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73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: buter1ma on November 14, 2019, 09:30:15 AM

Title: 86 c10 4.3 Radiator Swap w/ V8
Post by: buter1ma 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.
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: JohnnyPopper 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...
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: buter1ma 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.
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: JohnnyPopper 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.
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: zieg85 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.
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: buter1ma 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.
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: buter1ma 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.
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: zieg85 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.

Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: Stewart G Griffin 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.   







Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: 75gmck25 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
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: Stewart G Griffin 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.

Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: buter1ma 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.
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: JohnnyPopper on November 18, 2019, 09:53:54 PM
Man I hate it when my leg intersects with a tree!! Just wrong...
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: Stewart G Griffin 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.
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: buter1ma 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.
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: 75gmck25 on November 26, 2019, 06:53:36 AM
The TH400 is a very good transmission, but overkill for your application.  Its stronger than a TH350, but has more parasitic loss (loss of HP due to internal friction).   Its more appropriate for heavy duty use, such as racing, towing, mudding, etc.

The TH350 was used with all variations of 350 engines, including 3/4 ton 4WD's like my '75 K25, so it is definitely strong enough for anything but very extreme conditions.  TH350's are usually cheap to buy, and relatively easy to rebuild and/or upgrade.   

Another option would be the TH700R4 overdrive.  They were introduced in the '82 trucks, but you want to get a later version after they upgraded them for more reliability.  Also make sure you get the TV cable adjusted right on a TH700R4, or you will shortly have major problems.  Low rear end gears (3.73?) and a 700R4 would help make that V6 feel powerful.

Bruce
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: buter1ma on November 26, 2019, 07:17:54 AM
I did not know that about the TH400. I have thought about the 700R4 but I have the 10 bolt rear end gearing (2.72), so Ill never use the over drive. Plus I heard the 700R4 aren't as robust as the 350/400.
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: zieg85 on November 26, 2019, 09:37:22 AM
FWIW the TH350 short tail shaft is your best bet.  In 86 GM had already phased out the TH350C and the standard 3 speed automatic became the TH400.
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: Stewart G Griffin on November 28, 2019, 08:55:02 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"?

Probably because of this:
FWIW the TH350 short tail shaft is your best bet.  In 86 GM had already phased out the TH350C and the standard 3 speed automatic became the TH400.

i always thought it was odd that the TH-400 came behind the 4.3----totally overkill---sort of  like using a sledgehammer to crack peanut shells.

Then i thought about it, and i think GM stopped producing the TH-350/350C by 81?   Gm still wanted to offer a 3-speed auto with the trucks and the only one left in production was the TH-400?

2) Now about your radiator question:
Yes, again, the upper and lower coolant hoses from the v-6 should plug directly into the v-8 radiator outlets.  No need to buy different hoses.    The heater hoses should also plug right in.

For an auto trans to work with a v-8 radiator, then you either need to get the hard-metal trans cooler lines (or make your own) for the v-8 radiator -OR- and i think this is easier, get rubber or steel braided lines:
https://www.jegs.com/c/Fittings-Hose/181705/10002/-1?N=1181705&Ntt=trans+cooler+lines&Tab=SKU

a) If you go stock metal lines, i'm not sure if TH-400 and TH-350 use the same exact lines, so you may have to go trans specific.

b) Irregardless of a), i'm pretty sure you need to go chassis specific.  For example lines from a monte carlo likely will NOT fit a truck

So, you can see why i think going flexible rubber  or steel braided line  is much easier, cheaper and faster.   If you decide to go this route, we can help you.   There may even be a kit that i haven't found.
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: buter1ma on November 30, 2019, 07:48:29 AM
The thought was buying a radiator from rock auto for a 5.7 that comes with trans cooler ports. Then I won’t need the external trans cooler. Then it should just be standard lines from transmission to radiator.
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: Stewart G Griffin on November 30, 2019, 08:56:41 AM
The thought was buying a radiator from rock auto for a 5.7 that comes with trans cooler ports. Then I won’t need the external trans cooler. Then it should just be standard lines from transmission to radiator.



Next, how are you going to operate the shift selector on the auto trans?
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: buter1ma on December 05, 2019, 06:36:52 PM
I am getting a steering column out of a suburban.
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: zieg85 on December 05, 2019, 07:37:54 PM
If your column is still in good condition it is worth quite a bit.  Those purist, old school like the 3 on the tree.  I gave up my search after about 6 years of looking to find a good column 84-87 with linkage.  I just couldn't find one at any cost.  Replacement parts were NLA as my truck was converted to the 3 speed floor shifter after the shift collar broke on my 86.  I wanted to go back stock but opted for a 4 speed instead and replaced the column accordingly.
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: buter1ma on December 21, 2019, 07:11:41 AM
I have decided to just go with the TH350 short tail as my transmission instead of the TH400. Also, Ill be picking up a 350 SBC that has been rebuilt but has been sitting for a long time. Going to tear it down and see what needs to be done or not done.
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: buter1ma on December 22, 2019, 07:29:52 AM
Ok, I am a noob. The more I learn the more I change my mind. Now I am thinking 700R4....

I am like a kid in a candy store lol.
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: 75gmck25 on December 23, 2019, 06:25:44 AM
Let me complicate your decision even a little more - take a look at the 200R4 overdrive also.   It has better low gear spacing than the 700R4 (which has big jump from 1st to 2nd).  Its the same length as a TH350, so its sometimes used to replace a TH350 without needing to change driveshaft length.

Bruce
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: zieg85 on December 23, 2019, 09:43:27 AM
this may help
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: JohnnyPopper on December 23, 2019, 08:20:57 PM
If you're in it this deep go for an overdrive, you won't regret it, but you might be sorry if you stay with a 3-speed.  ;)
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: VileZambonie on December 24, 2019, 07:30:09 AM
Zieg, post that image in the tech section for reference.

Unless you just putt putt around town, a 3 speed just won't cut it these days.
Title: Re: 86 c10 4.3 Radiator Swap w/ V8
Post by: buter1ma on December 24, 2019, 08:08:55 AM
That is why I am going to go to the 700r4. It might be more then I need but if I decide to use it more on expressway or change my rear gearing. The overdrive will be already there already.

I ended up getting that 350 engine on Saturday. Going to start tear down after Christmas.