caleb_fd

Hi

I Have to take the flywheel off to replace the rear main oil seal. Would it be a good idea to go over the main engine bolts to make sure they are still set to the required torque setting, or could this cause trouble (there are no wet bolts that share a oil or water gallery where a seal or Oring might get upset)??

cheers
Caleb

Mahjik

iTrader: (1)

Yes

DaleClark

iTrader: (55)

I've heard Pettit Racing in Florida likes to re-torque the tension bolts on cars they have the flywheel off of. Personally, I don't think you'd gain anything from this and could potentially cause harm.

The bolts seal at the back with rubber lined washers, torquing them after installation could tear the rubber washers. I don't think this would cause a leak or anything, but ya never know.

Really, I've yet to see an engine that failed due to tension bolts coming loose or something. I'll let others chime in as well, but I just don't see where you'd be helping anything - I think you have more to lose.

Dale

fd_neal

iTrader: (4)

personally I wouldn't.

Mahjik

iTrader: (1)

I'd be more concerned with engine flexing without the proper tension. One of the local Pettit followers to me (RTS3GEN) used to torque the engine studs when in the area per Cam. He mentioned they were typically several lbs off. He ran a Pettit engine for many years with many road course events, drag runs and normal ripping around the street per year. With the amount of hard driving I had seen him do over the years, I know there were a lot of things he was doing which was definitely "in the right" to take that kind of use and still keep going. He had no fancy AI or anything, just good old fashioned "maintenance".

I'm not saying his engine took everything he threw at it solely because of re-torquing the engine bolts, but I'm sure it didn't hurt either.

Sgtblue

iTrader: (16)

I have, and have heard of others re-torquing the tension bolts when they have the opportunity. I have never heard of anyone having issues with a washer afterward.

arghx

iTrader: (3)

When I tore my engine down (only had about 5k on it) I noticed uneven torque among the bolts, and I know it had been torqued properly during assembly. I'm not sure if re torquing could harm the tension bolt seals or not. Just be careful you torque it in the right order. That won't be so easy when you are under the car.

TwinCharged RX7

iTrader: (14)

I did mine, but for another reason. I bought a rebuilt engine, installed it, and kept getting air pockets in the coolant system causing high temps. I also noticed coolant coming from my bell housing.

Thought it was a bad freeze plug, turns out that 5 of the engine bolts were leaking. So i re-torqued them all. No problems since.

ttmott

iTrader: (1)

A couple of facts on the bolts you may or may not know that may help determine to retorque or not:
The engine is a metal to metal assembly so there is no crush or compression to achieve.
The torque is to put the bolts into elastic stress range so a constant force is maintained on the engine assembly.
As long as the bolts are in their material's elastic range re-torquing is not necessary.
If the bolts are under torqued they will not be in their elastic range and will not hold the assembly together properly.
If the bolts are over torqued the material will be yielded and the bolts will loose their capability to clamp the engine assembly.
So my opinion is if there is no material to crush like a gasket (which there is none) and the engine was properly assembled and the bolts were stretched as per specification there is no need to touch them again; in fact if they are retorqued there is a chance one could yield the material as the lubricant for the threads is not as originally assembled and the bolt material could be forced into a yield condition reducing the clamping force.

Sgtblue

iTrader: (16)

But the engine metals aren't the same....iron to aluminum. In addition to the uneven heating and cooling cycles to the bolts themselves, would the dis-similar metals not affect things during those heat cycles?
And isn't there is a compressable material on the washers?
And aren't you assuming that the iron to housing interfaces...all four of them...are EXACTLY uniform? I guess I assumed that the reason there was a specific order to the torquing is to make sure it's uniform across all those large, broad surfaces that aren't exactly perfect.

You apparently have some formal background in this area and I'm just a dense goverment worker. So I'm asking, not arguing. But my experience on both occasions that I've re-torqued mine, two or three have been found just a little off...maybe one or two ft/lbs. Of course that could be from variance with the wrench itself, but........

pomanferrari

iTrader: (1)

With 29K on a reman and due for a clutch change, I checked the torque and it was loose. In other words, I used a torque wrench and it took alot less than the factory torque number to loosen it. I noticed this on my prior 2 engines. Was told by Cam at Pettit to torque 'em every 40K.

Ended up torquing it 10% higher than factory values.

C's-7

iTrader: (3)

ttmott there is some respectable information in your post, however I had to pull out a few sections that are just plain not true. Just because a bolt is in its elastic range it does not mean that you can go without re-torquing. Furthermore, these bolts are not taken up to their yield point and you do not run the risk of yielding these bolts by re-torquing even if assembled dry. In fact bolts assembled dry are often taken to an even higher torque specification and still do not reach the same clamp load as a lubricated bolt at a lower torque value.

Typically bolts are taken to a percentage of proof or yield...granted there are some applications were bolts are taken to or near yield...however this is not one of those cases.

The first rule of bolt tightening is to tighten the bolts and keep them tight. There are many factors that ultimately reduce preload on a bolt. Some of the main contributors are self loosening (due to vibration), preload relaxation (due to the fastener, member/gasket, and contact area), and differential thermal contraction (a larger contributor with dissimilar metals).

To add a bit more detail torque is specified based on its application. In this case a specific torque value was assigned based on the forces and pressures acting on the components making up the rotor assembly. The clamp load is set to withstand these forces.

An example would be two plates being pulled apart while bolted together. The bolt itself does not react to the forces pulling the two plates apart because a torque value providing clamp load is greater than the forces acting on the plates. Forces must be known before a bolt is specified so that the right clamp load can be reached. Hope this make sense.

For this particular assembly the bolt torque should be taken back to specification.

C

ttmott

iTrader: (1)

Keeping the bolted assembly properly clamped with the bolts within their elastic range is critical. For the length of these bolts the elastic range should be from just over +.001" to around +.012" stretch (maybe more depending the bolt material). Rotational torque is a flawed method to measure the stretch due to the inderminate frictional characteristics on the threads and under the bolt head. A length measure is the only real way to obtain the proper stretch and consequental clamping force. Regarding the different materials in the engine assembly (alum. and cast iron) and their different expansion coefficients you will find within the narrow temperature ranges these are exposed to that the growth / shrinkage will be very small (probably less than .002") and well within the elastic range of the assembly bolts. When the bolt material is stretched beyond its elastic range it is yielded and will take a permanent set close to the yield length; additionally the tensil strength of the material is greatly reduced after yield and should not be used again. I will agree with the arguement that vibration can contribute to loosening of the bolts but unlikely. Going back to the flawed method of torquing I will tell you this: every torque wrench is different unless it is calibrated just before use and every time you rotationally torque a bolt it will be different. All I am saying it's your choice but approach with the proper knowledge. You may want to review ARP's tech. site http://www.arp-bolts.com/Tech/Tech.html

caleb_fd

ok thanks for that.

the main reason i ask is, i have noticed each time i check the coolant, the level seems to be a little low down the filler neck, (is this common, i wouldnt have thought so) I was thinking maybe i was losing coolant into the combustion chamber if the bolts are slightly lose, but i am not sure, i am only new to the rotary world, i have not noticed any leaks on the concrete floor.

With the rubber seal on the washer of the tension bolts, is there a water or oil gallery that shares the bolt hole, ( what is the washer sealing in).

cheers
caleb

C's-7

iTrader: (3)

As a very general statement, yes you should stay within the elastic range. I'm unsure why you keep bringing up yield point. We have torque specifications the bolt is not going to yield.

.012" Please show my how you calculated this.

It is true there is no way to measure stretch by simply torqing a bolt, but there are methods to calculate.....and "inderminate frictional characteristics" I don't even know what that means....and if you meant "intermittent frictional characteristics" I still don't know what that means. This is accounted for in your calculations by a frictional factor. Measuring stretch is a desired way to determine clamp load, but not the only method. Calculating clamp load based on torque is a very proven method.

Let's just run with your .002" growth/shrinkage, which is significant.........and let's just run with your .012" stretch (still would like to see how you calculated this) That is a 16.6% reduction in preload.

I suppose I better start measuring the stretch of every bolt on my motor then.
I digress.

C