Author Topic: 454 to 350 1991 v3500  (Read 1316 times)

Offline Trucker2k16

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454 to 350 1991 v3500
« on: November 02, 2020, 12:40:09 PM »
Hello everyone and thank you for letting me join the forum.
I have a 1991 v3500 that had a 454 im installing a 383 stroker im using the 454 mounts but i seen some where on here the the mounts that bolt to frame are different or is that if i was to use 350 mounts?

Offline ehjorten

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Re: 454 to 350 1991 v3500
« Reply #1 on: November 02, 2020, 01:53:44 PM »
The 454 Mounts are bigger and mount to the frame with a triangular, 3-bolt hole pattern. The 350 mounts are smaller and bolt to the frame with a somewhat rectangular, 4-hole bolt pattern.
So...the frame side mounts are likely different, but the height difference between the 350 and 454 mounts is only 1/8". Don't quote me, but you can probably just use the 454 mounts.
-Erik-
1991 V3500 - Gen V TBI 454, 4L80E, NP205, 14 bolt FF, D60, 8" Lift on 35s
1977 K20 Silverado - 350, THM350, NP203, 14 bolt FF, D44, Stock Lift on 31s
1969 Chevelle Malibu Sport Coupe - EFI350, THM350
1968 Chevrolet Step-side Pickup - 300HP L6

Offline Trucker2k16

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Re: 454 to 350 1991 v3500
« Reply #2 on: November 02, 2020, 02:06:18 PM »
Good thing is ill have electric fans but also the geometry of the transmission transfer case a while back I took a 85 k-30 they had a small block Chevrolet in it and put a 6.2 L diesel in it and used the 350 mounts it's been so long since I've done swaps and whatnot on these Square bodies I actually just got this 91 V 3500 for free the first square body that I've owned in probably about 2 years

Offline ehjorten

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Re: 454 to 350 1991 v3500
« Reply #3 on: November 02, 2020, 02:21:23 PM »
350 mount on left, 454 mount on right:


350 frame mount bolt pattern:


454 frame mount bolt pattern:


Bolt patterns laid over each other:
-Erik-
1991 V3500 - Gen V TBI 454, 4L80E, NP205, 14 bolt FF, D60, 8" Lift on 35s
1977 K20 Silverado - 350, THM350, NP203, 14 bolt FF, D44, Stock Lift on 31s
1969 Chevelle Malibu Sport Coupe - EFI350, THM350
1968 Chevrolet Step-side Pickup - 300HP L6

Offline Trucker2k16

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Re: 454 to 350 1991 v3500
« Reply #4 on: November 02, 2020, 02:26:44 PM »
That part i understand what i mean is the mounts that bolt to frame i seen someone on here mention it i have new 454 mounts im just wondering about the ones that bolt to frame

Offline ehjorten

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Re: 454 to 350 1991 v3500
« Reply #5 on: November 03, 2020, 09:30:27 AM »
that bolt pattern is the pattern that bolts to the frame side. If you have a frame that was intended for 454, you likely have the 454 mounts, but I am not certain that there are different frame side mounts. See attached picture. This is from when I put in the aftermarket crossmember. See there is an extra hole that might fit the 350 mounts? You would have to try it. The bottom center hole is the one that fits the 454 mounts.

-Erik-
1991 V3500 - Gen V TBI 454, 4L80E, NP205, 14 bolt FF, D60, 8" Lift on 35s
1977 K20 Silverado - 350, THM350, NP203, 14 bolt FF, D44, Stock Lift on 31s
1969 Chevelle Malibu Sport Coupe - EFI350, THM350
1968 Chevrolet Step-side Pickup - 300HP L6

Offline Trucker2k16

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Re: 454 to 350 1991 v3500
« Reply #6 on: November 03, 2020, 11:34:04 AM »
I see now i was confused my mistake idk what i was reading but im gonna use the 454 mounts being it sat perfect in truck before i pulled engine