I will be re-torquing my Edelbrock aluminum heads and would like some clarification. Anyone that has experience with flatheads know the heads are to be retorqued after the initial start and run in period. There are several variances as to how many times you re- torque. Vern Tardel says in his book to run engine for 10 minutes , let cool completely and re-torque . he describes doing this once. I have read others whom re torque 2 to 3 times . Now for the main question, when re-torqueing are you suppose to backoff ( loosen) the headbolt and then re torque or do just retorque ( no loosening ) ? I have read several post and seems it goes either way. What made me ask was I just purchased a new torque wrench ( craftsman) and the instruction say " Never torque a fastener that is already tightened" It has been discussed whether you are suppose to actually re-torque or simply check the torque. Just checking would imply you are seeing if the fastener is torqued to spec . For instance , you might be torqueing wheel lug nuts and you think to yourself , "crap did I do all of them?" Most folks would just place the wrench in the nut and do a quick check. Doing a re- torque could mean to back the fastener off a bit and torque to spec. I tried to call Edelbrock but they are closed till Monday . I gotta admit , I have done it both ways on various applications but this is the first set of aluminum flathead heads I have dealt with and I am thinking aluminum is less forgiving than iron in most applications so just being a bit cautious even thought my question would apply to any application be it aluminum or iron heads. Thanks Darin
No way would I loosen an already torqued head nut to check it. I would check it after an initial run in (let it cool), then again after another run. Then after another. I don't think it can hurt to check as many times until they come into consistency. Then check it again next year. Note I said "nut". I believe a flathead needs a good sealant to prevent those weeps of water up the threads and onto your heads. I think sealing some studs in place is best. Then you never need to break that seal every time you retorque the nuts.
I think I redid the torque sequence on my Offy aluminum heads 4 different times before it stopped piddling antifreeze from a few studs. I didn't back them off I just took them down to the suggested number in the proper sequence after heating the engine up each time. Seems to be good.
I checked the torque after the 20 minute burn in. As I recall none of them budged but I did use all new ARP studs, thread sealant, machined the nut surfaces on the heads to assure a flat surface and used washers under the acorns to make sure the studs would not bottom out inside the nuts. It has been a few years now with no issues.
Bolt/nut torque and clamping force are 2 different things. Static friction and moving friction are 2 different things. Understanding these will give you the best tightening method.
Many years work as a Quality Analyst for Volvo-GM heavy truck. Some of the checks were torque verification. It was a simple check with a torque wrench. Never did we loosen the nuts/bolts to re-torque them. I have always tightened a newly attached head three times after a heat cycle.
When I did mine I retorqued the bolts 3 times after a heat and cooling cycle. I didn't back them off, just retorqued them. They did move a tiny bit each time. No leaks after a year of driving.
Not an 8 but on my banger I just swapped the head .every heat cycle(5 until they stopped moving)I just put the wrench on there and went to the torque spec,didn't back off first.the first couple cycles they moved a lot then less until nothing.
Got both heads torqued. Ended up not backing any off, just went with it. Seemed like quite a bit of movement on some but I was doing some short strokes because of some clearance issue's. thanks to all for inputs.
Now that all of that is settled, I need to go back and modify one of my statements slightly. I said, "Understanding these will give you the best tightening method". It should be, "Understanding these will give you a tightening method". The best and most accurate method is with a stretch gauge or dial indicator. Not needed for a common street engine.
Check them as many times as you need to until the bolts or nuts no longer turn when you torque them up. Mine took 5 checks before everything settled down, the gasket is being squished as the aluminum expands from heat, when it cools the head shrinks but the gasket is now effectively thinner which is why the fasteners will take more torque to their specified tightness.
You want to find out what is correct? Mark the bolt/nut position, back it off and re-torque it. If it ends up in the same place, it was properly torqued. If it moves, it wasn't tight.
Nope not at all.. I have built numerous flat motors and have never ever undone a head nut / bolt before re torque down . You can never re torque heads too many times . But realistically 3 or4 times should do it . I have had the odd issue with a leaky stud but removing offending stud and drying out Carefully and re sealing always get good results , occasionally on a stubborn one a second effort is needed. But dont back off a stud. Why.... correct torque is just that correct torque as long as the thread is properly lubed there is no need to back off.[/QUOTE]
Okay, while we are on this subject let me ask this. In doing this job on a fresh machined block you need to install all the Studs for an early Motor. Do you use a Locktight thread sealant to help stop coolant from getting to the threads? If so what one. Locktight and other brands have several types that sound like the right stuff. Next is installing the Nuts on the actual studs. Do you add Oil to the threads or a Never seize product. Some say just a dry assembly. I've never been one to do head Bolts dry. That said it brings another question. On the 49-53 motors you have Head Bolts, not studs. What's best to use there? Oil for good torque or sealant to keep coolant from wicking?
Aay, there's the conondrum. I don't have any late model flatheads, but if I did I'd use studs. The last ones I installed I glued in with some brown Permatex, but the next one I think I'll try the GM sealant that gets talked about here every now and then.
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