So I'm not exactly planning to do an engine swap right away, but I figured doing a bit of research and gathering some opinions now wouldn't hurt. I have a '91 Firebird. Down the road when I can swing it, I'd like to add some more power to the car than the 305 TBI has to offer (can you blame me?).

Since it's a '91, It will still need to be able to pass emissions for a few more times (and I plan on keeping this thing for a while). This probably rules out carbed engines making good power, so this probably means looking into either the L98, LT-1, or LS1.

Obviously the LS1 would be the best choice, but depending on it's cost, I may have to go w/one of the other two for budget reasons. That, and the fact any of these swaps will probably justify a new transmission to handle the power (stock 3rd gen T-5 in mine).

Power-wise, I'm not looking for anything too insane. Just around the 300-350 HP range. Enough to make the thing nice and fast.

Which engine offers the best power/price ratio for me? Which is the easiest swap? Also, How much does a T-56 trans usually run? I'm debating going with a used one, or a brand new aftermarket Tremtec T-5 from Yearone (over 500 ft/lbs TQ rating) that can be had for $2K. Can you hook up a 5-speed to the LT-1? All answers are appreciated!

P.S: Will a better exhaust/headers set-up for a 305 be transferable to a 5.7L engine? Or no?

 

I read that twice, just to be clear, and I suggest you do an LM7. That's the truck version, in the extra-common 5.3L flavor.
It'll get you 350 rwhp with very few mods, and not be too insane for the T5. In fact, you won't even need the overpriced hawk's headers to hit your goal. Get some used '98-'02 Z28 exhaust manifolds, get a custom y-pipe made, and put a 3" cat in the place of your stocker. Add a 3" cat-back, the exhaust is done.
The truck cam is un-necessarily lame. There are lots of choices, but the mildest thing that'll meet your goal is Lunati's smallest VooDoo cam. It'll be awesome up to 6200 rpm, but has a very stock idle. You might get 6500 in first, with good aftermarket pushrods. Don't forget the Z06 springs The '01 version of the springs will work with this cam, and may be cheaper than the '02-up, which would also work. Stock-length pushrods are fine if you don't have the heads milled more than about 0.010", which they don't need anyway.
You don't need the LS6 intake manifold to reach your goal, either. Save your money for a custom tune.
If that doesn't get your goal, then you got the wrong muffler.
LM7s can be had with low miles and a guarantee for under $500. Get an '01-'03 version. They have the best parts.
Your stock gearing should return nearly 30 mpg. But you'll get much better acceleration with a 3.73:1 axle. This would drop mileage to a best of 25 or so.
Your stock axle will also survive if you're not abusive. If you like the stock gearing, just add a conversion-style locker.
The big issue is that the LS flywheels are all the 168 tooth, and that won't fit in your bellhousing, which otherwise would bolt up to the engine. McLeod offers a scattershield that will work, but it's around 1/2 the price of getting a used T56 from an LS1 F-car.
If you want to really push it, get 4.10:1 gears, and Speed Inc.'s TBSS cam. It'll still pass a tailpipe sniffer test. Add ARP rod "bolts" and Hawk's headers, you'll be over 380 RWHP up around 6700 rpm. It also calls for the LS6 intake, and the '02-up Z06 springs. Also do an underdrive pulley with this more aggressive combo.

 

Wow, what a cheap price to pay on that motor for the stock power it puts out! (I see 305 TBI's go for $500...) Why so cheap though? Is it just typically overlooked in favor of the various 5.7L engines and up that have come about over the years? Also, how easy of a swap is it? Will the stock motor mounts work? I ask because I'm not exactly a well rounded mechanic, so it's going to involve seeing if I know anyone who can help (a good possibility), or having someone else do it. And not that I'm planing to use this car as a daily driver anyway, but now I'm curious as to which is a more dependable motor, between the L98 and the LM7? Those seem to be the two most budget friendly options for the motor at least.

 

The L98 is a far easier route for a newb. Getting the LM7 for $500 isn't the challenge, try www.lkqcorp.com. No, the challenge is the wiring. The newb approach is to just pay Speartech's asking price for a custom harness. That's a bit more than swapping in the L98 harness. Mounting the LM7 is easy with Hawk's LS1 stuff. But again, it adds to the cost. Nearly $200. Still, to get to 350 rwhp with an L98 is going to require nitrous and headers. The LM7 ends up at around the same money. Add a smaller hit of nitrous to it, 450 rwhp is real.
Get five7kid and Pocket to chime in. kid and I are both old hands at SBCs, and we're both on a steep learning curve sticking these newer engines into our own third gens. Pocket isn't much on the old SBC, but he seems well up on the newer stuff.

 

The LM7 is a nice engine, and you can get them fairly inexpensively. The problem I've seen is they usually don't include the harness and PCM (like LS1 drop-outs do), or transmission. If going in a 3rd gen, first you need to replace the intake (LS1 intakes are fairly inexpensive, since most LS1 guys go for a LS6 intake), oil pan (which means oil pump pick-up and windage tray as well), and all the front accessories. You've almost doubled the price of the engine already, and you don't have the harness and PCM handled yet. Or exhaust. Or transmission. Plus the special swap mounts mentioned above.

Not trying to discourage anyone from an LM7 swap, but don't assume you can do it inexpensively just because the engines don't cost much.

 

No, this is good information I should know!

Hmm..Well, how much of a cost/difficulty difference is there between an L98 or an LT1 swap? I'll actually occasionally see LT1's out of Caprice's go fairly cheap on CL (w/the ECU, and everything). The HP figure I give in my original post is really more of a crank # than a rwhp # to be honest, but I suppose it shouldn't be a super difficult goal either way.

Not really looking to go the Nitrous route, (at least for now) . Hoping to acheive somewhere around my target w/bolt-ons, and/or minor engine work. Essentially, I'm after a nice weekend/trip warrior that I could take up to the strip for fun once in awhile

 

Many have gone the Caprice LT1 route, although most go with auto transmission. LT1/T56 drop-outs are typically in the $2-3k range, while a full T56 swap will run you about half or more of that.

The nice thing about LT1 swaps into 3rd gens is the only modifications are the wiring, and K-member if you use the LT1 AC compressor. Exhaust can use 3rd gen stuff. Fuel isn't hard to hook up. The PCM wiring is the most difficult part, and has been well covered by TGO members in the LTX and LSX sub-forum and LT1 swap sticky. And, since LT1's were only put into passenger cars by the factory, the emissions part is easier to deal with.

 

you can always go with a 350 short block and swap over your heads, intake, and front accessories from the 305 and keep it emissions legal. i dont know if the 305 throttle body can flow enough to feed a 350. but you can always get a tb off a 454 and tune the ecm to run it. im sure you can get a 350 short block for cheap and as long as you dont do a lot of "spirited" driving the t-5 should hold up.

 

Alright, well, one more question I have is, what are the average selling prices for a decent, used L98 or LT-1? Either should be capable of 350 crank HP without too much trouble, right? I still debate between the idea of the LT/LS and T56 swap, or using a different 350 of some type, and mating it to a beefier 5-speed.

Also, if I want to install a posi rear axle, should I just pull one off another 3rd gen? or buy an aftermarket one?

 

well here's my thoughts. honestly i think if your more of a first timer i would go the L98 route. do it right and your have a good supply of power with the torque you need, good reliablity and mileage, and fairly cheap. also easier to install i would belive. but if you feel comfortable with the work defintly go lt1. totally up to you though good luck!

 

Part of it depends on the cost of the motor too. Something tells me getting an LT-1 might be the best route, as I'm guessing the cost of an L98, plus mods to get it to stock/lightly modded LT-1 numbers, would outweigh the cost of getting the LT-1 in the first place, am I right?

What is it that it so restrictive on the L98? 230-245 HP, but 330-345 ft/lbs torque stock? Seems like a beast that's just begging to breathe, lol. Is this a fault of the TPI system? or more internal engine components?

 

The L98 was mostly limited by the stock TPI system. Stick an HSR on there and you're equal to the LT1, for cost and power.
LT1s are a little hard to come by, and any 350 can be turned into an L98 very easily and relatively cheaply.

 

So, other than the Intake/TPI system, what are the main differences between the L98 and LT-1 anyways? Are they basically just both 350's w/minor build differences? (Cam, intake, heads?)

Also, will the HSR pass emissions? I'm not trying to build up to insane HP numbers, if that helps, lol. If the L98 can meet all my needs, I really have no problem going that route, since it sounds like the easiest of all the swaps I'm considering.

P.S: Just for some additional guidance, what are the typical price ranges on used L98's and LT-1's anyway? on CL, I've seen an L98 (out of an 87 'vette) someone was asking $1450 for (seemed a bit high to me, but am unsure of mileage), but I also saw one out of an 88 Iroc-Z someone was only asking $400 for (seemed too good to be true if it was a good motor).

 

The LT1 is enough different to be referred to a "Generation II" SBC (1955-1992 SBC's, even with all of their changes over the years, are bunched together as "Gen I"). It has reverse flow cooling (coolant from the radiator goes to the heads first, then block, then back to the radiator), the "distributor" (Optispark) is mounted on the front of the engine with both it and the water pump driven by the cam, and has a sequential injection system (vs. batchfire for TPI). Internals such as pistons, crank, rods, bearings, cam, lifters, valves, oil pump, etc., are interchangeable with L98, but the block, heads, intake, front cover, etc., are different.

 

To also swap out to an L98, you will also need the computer harness, computer, possibly a dash harness to ensure that it swaps with no problems.

Don't forget five7 that the LT1s had PM rods, lighter pistons aluminum heads (if it's an F-body or vette version), they were rated at 275 at the crank.

 

Alright, so based on some research I've done, along with all the advice I've been offered here...

- The L98 is basically just a Gen I SBC, with electronic fuel injection, and the LT-1 was the "Gen II" SBC, which was more or less a prelude to the more popular Gen III+/LS series engines (but much closer in design to a Gen I than an LS series engine)?

- TPI is the main weak point of the L98, due to not flowing very well at higher RPM's. A better intake set-up can dramatically improve the top end on even a stock L98?

Correct?

And my last question that will help my make a final decision here, is which engine is the better option for a newb on a budget? I heard some LT-1 only parts can be spendier, but I'm here to ask those who know!

 

the L98 is the easiest swap. the HSR isn't technically legal, but it'll get you the top end power the cheapest. It can run on a stock L98 tune. The '87-'91 'vettes all had aluminum heads, avoid any iron heads with 193 as the last 3 digits of the casting number.

 

I was only listing some things that would swap between Gen I and Gen II, not necessarily what was "new".

 

.

 

Oh? What's wrong w/the iron heads? I figure aluminum is what I want anyway, but I'm curious.

Also, is the HSR a mechanical or electronic fuel injection system? Is there a smog-legal system that will create good gains? (which, I'm assuming costs more?).

 

Most iron SBC heads are fine, the iron isn't the problem. The problem is the 193 version. These are common on all '87-'95 truck 350s, but except for the casting number, they look identical to the superior iron heads used on the F-car 350s. Just something to watch out for.
The TPiS Mini-Ram is legal, but definitely not cheap. Getting the HSR to be quasi-legal is easy if you have talent to fabricate an external EGR. there are other choices. They all cost even more.
The HSR is the cheapest way to have top-end power with EFI, run it 364 days a year, then put the stock TPI back on the day of your annual smog test.
Some people adapt the LT1 intake, but this is more trouble than it's worth, and ends up neither better nor cheaper than the HSR, and still isn't legal.
Accel sells the SuperRam which Lingenfelter designed. It's legal, but it's more for midrange with a 383. and costs more than the Mini-Ram.

 

I was kind of thinking about doing that too . From what I've gathered, it's a pretty dang easy thing to do yourself if you have at least some mechanical knowledge?

Anyways, I think I'm just gonna go the L98 route for now, as it's starting to sound like it will work out well for me. Any Corvette or F-body one should be good, just watch out for the truck 350's from that era?

 

There's nothing wrong with the truck blocks, cranks, rods, pistons, et cetera. just beware the truck heads.

 

I see. Were they prone to failure? or just don't flow very well?

Also, I read that the HSR is about 2 inches taller than the stock TPI setup. I own a base model firebird, but was planning to add a formula hood to it. Will it fit under the hood w/out any clearance work?

 

They are the second worst flowing SBC heads ever. the HSR fits under a stock IROC-Z hood, IDK about your hood.