OK - First of all I am not a mechanical wizzard. I'm just a dreamer of sorts.

Now for my question. What about swapping in a big block V6? Just the sound of being able to say that I had 478 cu. inchs under the hood.... What would be the hard aches with a swap of this type? Advantages? Disadvantages?

Do you know how much those engines weigh? Think 750-900 pounds without fluids. And they don't actually produce all much torque or horsepower for their displacement. Not stock.

Even if you're not bothered by adding 300 to 500 pounds to the back end of your Fiero, you have to fit an appropriate transmission, axles, exhaust, etc. Assuming the engines with accessories fit, you need to find a transmission that will mate up and/or have an adapter plate machined. Then you're still using some very old technology, that, unlike, say, a small block v8, apparently wasn't good enough to be carried into modern production. If you didn't use a transmission that was made for the engine, your gearing will be absolutely horrible for those engines.

If you want an engine with big cubes, I suggest you look into a small block or big block v8. They'll take less research and innovation to shoehorn into the Fiero and almost certainly be cheaper.

Here is a pic of a 305 GMC V6:



Looks like it is as long as an SBC and probably weighs more as well. The manifolds appear to be fiero friendly and the massive oil filter is off the side of the block (might have room for the starter behind it).

I googled around and theres quite a few people modding up this motor. HEI conversions, big carbs, headers, etc. I think a 478ci V6 with alot of mods to make up the HP would be sweet. It would take a ton of work to mount it and make it fit and to do all the engine work but if you've got the time and money, go for it. You'll need one hell of a tranny to hold that much low end torque. Built 4T60 perhaps?

We've discussed this on at least one other thread. The engine was used for school buses and is a torque monster, but the rpm potential is low. No aftermarket for performance to speak of and definitely not a good hp to weight ratio. Interesting engine though

Arn

Here is an old thread with a URL

https://www.fiero.nl/forum/A...070315-6-043212.html

[This message has been edited by Arns85GT (edited 12-09-2007).]

quote Originally posted by Arns85GT: We've discussed this on at least one other thread. The engine was used for school buses and is a torque monster, but the rpm potential is low. [/URL]

They aren't even torque monsters for their displacement, especially not compared to modern engines. They don't rev high enough to get their volumetric efficiency anywhere near decent and their compression ratios are pitiful.

[This message has been edited by Fiero Brick (edited 12-09-2007).]

Like I said - I dream alot and do very little.

I just liked the idea of big cubes in a small engine and the fact that it looks alittle bit like a small 409.

I figured it would not be a great swap or someone would have done it by now.

Those big truck engines are what I call "lazy engines". They don't put out a lot of power for their size, so there is not a lot of stress in the engine. They are built for the "long haul" (as the commercials say), not for short bursts of high power, which is what you would want in a Fiero.

Didn't they also have a V12 based on that engine? I think it was actually 2 of those put together. It had 4 heads 2 intake manifolds if I recall. That's a LOT of cast iron.

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1986 SE 350 V8

Yeah, they had a v12 based on the v6 engines. Definitely a lot of cast iron. 1,400 pounds of it. Half a Fiero GT.

The 702 V12 was a 1 piece block with 12 cylinders, and only had 1 flywheel, and a 1 peice crank. However it used 4 heads, 2 intake manifolds, 2 carbs, and 4 exhuast manifolds. They were primarily used by farmers to pump something like 2,000GPM out of the ground for irrigation systems, some wound up in military haulers, and combines as well.

63 GMC 7000 single axle semi tractor
http://rides.webshots.com/album/560407755NLypFl

Man that's one monster!!

There was a guy I went to school with that had a '64 or '65 "SixPack" GMC pick-up that had this very V6 in it. That was the first time I had ever seen one, this picture in the thread is the second one I have seen. I remember him telling me that that engine could shred tires on thru 85 MPH, exaggeration I'm sure, but that was about top speed for the truck as the engine lost all steam by then.

I do not think I have ever seen an engine with the spark plugs on the intake side of the valve covers or spark plug wires that long.

Also, that dist with dual V6 dists mounted sideways is interesting as well.

quote Originally posted by AquaHusky: I remember him telling me that that engine could shred tires on thru 85 MPH,

Absolutely. The qualifier is that with the back end light and half a tonne of engine to push, you could pop the clutch, floor it, and not move an inch, but oh the smoke

Arn

years ago when i had my first 4.3 done I had the guy price boring and stroking
it to 5 liters. It was cheaper to turbocharge lol

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87 Fiero GT 5sp with Vortec L35 4300 Turbocharged V6
Bully Stage 2 clutch
Syclone intake manifold and engine management with Moates adapter and chip burner
Air/water intercooler and Devil's Own progressive water/alky injection
50lb injectors, 3 bar map sensor, Walboro fuel pump and Jabasco Intercooler pump
LM1 wideband on custom manifolds and 3" stainless exhaust system
T31/T04B S4 turbo with a Super T61 in the box
S10 caliper conversion.
Murphy's Constant Matter will be damaged in direct proportion to its value
Murphy's Law of Thermodynamics Things get worse under pressure.
Arthur C. Clarke "Any significantly advanced technology is indistinguishable from magic"

quote Originally posted by fieroguru: Here is a pic of a 305 GMC V6:

I remember seeing one of those. It was in 72 or 73 or so. Haven't seen one since.
I was like... WTF?! It's a 6. But it looks like an 8. And it's as big as an 8. Seriously. It actually looked to be as big as an Olds V8, IIRC.
I just couldn't figure out why...

quote Originally posted by fieroguru: I do not think I have ever seen an engine with the spark plugs on the intake side of the valve covers or spark plug wires that long. Also, that dist with dual V6 dists mounted sideways is interesting as well.

can you imagine how long that cam is? much less the crank. I want one

Russ544

quote Originally posted by Russ544: can you imagine how long that cam is? much less the crank. I want one Russ544

Ah! But does it have one long cam, or two still-pretty-darn-long cams?

quote Originally posted by Fiero Brick: Ah! But does it have one long cam, or two still-pretty-darn-long cams?

Someone said it was a one piece block, so it must be just one mighty long cam. that is just SO cool. It could be like an Allison in a bucket T. I'll bet it could be made to fit in my 36 Ford/Topolino project

Russ

[This message has been edited by Russ544 (edited 12-11-2007).]

http://www.6066gmcguy.org/Jolly-702v12.htm

One block. One crank. One cam.

One hell of a lot of cast iron.

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1986 SE 350 V8

There's one feature on that V6 that I wish we had on our 2.8s: The cam gallery is shaped such that it holds a puddle of oil high enough for the cam lobes to partially submerge in. That means that the cam/lifter interface has oil on the very first turn of the camshaft, way before the oil pump has time to pump oil up to the lifters and then the lobes.

Man, why didn't GM do that on all engines?

JazzMan

630 ft lb of torque at 1600 rpm is nice 2400 rpm redline is not

quote Originally posted by Russ544: 630 ft lb of torque at 1600 rpm is nice 2400 rpm redline is not

Just need more gears, hehehe...

JazzMan

Some seriously easy flowing headers, the biggest valves you can find, serious porting a polishing on th heads, balance the cranks, and build a custom intake manifold would have to be in order. You'd also need a wild cam but I doubt summit keeps them in stock .

THAT made my sticker peck out!

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carpe diem

Take that V12 and bolt it to a TH425 and mount it longitudinally. I do not think you will notice the weight of the tranny past the axle centerline with 8 - 10 cylinders worth of engine in front of the axle centerline. It would make quite the conversation piece and you could even use it as a tow rig for your other fieros!

[This message has been edited by fieroguru (edited 12-11-2007).]