Piston Slap: The business about a big-block’s bracketry?


Mike writes:

Sajeev, I recently replaced the power steering pump on a 1970 Chevelle resto-mod. It has a 454 BBC. I believe it’s 1980s-ish truck block, 4 bolt mains. I have run into a problem where the power steering pump unit pulley doesn’t line up correctly with the crankshaft pulley and the air conditioning compressor. I believe the problem is the “boss” that holds the PS pump pulley is longer on the replacement pump.

Since the car originally had a small block, and the person who put in the BBC may have moved the PS pump and A/C compressor and may have kluged it all together. The question is this: Is there a difference between the PS pump for a small-block and the PS pump for a big-block, or could the mounting brackets be different?

Sajeev answers:

The simple answer is that big and small block (Rat and Mouse, if you’d prefer) Chevy V-8s use the same power steering pump. The particular pump I see for your application was used from the 1960s until about 1974. A quick check to see the difference in brackets netted this website and the following photos:

From the looks of it, the small block’s bracketry is significantly different from the big block. Which also makes me wonder if you currently have the donor big-block’s bracketry on your Chevelle? And maybe even the donor vehicle’s pump, too? Oh boy, this could get complicated!

Once you’ve verified you have a 1970-style pump (look at photos on Rock Auto to verify), getting the right brackets will likely make everything better. But will the big block kit fit on your later model 454 engine block? I am optimistic, but check the block’s mounting holes to ensure they line up with what’s presented here.

Once the bracket kit is installed, you should have no problems. But if you still do after all this effort, get some shims to go either between the pump/bracket or between the bracket/block to move the assembly backward or forward. It might take some time and bring a lot of frustration, but the end result will be worth it!

Have a question you’d like answered on Piston Slap? Send your queries to pistonslap@hagerty.com, give us as much detail as possible so we can help! If you need an expedited resolution, make a post on the Hagerty Community!

Read next Up next: Building adjustable links with heim joints

Leave a Reply

Your email address will not be published. Required fields are marked *