Hi there... 1st time poster but I love this site, lots of good info here. ANyway, I have something that is boggling my mind here and Im hoping someone that is familiar with Dodge might be able to shed some light on this. I recently bought a 99 Intrepid for a great price because it needs a head gasket done on it. It's got the 2.7 in it. Well, through your site I found the actual service manual for the car and was reading up to get ready to yank the heads on it and get it done. Here's where I'm confused... In the installation insructions for the head itself, the manual tells you to torque all the head bolts in sequence to spec, than retorque to a higher spec (I understand ALL of that so far, no problems... making sure the head is evenly torqued=good lol) After the second set of torquing specs, it says to turn each bolt 90 degrees!

Now I was prepared to just "1/4 turn it" but my father is losing his mind saying "better not be 89 or 91 or you'll screw the whole job up" lol...

I guess the question is this... why would they give such a loose guide for tightening 10 bolts that they insist must be torqued and higher torqued to specs? Is there actually a tool that Ive never heard of that will turn 90 degrees? Im still prepared to put a quarter turn on these bolts, but would really hate to do all the work involved with ripping down to the gasket and back up again only to find that I screwed up by 4ftlb because I eyeballed the 1/4 turn.... Any input as to why the guideline is so loose after being so specific would be really appreciated... Im a Chevy man, always have been, but Dodge has always caught my eye and Im ready to see if it's for me lol

 

Some of the big truck diesels used to use that method. I don't remember the exact degrees but one or two wouldn't be that critical in my opinion.[sm=americanasmiley.gif]

 

One or two degrees don't matter at all.The reason you do this is because the bolts are "torque to yield" and can not be used twice.
I don't know why they don't just give a torque value to tighten them to because I have put together engines that used the same tightening sequence but the manufacturer of the parts that I was installing said to use a certain torque value instead of the 90* turn.The new way caused the bolts to turn about 90* anyway.
It DOES matter that the bolts are prepped in exactly the way the bolt manufacturer says,ie,lubricating with a certain lube,burnishing with a wire brush,or just cleaning the threads inside and out.ARP makes about the best bolts to use when rebuilding an engine.

 

After a bunch of research, I came across this, and figured I would share... This a copy of part of a page from http://www.centuryperformance.com/fasteners.asp
Thanks for the input so far, but I get it now!! :-) (Its actually much more specific and specialized a measurement than i thought it would be

The Torque Angle Method

Since the amount a bolt or nut advances per degree of rotation is determined by the thread pitch, it would appear that the amount of stretch in a given bolt or not can be accurately predicted by measuring the degrees of turn from the point where the underside of the bolt head or nut face contacts the work surface. Termed the "Torque Angle" method, this procedure has long been the standard of civil engineering. It has been suggested that torque angle is a relatively simple and valid procedure to use in our "blind" installations where it is not possible to physically measure the actual bolt stretch.

Simple calculation of bolt stretch based upon thread pitch is not accurate. No material is incompressible! When a bolt or stud is pre-loaded or stretched, the components being clamped will compress to some extent. When we are looking for bolt stretch in mere .001's" of an inch, the amount of clamped material compression becomes a real factor. Investigation has proven that installed stretch is dependent upon not only the pitch of the thread and degree of rotation, but also on the amount of compression of the clamped components, the length of the male fastener, the amount of engaged thread the type of lubrication and the number of times the fastener has been cycled.

For Example: given the same degree of rotation, the actual amount of bolt stretch will be critically different between an Aluminum cylinder head vs. a Cast Iron one. Or even a steel main cap on an Aluminum block vs. a Cast Iron block. Further, there is a significant difference between long and short head bolts or studs on the same head. The torque angle method can be accurate, but only if each individual installation has been previously calibrated by direct measurement of bolt stretch.

When using the torque angle method, it is best to begin rotation from a small measured torque (no more than 10 lb./ft), rather than the first point of contact with the work face. To achieve accuracy it is also best to cycle the fastener five times before either calibrating or installing.