Big block in a 1978 Impala - Impala Tech
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post #1 of 4 (permalink) Old 03-05-2012, 06:47 PM Thread Starter
Join Date: May 2009
Location: MI
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Big block in a 1978 Impala

Came across a clean "Granny" 1978 Impala......small block now (of course) w/ difficult to install a big block and th350....I know the 200 in there now will interchange with a TH350...but not sure about the big block....any help would be great!....I know you guys will be thinking WHAT?...Thanks again
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post #2 of 4 (permalink) Old 03-05-2012, 09:29 PM
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Welcome to the Team Jim!

I have one in my 1985 and it is the same car as your 1978. I used Hooker Competition Plus headers for a Chevelle but I chose the 4L80e transmission as a big block will break a TH350 or 700R4 transmission. If you want a three speed go for the TH400 instead of the TH350. I also had to make my own cross member for dual exhaust. To cool the added cubes I used a Griffin 1-1/4 inch twin tube radiator (Howe also makes a big radiator for the car as well).

I had to use a Chevelle oil pan from Moroso and even then I had to massage the front cross-member a bit with a sledge for clearance at the front of the oil pan (seven quart Moroso with kick outs 8-3/4 inch deep). Only other problem was the intake manifold and a Dominator carb left only an inch above a flat hood with a Victor intake manifold so I had to go to a medium rise dual plane to run an air cleaner to hide the carb and keep the flat hood I was looking for (my car looks like an old taxi cab and sounds like a small block with a hole in the muffler as I like to keep a low profile).

The beige car is the 582 big block powered car the brown one has a 406 small block under the hood that makes 513 horsepower.

Big Dave
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post #3 of 4 (permalink) Old 03-05-2012, 09:57 PM
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Love the oil pressure switch in the valve cover.....thats one way to monitor you pressure! .
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post #4 of 4 (permalink) Old 03-05-2012, 10:34 PM Thread Starter
Join Date: May 2009
Location: MI
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Wow...Thanks for the help....any special motor mounts, and relocation of the trans cross member for the TH 400? Will probably remove all the a/c stuff for more room....any other changes or problems to expect? Thanks a lot!
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