Hello All,

Thought I would share this info as I couldn't find this data when I was trying to determine if a major tear-up would be needed(or not) to put a G3 in a car setup with a mid and front plate for a big block.

I now have a couple of bare blocks (400 BB & Gen3-preVVT) on engine stands as well as a complete 2009 6.1 Liter. I measured from the trans bell mounting face to the water pump mounting face, except for the completely bare G3 block. I used an aluminum 4 foot yard stick with 1/16 inch increments. We know this wont be three decimal place accuracy, but it will certainly be a reasonably close approximation to use for reference.

400 BB = 23 7/16 inches

6.1 L = 23 1/4 inches (from trans bell face to front cover water pump mounting face)

5.3 L = 20 1/4 inches (bare block without anything mounted to front)

So, it looks as though the BB dimension is approximately 1/4 inch longer. I would think this difference could be made up easily with whatever means and thus avoid any major fabrication or tear-up to make the G3 retro to BB mid and front plate mounting work.

If anyone has similar information, please share so we can compare notes...

Thanks!

I bought a tube car that was a big block and the tabs on it worked out to be approximately 1/4" different then my gen3

Thanks for sharing, thats two of us with similar numbers so far. Hopefully, more will chime in.

Did you remove the G3 water pump and put a motor plate against the front cover?

I took a big block out and put a gen 3 in. I just used a midplate to make up the little bit of difference.

Yes, I used a .090 steel mid plate(it was a 1/4" alum before) and a 3/8 front plate in the pump area tapped for water 3/4"npt in and 1"npt out.

Then attached 1/4" plates on each side to the front of it to attach to the orginal chassis tabs.

So my front plate is 3 parts. Making a 3/8" step forward