rocket 350 to 455 conversion

grandmas73rocket · May 19th, 2003, 11:57 AM

I have 73 cutlass with a rocket 350 in it. the car has only 53,800 original so the car is a clean original. I have a person who has built motors for me before and he wants to drop a 455 big block in it. I need to know what I have to change to get this motor in the car. can I use the stock turbo 350 trans( will the bellhousing bolt up)? motor mounts, etc...

thanks
c.b.

jimfulco · May 21st, 2003, 11:48 PM

The Chevy has a different bellhousing bolt pattern. As far as mounts, big-block Malibu or maybe MonteCarlo hardware would probably work, but if you have clamshell mounts, they might be the same. Check out www.hotrodders.com & www.gmforums.com
Maybe somebody there will know.

crown14 · September 8th, 2003, 04:38 PM

jim- what chevy are you talking about??

c.b. yes the 455 OLDS big block will in fact bolt up to your turbo 350 trans... but if you plan on letting the beast out of that engine dont expect the TH 350 to last more than 6 months TOPS. Go with a good or even better a rebuilt TH400. This is how they built them and a TH400 can take all the abuse you can give it. Until it breaks.

72cuttyconv · February 16th, 2004, 10:29 PM

I'm doin the same thing thanks for the help

powerplant455 · September 25th, 2004, 04:06 PM

i have a 350 tranny behind my 455, and it runs strong. But i put a stage two shift kit in it though, to make it last. and i dont baby the throttle one bit. but i agree with going with the 400 because it is stronger. i have one on the floor for back up.

Is the 73 the same frame as a 70-72 frame? Is a 73 still an a body frame?

the chevy mounts wont work, theyll only work if u r putting a chevy motor in it, and if u put a chevy in it u need the bellhousing adapter plate. ur 350 headers wont work becuz a 455 is wider.

yogi442 · December 7th, 2004, 11:30 AM

The headers I used on my 350 to 455 conversion in my 76 are set for both. Either way it is never easy putting headers on either one. There is not that much difference in size (width) from Olds 350 and 455. Chevy has small 350. Olds, Buick and Pontiac 350's if not sure can be mistaken for big block motors unless you know what you are looking for. Though called small block, they are not small like the chevy. My 455 block destroyed the engine stand my brother used for years to build he 454 chevy motors. He was not aware of the weight difference.

September 8th, 2003, 04:38 PM	#3 (permalink)
crown14 Junior Member Join Date: Sep 2003 Location: Durham, NC Posts: 2	jim- what chevy are you talking about?? c.b. yes the 455 OLDS big block will in fact bolt up to your turbo 350 trans... but if you plan on letting the beast out of that engine dont expect the TH 350 to last more than 6 months TOPS. Go with a good or even better a rebuilt TH400. This is how they built them and a TH400 can take all the abuse you can give it. Until it breaks. __________________ '72 Cutlass S '71 Delta 88 Custom '67 Volvo 122s '91 Chev S-10

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May 19th, 2003, 11:57 AM	#1 (permalink)
grandmas73rocket Junior Member Join Date: Apr 2003 Posts: 4	I have 73 cutlass with a rocket 350 in it. the car has only 53,800 original so the car is a clean original. I have a person who has built motors for me before and he wants to drop a 455 big block in it. I need to know what I have to change to get this motor in the car. can I use the stock turbo 350 trans( will the bellhousing bolt up)? motor mounts, etc... thanks c.b.

May 21st, 2003, 11:48 PM	#2 (permalink)
jimfulco Junior Member Join Date: May 2003 Location: Shreveport LA Posts: 3	The Chevy has a different bellhousing bolt pattern. As far as mounts, big-block Malibu or maybe MonteCarlo hardware would probably work, but if you have clamshell mounts, they might be the same. Check out www.hotrodders.com & www.gmforums.com Maybe somebody there will know.

February 16th, 2004, 10:29 PM	#4 (permalink)
72cuttyconv Junior Member Join Date: Feb 2004 Posts: 3	I'm doin the same thing thanks for the help

September 25th, 2004, 04:06 PM	#5 (permalink)
powerplant455 Junior Member Join Date: Sep 2004 Location: north dakota Posts: 4	i have a 350 tranny behind my 455, and it runs strong. But i put a stage two shift kit in it though, to make it last. and i dont baby the throttle one bit. but i agree with going with the 400 because it is stronger. i have one on the floor for back up. Is the 73 the same frame as a 70-72 frame? Is a 73 still an a body frame? the chevy mounts wont work, theyll only work if u r putting a chevy motor in it, and if u put a chevy in it u need the bellhousing adapter plate. ur 350 headers wont work becuz a 455 is wider.

December 7th, 2004, 11:30 AM	#6 (permalink)
yogi442 Registered User Join Date: Dec 2004 Location: Blaine Wa Posts: 88	The headers I used on my 350 to 455 conversion in my 76 are set for both. Either way it is never easy putting headers on either one. There is not that much difference in size (width) from Olds 350 and 455. Chevy has small 350. Olds, Buick and Pontiac 350's if not sure can be mistaken for big block motors unless you know what you are looking for. Though called small block, they are not small like the chevy. My 455 block destroyed the engine stand my brother used for years to build he 454 chevy motors. He was not aware of the weight difference.