Hey all,

Ok, so this feels like about the million thread I've posted on engine swaps, but this project of mine just keeps getting delayed! (Too much so).

Fortunately, I've been able to learn quite a bit of stuff through this board, but I'm in a new dilemma of sorts - For the longest time, I've considered the traditional "chuck the 305 for a 350" route on this car - A good idea in the first place, since the 305 in my car is in dire need of a rebuild/replacement.

I wanted to stick w/TBI, and go yank an L31 longblock out of a truck, since that'd be a vast improvement over an L03 - But the cost of the Vortec intake manifold, along with an ECU upgrade, such as EBL Flash (Not to mention, the necessary fuel system upgrades to make decent power), makes me begin to question if that's really the most budget-friendly route for what I'm trying to do anymore?

I've noticed that complete LM7 pullouts go for good prices these days - Not to mention, they are plentiful availability-wise, and can often be found with pretty low mileage - And a stock LM7 w/bolt-ons would not only meet, but exceed my power goals with my car, whereas I'd have to look into a new cam, and machine work on the heads to do it w/a gen 1 motor...

Is there anything else I should take into consideration? I've been told you need to change the motor mounts, and fuel stuff to do an LS-based swap. Is there some real trickery involved with getting it to work right w/a Firebird's electronic dash gauges, and a T5? (Which I would get an upgraded case for if I did the swap).

Just trying to get some more info/opinions on this. Thanks!

 

The stickies in the LS forum will answer all of your questions, plus the other 5,000,704 questions that will inevitably pop up as you start digging into the possibility of an LS swap.

 

Let's assume you pay the same price for the LM7 as the L31. As you mentioned, you'd have to do some upgrades to the L31 to get the same power level as the LM7. But, the cost of putting the LM7 in the 3rd gen would cost you about the same, or more - mounts, upgraded fuel pump (which you should probably upgrade from LO3 for the L31, anyway), exhaust hook-up (LM7 exhaust manifolds won't fit in a 3rd gen f-body), oil pan swap, intake swap, accessory swap, etc.

But, one of the real "tricks", IMO, is to NOT use a 3rd gen transmission. Get an LS transmission, whether manual or auto. The reason is both for fitment and strength - you can make them "fit", but they are going to be weaker than the LS counterparts.

When done properly, there is no doubt in my mind that you'd be happier with the results of an LS swap. BUT, don't go into it assuming it's a cake walk.