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Discussion Starter #1
I am in process of doing the swap and have a couple of questions. MY s10 is an 87 2wd 5 speed. First can I use the pickup tube from the 3.4 with the 2.8 oil pan? Also can I use the 2.8 harmonic balancer?

I seem to be having a hard time finding a 4.3 TBI. I went to pick and pull but couldn't find a astro with a TBI that would work. It seems they don't make the Holley 502-3 anymore nor did I want to drop 400+ dollars on it. I found a refurbished TBI on ebay here http://http://www.ebay.com/itm/GMC-87-95-4-3-V6-TRUCK-VAN-SIERRA-ASTRO-S15-RALLY-JIMMY-TBI-THROTTLE-BODY-/191631943604?fits=Model:Astro&hash=item2c9e2767b4&vxp=mtr

I think this would work but would like another opinion. I hate buying something sight unseen plus dropping 200 bucks and it not work would be a major bummer. Any advice would be greatly appreciated.
 

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The harmonic balancers are all the same for the RWD 660s as far as performing the same goes, so yes you can use the 2.8 harmonic balancer on the 3.4 since you are going TBI with it.

You will need to compare the pick ups. I believe they are the same installed hight, but a simple measurement of the pick ups side by side from a reference point will determine whether they are or not.

IIRC, the 4.3, 5.0 and 5.7 all use the same bore size and since you will be swapping in your injectors anyway (I believe that's what people are doing), then you can use any of those TBIs.

You can also make the injectors adjustable, but it's difficult to get them matched exactly when using a pair (or more), without a proper test and set-up rig.
 

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So are you saying I can use any of the above throttle bodies but swap injectors. For the 2.8 or 4.3? I kinda assume these TBI's have different flow rates? Will that affect anything? I notice the throttle body I was looking at in the first post is missing a vacuum connection
 

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Hey unless he sold it, GEARS has a Holley unit for sale. Cheap too...I think $150?

Raven is right on bore size. You can use any of them from 4.3 up to but not including the 454. The only thing to bear in mind is the number of vac ports (no biggie) and the lack of the mounting points for the throttle bracket on some of them. That's not huge either if you can tap them. There's plenty of meat on there to do it.

Use 4.3 injectors. You will require some tuning. There's a learning curve to that. I haven't even gotten around to tuning mine due to my schedule, but I'm not driving it that much either.

Y
 

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Discussion Starter #5
I actually seen that gears had a holley for sale. I messaged him but haven't heard back. What would I do about the vac port situation? Can I just leave the smog pump line unhooked?

I made some good progress last night got the cam in and threw the heads on starting to come together. I'm hoping I can be installing next weekend. I'll make a trip to the junkyard next week see what I can come up with.
 

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Jimmy seems to forget that I've done this swap, and I'm going to beat the shit out of that horse too.

If you can't find a 4.3 throttle body to work, then the next easiest step is to take the throttle cable bracket off the 2.8 throttle body and put it on a 4.3 throttle body. Just grind lightly where the shaft is pressed on and then tap and thread the 4.3 throttle body shaft with a 10-32. One washer, one 10-32 nut and some blue loc-tite and problem solved.

Use 4.3 injectors. This will help with the lean condition that the ECM will see.

Next up is the consideration of retuning the spark and ve tables in the eeprom. Most people think this set up is plug and play. It's not, your engine, your choice.
 

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Discussion Starter #7
Found a throttle body today but it has a different style tps so I grabbed the connector with it and will splice it in. There shouldn't be any issue with using that sensor right?
 

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No, there won't be.
 

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I had to change mine too.
 

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Discussion Starter #10
I'm about to drop this thing in Another question does the Orange wire around starter location does it go on the same terminal as the black one it's been so long since I took this thing apart I can't remember.
 

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Discussion Starter #11
Got the motor in today wondering what do do about the missing vacuum port on my tbi is there I particular one I should tee off of or if I could use anyone of them.
Also still wondering about that orange wire around the starter.
I'm hoping to get the tranny put in tomorrow after work then fire this thing up.
 

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yes on the orange wire.

google vacum dia. theres many that show what port on the tbi goes were.

then you can decide if any needs to be caped.
 

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Discussion Starter #13
I'm trying to start this thing but having some trouble a ground wire on my fire wall going to the back of the drivers side head was getting really hot started smoking I think it was just melting some plastic around it. It's attached to four other wires tan, tan/white, two blacks I think. What is this wire and whys it getting so damn hot.
 

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It's a ground wire and getting hot is the sign of passing lots of current.

Check to make sure all of the connections are clean and tight, for all grounds. There may be a poor connection at the main battery to engine ground.
 

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Discussion Starter #15
I ohmed That wire out straight back to the negative terminal at first was getting 17 ohms tighted terminal and it dropped to one. From batt to engine was same 17 to one after tightening. It's also barely cranking so I threw the charger on will give it a few then try again.
 

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Discussion Starter #16
I got it to fire had my buddy turn the cap counterclockwise while I was cranking. It ran smooth so my timimg is off. But I still have wiring issues with grounds getting hot. Everything ohms out until I turn the key on then I'm getting a high resistance on my ground like 45 ohms. Could I have the starter wired wrong? I wasn't sure about where the Orange wire went it's currently landed with the hot from the battery.
 

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Discussion Starter #17
I'm kinda at a loss checked all my grounds everything ohms out fine till I turn the ignition switch on. Then I'm getting like 40 or so ohms. I've tried isolating the starter but nothing any suggestions as to what else to look at. It's also barely cranking?
 

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is there paint still on the firewall were the wire bolt is???

if so get the paint off.......

also make sure were the ground strap bolts to the engine its clean..

i have replaced both my stock grounding straps with better 1/0 wire.
as i have put a big audio system in my truck.

but that will help you out of you do that.
also do the ground from battery to engine and battery to frame.

but if you dont want to do that, make sure all your grounds are clean and tight.
 

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Discussion Starter #19
Finally got it Rollin again but it got hot really fast. Am I just running lean? Do I need to throw on an adjustable fuel pressure reg? I'm sure it didn't help I had a loose coolant hose leaking fluid but i felt like it got hot Really fast. Also my idle seems like it way to high. The tps I had to switch to isn't adjustable like the old one so how do I adjust. Thanks for all your guys help I couldn't of done it without this forum.
 

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donv35
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