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Old 08-07-2017, 07:58 PM   #1
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Oldsmobile 425ci into 71 K10.

Anyone able to share some light if a 425ci 1965 Olds 88 engine work for engine swap into a 71 K10. I'm not a big car savvy dude so any help is good. Thanks

Also before I have some troll come... yes I tried searching, didn't find what I was looking for. Thanks
1971 Chevrolet K10 Fleetside
- 350ci w/ 4 speed

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Old 08-07-2017, 08:24 PM   #2
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Re: Oldsmobile 425ci into 71 K10.

Big blocks get put in these trucks all the time and obviously there were many that came from the factory, just not 425s. I suppose the issue is mating to your transmission and possibly some clearance issues but in can be done.
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Old 08-07-2017, 10:59 PM   #3
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Re: Oldsmobile 425ci into 71 K10.

I can't provide much help yet, but I am building an Olds 455 to put into my '64 C10. You'll definitely need to get Chevy engine mounts.
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Old 08-07-2017, 11:17 PM   #4
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Re: Oldsmobile 425ci into 71 K10.

I have installed a few in Chevy cars and a C10 and use the BOP tranny so it will bolt up cause the bolt pattern is different so a 2wd is fine but not sure mating the BOP (Buick, Olds, Pontiac) trans to a transfer case, have never thought about it or done it, usually put a big block Chevy in everything I own, simple, yours I think w need different motor mounts and exh manifolds of course, keep us posted. Interesting.
71 GMC K10.
454/530hp. 5"lift w 35" Pitbull Rockers.
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Old 08-11-2017, 09:38 PM   #5
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Re: Oldsmobile 425ci into 71 K10.

I put a 455 Olds (same block as your 425) in my '78 K truck back in the '90's (I also have a 455 in a 2wd truck so this is right up my alley). Too bad photobucket has dicked up the whole situation as I have some photos of mounts, ect. that won't show up any longer.
With a little planning & some small steps made in the week prior...I was able to do the swap from a 350 Chevy to the big Olds in the 4X4 over a weekend. I was younger then too though!

A few things to work out will depend on what you have now. I have done the motor mounts 2 different ways using the Olds rubber mounts & frame stands but have seen guys use the Chevy rubber mounts & adapt the upper to the Olds block. On the 4X4, I added 1 1/2"x 1/8" plate to the front of the plate the frame mount sits on & bolted the mounts in the "forward" position on the block. On the 2wd, I made a plate across the 3 bolt holes on the block & then placed the mount in the center to sit in the "correct" place on the crossmember. Either way works fine.
On the 2wd, I'm using the HEAVY TransDapt adapter plate to mate up to a 4L60e...which is a fine way to go. Just stay away from the cheapy $75 thin plate version. On the 4X4, I had the output shaft installed in a multi-bell TH350 prior to the swap in preparation...never even changed the trans. dipstick tube...I just put a nut on the bolt though the bell housing.

The upper rad hose will need to be for an Olds, the lower from the truck works great. Fan shroud, ect all works fine. Just need a little longer rubber hose for the fuel line to the pump. Exhaust manifolds work out good. I suggest getting the Left battery tray for a diesel set-up to neaten up the battery cable. Depending on which oil filter housing you have it may need changed to clear the front driveshaft, but there are several versions & all 260-455 Olds interchange.

You will need to shuffle a bit of wiring due to the starter on the opposite side, however it works out fine. You will need to lengthen the oil & water sending unit wires, but that is about it.

That should cover it, but if you have any questions...just ask! Oh, by the will Love the low RPM, BIG torque of the Olds! Lorne
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Old 08-11-2017, 11:43 PM   #6
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Re: Oldsmobile 425ci into 71 K10.

I also used the Olds accessory brackets when I did mine.
If I didn't build it or fix it, it's probably not mine.
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Old 08-12-2017, 08:17 AM   #7
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Re: Oldsmobile 425ci into 71 K10.

I always wondered where to get the engine mounts. I love Olds power.
76 Chevy K20
76 GMC K15
77 Chevy C10
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