[crabandy]

I have managed to drill/dimple the doublers on the firewall with the engine and mount attached except for these behind the vertical tube on the Gascolator doubler.

I can fit a structural 4- blind rivet on the outer 2

The inside 2 are too close for a blind rivet

Is it worth removing the engine and mount for those 2 rivets? Other ideas?

 

[WingsOnWheels]

The engine mount is easy to remove, I would just pull it and put solid rivets in. I need to pull mine shortly (with the engine attached) to add a couple nutplates, it's not really a big deal.

 

[crabandy]

Unfortunately I don't have an engine hoist and either need to buy one or wait several weeks to borrow one.

 

[WingsOnWheels]

Unfortunately I don't have an engine hoist and either need to buy one or wait several weeks to borrow one.

Gotcha. Unless this is the last of the item you have to attach to the firewall, it is likely you may have this come up again. There are nutplate to attach the crank breather and oil pressure cushion clamps that can be hard to get to with the engine hung. you may just want to cleco it for now and wait a while. Once you have 3-4 things to rivet, pull the engine and do them all at once. FYI, I bought a 1/2 ton hoist from harbor freight for around $130 (on sale with coupon). It might be worth the investment.