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  #1  
Old 08-19-2019, 08:21 AM
PhatRV PhatRV is offline
 
Join Date: Mar 2018
Location: Buena Park, California
Posts: 68
Default Should I Drill The Reference Engine Bracket Holes?

Each of the engine mount brackets has a large #12 hole that corresponds to the hole on the stainless steel firewall. Should I drill these out while assemble the firewall or leave them alone until I install the engine mount. Van's manual doesn't mention anything about these holes in the instructions at this stage of the build.

Here is a picture of the hole

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Last edited by PhatRV : 08-19-2019 at 08:23 AM. Reason: spelling.
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  #2  
Old 08-19-2019, 11:47 AM
Ralph Inkster Ralph Inkster is offline
 
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Location: Calgary, Alberta
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You could drill to #12, but before doing that, read page 11-1 to understand following steps.
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Old 08-19-2019, 11:50 AM
SHIPCHIEF SHIPCHIEF is offline
 
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Location: Seattle
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Default

I suggest you wait until you get your engine mount.
Nothing like trying to fit a mount to unmatched holes.
Once your mount arrives, you have 3 choices; drill to the plans, drill to the mount, or send it back.
Otherwise, you may end up with some '8' shaped holes.
I just rebuilt my wife's RV-4 engine mount....Actually Russ McCutcheon Metal Fabrication rebuilt it on his fixed tooling, and it fit back on the airframe perfectly.
So the original builder maybe drilled to the plans and everything fit, plus after Russ rebuilt it, it fit again! Who could be so lucky?
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  #4  
Old 08-19-2019, 04:56 PM
BobTurner BobTurner is online now
 
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Location: Livermore, CA
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Wait. My engine mount only came close to the pre-punched undersize holes with a lot of "encouragement". Use the mount for the drill guide.
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  #5  
Old 08-19-2019, 07:00 PM
PhatRV PhatRV is offline
 
Join Date: Mar 2018
Location: Buena Park, California
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Thanks everyone for your advice. It seems prudent for me to wait until I decide on the engine and engine mount before attempting to drill these holes. I am planning to purchase a new engine from Vans but that time is in the future, or depending on my financial state at that time, buying a used engine from somewhere else.
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  #6  
Old 08-20-2019, 04:17 PM
ksdflying ksdflying is offline
 
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Location: Antioch, Tennessee
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Default

“Wait.”
I second this. Yes, definitely wait until mount is in hand.
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  #7  
Old 08-20-2019, 04:21 PM
PilotjohnS PilotjohnS is offline
 
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Default My Rule

When it comes to drilling holes in a Vans kit I have a rule, " always wait as long as possible to screw up a part"
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  #8  
Old 08-20-2019, 06:41 PM
RV7ator RV7ator is offline
 
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Location: Boise, ID
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Default Clamp!

When you drill to the mount, clamp that mother down. Clamp, clamp, clamp. Also bolt down each successive hole. The holes in the brackets will not be exactly centered on the mount holes. Th drill will walk trying to center on the prepunched hole and carry the mount with it.

It's also a whole lot easier to profusely clamp if the firewall is not riveted to the fuse. I also withhold riveting it until all fuse prep and riveting is complete. Being able to remove the firewall for forward access during the build is really nice.

Consider ordering the mount now if the firewall is still loose.

John Siebold
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  #9  
Old 08-20-2019, 08:44 PM
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N941WR N941WR is offline
 
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This is one of the easiest parts of the build.

Set the mount asdide then drill and ream one hole to final size, it doesn't matter which one. Bolt the mount to that hole.

Get a brass bushing that fits in the mount's bolt holes. Drill the second hole under sized using the bushing. Remove the mount and drill & ream that hole to final size.

Reinstall the mount, bolting it down with two bolts.

Repeat for the remaining holes.

Get the mount as close to the prepunched holes as possible but don't worry if they are not exact. It won't matter if your engine is slightly cocked to one side because you aren't going to see it under the cowl, or with the cowl removed.
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Last edited by N941WR : 08-20-2019 at 08:50 PM.
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  #10  
Old 08-21-2019, 06:49 AM
PhatRV PhatRV is offline
 
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Location: Buena Park, California
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Quote:
Originally Posted by PilotjohnS View Post
When it comes to drilling holes in a Vans kit I have a rule, " always wait as long as possible to screw up a part"
Very true. Most of my replacement parts were the results of me drilling the wrong holes.
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