Has anyone here dropped a big block into a 73-77 Chevelle using the existing small block frame mounts? These mounts are the ones bolted to the frame, not the engine. GM discontinued the OEM frame mounts and a parts search showed none were available. I bought a so-called set of big block frame mounts from a guy over the net but when they arrived, they were identical to the small block frame mounts currently on my 75 Laguna. The GM parts book carries two part numbers, one for the small block frame mounts and one for the big block mounts so I'm going to conclude that they were different parts. So if I drop in the 454, looks like I'm stuck using the small block frame mounts.

Anybody here done this and what problems like frame and/or firewall clearance did you encounter?

A friend of mine used the same brackets switching from a big block to a small block.

The ostracised 1973-77 Chevelles used a sandwich cushion that is common with 1973 - present Chevrolet vehicles, and a block bracket.

The block bracket from a small block should bolt onto any big block; the big block only lasted for 3 model years for the 3rd Generation A-car.

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Weyoun X (the tenth clone)
descendant of a former Chevelle owner

http://www.angelfire.com/tx/lonestarclassics/acar.html

1969 Chevelle Memories Page
http://members.tripod.com/~seributra_d/time_and_memories.htm

Chevelles (and A-cars) On Screen
http://www.geocities.com/MotorCity/Downs/5196/a_car.html

Disco-Era Classics
http://homepages.go.com/~55498/hooptie.htm

73 Was the last year for the 454 in a Chevelle, the Elcamino and Sprint had them till 75, I have read that some 74's had them and not also. So who knows for sure. Should be a easy swap. There is a part # a specific power brake booster as well, may not be actually required. I used the same frame mounts from my six with my Small Block, the motor came out of a 77 Monte, so had the right block brackets. There may have been a factory specific part# for the 454 but according to the other guys the SB unit fits.

Frank

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I dropped a 427 in place of the 350 in mine using the factory mounts for the sb, I had no clearance problems but a small distributor like a Mallory or similar units does free up some space over the monster HEI.

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Sean
Heavy '73

Even with my 305 there is not much room between the firewall and the HEI, Greg how close to the firewall was the factory HEI in your 75?

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There was adequate room for everything with the 350 in there. HEI was no problem. I'll probably run some sort of small cap distributor with the BBC.

The main point I'm wondering about was with the 454 and the factory AC.

Nope, 75 was the last year for the 454 in both the Chevelle and the Monte Carlo. I know because I had a numbers matching 1975 454 Monte Carlo.

Interesting note about the 454 Monte. It is annoying to read conflicting info about engine avail / specs etc. I have seen the 73 454 rated from 215 to 245 hp in print, my original sales brochure lists 245 so I tend to believe that more, but I dont have a 454 so I shouldn't care but these things bug me none the less.

Frank

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Greg,
I just completed replacing a 305 with a GM LS6 454 crate engine into my 76 Malibu. http://www.chevelles.com/forum/smile.gif As for mounts(ones that do mount to frame). These were still available through GM a few months ago. To my surprise the new mounts I recieved were similar to the 305 mounts with an exception of placement of bolt location. However you will find that on your frame there is more than one location for bolting your mounts down,Therefore SB mounts will work. What you will find that won't work,
isn't interchangable and are discontinued will be your brackets that bolt to the engine block that bolt to the mounts. I was unable to locate factory 454 engine brackets for 73-75 Chevelle or Monte Carlo so we purchased 76 Caprice 454 brackets which were still available and relocated the mounting holes that your bolt goes through to connect mount to bracket. Worked great even with the deep oil pan.
As for firewall clearance you will have no problem. Even with factory GM HEI. Any other questions feel free to E-Mail.

Larry

73malibu,

My friend who runs a tranny shop has 2 73 big block cars. One he bought new. He said the different power ratings was because some cars came with just single exhaust. Can you imagine?

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Jeff ACES#841 TCG#158
68 SS396(454)
68 L78 Project
87 MC SS

the 74 chevelle that came with duals, did they have catalytic converters

The 454 was last offered on Chevelles & Monte Carlos in California in '74, '75 elsewhere.

The catalytic converters were used from '75-on. At that time the double hump crossmembers (they allowed clearance for dual exhausts) were replaced with a reconfigured single hump crossmember that allowed clearance for a large single catalytic converter.


In '73 the 245 horse rating was for dual exhaust 454s, while the 215 horse rating was for single exhaust (only used on full-sized Caprice / Impala etc wagons).

GM dropped the big block motor mounts for this generation many years ago (decades). I figure that some other type could be used sucessfully, but I personally can't speak on it since I have no experience.

thanks, i was worried about emissions hopefully i shouldnt have any problems passing. i have a 74 chevelle but in wisconsin i have to take emissions before i get my classic car plates, its a one time deal but i was worried. i have the double hump cross member but it came with a 350. so i guess its original

73 Was the last year for the 454 in a Chevelle, the Elcamino and Sprint had them till 75, I have read that some 74's had them and not also. So who knows for sure. Should be a easy swap. There is a part # a specific power brake booster as well, may not be actually required. I used the same frame mounts from my six with my Small Block, the motor came out of a 77 Monte, so had the right block brackets. There may have been a factory specific part# for the 454 but according to the other guys the SB unit fits.

Frank

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Sorry, you're wrong. I have a numbers matching 74 454 Laguna.

Sbc mounts will work fine with your BB transplant

When I put a 454 in my 74 years ago I used the complete small block mounts worked just fine even with a HEI no problems at all.

by the way would anyone knows how much a 74 chevelle w/sbc weigh from the factory.