finally got the heads on today and snugged up the bolts. then i got to thinking. Do i still use the 55 lb torque rating that the book calls for on the 215 engine? since i am only running 10 bolts instead of 14 do i use a different value? all the threads in the block have been drilled and tapped for 7/16-14 helicoils. but i am still weary that the factory aluminum is very soft and might give a bit. just looking for opinions on how to proceed. i would hate to strip out the oversized bolt hole threads and have an even larger problem on my hands.
http://dodgeram.org/tech/specs/bolts/SAE_bolts.html The above site says 35 ft lbs for a 7/16" bolt into aluminum. When I was machine building they had us use a lower % figure(can't recall what it was) for bolting into aluminum vs steel. If the heli-coil is shorter than the original thread engagement the bolt had it will be weaker than without. If you have the same amount of bolt engagement you should use the torque value that it calls for the al. 215 block. In aluminum you can't tighten a bolt enough to get a proper stretch value because the al. is much softer than the bolt and the threads would pull out before that value would be reached. Instead you need to get the max thread pull the al. can handle to clamp down what is bolted to it.
thank you for the information. unfortunately 4 of the bolts were not able to be torqued. at 55 ft lbs they lost tension. the previous owner did all the thread inserts. they appear to be the shorter ones. just shy of 1/2" long. they were also driven all the way down to the bottom of the bolts hole. so i believe, as you mentioned, that not enough thread engagement to achieve the desired torque is what is happening. on most of the holes, the remaining upper threads are decent enough to run the .875" long helicoils. i just dont know whats the better route. spending all the time necessary to remove and replace all the helicoils. and having to buy all new bolts. (not enough thread length.) or just buying a head stud kit for the engine. which i dont know if the 300 head stud kit will work in the 215 block or not. if there is a good alternative for the headstuds (SBC,SBF,BBC,ETC) that will work for me, im all ears. at this point im starting to get a bit frustrated with this build. it has thrown so many curveballs at me, im starting to regret not going LS. But trying to stick with is because of the cool factor of the engine once its completed and swapped into my project.
I once stacked double helicoils but it sounds like maybe you are beyond that if you've already pulled the threads on some of the inserts. Next step, you can buy solid steel inserts. You will have to shop a bit to find them, maybe McMasterCarr.com would have them. Probably have to go close to 5/8 on the OD by now and most likely use the longest ones available. They screw into place and then have one type or another of locking mechanism. Good idea to also loctite them in with studlock. And then use studs. Only way I can think of to deal with the BOP head bolt issues. (I punted and went to the iron block.) Jim
well, it seemed like it was a simple fix, but it has given me a fair amount of trouble. stacking helicoils did not work with the new bolts. so i ordered head studs thinking it would fix it. a couple studs still lost tension. so i ordered a time sert kit. had to remove double stacked helicoils on 20 holes took forever and sucked. when i ran the tap down the threads, a couple threads pulled out like pigtails. if they didnt pull out, they were crumbling as i ran the tap through them. the threads seemed fatigued and brittle. so i measured and it seems that a big sert kit is my best option. Freaking 200 bucks just for the kit and inserts to do the job. i figure if im already doing it. might as well go all out and big sert every head bolt hole. it will all be fresh metal and a positive locking insert. im thinking with studs i should be good to go. keeping my fingers crossed.
