Hello! I'm new to the board, and have a question about an engine swap. I have an 89 Firebird with the 305 TBI and I'm considering a 350 swap. I'm not after a screamer, but I would like to have a little quicker car.

Would it be better to find a wrecked newer model car and take the 350, order a crate motor, or rebuild an older 350? Also I have the 700R4 tranny, would that work with a 350 or do I need to look at swapping that too? (Obviously I have limited knowledge of cars).

Thanks,
Tracy

 

your tranny will work just fine. as for which motor that mostly depends on what you want out of it, and more importantly...funding. look at the threads titled "rebuild kit" and "LS1" cam (they are in tech/general engine). mine is the ls1 and stekman is helping me decide which parts I need for a rebuild. I got a 350 tbi from a junkyard and put that in my car (its a easy swap) of course being a j/y engine it wasn't quite up to what I want it to do, so time for an overhaul. crate motors are good too in my opinion but you are basically stuck with whatever parts are in there (unless you swap parts into it but if you are going to do that why not just rebuild a used motor); not that thats a bad thing. as for a wrecked car, I don't know anything about that, someone else is sure to though.

well all that is just the little bit that I know with some opinion thrown in there, good luck

 

Is there any particular reason you are wanting to swap the engine? I.E.: rod knock, low oil pressure, etc...
If not, then you can look on the TBI boards and such to do mods to the 305 that will get you more power, and save much needed block money for things like good exhaust, heads, cam, and such.

 

Its more fun to mod that 305!!!!!!!(haha)
I have considered getting a 350 myself but decided to mod what I have and I am thrilled with my performance. Don't fall into the peer pressure and get a 350 there is potential under your hood you just need to tap it. Then if you want to kick it up a notch use the money you saved by waiting and modding what you have and get the baddest crate motor on earth and cram it in there and leave the RS badges on for sleeper fun.

 

Thanks for all the replies. I didn't know how much was available for the 305. I'm not looking to spend a fortune, adding parts sounds like the way to go. There is nothing wrong with my motor, I just want to go a little faster.

Thanks again!

 

I'm with SGT on this one, too. If my engine didn't have a rod knock, I'd have probably kept it and just spent money on mods. Instead, I got a 350 with bigger injectors, had to get a new knock sensor, a new EST module, and various other parts to try to get the 350 to run right. I still have to get a 350 prom, and then a higher volume fuel pump, just to supply the new engine. So you see, you already have a good head-start on me, because you have a good running engine. If you just want a little more power, do the exhaust from the engine all the way out.
As far as cam and heads go, you may want to just wait and get a used 305 block (a dime a dozen, from everybody going 350), and then have the block done, with new bearings, cam, and then you can get the heads at your leisure. This way, if the car is your daily driver, you wont have it out of comission while you are building the other engine. I wish I had had that option when I got my bird.
Here's a site so you can see some recommended mods for your 305, from tbichips.com
http://www.tbichips.com/305mods.htm
Good Luck and keep us posted.

 

Up to a point, the 305 is perfectly OK to mod. In fact, alot of the things you'd do to it to help it out, would also be necessary to get the full benefit out of a 350. So I'd suggest starting there first.

There are 5 major impediments to performance on that engine. The exhaust, all the way from the heads to the street; the cam; the heads; the gears they put in the rear end; and the air cleaner.

Get yourself a set of good quality, chassis-specific headers for one of these cars, BUT NOT FOR THE L03; and a high flow cat such as a Catco or CarSound, and any of the multitude of cat-back exhausts you can get from Hooker, Flowmaster, Edelbrock, Dynomax, etc. etc. I'd suggest getting the ones for a TPI 350 of about the same year as your car.

The heads to get are the ones from a TPI 305. They will have a casting number ending in 081.

A good cam you can pick up for cheap is the stock cam from a F-body or Y-body (NOT a B-body if you can help it) with the LT1. It's easy to swap that at the same time as your heads.

Your rear gears are 2.73s. Your car is GM's sacrificial lamb to CAFE. It was carefully de-performanced in order to maximize gas mileage, by, among other things, a choice of gears that guarantees that the engine will never rev high enough to make any power, and then by designing the engine to make no high-RPM power whatosever. Once you get the engine to have some rev capability, the gears will alow it to do so. 3.42 is what people usually find about the best choice. The easiest way to come up with that is to look in the junkyard for a 90-92 6-cyl/5-speed Camaro or Firebird. It will have what you want, in a direct bolt-in, for cheap because it's out of a 6-cyl car.

The best air cleaner is the L69 dual-snorkel one. NOT an open element. Those are a bit hard to find, but it's not hard to fab up an acceptable substitute.

There's a TBI forum on this site; unfortunately alot of the people there aren't really very experienced at performance mods, but some definitely are. It's usually not too hard to tell the difference. Go there, and look at what the people who have actually made their cars (not just their mouths) faster are doing.

 

Inspiring news. My 305 runs soooo good as is, would be a shame to replace it. I swear, the thing runs better every day, and I've just got an open air element and a Flowmaster catback with big pipes. I think my cat is still stock, and everything else. Still it gets up and goes.

BTW, what's wrong with an open air element? Because of Thermac? I live in San Diego, so cold starts aren't an issue. Makes a big difference in power over the stock air cleaner for sure.

Have been thinking about motor swaps, but after reading this thread, think I'll try and go as far as I can with the 305.

91 Firebird 305 TBI, auto
open air element, Flowmaster catback

 

It sucks in hot underhood air, which isn't as dense as cold air.

The L69 unit gets its air from the headlight openings. Fresh, cold, dense air.

 

Yah, I tried to mitigate that by running a big dryer hose, from under the nose up alongside the radiator, so it was blasting fresh air under the hood, but it was throwing dirt all over my motor--opening was too close to the road I guess. So I took it off. I noticed my car is definitely quicker on cool days, and at night when the air is colder.

Want to get either the ram air hood, or the "superduty" hood--has a Camaro SS type scoop that will feed the air cleaner. Cowl induction hood looks nicer, but forcing cold air in at speed seems like the way to go.

Would the dual snorkel give as much air as hood scoops? I like my stock hood, so that might be the best solution. I saw one pic on the Fabrication boards, that had the single snorkel, pointed straight ahead, connected to a TPI style intake ahead of the radiator. Looked like he was running a bigger piece of flex hose, not the original snorkel.

"Super Duty Hood" pic: :hail:

 

Here's what my filthy nasty one looks like. Needless to say it fits under a stock Camaro hood, since it's factory. But like I said it's not too hard to fab up a respectable imitation.

 

That looks great! That would easily flow as good as the open element, plus you get the cold air. What if you made openings in your hood over the intakes? I know it's always better to stay stock, but if you had two rectangular openings with mesh grills, it might look cool.



Attached is a Photoshop'd pic of what ramair slots might look like for your dual snorkel setup. Blasphemy, I know, cutting the sheetmetal, but it's fun to try and think of new ideas.

 

I guess you could do that, but it isn't really necessary.... the hood doesn't come down all the way to the headights, so the scoops are pretty much completely exposed to the outside world, yet both in out of the rain and up high so they don't get as much sand and whatnot as they might otherwise.... If you look up under the hood there, you'll see what I mean. It's really already ram air, using the headlight pan as the duct.

One of those things the factory definitely did right. I wish there were more things about these cars like that.

 

Makes sense. I've got a 91 Firebird though, and the hood pretty much covers the stock intake, and meets the headlight covers, meaning that any air you get is whatever can make it past the turn signal lights down below and through the small holes in the surrounding sheetmetal.

One guy on here ran ducts down to the two openings in the front of his Bird, and put his turn signals underneath. Cool idea, but I like my lights where they are. I guess I'd still get colder air with your setup, but not as much as on a Camaro. I think the Camaro guys came up with that intake opening, and then stuck it on the Firebird, when they should have come up with a design to accommodate the lack of headlight openings. Still works but not as good.

I might be able to do this setup, that some other guy on this site did, and then fab a K&N TPI type ram air box to go with the ram air hood on my wishlist. See pic below:

Or I could just make an airbox on the underside of the ram air hood (4th gen WS6 style) that fits over the open air element. That would get the most air I would think.

 

Here's the hood I want...

91 Firebird 305 TBI, open air element, Flowmaster catback, 160* stat

 

Yeah, the Birds require a bit more ingenuity.... their hood lines are somewhat of a handicap in that area.

 

Thanks again for all the replies, this is the kind of information I'm looking for. Thanks to RB83L69 for taking the time to write all that info up.

 

dont let him feed you that dual snorkle mumbojumbo its already been done by someone on the tbi board i think the open element won by .2 of a second... and also look at me ive got an open element plus a hawks 2' inch cowl hood and trust me it sounds cool it runs great and it looks great aso along with my engine temp is down my performance is up and plus everyone comments and complaments when i drive down the street so think about it spend 200 bucks for a dual snorkle or spend 35 for an open element? ill take my 35 dollar open element anyday of the week well thats just my opinion

 

Whether it's a dual snorkel or open air element, the point is to get more air to the motor, preferably cold air. I have an open air element, which helps a lot--burly intake sound and noticeable SOP difference, plus higher revs.

But, and here's the big but, I don't have a scoop, so I'm gettin' the stuffy hot air from right under the hood. Cowl hoods supply cold air, but I like the idea of forced induction. That happens somewhat with the cowl at speed, but more so with any kind of forward facing scoop, like the dual snorkel setup.

I don't currently have 5 bills for an ACSD hood, and I've been looking around for a scoop I could glass onto my existing hood. It would be cool to drive around with no hood, but then someone could swipe your battery. Plus I don't have the chrome valve covers (5 rwhp) yet. And the chrome dipstick (25 rwhp).

The other thing about hood scoops is, if you don't stay with a stock or near stock design, like ram air or cowl, you could end up on www.ricecop.com. Saw some guy that made his own scoop out of tin. Very sad indeed.

Any ideas on hood scoops please send pics. I have a 91 Firebird, GTA nose and body kit, that needs cold air.

 

These boards are full of ideas for souping up the TBI motor. All I've got so far is, the open air element, and a flowmaster system with big pipes from the cat on back, and the 160* thermostat. Already it's a quicker car, and plenty fast for me. Want to go faster though, so I have a whole grocery list of stuff I want to get, all ideas I got from this site.

Another option mentioned here (when your stock motor finally needs a rebuild) is to stuff a 350 crate motor under the hood--can use your stock fuel delivery system with some modification, same ECM, harness etc.--350 TBI. I found a motor that makes over 300 hp, using your stock TBI setup. Much easier than an LT-1 swap, and making as much or more power.

I found several engine builders that specifically make replacement high output motors for the TBI thirdgens. They were advertising on Ebay.

No need to replace a good running motor, though, when there's so much that can be done to it.