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Discussion Starter · #1 ·
Currently swapping motors on my 1971 C10. I'm taking out a 350 SB with manual 350 tran; installing a 454 BB with a TH400 tran. Running into some issues but then when don't you on projects.

I understand that I might need to change the drive shaft and yoke to match up with the new TH400 and the transmission cross member might need relocated to match up.

The BIG question I have is the motor mounts and motor mount perch(towers). I have the original mounts and perches from the donor vehicle with the 454 (which is a 1974 1 ton dually flatbed). I also have the original mounts and perches from the 350. I have not held them up to the frame yet but when I measure the distance between the holes it doesn't seem to line up plus the 350 perch is a 3 hole and the 454 perch is a 4 hole. So the QUESTION is: Can I use the 350 perch with the 454 mounts? or Can I use the 350 mounts and perch on the 454? Which way is best.....

Really do not want to chop stuff up or modify things that should not be modified. Really appreciate any help as I am new to this.
 

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not sure about truck but I have used sbc mounts for bbc before with no problems. Rich may know more about this. The only thing I see that may be aa problem is the distributor location. The bbc may be back to far with the sbc mounts ....I would do some measuring there the rest can be handled with spacers. The trans mount will be different
 

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Discussion Starter · #3 ·
Thanks for the info Charlie. Will do some measuring. This is my first project so its a learning process and will take some time. Will let you know what I figure out. Hopefully Rich will post something before I get to installing the 454 BB.

Thanks again
 

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Small block mounts and perches will work fine....you will need a new yoke for the th400 and shorten the drive line..one question remains, on the `64 to `66 trucks there are two locations for the perches to bolt on to the frame/crossmember a rear set of holes and a forward set of holes in the frame/crossmember, does the `71 have this...?
 

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Discussion Starter · #5 ·
The '71 has three holes on the frame where the perch goes (See attached photo).

I figured I would need to change the yoke and shorten the drive shaft. Charlie mentioned the distributor location might be to far back, do you know if this will be the case? I'm just not sure how to measure to check if this will be a problem. Any help would be great.

Thanks for the info on the mounts and perch, that will save some time and money.
 

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measure back from mount on engine you can use a carpenters square to the rear of the engine then measure from the mount hole to the fire wall the difference is what you will have for distributor clearance. Depending what distributor you use
 

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Discussion Starter · #7 ·
Engine swap issues.....Questions.

Ok so I got the 454 into the 1971 C10 truck using SB perch and mounts, no issues with distributor fitment but sure have other fitment issues. Hoping someone has some advise.

First issue is the Fan and Radiator. At first I couldn't even fit the radiator in to the engine compartment because the fan was to far forward. I measured the spacer an it was 1 1/2 inches so I bought a 1 inch spacer. This let me fit the radiator into the truck but the fan still hits radiator on the right side due to how motor sits in engine compartment. I'm afraid if I go any smaller on the spacer that the fan will be to close to my belts and pullies. Any advise on how to solve this issue without breaking the bank would be great. Right now I am thinking I will have to put dual electric fan in front of the radiator which looks like it will be expensive. So any ideas?

Second issue is the headers. Using the SB perch and mounts causes the headers to hit the perch with both the left and right front two exhaust ports with the stock headers. Any suggestions on a brand of headers to use and maybe a part number for me to check out?

These are my biggest issues I face right now, have other small issues but I hope to figure those out little by little. Like I said before, first time for this guy to work on something other than a motorcycle.....hope I didn't bite off more than I can chew. Thanks for any help you all can give me.
 

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Gm put the big block in the `71 series trucks, so we know it fits, you may have to change to the standard C10 `71 big block mounts to correct all the issues, the mounts are all the same from `71 to `85, they had changed to the clamshell mounts to prevent rubber isolators from pulling apart. the uppers you have from the other set should be the same as the clamshell, you`ll just need to change the lower towers. this will effectively move the engine back as well....
 
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