New Goetze Head Gaket Torque

[86esprits3]

I am in the process of putting my 1986 esprit HCI 910 engine back together. I hear that there is a new method to tightening the head bolts-you tighten them to 15 ft/lbs, then turn 75 degrees, then turn 40 degrees, wait 5 minutes, then 20 degrees. I do not have an angle indicator wrench. Same tightening sequence applies. Oiled threads.

Did anyone ever work out what the actual torque is on this if doing it with a normal torque wrench? I dont see the big deal here. I can pretty much guess the degrees of rotation.

If the 15 ft-lbs start up is accurate as a reference, then why cant the rest of the sequence be done with a torque wrench?

thanks

Edited May 28, 2007 by markd

[andydclements]

I am in the process of putting my 1986 esprit HCI 910 engine back together. I hear that there is a new method to tightening the head bolts-you tighten them to 15 ft/lbs, then turn 75 degrees, then turn 40 degrees, wait 5 minutes, then 20 degrees. I do not have an angle indicator wrench. Same tightening sequence applies. Oiled threads.

Did anyone ever work out what the actual torque is on this if doing it with a normal torque wrench? I dont see the big deal here. I can pretty much guess the degrees of rotation.

If the 15 ft-lbs start up is accurate as a reference, then why cant the rest of the sequence be done with a torque wrench?

thanks

Pure speculation but, since it's a rotation specification it must be that the amount the new gasket etc are compressed needs to be a defined distance rather than to a certain pressure.

Andy

[86esprits3]

Pure speculation but, since it's a rotation specification it must be that the amount the new gasket etc are compressed needs to be a defined distance rather than to a certain pressure.

Andy

This method has become common with aluminum cylinder heads

[WayneB]

Mark you are refering to the tightening technique which is used with modern " Torque to Yeald " cylinder head bolts (which our old Esprits dont have, using studs and nuts instead)

The last turn with the angle indicator is to stretch the bolt a couple of thousands of an inch to use the inherent elasticity of the bolt to clamp the cylinder head down (these fasteners are designed to be used only once then chucked)

It will be interesting to see what Trevor Knowles says about this subject (as he has probably forgotten more than I know on this matter)

[USAndretti42]

Like Wayne says, it sounds like they have gone to a torque-to-yield setting for the head. It sets the clamping load much better than torqueing which is very dependent on the friction between the threads and between the bolt head and its mating face. As the head heats up and expands, the load stays constant so the gasket is not over-crushed and leaks when it cools down again.

Also, like Wayne said, it's usually used with bolts which are replaced every time but I suppose that you don't plan to replace the gasket very often. It does need the right fixings though to make sure they are stretched by the correct amount based on its cross-section area and material yield strength. If the studs are too strong, the head bosses could yield which is not what you want.

Where did you get the information from? It could be worth checking with Lotus' technical department. Their 'phone number is on Bibs' signature.

[910Esprit]

From memory, the sequence described sounds correct and certainly has worked fine for me. IIRC the angle guage I bought only cost

[86esprits3]

From memory, the sequence described sounds correct and certainly has worked fine for me. IIRC the angle guage I bought only cost