Re: Motor Mounts for a 4.3L Merc
Jason
Sounds like your making progress!
From a mechanical strength perspective the wood is the weak link. In many cases bolts can easily overpower and compress (smash and weaken ) the wood. Cases such as this where you cannot get to the head the bolt would add limited vaue and add some risk of damage if overtightened.
Using lags that are as long as the original ones will be sufficient.
However;
If you really want to add strength with bolts; bolting to some sort of metal will be required to make it effective. Using a harder wood such as white oak or ash will aslo add strength if you want to stay with lags and its less cost & labor. (White oak has better rot resistance)
As you can see in the pics I posted for you earlier I lag bolted some plates of Aluminum to my stringers. 1 inch deep Threaded holes and stainless steel bolts hold the mounts. The aluminum will spread the weight should the stringer start to rot in the future. It also allowed the use of pressure teated lumber which is not a hardwood. Many would argue this was overkill but I had the materials on hand and a long winter work on it. Cabin Fever / Mad Science -- you decide???
1 Note -- ( Pressure treated lumber is best when aged a bit to allow it to dry & shrink before usage )
I supoose you could add some plates to the bolt heads ( welded or square holes and cairage bolts to prevent spinning of the studs and allowing them to spread any tightening forces. These would need to be imbedded in the stringers as well.
Also -- Check out us composite web site for epoxy and polyester resins & cloth.
http://www.uscomposites.com/
West system epoxies are very good also but more expensive.
( correction ) Polyester resin has less adhesion strength when adhering to cured fiberglass but is apparently quite sufficient according to those who have used it . As far a strengthening or patching rotted wood I personally would avoid that if you have the engine out and are going this far. Rotted wood starts with prolonged wetness and the resulting occurence of mold which breaks it down. Thats what you are trying to stop and avoid. The repair will tend to last longer if no molds are present. Sealing all new wood withresinis also key to longevity. If you decide to patch -- soaking rotted wood with resin, adding cloth where possible or using Tigerhair body filler are among the options.
Hope this helps. Its really your call as I am sure you are aware.
