SBC to BBC swap

by Landonus Fri Jan 04, 2013 7:56 pm

Will I need to change my coils when swapping out a 305 for a 454? Also, anyone running coilovers, struts? Seen some somewhere for our cars and considered the upgrade.

by JB2wheeler Fri Jan 04, 2013 9:35 pm

Depends on equiptment on the new engine. I still have my original front springs on my small block factory engined Elky. My 540 has aluminum heads and intake and long tube headers and the modern air conditioning unit, which all weight much less than original and my front end sits at the same level as originally. JB

by BlackChevelleSS Sat Jan 05, 2013 12:03 am

If you currently have AC and will not be using the AC compressor or brackets, Usually this alone will be enough weight loss to compensate for the big block.

This is the SB with AC 73 with iron headed aluminum intake and headers 454 and no ac. Also was a th350 car with th400 under it. so that also add a little weight.

SBC to BBC swap 2997675_7_full

by LSANTI76 Sat Jan 05, 2013 1:18 am

If you are keeping your factory AC... 13 yrs ago I did the 305 to 454 (aluminum intake & headers turbo 350) swap. I replaced all small block brackets & pulleys with a big block setup to keep the factory driven accessories/AC. At that time I replaced the worn out factory coil springs with new Moog 5404s. Which is a factory spring for a small block 76 Malibu. These worked out fine for 10yrs & 15,000 miles...but then became spongy & the front ride height sagged 5/8" which is why I replaced my springs last year with Moog 590 coils. These springs have a higher spring rate (not to firm or soft) restoring my ride height to 26" from the ground to the wheel well lip. I have read before that an iron headed 454 is roughly a 180 - 200 lbs difference when compared to a iron headed 305 or 350. As already mentioned...spring choice really depends on if you are planning on keeping your factory AC and or if you will have aluminum heads.

by Landonus Sat Jan 05, 2013 5:27 am

That's exactly what I wanted to hear from you guys. I got a deal on a 78' 454 with 28,000 miles for $900 with everything still attached that I am planning on trading for. My factory AC still works so I will definitely be keeping it even though I'd like to go to a smaller compressor and possibly change to serpentine also but that's work for another day. I plan on setting it up with headers and aluminum intake before install but will for the time being keep the same heads for who knows how long. I might consider the Moog 590 coils if I can't find BBC coils from my friendly neighborhood salvage man. Thanks for the info. I'll keep everyone updated when work begins.

by Joe73 Sat Jan 05, 2013 9:10 am

Rockauto.com has some big block front springs for a 75 malibu w/ac for $67. I think I'd go new instead of some "pre-sagged" used ones. Your front end will be high for a while until the new springs settle down.

by Landonus Sat Jan 05, 2013 11:54 am

That's right. 75 Still had the 454 available through 1/2 the year, right? I remember buying SBC A/C springs for my Nova when I added a BBC and it never squatted down.

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