GEN V 454 Swap ?

80355BU

New Member
Mar 18, 2019
4
0
0
Greer, SC
Guy has a rebuilt 1991 Gen V 454 w/accessories and a TH400 for sale in my area. I have/had a 355 with 3spd manual. What pitfalls am i looking at with this swap? I have the Double Hump crossmember for the 3spd so i assume i will need a different one for the TH400? I know headers will have to be addressed. What about motor mounts? I cant recall if the BBC will use the same mounts on the frame or if they will need to be moved? Any insight any one can add is greatly appreciated.
 

prairiehotrodder

Pro Stocker
Dec 17, 2005
1,570
1
38
43
Melfort Saskatchewan Canada
you will need to move / modify or change the trans crossmember to use your turbo 400. You will need to shorten the driveshaft. You can use the same motor mounts. Depending on the valve covers on your 454, you may need to remove or modify the heater / AC box for clearance. I've had a big block in my 81 malibu for many years and am very satisfied.
Brian
 

80355BU

New Member
Mar 18, 2019
4
0
0
Greer, SC
prairiehotrodder said:
you will need to move / modify or change the trans crossmember to use your turbo 400. You will need to shorten the driveshaft. You can use the same motor mounts. Depending on the valve covers on your 454, you may need to remove or modify the heater / AC box for clearance. I've had a big block in my 81 malibu for many years and am very satisfied.
Brian
I am going to go with a double hump cross member from Jegs for the TH400. I have a GN 8.5in rear diff with the GN driveshaft. Will i still need to shorten it? Also can you recommend any headers that arent going to break the bank? Also thank in advance for the input so far as its greatly appreciated.
 

prairiehotrodder

Pro Stocker
Dec 17, 2005
1,570
1
38
43
Melfort Saskatchewan Canada
i would save the GN driveshaft and just get a new driveshaft built with 1350 joints. I would also bit the bullet and get the hooker super competition swap headers that are made for the big block G-body. They turn up used occasionally if you can't afford new. I've tried cheaper A-body (chevelle) big block headers and they can be made to fit with lots of beating but then you feel sick afterwards.
 

80355BU

New Member
Mar 18, 2019
4
0
0
Greer, SC
prairiehotrodder said:
i would save the GN driveshaft and just get a new driveshaft built with 1350 joints. I would also bit the bullet and get the hooker super competition swap headers that are made for the big block G-body. They turn up used occasionally if you can't afford new. I've tried cheaper A-body (chevelle) big block headers and they can be made to fit with lots of beating but then you feel sick afterwards.
Do i have replace the oil pan for sure? Seems like a lot have been swapping theirs to various oil pans? Figure if i need to then i need to do it before i start to put it in lol Also this will be a street car and not a track car if any of that makes a difference.
 

prairiehotrodder

Pro Stocker
Dec 17, 2005
1,570
1
38
43
Melfort Saskatchewan Canada
Not sure on the oil pan because i don't know what you are using. You could just measure from the flexplate to the front of the oil pan sump, then measure your car from the torque convertor to the crossmember to see if it will fit. You can also notch your crossmember if needed. If its a street car and power isn't a concern then you can just use exhaust manifolds instead of headers. But i guess if power wasn't a concern the stock 267 would still be in there.
Brian
 

80355BU

New Member
Mar 18, 2019
4
0
0
Greer, SC
prairiehotrodder said:
Not sure on the oil pan because i don't know what you are using. You could just measure from the flexplate to the front of the oil pan sump, then measure your car from the torque convertor to the crossmember to see if it will fit. You can also notch your crossmember if needed. If its a street car and power isn't a concern then you can just use exhaust manifolds instead of headers. But i guess if power wasn't a concern the stock 267 would still be in there.
Brian
Going by the casting number on the block its a 1990 GEN IV 454. I want power but im not trying to make huge power. The car might see a grudge night here or there but its mainly a cruiser. Not looking for a full on drag car. Im in my early 40's and my 80 malibu was my first car. Ever since i bought it back in 1993 i have wanted a big block in it. Ive had a sbc 400 and a sbc all roller 355. So this deal for this engine i felt like was a good enough deal since it came complete air cleaner to oil pan along with all the accessories and brackets. Also the TH400 is still mated to it. So i figured it was a sign to go for it lol
 

MalibuRacing

Top Fueler
May 5, 2003
3,469
0
36
www.maliburacing.com
Pretty sure you won't be able to use the oil pan unless you carve up your crossmember. The front of the pan sump will hit the crossmember. That was my experience trying to use a Gen4 truck oil pan. The GenV 454's are pretty anemic. The heads have really small ports (smaller that older oval ports). But, it would make a good cruiser. Personally, I would rather spend the money on a LS swap. But, I get the wow factor of a BBC.

Good luck,
 

TURNA

MalibuRacing Junkie
Jul 6, 2003
6,031
0
36
Socialist NY
Gen 4 pan is a 2 piece seal Gen 5 1 piece seal