin.....sometimes a cold garage with too much assembly lube makes it feel stiffer.

[kav]

Originally Posted by MBruns

Kav, there are alot of variables once you get past the short block and even with that depending on what you use for assembly lube, but I have seen mag cases that will hardly turn over with new bearings or are so stiff you need a pull bar to get it to move, not so much with the 3.0 based cases but I always check. beyond the bottom end piston ring drag, cyl wall finish,cam lift and valve spring pressures etc... I can share one from a 3.8 TT that the file is still on the table and a 3.0 that is going together now, both have heavier springs and agressive cams but it will give you an idea.
Mike Bruns

Understood Mike, I'm just trying to find any reassurance along the way. Sounds like I'm off to a good start and this is one of the more critical steps for tolerances etc as there is no real going back easily.

Cheers.

-Kav.

[kav]

Originally Posted by Catorce

Unfortunately you are not going to get quantifiable values throughout the process. If there was a defined numeric torque value it would have been listed in a Porsche manual.

After building more engines than I can remember, you learn to work by feel. You turn the crank and you can just feel whether it is right or not.

Of course this comes after experiencing self made mistakes like bad bearings, wrong clearances, and even cams installed 180 degrees out, all of which can be felt when rotating the motor. Just takes experience.

In the OP's case, turning the motor with just the crank in it should have just a touch of the slightest drag and be ridiculously easy to spin.....sometimes a cold garage with too much assembly lube makes it feel stiffer.

I wouldn't say 6.7 ft lbs is a ridiculously easy spin but as you say I used lots of assembly lube plus oil pump on the intermediate shaft, flywheel, timing chains dragging over the ramps etc all have an affect. Sounds like I'm in the zone which is reassurance enough for me at this stage!

Cheers.

-Kav.

[faapgar]

Ease with turning a newly assembled engine has so many variants.Spin an engine with 75 lbs. of valve spring pressure with Titanium Valves and one with Aase Bros.springs and steel valves and it is a big difference.My only real concern is the bottom end.If you have bolted it together and checked with a bore gauge then installed the bearings and bolted it together and clearances are good you are fine.A race motor with 1 thousandths more clearance will turn easier as well.You check drag on differential bearings when new and SKF bearings are 35 inch lbs. and Fag is 25 inch lbs.SKF is a better bearing and less likely to rock the differential when warm due to a higher preload.It is advisable to check crankshaft end play on new assembly as well which does not get much discussion here.Not all bearings are made equal.Ciao

[faapgar]

One more tip.When possible let the crank sit several hours in the crankcase and turn slightly every hour to make sure it is settled before bolting the halves together.

[Mark Henry]

Shortblock, if you could hang the chains right, one finger to spin it. Like everyone said once you add rings and valvetrain it will need a bit of leverage (wrench) to spin.

996 engines I torque a lot of 6mm bolts at 7.5lbs, to me that's not a lot of torque...I have to use a inch pound torque wrench.