I currently have a 91 Firebird: L03 305 TBI and I would like to upgrade to a L98 350 TBI. My goal is to get 300-350hp. I will not be racing it. I'm also on a budget, and I want this swap to be as simple as it can be.

I've read so much on the topic that I think my head is going to explode. I either can't find the answers to my questions or there are so many answers that they contradict each other (or they just aren't clear enough for the clueless like myself). Is it really that difficult/expensive to swap?

This is the motor I plan on getting for the upgrade (is there an engine that will work better for the same or lower price?):
https://www.sandjengines.com/rebuilt...-350RLB-4/9665

Will it work or because it's a 350 TPI will transferring over the TBI from my 305 not work? Can the TBI setup on my 305 even be used at all with any 350, or do I have to buy a specific TBI setup made for a 350? if so how much is this going to cost/where can I get it?

From reading the How to: 305 To 350 swap....everything you need to know thread I know that I need to replace these things:

350 injectors
350 specific knock sensor
350 ESC module
350 chip

But what part numbers are they? What motor do I tell them it's for...I was thinking the caprice since it was a 350 TBI? Does that work or no?

Last thing is I've read that I should replace the exhaust system from the headers back because the L03 is so restrictive...is this a must? Or could I just upgrade the headers and muffler and be ok?

Basically what can I use from my 305 to keep costs down, and what will I need to replace for the 350 TBI/upgrade to accommodate the power I'm looking for?

What am I really getting myself into?

Thanks.

 

Not going to race it? Why do a swap then? If you are not going to do anything with the car besides drive it to work and back, leave it as is.

Anyways, L98s are really overpriced here, used or new. I would just rather save up the money for something better down the road. Used good condition L98s can be had for $500-$950. Depending if everything is there.

Another thing is, why slap on a TBI on a L98? If thats what you want to do, just get a L05. My friend has a L05 bottom end with TPI ontop and its a very fun ride. Although he is not no where near your goals. Which will require head work or better heads, cam, full exhaust and a good trans to back it all up. If you are on a budget then to be honest just dont do it.

In the end if you are on a budget, don't get into this. Even more when you want to get 300hp+ out of the swap.

 

I've done so much to the exterior and interior of the car that leaving the engine stock and dirty just seems like a waste to me.

If I shouldn't go with the 350 swap then what could I expect to do/spend on building up the L03 I have in it now? I've just read that they are complete crap to work with and after putting in all the money it would have cost the same as swapping the 350; and the 350 would have way better results. Is this information correct, or is there hope for the L03?

Honestly I would be happy with a 250hp (or better ^_^) engine that was clean and ran smooth. I think this would compliment the interior/exterior mods I've done, and keep it a nice cruiser for the (few) sunny days we get up here in Washington State.

Is that possible...if so how far would $2100 get me? (to start)

 

I built and swapped in a 350 for roughly 3k when I was all said n done. But I went carbd and axed my tpi, just to give you a price figure.
And if you want power, a 350 swap is the way to go, but I wouldnt get the motor in your link without knowing exactly what is composed of

 

If I went with a carb instead of TBI would that mean I could chuck the computer and not have to worry about all that complicated chip stuff/wiring harness? If so that sounds nice to me.

 

It is. Except there is one thing to think about. Do you have a 700r4? If so you have to install a kit for the lockup feature (its not hard. took me half an hour.) And if you go this route, as long as you dont blindly hack at the harness all gauges will still work. Oh another thing with this route is you have to either put a regulator in the fuel line, or take the pump out of the tank, braze on a tube and put a mech fuel pump on the motor.

 

I knew someone who left the stock pump in the tank and used a mechanical to suck thru it, never tried it myself, but it seemed to work for the friends car, had a Holley on top.

 

I dunno bout that personally, since the PO cut the hole above the tank on my car, I just did that. and spent a good bit cleaning up his hack job at cutting a hole.

 

I did terribly at cutting the hole too. But it was well worth it to not have to remove the rear axle. Could you just get a regulator For the fuel pressure and crank it down to like 6-8 psi or whatever?

 

The only hard part would be swapping the engine. It would be a basic swap. There are a few extra things you should swap while you are doing the work but it will mainly depend on how much of a budget your on. You can throw a 350 in your car for 2k easy if you shop around and buy used stuff. I am working or wrapping up an engine swap on my two trucks. I replaced a whole lot of things I didn't need to but I did because I was in there. Needless to say I am going cheap on the truck that I am going to sell when it is all done. Personally I would never drop fuel injection for a carb on a street driven car. The drivability is so much better, TBI's are pretty basic, and getting it inspected might be a problem.

 

a regulator would be just sending most of the fuel back, but yeah you can. and I had no problem getting my camaro inspected after i swapped tpi for carb. I went carb for simplicity and its cheaper then having to buy injectors and what not.

 

Well the car already has TBI so simplicity is out the window can get much simpler than unplugging stuff and plugging them back in. If you were just wanting to get the extra cubes the cheaper wouldnt really fly either. You would be looking at a regulator, carb, manifold, then the op would have to figure something out about his tranny for a carb swap. The only thing he would HAVE to change on his swap would be injectors and chip. Then you would only be talking about a couple hundred on top of the engine. Not to mention the fuel savings over time with fuel injection.

 

Yes you can just go get those 350 parts out of a full-size car or a truck, and they should fix you right up.

IMO you'd be better off leaving it TBI since you don't seem to be specifically interested in making the carb change. As said, unplug and replug is about as simple and near idiot-proof as it gets. No sense taking on unnecessary work and risks if you don't have to.

 

Swapping in a tpi 350 won't be that difficult as long as you do your homework and become familiar with the parts you need. Aside from the motor itself, you'll need the tpi fuel pump, fuel lines, computer and harness. It sounds like a lot, but it all bolts in.

 

Thanks for all the info.

Basically at this point I don't know what I'm going to do, mostly because I think I have to many options. I guess I'll just keep looking into it all and figure out what is best for me sooner or later.

 

You could always look into an L31 swap.

 

After some though I think I'm going to go with something a lot simpler. (Any thoughts or suggestions would be great)

Clean up the engine,
Rebuild Kit
Dress-up Kit,
Braided steal hoses,
Hedman headers,
High flow cat,
and cat-back system from flowmaster.
Maybe a Shift Kit


This won't give me much more where power is concerned, but it will be nicer than stock, easier to do, and it will give it a nice clean look under the hood to match what I've done with the rest of the car. Not to mention it's a lot cheaper. Since I just want it for cruising around, I really don't see a need for all the power I originally wanted.

One question, what do I do about getting a new chip programmed for the changes? From what I read I would need to have a different chip. Or is it just if I replaced the heads and cam that I would need a new chip?

 

thats what id do.using the gm tbi intake.though tuning it may be difficult.

 

Trying to make horsepower with a stock TBI system is going to create more headaches than it solves.

 

I'm currently building a 350 to drop in my 84 Z28. It has the 305. The PO carbed it and go rid of all the computer stuff, so I'm going to continue that trend. However I'm lost on the 2 things described in the quoted post. I have no idea if there is a lockup kit. Where is it? And regarding the fuel pump, I have a mechanical on there now. What do I need to look for/do to ensure the job was done correctly on the conversion from electric to mechanical? Thanks!

 

Honestly swapping in a 350 in place of a 305 is as easy as it gets. Every option you have, you can bolt right in. Everything fits. It's just a matter of getting all the accessories and packaging done properly.

Swappig to carb is not something I would generally recommend, ESPECIALLY if you have no intentions of racing.

You will need to get a 3-port return style regulator, wire that up. Deal with the TV cable bracket. Deal with how to turn on the fuel pump, then you have to figure out how to get the 700r4 lockup converter to work properly again or buy the kits ($75-$200) to do it. Plus the carb and fuel lines and fittings and distributor and intake manifold... etc etc.

Im no fan of the TPI, but it's a good streetable intake system and it looks mean as hell. If you dont want to do that I think you should give a shot to tuning the TBI using the EBL system.

No matter what engine you put in there, if you're making decent power at all it's gonna require tuning and tuning know-how. If you dont know how to tune an engine it isn't hard to learn, but dont be afraid of doing it by burning ROM chips instead of buying jets and using a screwdriver on a carb. I would always recommend staying EFI if at all possible. The TBI pump may need to be upgraded to a TPI pump and you may need to use a 3-port regulator to dial the pressure down to standard TBI levels. Then you'll need to get some larger TBI injectors to support the larger engine and a new knock sensor maybe.

Either way, it's a much simpler option, and as long as you stick with a stock-ish cam (not that you should but still) the factory TBI tune should still run the engine, it just wont run that well.

Do you not feel the torque converter lockup? In most cars once you get to a stable 40+ mph cruising speed you'll feel a brief jutter from the transmission. Feels kind of like a gear is shifting.

Count your shifts, when you get to four go another 10 mph faster and just cruise and see if it will "shift" again. If so, your lockup is working. If not, your 700r4 will slowly burn itself into a horrible death over time. Maybe.

 

im using a 3 port regulator and its perfect, also i took the fuel pump wire(gray) out of the harness under the hood and ran it to a 12v in the harness that only comes on when the key is turned, been this way for 3 years without issue. i never messed with the lockup and have had no issues.

i would honestly make the switch to carb, only if you are going 350 though, for ease of install.

 

Thanks guys. I'm going carb not only for ease of install, but when I got the car, the Holley street avenger that was on there ended up needing some work, so I put on a new edelbrock 1406. Regarding the lockup, I'm definitely not feeling that. I have 4.10s and it gets to 4th gear quick-maybe 25-30 mph. Hell, it hits second as soon as it starts moving. Maybe I'm missing it cuz of the shift characteristics? Or due to the gearing? Anyway, if this is something I need all help is appreciated.

 

http://m.summitracing.com/search/Par...-Lock-up-Kits/

Is this what I'm looking for regarding a lockup kit? Which one is recommended if I end up needing one? And if im not feeling anything like a shift after 4th, that would be a pretty good indicator that I do (as previously stated )? Also (and you'll all think I'm stupid), does this require dropping the pan on the tranny? Some of the kits seem to have gaskets and others don't.

 

I would nix the braided lines. Sure they look good new but give them 6 months and they look like crap unless you go out every weekend with a toothbrush and clean them. The dress up kit is your call. On my truck I bead blasted everything including the edelbrock mainfold and painted it gloss black. I like it to look stock unless someone looks close. If you want a nice budget tbi combo send me a pm.

 

I've had SS braided lines on my car for a year and a half now, it sat under a car cover last winter and the intake/valve covers/acc. brackets etc all started getting corrosion but the lines still look like the day I put them in and I havent touched them since that day. There just the Summit special to.

 

If you have a 700r4 trans you Need a lock up kit, and yes that TCI 376600 Is what you need (it also happens to be the kit I used), that locks the lockup torque converter by a vacuum switch rather than the computer telling it to do so. Yes it requires dropping the pan so put new fluid and filter in the trans while you are at it. Again this is if you have a 700r4. Look around this site and you will see a RPO decoder program, download it and install it and it will tell you what trans came in the car, other than that you can look up and see what the trans pan looks like in order to positively identify

 

i would just deck out the top end of the 305. Alum heads-headers- roller rockers and lifters and then when that engine goes drop in a 350 and use all the parts from the 305.

There will be so much down time if you pull it,- its only 50 cu

I would also buy a book on chevy 350 builds- it will show why certain power combos make better power bands than others. Also why a Medium curve is so valuable.

 

when these "hole cutters" get to the pearly gates,they better hope st.pete aint a 3rd gen fan that likes things done PROPERLY!!!!!

 

you could always just spruce up what you already have.assuming the engine is healthy.port your heads.get a nice cam,do headers and a exhaust.you may just be satisfied with that alone AND it is your least expensive option to boot

 

Thanks man. Yep. I've got a 700R4. Im positive. I had it put in 3 days after I got the car.

 

Here is what I ended up getting (doing the swap after I fix a bit of a wiring problem):

Open Element Air Filter- Edelbrock Elite Series # 4207 http://static.summitracing.com/globa...e/EDL-4207.jpg
Edelbrock Valve Covers Elite Series # 4246 http://static.summitracing.com/globa...e/EDL-4246.jpg
Hedman Headers + Y-Pipe # 68481 http://www.jegs.com/images/photos/500/500/500-68481.jpg (purchased at summitracing.com jegs just has a better pic...)
Magnaflow High Flow Catalytic Converter # 93456 http://images.magnaflow.com/02product/parts/93456.jpg
Magnaflow Cat-Back System # 16829 http://static.summitracing.com/globa...pe-16829_w.jpg
(plus just some good old cleaning and repainting of the engine/engine bay)

Also a 180 degree thermostat to go with the stage one chip from TBIchips.com...just seeing how she runs with it in there, if it doesn't run right I'll return it or have him make a custom one...

What do you think?

 

it should help your engine breathe easier. the car should sound the way you want it and should pick up a few hp. as far as the air filter and valve covers, obviously just for asthetics.

not sure on the chip though, im sure someone has used them before

 

I am running one of Brians stage 2 chips in my truck. It is boarderlining on needing more than his stage 2 chips will provide but drivability is fine. I could probably pick up a few more hp with a custom tune but I was in a rush and trying to keep the budget down.

I would look into an injector spacer they will free up a little more air. They are cheap and while your in there get a tb overhaul kit and overhaul your regulator. If you do much more you might want to keep an eye on your tranny for slipping. Depending on how old it is a little hp increase can start to cause a little slipping.