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3.4 Engine swap

10-19-2004, 04:16 PM
Hi I have an 86 GT with 188,000 kms ( four speed )on it and I am considering doing an engine swap, I want something easy and something thats not to expensive.
I am considering the 3.4 because the increase in power is pretty good and there are lots of them kicking around ( the ones from the 90s camaros and firebirds)
I was wondering if that engine will need a new wire harness and were I can find them and also how much $ do you think I can do it for?

10-19-2004, 08:54 PM
New wiring harnesses are thousands of dollars, at least the one I checked on for a Beretta that had an engine compartment fire was ($2,399 direct from Chevrolet) so your best bet is Ebay or salvage yards, keeping in mind salvage yards normally rape the snot out of wiring harnesses when they pull engines. Because Camaros and Firebirds are popular, you should have better luck getting one for a decent price from someone doing a v6 to v8 conversion (Try the Camaro Forum here on AF) who no longer needs it. As far as the engine goes, the 3.4 block is almost identical to your 2.8, so it'll bolt right in with no heavy mods. The starter holes are on the wrong side of the block, but it's easy to drill and tap new ones on the correct side. The water pump plumbing will take a little home grown engineering but isn't too difficult.

10-19-2004, 08:57 PM
So, whats easier the 3.4 swap or a 350 because a 350 doesn't have much wiring am I right?

Old Lar
10-19-2004, 09:09 PM
If you are using a Camaro 3.4 replacing your 2.8, the wire harness you have should suffice. Just use the Fiero intake and valve covers and when your done, it should look like a stock Fiero engine. (They probably need some cleaning). When you swap in a 3800, 3.4 DOHC or 350 new harnesses are needed and can get pricey and need lots of checking to insure they are correct.

10-20-2004, 07:01 AM
So which is the easiest and the cheapest because I heard on this site were the guy did a 3.4 swap he said A new wire harness after you send in the fiero and donor car one is $350, so couldn't you just buy one without sending your own?

P.S I have never done my own motor swap and haven't any major work to motors but I know a thing or two how hard is the 3.1 conversion and how is the wire harness in that?

10-20-2004, 09:04 AM
I was gonna go for a 350 swap but after I looked at the cost i figured I might be able to do something alot cheaper. I was looking at just turbo the 2.8, but thenI thought if the 3.4 is a direct bolt in why not do that and turbo it.

So will the 2.8 wire harness work on the 3.4?
Will the 2.8 computer work on the 3.4?
Do all the mounts, the dog bone and the driveline shock bolt up to the 3.4?
Will the muncie 4 speed bolt up to the 3.4?

10-20-2004, 03:55 PM
Yeah could someone help with GoatNipples questions because I have the same ones and would like to know the answeres


Old Lar
10-20-2004, 07:53 PM
The Camaro 3.4 can be a direct replacement for the 2.8 except the need to relocate the starter. I believe that the 2.8 ECM will work for the 3.4 and that the wire harness from the 2.8 will work with the 3.4. That is why this swap is one of the easiest. I even think that the four speed should mount to the 3.4 with the usual degree of difficulty putting in a transmission. I had the "ultimate" dogbone installed in mine and that is a direct replacement for the stock dogbone.

There were some modifications to my car for I had a 440t automatic installed at the same time the 3.4 was put in.

The easiest way I've seen for engine swaps is to obtain a good cradle and install the replacement engine/transmission on that, then install the new cradle and engine. Especially if the car is used as a driver and is still in operating order. The car can be used while you make sure the new engine/transmission is all together

10-20-2004, 08:56 PM
For some reason I was thinking the 3.4's had TBI (duhhhhh I must have been sleepy that night) but yea, the 2.8 ECM will run a 3.4

10-20-2004, 09:51 PM
What about the wire harnnes were can I get one because I heard they ran for about 400 when you send in a fiero and 3.4 harness so were will I get my hands on one, and also will the stock 4 speed work ?

10-21-2004, 09:58 PM
There's no need for a new harness. The stock Fiero harness that's in your car now will work fine as long as the 3.4 you get is pulled from a car with a distributor, or you swap out the coil pack DIS for the Fiero's original distributor and coil (all you need to do is pop out the dummy plug for the oil pump drive and replace it with a distributor. The crank and cam sensors can be left in place unused, or removed and the holes welded shut and ground smooth). A 3.4 is no more then a bored and stroked 2.8, so the timing and firing order of the 2 engines are identical.

10-21-2004, 10:03 PM
whats the hp difference between the 3.4 and 2.8??? just curious

10-22-2004, 09:55 AM
So what year car does the 3.4 have to come out of so that it has a distributor

10-23-2004, 10:19 AM
So basically all I will have to pay for is the motor and a rebuild if I decide on it because I will probably try to do the swap more question about the wiring, If in the fiero there is a wire that goes say to the coil or anywhere else will it go in the same place on the 3.4 or how does that work?

10-23-2004, 10:02 PM
GM has always had a nasty habit of changing wire connectors a lot, so plugs aren't always what they need to be. The best way is to use the stock2.8 Fiero coil and distributor on the 3.4. Optionally, an aftermarket high performance coil designed for the Fiero will add a little ooompf to things. Aftermarket ignition parts should be ordered for 2.8L V6 86' Fiero, NOT a 3.4L Camaro, so the wiring connectors are correct.

You can also have your 2.8 rebuilt with a bigger bore and stroke, creating a 3.4 without buying a different engine. This eliminates any random swap hassles and starter relocation issues, and allows the use of stock exhaust if needed.

10-24-2004, 12:12 AM
I like the idea of swapping so I think I will go with that but can I leave the appearence of the engine stock or do I have to put the fiero fuel system and intake on it? And which year am I looking at if I want the engine with the distributor?

Old Lar
10-26-2004, 07:14 AM
The 3.4L Camaro engine was rated at 175 lb torque and 160 hp. At the wheels on a dyno, mine developed 170 lb torque at 3000 rpm, but only 115 HP going through the t440 auto. At 5500 rpm in third gear the car was running at 142 mph.

I have never tried a top end run, but did have the car in third at 120+ at ~4500 rpm. Fast enough with touring tires, Fiero brakes and on public roads.

03-17-2006, 10:20 PM
i have a 86 feiro GT 2.8L with automatic tranns. and what engines will interchange with the trans. i heard a pontiac 6000 would but anyone know any others and the years and may still use all the wiring and mount thats in my car

03-19-2006, 01:56 AM
whats the hp difference between the 3.4 and 2.8??? just curious

2.8 was rated at 140 bhp, 170 ft-lbs

3.4 was rated at 160 bhp, 200 ft-lbs

so not much difference, would drop in something more substantial for the trouble of swapping

08-02-2006, 08:55 PM
i know your doing a 3.4PR swap, but i am doing a 3.4DOHC and my custom harness was only $300.

also the HP increase from the 2.8l-3.4l isnt much... prolly be jus as expensive to turbo the 2.8L and you will walk away with more power than the 3.4L and could have it done in a few hours. there is one guy who has been running 10psi non-intercooled through his 2.8L for over a year with no problems...

08-04-2006, 03:04 PM
Yes these isn't a huge difference in hp/tq between the 2.8,3.1,3.4 pushrod motors but the real gain is in structural integrity and the oiling systems. The 2.8 is the $HITTIEST motor chevy has produced, IMHO.

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