Re: BB vs SB motor mounts

by 74Malibu383 Fri Aug 15, 2014 3:47 pm

The BB I'll be using is a tall deck. Anyone have experience with that?

by Trbulnc Fri Aug 15, 2014 5:24 pm

Everything I have been looking and studying says my biggest concern is brake booster. They make smaller diameter boosters which I am 99% sure I will need. Obviously hood clearance also. I'm a little worried about my AC stuff but think I will be ok. I can always modify it, just glass work. I have an overlay at home showing short deck vs talk deck and dimensions. I'll find it for you.

by bracketchev1221 Sat Aug 16, 2014 8:36 am

74Malibu383 wrote:The BB I'll be using is a tall deck. Anyone have experience with that?

That changes everything. I am assuming its a gm crate 572 that you are looking at. A tall deck is going to move the heads up and out more than a short deck. A tall deck is 10.2" compared to 9.8 for the short deck. Meaning headers will be a real pain. Also like was said this will bring tall valve covers closer to a brake booster and a/c box if you have them, but I don't remember if your car does. Finally standard accessory brackets will not work. The relation from the water pump and block to the head mounting holes are different. It has no impact on the block mount question though. If you have any big block engine questions let me know.

by 74Malibu383 Mon Aug 18, 2014 11:35 am

Yup, ZZ572, should be here today. Got a great deal from a guy on another forum. He has a dyno sheet with it making 648hp at the crank, and never installed it. So, hopefully it will be everything it seems to be. I ordered up a serpentine accessory kit from ProCharger since I plan to put my head unit on this engine as well. I don't have the A/C box with the Vintage Air system, but I do of course have the stock style booster. Can I assume I'll need to step down to the smaller booster? I ordered some Hooker Competition headers in painted form. I figured I would have to modify them, and plan on getting them coated after I do.

I've read that there could be a difference between the block mounts in relationship to how high the block sits. Is that not the case?

by bracketchev1221 Tue Aug 19, 2014 8:27 am

The block mounting points are in the same place for both blocks, short or tall deck.

by g3chevy / Mr Pontiac Sat Sep 06, 2014 11:48 pm

Not sure if this helps but here's a few pics of the motor mounts for my 75 SS el camino with 454 removed. Excuse the poor quality of the pics, I took them with an old cell phone. The motor mounts are different from the small block motor mounts. You'll notice the top of the mount has 2 holes where the bottom of the mount only has one. On the small block mounts there are 2 holes top and bottom.
BB vs SB motor mounts - Page 2 Motor_10

by Joe73 Sun Sep 07, 2014 6:54 am

Those look like they're positioned just like my small block mounts on both of my frames sitting here. Also only 2 bolts on top and 1 on the bottom. Bottom front edge of the mount overhangs the frame a bit.

BB vs SB motor mounts - Page 2 Hv9xjc

by Dinomyte Sun Sep 07, 2014 9:19 am

They look just like mine too, positioned with the 4th hole off the frame. I had to ask if that was right when we pulled the old motor (305) out a couple of years ago.

by Joe73 Sun Sep 07, 2014 9:35 am

If I remember correctly, the bolt hole spacing on the mount is slightly different from either end. Just slightly.

by g3chevy / Mr Pontiac Sun Sep 07, 2014 8:16 pm

I took some better pics of my factory big block mounts and compared them to the small block mounts I have for another project. Not sure if you can tell in the pics but the big block mounts are definitely bigger by about a half inch. They also have the bolt hole in the middle of the bottom side and rivets on each corner. The small block has the rivet in the middle and bolt holes on each corner of the bottom of the mount. The top of the mounts for both look the same. Here are the pics. Hope this helps.
BB vs SB motor mounts - Page 2 Motor_13

by 74Malibu383 Wed Sep 10, 2014 2:46 pm

Thanks for all the photos. I guess I won't know till I get it torn apart. Planning on taking it down the track this Friday to see what numbers I can get with the current set up. After that, it's install time!

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