I have a 1985 Monte Carlo that had a v6 throttle body in it and I got a 454 v8 carb engine with a 400 tranny. can someone help me with where I need to start with the conversion and how hard this is?

Douglas Parks

Asked by May 23, 2015 at 10:36 AM about the 1985 Chevrolet Monte Carlo

Question type: Car Customization

I have a 1985 Monte Carlo it had a v6 throttle body engine in it.  I just purchased a 454 carb
erased 3 fine and I am not sure what I got myself into with this. THE 454  has a tranny on it
it's a complete motor so I am trying to figure out what I'll need to convert this.  Any help
would be awesome

8 Answers


First off would be motor mounts, transmission cross members, and drive shaft length.

1 out of 1 people think this is helpful.
Douglas Parks

Do you happen to have any idea how much this conversion will run me

Dont forget the upgraded suspension and brake system. All told? Its going to cost alot unless you do it ylurself, and then you would still be better off getting a Monte built with a factory 305 and go from there.

James Kitlas

Start with the correct big block upper & lower motor mounts, for an 85' Monte Carlo from Chevrolet parts dept. A 400 trans cross member & shorten or buy a custom length drive shaft. The 400 trans tail shaft is much longer. SS Chevelle parts might interchange. Install the motor with the front off it makes it much easier. A big block project Monte! Sounds cool.


Sell the big block and put an LS1 in it, you'll be a lot happier with it in the long run, you won't have to modify the brakes and suspension to accommodate the heavy set up the only mechanical mods would be what JRK mentioned and will up the value of the car when you sell it with an injected engine.

1 out of 1 people think this is helpful.
James Kitlas

Since you already purchased the 454, keep the car 1985 period correct. Big block Monte Carlo's were rare & so cool. And during this mod add tube headers & a shift kit valve body & 3000 rpm stall speed convertor for that turbo 400 trans. I hope you have a posi rear end (4.11 - 4.56 ratio) too for this monster?

James Kitlas

I did a mod similar to this swapping out a 396/375 hp for a 427 /430 hp L-88 in my 1969 SS Camaro. The stock 396 turned 13.00 sec's flat in the quarter. Not bad in 69'- 70' & a A/SA class, Mopar Hemi killer! The L-88 turned high 10's low 11''s all with the turbo 400 trans. But I'm "old school" but still cool.

James Kitlas

Again remove V6 engine & trans. Remove fenders & wheel well assembles. Remove cross member & radiator. Position new 454 motor lower mounts on frame & weld-in. The motor posistion is determined where the trans bolts up to the new trans cross member. Buy one from Chevrolet parts dept or a salvage yard, A Chevelle auto trans cross member will work too. It might have to be repositioned too? Due to longer length. You can "hang" the motor & mark on the frame where the mounts should be welded in. This mod is medium to major, get a motor head friend to help.

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