Advanced Engineering Tech - Those who build/have built many different types of engines...
08-14-2006, 04:00 PM
How do you know what the tq/clearances/assembly routine is for each type of engine varying from say our LS1's to a big block to a small inline 4 cyl and on and on? Do you just get a "feel" for how tight things should be or do you have to reference books and such? I've always wondered how a high level mechanic could have so much knowledge or if they depended on other resources.
08-14-2006, 04:16 PM
torque's are generally a set value and I don't tend to alter them much(too many years working on airplanes I guess) As afr as assembly "routines" mine have been set for years just because it's what I feel comfortable with and it works. Now clearances and "tolerances" are something that can and will often change from motor to motor depending on what you expect it to do and also what you want for life expectancy. I build a race motor pretty loose compared to what I do a street motor for because it's a learned art and it's worked(once again) for me for many years and many motors. My first motor I ever did was built using a Hot Rod magazine(a series on how to build your first motor) back in about 1972/1973. It was a 283 4bbl motor in my first car which was a '66 Nova SS. I've been a gearhead for too many years I suppose but if you want to build a motor, talk with some locals that have a good reputation, feel them out on practices they use and even befriend a few to see if you can watch. I'm pretty impatient so taking my time on a good build was always my weak point but I force myself to slow down quite a bit and always check everything at LEAST twice.
08-14-2006, 05:22 PM
There's a world of wisdom in bygblok's comments. Especially the part about slowing down and checking everything twice. There's only one thing that I would add: Never "assume" anything!! Parts are sometimes mispackaged, machine shops sometimes make mistakes, and even published specs are sometimes wrong. If you're not sure after you've double checked everything, ask questions. What's that old saying? Can't think of the old saying so I'll make one up. "Better to ask questions and be thought to be a novice than to barge ahead without asking and prove it."
08-14-2006, 07:04 PM
But the tq specs on our heads as compared to an inline four head can't possibly be the same. That's what I'm wondering, how you know how much to tighten something down considering the engine and the materials the components are made out of. I would think that these specs would differ greatly from one engine type to another (big iron block to small 1.8L aluminum).
08-14-2006, 07:17 PM
you have what I said very wrong when it comes to torque values. Torque values are something I don't ever alter because generally the written ones are quite good and don't need to be changed unless you change the fastener size or type of material it's formed from. The factory manuals will have specs for everything down to pan bolts and cam covers and you'll do good to use them. Most aluminum headed motors are a torque + 90 degrees now anyway because aluminum torques at a different rate than iron. Also a good thing now is NOT reusing head bolts on aluminum motors. The bolts aren;t cheap but with bolt stretch being a consideration now it's better to start new AND with clean threads both on the bolts AND the block. This will hold true especially for a forced induction or heavily sprayed motor. The biggest secret once again is take your time, go slow, check it again and if it still doesn't seem right, it's probably not. Oil downs suck(especially for the other guys) and a good build can keep it from happening and saves face as well as cash(two very important things......) Even the BEST parts can be junk if you don't do it right the first time(and I can be the poster child for this!!)
08-14-2006, 08:15 PM
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