Torque to turn over assembled engine? Seems tight...
09-09-2018, 02:55 PM
#1
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Torque to turn over assembled engine? Seems tight... Hello,
I have a 454ci ERL block (I built the short block) with PRC 285cc heads with their LS7 stage 4.2 camshaft.
I have my finished engine sitting on a cheap harbor freight stand that has a bit of wiggle in it but I am worried about the torque required to turn this motor over.
I could turn over the short block with about 35-40ft-lbs. My motor has sat (assembled) for about 6 months now. I got some oil poured over all the rockers and down the valley to try and lube it back up to turn it over some more.
It is taking about 75ft-lbs to get the motor moving according to my click-style torque wrench. This is a high-performance build so I would expect it to be tight but that number is a little concerning.
This is fully built (stiff springs and high-lift camshaft) but without spark plugs installed.
Any insight here? I really don't want to tear the whole thing apart again. Would the Melling oil priming system help reduce this before turning it over with the starter?
Thanks,
Dustin
I have a 454ci ERL block (I built the short block) with PRC 285cc heads with their LS7 stage 4.2 camshaft.
I have my finished engine sitting on a cheap harbor freight stand that has a bit of wiggle in it but I am worried about the torque required to turn this motor over.
I could turn over the short block with about 35-40ft-lbs. My motor has sat (assembled) for about 6 months now. I got some oil poured over all the rockers and down the valley to try and lube it back up to turn it over some more.
It is taking about 75ft-lbs to get the motor moving according to my click-style torque wrench. This is a high-performance build so I would expect it to be tight but that number is a little concerning.
This is fully built (stiff springs and high-lift camshaft) but without spark plugs installed.
Any insight here? I really don't want to tear the whole thing apart again. Would the Melling oil priming system help reduce this before turning it over with the starter?
Thanks,
Dustin
09-09-2018, 03:56 PM
#2
Since we all know it takes more force to get something moving than it does to keep something
moving, is a click style torque wrench the best way to measure what you are concerned with?
moving, is a click style torque wrench the best way to measure what you are concerned with?
09-10-2018, 10:32 AM
#3
Heh, you have a pretty close setup to what I have, only difference is I have a TSP block as ERL was done sleeving when I went buying this winter...
I was able to turn my over with a breaker bar on the crank while on my back, but I had the plugs in. It took some effort, I don't think 75 lb ft would be far off the mark but that was fighting compression. I primed mine using the garden sprayer pressurizer through the driver's side plug. I didn't find it turned over any easier after doing so, as I was rotating it every few minutes by hand while priming. It was probably 6-8 weeks or so from when it was assembled at TSP to when I primed it in prep for first start. Liberal use of assembly lube should keep it well covered even after 6 months I'd say.
Look forward to hearing how your build does. Have to warn you that 4.2 cam with 32* of overlap is a bit of a bear on the street, it does not like life under 2 grand very much. I wish I had gone a hair smaller since mine's mostly a street cruiser these days. Did do 570/540 at the wheels on a still very green motor.
I was able to turn my over with a breaker bar on the crank while on my back, but I had the plugs in. It took some effort, I don't think 75 lb ft would be far off the mark but that was fighting compression. I primed mine using the garden sprayer pressurizer through the driver's side plug. I didn't find it turned over any easier after doing so, as I was rotating it every few minutes by hand while priming. It was probably 6-8 weeks or so from when it was assembled at TSP to when I primed it in prep for first start. Liberal use of assembly lube should keep it well covered even after 6 months I'd say.
Look forward to hearing how your build does. Have to warn you that 4.2 cam with 32* of overlap is a bit of a bear on the street, it does not like life under 2 grand very much. I wish I had gone a hair smaller since mine's mostly a street cruiser these days. Did do 570/540 at the wheels on a still very green motor.
09-11-2018, 04:25 PM
#4
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Heh, you have a pretty close setup to what I have, only difference is I have a TSP block as ERL was done sleeving when I went buying this winter...
I was able to turn my over with a breaker bar on the crank while on my back, but I had the plugs in. It took some effort, I don't think 75 lb ft would be far off the mark but that was fighting compression. I primed mine using the garden sprayer pressurizer through the driver's side plug. I didn't find it turned over any easier after doing so, as I was rotating it every few minutes by hand while priming. It was probably 6-8 weeks or so from when it was assembled at TSP to when I primed it in prep for first start. Liberal use of assembly lube should keep it well covered even after 6 months I'd say.
Look forward to hearing how your build does. Have to warn you that 4.2 cam with 32* of overlap is a bit of a bear on the street, it does not like life under 2 grand very much. I wish I had gone a hair smaller since mine's mostly a street cruiser these days. Did do 570/540 at the wheels on a still very green motor.
I was able to turn my over with a breaker bar on the crank while on my back, but I had the plugs in. It took some effort, I don't think 75 lb ft would be far off the mark but that was fighting compression. I primed mine using the garden sprayer pressurizer through the driver's side plug. I didn't find it turned over any easier after doing so, as I was rotating it every few minutes by hand while priming. It was probably 6-8 weeks or so from when it was assembled at TSP to when I primed it in prep for first start. Liberal use of assembly lube should keep it well covered even after 6 months I'd say.
Look forward to hearing how your build does. Have to warn you that 4.2 cam with 32* of overlap is a bit of a bear on the street, it does not like life under 2 grand very much. I wish I had gone a hair smaller since mine's mostly a street cruiser these days. Did do 570/540 at the wheels on a still very green motor.
I might pull the heads off and check it out again to see if that makes it considerably easier. That would at least save me from having to pull the balancer and timing set off. This has been years in the works so it's not worth wasting thousands of dollars to save a few weeks.
My car is a dedicated track car that may not be street legal - so no worries on the camshaft being a real monster. I also have a twin disc clutch (the Mamofied carbon monster) so I think it will be a handful if the DMV lets me go get coffee in it once a month...
Thanks, again!
09-11-2018, 04:53 PM
#5
Not apples to apples on engine design and components, but this will give you some knowledge and ideas of how much torque a SHORT BLOCK takes to turn over.
https://www.yellowbullet.com/forum/s....php?t=2537887
Typically you don't measure rotational torque of a long block due to the compression of valve springs, rocker/pushrod friction, etc. The rotating torque is typically used to determine the effects of different ring tensions used in THE SAME BUILD. The key being, it's only a reference if all other variables are kept the same.
https://www.yellowbullet.com/forum/s....php?t=2537887
Typically you don't measure rotational torque of a long block due to the compression of valve springs, rocker/pushrod friction, etc. The rotating torque is typically used to determine the effects of different ring tensions used in THE SAME BUILD. The key being, it's only a reference if all other variables are kept the same.
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09-13-2018, 06:44 PM
#8
TECH Addict
FWIW, there is a phenomenon related to rubber seals and o-rings where when left sit the seal/o-ring will displace oil until its virtually all gone between the seal and its mating surface, When a engine has been in mothballs for a while I shoot a little squirt of motor oil in the seal to lube it, It prevents baking/scrubbing the seal out waiting for oil from the engine to get to it.. Valve seals do the same thing, so your thought about oiling the valve train is a good one.. On some older cars this was the primary reason a rear or front main would fail, back when they were fabric and rubber..
The amount of torque to turn a stuck o-ring is crazy.. Hydraulic cylinders do this as well, shocks too..
The amount of torque to turn a stuck o-ring is crazy.. Hydraulic cylinders do this as well, shocks too..