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Old 10-18-2006, 06:50 PM
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Main bolt tightening sequence question

Okay, this sounds so simple, but I cannot find it in a bulding manual... When you tighten four bolt mains, which sequence do you follow? As I have been do the pre-fitting, I have been tightening the inners and outers equally in three increments. For example I go to the inners and do 35, then the outers at 35, and then I do them all in 55 and then 70.

Or should I go down the line of inners and fully tighten them in the three increments and then go to the outers? It's a pain because all of the engine building videos I've seen show a 2 bolt main being built.

Thanks for any input.

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Old 10-18-2006, 06:56 PM
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Dont think it really matters........You are doing the right thing and doing it in steps...........

I would start in the middle and work my way out with one torque....then increase it and do the same again and then the last time with the final torque.
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Old 10-18-2006, 07:18 PM
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Doc here,

"When in Doubt..Center out.." (I learned from an olde poet..).. in a criss~cross pattern..

The important thing as Poncho points out..Two step is the proper thing to do..35 then 70..

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Old 10-18-2006, 08:49 PM
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On all the blocks we machine for other shops and engine builders we line hone all the blocks that go through our shop and use the ARP hardware and using a bolt kit we snug the center bolts then torque to 40# then snug the outter bots and torque to 40# then the inner ones 65# then the outter bolts 65# With the ARP lube as we send a sheet with every block on the torque specs and sequence on how they are torqued so the customer can come out with the same results.

And we have found the torquing the outter bolts first DOES change the housing bore diameter.
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Old 10-19-2006, 06:29 AM
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Thanks for the insight CNC. Never seen this written any where, but makes sence and does point out that true machinist tend to look at "what happens when".

Trees
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Old 10-19-2006, 07:06 AM
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I snug the center cap, and the rear cap, loosen the rear cap bolts and seat the thrust bearing.

I then torque in sequence at 35 lbs, longer bolts first, then the outer bolts, and I also torque all the caps at 35 lbs. (Do all caps at 35, then 50 and then 65). I then torque to 50 lbs, in the same order, and then finally 65 lbs. I spin the crank as I go to check for binding. I use moly lube on the bolts.
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Old 10-19-2006, 04:14 PM
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I start in the middle, snugging to #35 first, and in a widening circular pattern (middle to out) I snug them all. Then back to the middle and go to #80 in the circular pattern, middle to out. Then back to the middle again taking them to the final seating pressure ...again middle to out in the circular pattern. If you look at the head bolt pattern, it's basically the same way. Good Luck! ...Mark
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Old 10-19-2006, 04:20 PM
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does anyone ratate the crank when they torque the mains?
how about puttin lube on the shoulder and threads of the bolt?
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Old 10-19-2006, 07:53 PM
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Quote:
Originally Posted by 11echo
I start in the middle, snugging to #35 first, and in a widening circular pattern (middle to out) I snug them all. Then back to the middle and go to #80 in the circular pattern, middle to out. Then back to the middle again taking them to the final seating pressure ...again middle to out in the circular pattern. If you look at the head bolt pattern, it's basically the same way. Good Luck! ...Mark
80 pounds on a 7/16 main bolt HMMMMMMMMMMM
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Old 10-19-2006, 08:00 PM
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Quote:
Originally Posted by nitro_baller4692
does anyone ratate the crank when they torque the mains?
how about puttin lube on the shoulder and threads of the bolt?
Why would you ratate the crank when torquing the mains and we use all ARP hardware and and we use the ARP lube on the threads and the washers. And we have used 40# the 65# as I have described above on the bolt kits and on the studs we torque them to 40# the 70# as this has worked for our shop for 32 years now with no related problems so far and on those studs we use the CMD-3 high pressure lube on the threads and washers.
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Old 10-20-2006, 06:23 AM
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Why would you ratate the crank when torquing the mains

i have not seen anyone talk about using a mic. or a dial bore gauge,if you torque all the caps down without turning the crank how would you know what main is the problem,if there is one.
has anyone hear heard of bearing missalignment,yeah bearings have locking tabs but some people still screw things up.
i'm not trying to offend anyone,i just think a crank should be rotated after every step in the assembley process of the rotating assmbley.
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Old 10-20-2006, 06:59 AM
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Quote:
Originally Posted by nitro_baller4692
Why would you ratate the crank when torquing the mains

i have not seen anyone talk about using a mic. or a dial bore gauge,if you torque all the caps down without turning the crank how would you know what main is the problem,if there is one.
has anyone hear heard of bearing missalignment,yeah bearings have locking tabs but some people still screw things up.
i'm not trying to offend anyone,i just think a crank should be rotated after every step in the assembley process of the rotating assmbley.
If you read my post about line honing all the blocks that go through our shop and to do that process a Sunnen bore gauge is used to check the demension of the housing bore.

And the Crank sould not be rotated till ALL the caps are Torqued as you want the bearings SEATED in there housing bores and if blocks are line hone properly there should not be any misalignment.

And again in most cases cranks will not spin freely until the mains are all torqued and the bearings have seated in there housing bores.
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Old 10-20-2006, 07:19 AM
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And again in most cases cranks will not spin freely until the mains are all torqued and the bearings have seated in there housing bores.

if the crank don't spin freely,then the crank needs to be checked for straightness or the align honing was done incorrectly.i've never had a engine that i assembled have the crank not spin freely.i will find the problem and fix it as to whats necessary.
when checking the bores with the gauge are you checking front and back on the main saddle and are you checking top to bottom and also just off the parting lines on both sides?
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Old 10-20-2006, 08:02 AM
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CNC BLOCKS N/E "80 pounds on a 7/16 main bolt HMMMMMMMMMMM"

...I'm talking big block Chevy here, as I recall the torque setting on the mains is 110 ft/Lb.s is it not!?? ...What are you talking about??? ....Honda?
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Old 10-20-2006, 10:17 AM
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Quote:
Originally Posted by 11echo
CNC BLOCKS N/E "80 pounds on a 7/16 main bolt HMMMMMMMMMMM"

...I'm talking big block Chevy here, as I recall the torque setting on the mains is 110 ft/Lb.s is it not!?? ...What are you talking about??? ....Honda?
I believe when the post was started they are talking SBC as the final torque they were talking about was 70 ans assune is a SBC as there nothing evr mentioned about torquing anything 70 foot pounds.

If thay are talking about a BBC I am way off.
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