Agree
Technically the wide deck is stronger and has thicker cylinder base flanges. What does that mean? Well like all the post above which I agree with 100%, no much. I having both narrow and wide deck engine. If you are going to hot rod and engine or run hard or race, you may want a wide deck engine. Other wise it does not matter if you build the engine stock.
RV6_flyer said:
The conical mount isolators are CHEAPER and I cannot tell the difference in vibration than I can with the more expensive dynafocal mounted engines.
I gather there is a correlation between narrow deck and conical mounts. I was not sure of the relationship but I assume most conical mounts are on narrow deck engines. Later year engines all went to dynafocal and wide deck.
I did have a RV-4 with narrow deck and conical mounts. I personally prefer dynafocal but conical is OK. Dynafocal is better and more stable, less engine movement and sag.
Just my opinion and experience but I found the less expensive CHEAPER conical engine mount bushings are not very good. You can get a set for $30, verses $80-$90 a corner for Lord mounts.
Her is my experience with conical mounts. I would not use the standard bushings. Lord Corp. makes vibration isolators (engine mounts) for conical engines, which are similar to the dynafocal ones.
The Lord isolators for conical mounts are as expensive as dynafocal vibration isolators. I would not personally run plan engine mount bushings in a RV with a conical mount engine and plan bushings. I found they wore out in no time, especially when doing acro. Also I had vibration issues. All this greatly improved when I installed the Lord mounts for conical engines.
[If you look at an RV-4 steel engine mount weldment, one of the top corners of the engine mount is just a strut. That top corner takes no torque or shear, just fwd / aft loads. It is not made like a dynafocal weldement. This design puts more force on the lower corner on the same side. I found the bolt worked through the conical mount rubber bushing in no time. Also you can never torque conical mounts bushings. You just tighten till the rubber squeezes out around the big washers (which are special piper parts not AN parts). With the LORD mounts there is a spacer and the pre-load is easy to obtain. The LORD mount is just better and gives more vibration damping. Now I ran and extend hartzell metal prop. If you have a wood prop vibration (buzz) may not be an issue. ]
There are other threads on conical v. dynafocal. The good news is if you buy a core to rebuild it is not too much money to have ECI machine dynafocal mounts into the case, however it must be done with a engine tear down and case overhaul. You can call ECI or look at the other threads on the subject.
No disrespect to RV6_flyer, he is right, the narrow deck/conical gets the job done. If you found one cheap in good condition, buy it.