Author Topic: 86 c10 4.3 Radiator Swap w/ V8  (Read 9048 times)

Offline buter1ma

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86 c10 4.3 Radiator Swap w/ V8
« on: November 14, 2019, 09:30:15 AM »
I have an 86 C10 with 4.3 v6. I am going to be doing a three on the tree to auto trans swap. I am having thermostat issue, which isnt a big deal. However, I am going to replace all the old hoses. With the swap I was going to put an external trans cooler but I am thinking since I am going to do a 350 sbc swap at some point that Id just get a v8 radiator with the trans cooling ports. Has anyone done this to know what issues I could run into? If I replace the fan shroud, it will be shorter then my current shroud. Will that cause issues. Any help is appreciated.

Thank you.

Offline JohnnyPopper

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #1 on: November 14, 2019, 11:02:31 AM »
Are you going to swap steering column parts as well? If not, there are challenges with that.

I am surprised if the radiator would be that much different in terms of form factor, that it would impact your fan shroud? Didn't that model come with Automatic Trans?

In any event, going outboard or radiator you will have cooling line challenges.

If it were me, go with radiator cooling, ditch the fan and shroud and go electric fan, and enjoy more horsepower. (instant)

Let us know what happens! We like knowing if we help or make things worse...
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline buter1ma

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #2 on: November 14, 2019, 11:23:47 AM »
It would be a full conversion. I got a friend selling a full steering column our of a suburban. Ideally I am trying to stay OEM as possible with this truck. Going to have TH400 since that was the auto used on my year of truck.

I am only thinking of replacing radiator because I dont want to do it twice once I do the 350.

Offline JohnnyPopper

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #3 on: November 14, 2019, 11:47:35 AM »
Nice, sound like a fun project!

I'm with you on the radiator, get it out of the way now while you're in there.

I recently did the electric conversion to my fan and wow what a difference in power! My wife even noticed it.

Post before and after pics if you can, would love to see your progress.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline zieg85

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #4 on: November 14, 2019, 01:45:21 PM »
Been there done that.  You can ask me anything.  I've done it, no big deal.  If you want to not deal with getting a new drive shaft, find a short tail shaft TH350.
Carl 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
https://www.facebook.com/groups/248658382003506/

Offline buter1ma

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #5 on: November 14, 2019, 05:04:12 PM »
I want the th400 because that is what the truck came with in 86. I belief it comes with a vacuum down shift vs cable that the 350 has.

Offline buter1ma

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #6 on: November 14, 2019, 05:05:31 PM »
Where would you get a new driveshaft?place doing the swap for me said they can shorten my driveshaft I have.

Offline zieg85

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #7 on: November 14, 2019, 05:13:37 PM »
I want the th400 because that is what the truck came with in 86. I belief it comes with a vacuum down shift vs cable that the 350 has.
I thought the kickdown was electrical on the gas pedal.  You will need the frame perches and mounts for the V-8 but I am sure you know that.  I only mentioned the TH350 so you wouldn't have to make any changes and most 350's will have the correct carb for the kickdown cable.

Carl 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
https://www.facebook.com/groups/248658382003506/

Offline Stewart G Griffin

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #8 on: November 15, 2019, 04:19:11 PM »
Sorry for the slow reply---i didn't have internet for a few days (pretty refreshing actually)

Anyways, the hoses from the 4.3 should plug right into any stock v-8 radiator.  If using stock trans lines, i would ASSume they should also directly fit? (Why not go aftermarket instead?)  My 4.3 plugged directly into my 305/350 radiator.   There was no need to buy any new hoses.

The 4.3's fan shroud might even fit.   








Offline 75gmck25

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #9 on: November 16, 2019, 07:29:29 AM »
I have been extremely happy with the JEGS Champion aluminum 3 row radiator I installed in my '75 GMC.  There is not a big variation in radiator sizes for the square body, so just check the catalogs (Rock Auto, etc.) to see what matches.  If its a larger radiator (3 row instead, of 2, etc.), make sure you also get the rubber inserts that are the right size to hold the new radiator. 

Combined with a Stewart high flow pump and high flow thermostat the aluminum  has great cooling capacity.  For simplicity I'm using the OEM steel fan, shroud and thermostatic clutch.

Bruce

Offline Stewart G Griffin

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #10 on: November 16, 2019, 10:21:47 AM »
X2 on the Champion radiator!

Works great.  i got the 2-row though.


But i wanted to ask, why not wait until you switch to the 350 and do everything at once instead of trans first?

If you switch transes first, then a v-8 torque converter may not work well with the 4.3.  You will likely need a converter  specifically for a v-6 (higher stall)  i am having difficulty this now----then engine won't idle well in gear.

« Last Edit: November 16, 2019, 10:30:04 AM by Stewart G Griffin »

Offline buter1ma

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #11 on: November 17, 2019, 07:38:51 PM »
The manual trans I have now is leaking and the synchros are going. I am having no issues with the 4.3 engine. This has 403k miles. I want to do the trans first because the 3 in the tree hits my leg and makes it uncomfortable to drive.

Offline JohnnyPopper

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #12 on: November 18, 2019, 09:53:54 PM »
Man I hate it when my leg intersects with a tree!! Just wrong...
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline Stewart G Griffin

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #13 on: November 23, 2019, 10:02:12 AM »
If it's 3 on tree, then i'm ASSuming there's no opening in the floor?   How are you going to select modes in the automatic?

Will you need a new steering column if you want column shifter?

There's nothing wrong with a TH-400, yes they did come behind 4.3's   Not sure why, but they did.  i think it was because this was the only 3 speed automatic left at the time?

But a TH-350 might be easier.  It's not a big deal to find a TH-350 crossmember.

You may want to get a second opinion on the following:

But, to  the best of my knowledge right now, a v-8 converter will not work very well with the 4.3.   Transtar industries Part# GM3H is what you need.   Transtar is high-quality reman.  i have not had time to drop my trans yet to install it.    The upside to this is, when  you do switch to 350, you'll have more fun with the higher stall converter.

If you can find a TH-400 that was originally equipped in a 4.3 truck or van in a salvage yard, then fine, that factory converter will work too, but then get the crossmember and all shift linkages and rods and the steering column if necessary.    Also, the 4.3 TH-400 combo came with strut rods that attach to the TH-400's dust cover.  Is this necessary?   Probably not, but just be aware.

Offline buter1ma

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #14 on: November 26, 2019, 05:32:45 AM »
I will have a donor steering column from a suburban with tilt, cruise, and delayed wipers. By the time I am done with it, it will look like a custom deluxe but have the comforts of a Silverado.

Why do you say "yes they did come behind 4.3's   Not sure why, but they did"?

I am not worried about changing the torque converter out when I do the engine swap. I'd love to do engine and trans at same time but cost is the biggest factor at the moment. Plus, I'd like to make it more comfortable to drive. There is a part of me that is thinking about keeping the 4.3 and having it rebuilt... but then I come to my senses. lol.

That is why I am asking about the radiator. I think I am going to get a radiator but a 350 with the trans cooler ports and put that in with my V6. that way that part is done when the engine gets swapped....eventually.