The Stovebolt Site Forums The Shop Area Engine Shop Cylinder head bolts VS studs

One thing we engine builders tend to overlook when building up our engines are those 70-something year old head bolts, and also the main bearing fasteners. These fasteners have been subjected to hundreds of thousands of heat/cool cycles, with the corresponding stretch/shrink situation. On a lot of the racing engines I've built, we usually discarded the OEM head bolts and other critical fasteners in favor of new, high strength studs. One critical advantage is the fact that once a stud is threaded into the block, it remains stationary- - - -all the torque is applied to the nut at the top, and the only load on the block thread is a straight up pull. On a racing engine that gets dismantled and reassembled frequently, that protects the block threads. That's not as critical on a street engine, but it's still a factor to consider. Ford 351 Windsor head studs have the same block threads as stovebolts- - - -1/2"-13. The top thread is 1/2"-20, and the head stud kits sold online include new 12 point nuts, and hardened steel flat washers. It's worth considering an upgrade, particularly considering the cost VS benefit comparison considering the overall cost of a rebuild.
Jerry

Jerry do you know what the Ford 351 Cleveland takes? Thanks

30 second search on Ebay- - - - -7/16-14 block threads, no length information.

www.ebay.com/itm/136925903061?

Jerry

Back in the day when we were drag racing a .030" 327 and 350. Bothe blocks were studied for the mains and a set of Brownfield cylinder heads. As I recall the nuts that were assembled to the studs were not torqued as high as the original stock bolts torqued into the blocks..

The fine thread stud nuts have a lot more clamping force than the coarse threads in the block. It would be pretty simple (but very time consuming) to set up a stretch gauge on each head stud and get exactly the same clamping force on every stud. Similar to measuring rod bolt stretch on H beam connecting rods.
Jerry

Thanks

Mainly the Aluminum Brownfield cylinder heads didn't require as much torque like your cast iron ones did. That is a good point you brought up about misc. bolts as such being used numerous times. Reminds me back when I worked for Lockheed aircraft and we had a crew that did nothing but removed and replaced critical fastners throughout the plane on a 200,300,500 etc. etc. hour schedule. Believe it or not, I kind of miss those good Ol days.. Thanks Jerry..

I've also got a background in aircraft maintenance- - - -USAF electronics tech for about 8 years. There were some pretty strict rules about reusing fasteners, particularly for the jet engine mechanics. It makes sense that after thousands of heat/cool cycles, a head bolt or main bearing bolt might not do its job as well as when it was new. Toss in a rebuild or three, and those torque-sensitive bolts just might not be as good at doing their job as when they were new. Some modern engines use "torque-to-yield" bolts which can only be tightened once, then discarded the next time the engine is rebuilt.
Jerry