Glen-L.com

Hi, This is my first post.
I am building the Monte Carlo.
Glen L sells a bellhousing for a 454- that looks like it has feet built in.
Does this mean that I will not need to use any kind of mount on the Velvet drive? Inboard harware Item Number : 90-781
Thanks,
Rick
rick@blevens.com

G'day from Melbourne Australia Rick.

I've rebuilt a few Velvet Drive 71C's & 72C's. It's normal to have a four point mount configuration when using Velvet Drives - two at the front of the motor (similar to how it would be mounted in a car) and two at the rear. The challenge is that you can mount the rear in one of two positions - either off the flanges at each side of the bellhousing (the basis for your question), or via seperate transmisson mounts bolted to each side of the transmission itself.

Apart from the weight of the engine, you have to consider several things here. Firstly, the alignment of the joining surfaces of the output flange on the transmission and the flange attached to your prop shaft needs to be fairly precise...roughly within approx 3 thou of an inch at the edge of the flange.

If you're bolting the engine and transmission directly onto the stringers in your hull without rubber mounts, then mounting off the bellhousing shouldn't be a problem as there'll be limited movement after installation. However if you use rubber mounts between the engine/transmission and stringers, the rubber will tend to compress over time and affect the alignment. This movement will be exacerbated at the prop shaft end if the rear mounts are attached to the bellhousing rather than the rear of the transmission. You get a seesaw/teeter totter effect where the bellhousing mounts act like a fulcrum and affect the vertical alignment of the transmission/prop shaft.

If your Chevy engine is putting out more than 350HP, you should also consider using a Velvet Drive 72C rather than a 71C. A 72 C is roughly 2 inches longer and a bit heavier than a 71C, but has a bigger set of internal planetary gears and more clutch plates, so can easily take a lot of power. Velvet Drives were originally designed for use in earthmoving machinery (backhoe's etc) but were later adapted for marine use.

If your email firewall will accept a 5Mb .pdf file, I'm happy to send you a soft copy of the Velvet Drive Service Manual which has details on how to mount them correctly.

Hope this helps.

Regards,

Gary H.