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Swap 455 olds with velvet drive to BBC help

Derekhobbie

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I’m looking to swap my 455 olds for a BBC, I currently have a velvet drive and I was wondering if can use the parts I have right now and just change the engine? Would the velvet drive bolt up to a bbc without any adapter? I know the engine mounting plates are different but would the bolt up in the same place as the stringer l brackets or do I need all new brackets and to drill new holes? My boat is a 75 Campbell day cruiser v drive
 

Shlbyntro

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Pretty certain you will need new mounting hardware.

Here's a link to Mercs version of the 454 that was mated to a velvet drive, should be able to find all the parts you need. Of course, they used block mounted motor mounts and not the timing cover or race mounts. I imagine you will have some modification of the mounting points but nothing extraordinary.

I'd bank on coupler, bell housing, and motor mounts at a minimum. Possibly transmission mounts too

 
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74 spectra20 v-drive

74 spectra20 v-drive
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Making the swap from the olds to BBC isn't difficult as far as what you need...
  • Rear cover for the BBC with Velvet drive, your olds has this right now but the olds and BBC don't interchange. You can find these on line, this is from Hardin. I just sold a couple of these that I had laying around, you can find them used as well. Some of these mounts have legs on them the one pictured does not so you would have to figure a mounting system up for the rear of the engine. I run this style on my Spectra and use the Velvet drive as the rear engine mount. A lot of boats were set up like this back in the day.
  • 1627531960412.png
  • I would put engine rails in your boat and then you can set that engine where ever you need it, possibly use the existing holes in the stringers to mount the rails. I doubt that the BBC and OLds would swap exactly and match the holes in your stringers.
  • Coupling the velvet drive to the engine you use a dampner plate that bolts to the flywheel, its a spring plate like on top of a clutch pack with the spline gear in it, more than likely you can reuse the one you have if you are not going to big power 500hp plus, if so I would upgrade that plate, I broke the welds off a couple when I started playing around with these in the mid 90's.
I added a velvet drive to a friends Sanger a few years ago, changed the rear cover and put new engine rails in and it set right where I wanted it. I found this mount and cleaned it up, it is set up with legs on the mount, my day cruiser (no real good picture) I used on with out legs and you can see the difference.

Shoot me a PM if you want to talk about this more, I have added the velvet drive to several flats and restored my Spectra just recently, and swapped it from an olds to a BBC.

NEW FRONT  VIEW.jpg
OLD REAR.JPG


IMG_0359.jpg
 

Derekhobbie

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Making the swap from the olds to BBC isn't difficult as far as what you need...
  • Rear cover for the BBC with Velvet drive, your olds has this right now but the olds and BBC don't interchange. You can find these on line, this is from Hardin. I just sold a couple of these that I had laying around, you can find them used as well. Some of these mounts have legs on them the one pictured does not so you would have to figure a mounting system up for the rear of the engine. I run this style on my Spectra and use the Velvet drive as the rear engine mount. A lot of boats were set up like this back in the day.
  • View attachment 1030987
  • I would put engine rails in your boat and then you can set that engine where ever you need it, possibly use the existing holes in the stringers to mount the rails. I doubt that the BBC and OLds would swap exactly and match the holes in your stringers.
  • Coupling the velvet drive to the engine you use a dampner plate that bolts to the flywheel, its a spring plate like on top of a clutch pack with the spline gear in it, more than likely you can reuse the one you have if you are not going to big power 500hp plus, if so I would upgrade that plate, I broke the welds off a couple when I started playing around with these in the mid 90's.
I added a velvet drive to a friends Sanger a few years ago, changed the rear cover and put new engine rails in and it set right where I wanted it. I found this mount and cleaned it up, it is set up with legs on the mount, my day cruiser (no real good picture) I used on with out legs and you can see the difference.

Shoot me a PM if you want to talk about this more, I have added the velvet drive to several flats and restored my Spectra just recently, and swapped it from an olds to a BBC.

View attachment 1030988 View attachment 1030989

View attachment 1030990

I really appreciate the response seems like you pretty much covered everything I would need to do in order to do the swap.

Where did you get the engine rails?
 

74 spectra20 v-drive

74 spectra20 v-drive
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I typically get my aluminum at Phillips steel in Long Beach any place dealing with metals you can get. If you have some basic tools there is no need to by this stiff as a kit from someone just build your own. I’ll pop up some pics of a couple rail systems when I get off this dam air plane. Trying to get home from Little Rock and was delayed in Phoenix.
 

74 spectra20 v-drive

74 spectra20 v-drive
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I probably went over kill on the Spectra and I used 3 x 3 x 3/8 angle and I ran 8' lengths to mount everything less gear box off of. I used 3 x 3 x 1/4 on the Sanger, one side was actually 3 x 4 angle that I ripped down to 3 x 3 less where I mounted the trans cooler on the 4" portion of the angle. Table saw with a nice Aluminum blade ($40 to $50) sawzall and flapper disks on a 4 angle grinder and you can shape anything aluminum.
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IMG_0382.JPG
IMG_0383.JPG
 
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