V8 Engine Swap
- Sep 6, 2013
- Reaction score
- Calgary, AB
- Vehicle Year
- Make / Model
- Engine Type
- Engine Size
Studs are used for 2 reasons:
1. Is for assembly - As the 3.0 was used in several different vehicles, and each needs a different set of exhaust manifolds, the engine plant couldn't bolt manifold to head before head is bolted to block. So, when it came time to install exhaust manifold on assembly line, it is tremendously faster to slide exhaust gasket on studs, slap the exhaust manifold on, spin a couple nuts on, and torque to spec than to try to line up manifold & gasket on head, then thread a bolt into the hole in the block (at least for 1st 2) and then torque down.
2. When you tighten a bolt, the shaft of bolt twists as you tighten. So, the torque on the threads isn't the same as what your wrench shows. On the other hand, there is very little twisting within a nut on a stud, to the torque on the wrench matches. Therefore, studs give much more accurate measurement. If you are building an F1 engine, you use studs not bolts.
Do you need that assembly assistance/precision in tightening? Probably not, so a bolt will work fine. You need to be careful that the bolt is not bottoming out at end of threaded portion, before it pulls tight or you won't properly tighten the manifold to the head.
Threads are probably in rough shape - heat and moisture will have accelerated rust in holes - that's part of why they are so difficult to remove. You can pick up a cheap tap for $5 and clean hole up in couple minutes.
As fewer than 1 in 100k Rangers every had to have exhaust manifolds removed under warranty, why would Ford spend more for individuals having issues 20+ years later (they would much sooner you bought a new Maverick). Enter comment about disposable society we live in.