I did not build my RV-4 to know the answer to the following.
I recently began working on my Condition Inspection. I noticed some corrosion on heads of the prop bolts which needed attention. I have the old 4" spool type prop extension with 3/8" prop/ext bolts and 7/16" ext/crankshaft bolts. Also, the installation has two front plates, one on either side of the front spinner bulkhead. The front has the groove into which the bolt head fit. The second is larger in diameter and thickness. (Photos below, though rear plate is hard to see.)
After removing the nuts from the prop bolts, the prop didn't want to budge. I attributed that to continued humid conditions in my hangar at the time. The bolts were very tight and next to impossible to move. I ended up using the old nuts threaded back on the bolts almost flush and then back them off against a a steel plate resting against the heads of the crank bolts. That pushed the entire prop and crush plates out from extension rather than just moving the bolts as I expected. At that point the prop was almost clear of the extension prop bushings. Rather than forcing anything, I called it a day. I went home and ordered a new set of prop bolts from Van's that evening.
I went back a few (dry) days later and was able to slowly work the prop loose and got it off okay. Even then the bolts were still extremely tight in the prop and didn't want to move. I took the prop home and kept it inside the house to help with any humidity issues. After a couple of days, I was able to tap the bolts out of the prop...though they were still tight in the two crush plates/spinner front bulkhead.
Once I had everything off the prop, I worked on getting the plates, which trap the front spinner bulkhead between them, off. I ended up putting penetrating oil on the bolts and was able to pull everything apart. Once apart, I was able to determine the bolts were extremely tight in the front plate, the one with the recess that traps the bolt heads so they don't rotate, and snug elsewhere, but not interference fit tight.
I'm a bit concerned about how difficult it was and that putting new bolts in will possible problems. I don't want to bugger up any threads and certainly don't want to have to hammer the heads.
All that said, should the bolts be that tight tight in the front plate? Should the plate be reamed?
My prop is a Props, Inc wood prop with a 4" thick hub. I've removed and installed several props over the years, both wood and metal, and have never had one this tight.
The plane has approximately 1050 total time engine/prop/airframe. From looking at the logs, I don't see anything indicated the prop/prop extension has ever been separated/removed since 1994. Due to the tightness, I was expecting some corrosion on the bolt barrells but found none, though the cad plating was pretty scuffed up by the time I got them out.
I'm glad I decided to pull the prop off and replace the bolts now.
See attached photos which will hopefully make my long-winded description more clear.