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V6 to V8 swap for '86 C10

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Old 10-12-2005, 06:15 PM
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Default V6 to V8 swap for '86 C10

Buying a used Gen III 5.3L V8 crate (LM7) this Friday. Need info on mounting hardware. Are there any kits available to mate in an 86 C10 that was set up with GM's 4.3L V6 (L35)?

Trans Dapt has got kits to mount the LS1/LS6/Vortec 4.8, 5.3, 6.0 crates into an S-10 w/ 2.2L or 4.3L crates. The 4.3L in the S-10 is the same as my 4.3L in my C10. Will this mount properly in my C10? What is the difference in distance b/t the frame rails on the S-10 vs. the C10?
Old 10-12-2005, 10:29 PM
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i used some brp mount adapters. they worked out real well. My truck is an 81 c1 but originally had a 305 in it. I would think the frame mounts and engine mount cups on the 4.3 would be the same from the 4.3 to the sbc. So i would think you would only need the conversion mounts and should be ready to go to work
Old 10-13-2005, 10:31 AM
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Any suggestions as to where to look for these conversion mounts? Most websites I run across have no info on this type of conversion, and have no idea as to what would seem logical to be fact. Looks like I'll be going forth blind, buy a kit, test fit, and I'll be sure to post in the coming weeks.

I find conversions online for S10 with the same crate I have (4.3L V6). Some other places I find that some say the mounting hardware are the same b/t the S10 & C10. Don't know if true, so which way now...
Old 10-13-2005, 11:03 AM
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Here's BRP's website, they could probably help you out:

http://www.brphotrods.com/
Old 10-13-2005, 12:41 PM
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Thanks for the tip. Talked with Mr. Brewer, and bought the plates over the phone. He said I should have them by early next week. If the 4.3 mounts are the same as the 350 mounts, I should be able to pull the 4.3 out of the truck, remove the mounts, bolt the plates to them, then bolt the plate to the 5.3, and line the 5.3 in the truck. Is this the correct assumption?

I know there's more work than stated, but am I on the right track? Bill said that their plates are steel, and not tapped aluminum. For the price, it's worth a try.
Old 10-15-2005, 09:21 PM
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I am getting the pieces together to do a similar project. I have a 93 1500 Sierra with a 4.3L, and I think the front seal on the trans just went today. Time for the swap. Please post if the 305/350 plates work out for you application. I am fiarly certain the V6 and the V8 mount into the truck in the same place, but I would like to be sure before I pull the motor.. Thanks!
Old 10-15-2005, 10:20 PM
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I'm glad somebody asked this. I am going to restore my dads old truck that he bought new. It is a '86 C10 with the 4.3. My father said he wanted a little more power, after 300,000 on the engine its getting a little tired, but it still passed emissions. It was one odd truck, he bought it at the end of the year and it came with some strange options. It has a TH400 tranny, a 4 barral carb., headers intead of the normal exhaust manifold, and a 2.73 rearend. It has been the best truck he has ever owned though.

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Old 10-15-2005, 10:34 PM
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The 4.3L motor mounts are closer to the firewall. I swapped a 355 into my old 1990 c-1500 it was a 4.3L, it used a bracket mounted on the frame to move the mount back to meet the 4.3l. All I had to do is remove the bracket and bolt the V8 mounts to the frame. I would think the c-10's would use something similar.
Old 10-16-2005, 08:29 AM
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I was told that I would need to move the brackets forward (approx. 4 inches). I took a look at my current location, and saw there are pre-drilled holes to move the bracket forward. My biggest concern was being able to mount the 5.3L V8 using conversion plates, and still have wiggle room for the radiator/condenser (and maybe an intercooler & trans cooler). My eyeball confirmed I'd have approximately 2 - 3 inches b/t the fan & radiator (w/ rad in stock location).

Once I get a chance, I'll take a look at the trans location. I'm not in any rush to start, but anticipate pulling the 4.3L V6 before Thanksgiving (unless I get lazy). Haven't familiarized myself with trans mounts yet. I hear that crossmember can be moved to accomodate the 4L60E. Two questions I do have:

#1: Is it required to change out my driveshaft?
#2: If current driveshaft is usable (length-wise), will it mate to 4L60E?

Here's my current setup:

4.3L V6 (L35)
Rochester Q-Jet
Stock Exhaust Manifold
TH350 trans
2.73 gears (non-posi)

P.S. - The TH350 is in good shape, just need vacuum modulator changed. Up for sale after my swap is complete. The engine has a bad piston ring (fouled & wet plug). I'll be parting out the accessories when swap is complete.

Last edited by 95ImpSS; 10-16-2005 at 08:37 AM.
Old 10-16-2005, 01:23 PM
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Originally Posted by ZRO26T
I was told that I would need to move the brackets forward (approx. 4 inches). I took a look at my current location, and saw there are pre-drilled holes to move the bracket forward. My biggest concern was being able to mount the 5.3L V8 using conversion plates, and still have wiggle room for the radiator/condenser (and maybe an intercooler & trans cooler). My eyeball confirmed I'd have approximately 2 - 3 inches b/t the fan & radiator (w/ rad in stock location).
.
I looked under the hood of my 93, and the 4.3 uses some brackets from the frame to the motor mounts. It looks like all you have to do is pull the brackets, and attach the stock V8 mounts on the same holes.

Originally Posted by ZRO26T
Once I get a chance, I'll take a look at the trans location. I'm not in any rush to start, but anticipate pulling the 4.3L V6 before Thanksgiving (unless I get lazy). Haven't familiarized myself with trans mounts yet. I hear that crossmember can be moved to accomodate the 4L60E. Two questions I do have:

#1: Is it required to change out my driveshaft?
#2: If current driveshaft is usable (length-wise), will it mate to 4L60E?

Here's my current setup:

4.3L V6 (L35)
Rochester Q-Jet
Stock Exhaust Manifold
TH350 trans
2.73 gears (non-posi)
As far as driveshafts are concerned, the 4L60E is longer, so you will have to shorten your driveshaft. I have the difference in length written down somewhere, I'll post whn I find it again. The 4L60E on the 5.3L is about 1" longer than a 700R4 (Gen-III V8's also got better torque converters that required the bellhousing to be a little longer), perhaps the difference would not be a big deal if you founfdthe driveshaft out of a C10 that had a 700R4, I think 87-88 V8's had them, perhaps other earlier years as well.


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