LS3 vs LSX vs Pontiac motor swap ?

[bsalie]

I have a 1979 Trans am that has the original 6.6l 400 Pontiac. I am looking at making it into a pro-touring car and it needs an power upgrade. I am leaning in the direction of an LS3 swap, as I have an LS3 swapped into my 2002 Corvette. I was wondering what the weight differences would be between the LS3, an LSX based engine , or getting a Pontiac based performance engine. I do plan on autoxing the car in the SCCA CAM class
thanks
bill

[F-Body International]

http://www.hotrod.com/how-to/engine/...-alloy-indian/

With aluminum Pontiac blocks, a stock style Pontiac can be just as light as an LS. The link I posted claims 415 lbs for a 535ci aluminum Pontiac from carb to pan and even the starter on it. This engine has everything done to it to make it light though...aluminum rods, block, heads, intake, carb, etc.

I have a '79 T/A 400 4spd myself. For me, I found it most logical to go with FAST brand for converting the original engine efi. They have an efi style distributor, ecu, harness' and everything covered for a Pontiac engine. The easiest setup for a shaker hood assembly would probably be an Edelbrock Torker 2 Pontiac intake with FAST EZ EFI 2.0 on top or the XFI Sportsman.

If wanting to with LS style engine, it would be easier with something like the E-Rod engine straight from GM. The difference in weight over an iron pontiac comes in around 100-200lbs depending on what you have all together.

[Mr.VENGEANCE]

Ls3.. $6000


built Poncho aluminum block motor... $20,000


might want to consider that..

[andrewb70]

I call total BS on that Pontiac engine being only 415 ponds, carb to pan. An aluminum block LS engine, as a non-dressed long block is 375 pounds. That's no starter, exhaust manifolds, or accessories, and a plastic intake.

The difference between an aluminum block Ls3 and a LSX based engine (assuming you mean the iron LSx block) is about 80 pounds, ceteris paribus.

Andrew

[Mr.VENGEANCE]

^ I didnt want to say it cause I dont have proof but I did my homework for my 70 firebird on it and saw that the price and weight just all didnt add up.

[badazz81z28]

B

Ls3.. $6000


built Poncho aluminum block motor... $20,000


might want to consider that..

That would enough for me...there are more attributes to the LS design that makes it a light package other than just aluminum block and heads.

What is meant by LSx? All that means to me is the LS is in car it didn't come in. The lsx454 is a different animal. Iron block, more head bolts etc...I wouldnt go that route unless your doing something a production LS can't.



I would go LS7 if money wasn't an issue

[Aficionado]

^ I didnt want to say it cause I dont have proof but I did my homework for my 70 firebird on it and saw that the price and weight just all didnt add up.

What he said.

[T_Raven]

I call total BS on that Pontiac engine being only 415 ponds, carb to pan. An aluminum block LS engine, as a non-dressed long block is 375 pounds. That's no starter, exhaust manifolds, or accessories, and a plastic intake.

The difference between an aluminum block Ls3 and a LSX based engine (assuming you mean the iron LSx block) is about 80 pounds, ceteris paribus.

Andrew

I was thinking the same. I'm keeping a Pontiac engine in my 67. I've considered getting an AL block but after looking up weights in the past, I had figured the IA-II block was only about 40-50lbs lighter. I can't justify $5000 to save 50lbs.

I just did a little more searching. The aluminum IA-II block supposedly weights 138 lbs, and the MR-1A supposedly weighs 125lbs. GM apparently claimed a bare Pontiac block was 183lbs. That's 45lbs heavier than the IA-II so that must be where I got that number. I found a thread where a bunch of guys listed 202-207 for a bare block with caps and filled to the bottom of the core plugs. ~70lbs is still not enough to justify the cost of the block.

So we're talking -70lbs for the block, -60bs for AL heads, -20lbs for AL intake, makes about 150lbs lighter for an all aluminum Pontiac. I've always read an all iron pontiac was 650lbs, so that'd put you at about 500lbs. Idk how much AL connectings rods would save, but it's not 85lbs. If everything is a little lighter than I think, then I guess you'd be getting close to the 415lbs they claimed in that article, but I'd expect it to be closer to 500lbs.

Anyway, for the money, I'll stick with a stock block. If I was ever going to make enough power to need an aftermarket block I'd spend the extra $2000 to go aluminum over iron since the aftermarket iron blocks are around 100lbs heavier than the AL versions.

[T_Raven]

B

That would enough for me...there are more attributes to the LS design that makes it a light package other than just aluminum block and heads.

What is meant by LSx? All that means to me is the LS is in car it didn't come in. The lsx454 is a different animal. Iron block, more head bolts etc...I wouldnt go that route unless your doing something a production LS can't.

I would go LS7 if money wasn't an issue

If building from scratch, I'd get a sleeved LS2 or LS3 block. They are better than LS7 blocks and only a little more expensive. I don't remember all the numbers, but after researching all the block options for LS engines, that's what I decided I'd use.