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sbc to bbc motor mount question


Steve G

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I am sure this has been covered before but i gave up using the search option.

 I have a complete 402 from a 71 including the trans and every accessory it came with... 98% complete. the 2% missing is the motor mounts and brackets.

 I am trying to find out what i need thats specific to the bbc in the way of motor mounting brackets. and where i can get them. 

Some have said use everything from chevelle but after trying to use LS swap kits from chevelle i dont believe they can be the same

 Thanks

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Small block and big block frame and engine mounts for a Monte are the same. I'm not 100 percent sure the 68-72 chevelle frame mounts are the same. I believe I have a few sets of used Monte frame mounts if you are interested. Hope this helps.

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Yes True, There are some differences though. The Frame mounts are the same SB and BB even from a 68-72 chevelle but you can NOT use 307 or the 305 frame mounts from a 300 Deluxe chevelle they are different, they need to be a 350. The Block mounts from a 350 to a 402/454 are different as well, you need to get BB Block mounts.

 

Final thing you need to buy is a Big Block Wallet, a Small Block Wallet will never work as there is never enough money in a SB Wallet to run a BB..........!!   :grin:

 

Darren 

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Yes True, There are some differences though. The Frame mounts are the same SB and BB even from a 68-72 chevelle but you can NOT use 307 or the 305 frame mounts from a 300 Deluxe chevelle they are different, they need to be a 350. The Block mounts from a 350 to a 402/454 are different as well, you need to get BB Block mounts.

 

Final thing you need to buy is a Big Block Wallet, a Small Block Wallet will never work as there is never enough money in a SB Wallet to run a BB..........!!   :grin:

 

Darren 

 

 

Funny you say that about the wallet... as soon as i got the word out that i wanted to swap to big block... i got a complete 1971 drivetrain 402 with 70k miles on it and runs perfect, a fresh professionally built 454 with a fully forged bottom end with almost 10k invested 20 years ago still in crate and a dual carb 454 fully built up but has a blown apart bottom end, i wanted it for the vintage intake, valve covers, pan etc... . I acquired all this in one week for less than what i spent on my last engine build (small block ford) I guess i got lucky so far !

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I have done many big block swaps in Monte's. I have always used the small block mounts and frame mounts with no fitment issues. I did install the Chris Alston big block Chevelle motor mount kit because I got tired of replacing broken engine mounts. The only issue with the kit is you have to use the right frame mount for the left side and the left for the right side. Also had to drill one frame mounting bolt hole. So far NO issues with these mounts after many 1/4 mile passes and street beatings. Lol

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And LS5 is correct with the 307 frame mounts. They will not work. Lol depends on what route you want to go. Stock or aftermarket. I went aftermarket with my 70 SS because I don't want to change mounts anymore. Lolol

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If your going BBC, I'd buy a nice set of  Moroso BBC solid engine to your mount plates. So you won't have to replace broken ones. Have these on my small block with no issues. And with a Monte Carlo

 they are not that bad as far as vibration thru frame either.

Jim

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