I was talking with someone the other day and they told me that switching my car from the old 750 Qjet to Throttle Body would actually take away power. I wanted to see what all of you thought about this, since i dont really know. Thanks

 

Depends on the aplication and what kind of TBI system you'd be installing. If stock TBI swap in place of a stock carb then TBI is more power. Give us more info.

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, Jon (91 RS too many mods to list)

 

Depends on what motor you have.A 305 TBI has around 9.3:1 comp. ratio which is a good starting point since a carb has 8.6:1.This stock ratings.But a high output has 9.5:1.This is just a way of showing the differnce of power. It is just a matter of what headache you want.A carb runs good in alot of situations but bad milage. TBI good gas milage,but in some cases cost more to run the way you want it.Just check into and make your own call.

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Sounds like you all know what you are talking about. Here is some more info on what i have.....it was the Qjet from a blown 305....I removed the engine and replaced with a 350, kept the 85 carb. Im pretty sure it would be a stock TBI switchover. Besides the fact that my carb secondaries stick, and the carb itself is at about 80%. What else you all think?

 

Huh? What do you mean by "since a carb has 8.6:1?

1985-Z28, What 350 did you put into your car? If it's a stock engine, you'd probably be well off with the L05 350, TBI system, used in trucks and some cars.

If it's a high performance 350 maybe you'd be better off using a custom system, build it from scatch, choose the best PCM, custom chip, 454 or Holley unit, whatever would be best on yours.

[This message has been edited by Keith5 (edited March 05, 2001).]

 

Its a plain old run of the mill crate 350. What do you think?

 

Come on man, what did u think everyone was gonna say? LoL. This is a TBI board. If I was gonna say anything, EFI was the best thing that has happened to the automobile. Any speed shop mechanic will tell u that. Carb is still the best though for pro drag cars for them 1000+hp engines but for our daily street drivers. A swap to some sort of EFI system would be better. I ain't recommending TBI though. Sorry but I would look into something like Multi-port or Tuned Port fuel injection systems if your going to mod this motor and want a serious injection system that will deliver the fuel and air u need to power all the potential out of your car. Just my thoughts.

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Eric Natzke
91 Firebird 305 TBI
"It Ain't Stock"
http://members.aol.com/j007golden/91firebird.html
For info on certain parts or mods go to the site below
http://members.aol.com/j007golden/modeval.html

 

A stock carb is what I am talking about.Check any Haynes manual,look for vin. codes and compression ratios.


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Actually my Camaro carb is 9.5:1!! Thanks for playing though=)

 

Then you have an L69 4BBL carb.No playing at all.Tune-port has the same.

 

what year is the 350?after 87 the intake pattern is a different desing,but modifying can be done about the center bolt angles.depends on what you want to spend.

 

The 350 is brand new, just bought it from Scoggin Dickey last summer. Just a crate 350. No specials, just stock.

 

But what engine is it? You can get new stock 350's for more than one year and application. Is it a ZZ4, L05, L31. .. . What was it supposed to be in? Is it the 350 universal replacement?

jase, it sounds like you mean the carb determines the ratio.

I suppose maybe you're identifing the engine with the carb, tpi, and tbi? There were more than one carbed engine, and many ratios with a carb, the LG4 started out in the 8's and then ended up 9.5.


[This message has been edited by Keith5 (edited March 06, 2001).]

 

Keith5- Im pretty sure its just the universal replacement. I dont remember it being anything else when i bought it, so ill just go with that.

 

I looked up the information for my engine on the Scoggin Dickey site: its the 350 LM1, 249 hp, 304 ft/lbs torque....im guessing just a factory replacement.

 

Swapping to TBI would be a huge waste of time. The standard Quadra-jet is going to outflow a TBI, the small primaries will give you as good a gas mileage as a TBI as long as the car is tuned, and its cheaper to maintain, and your car is already setup for it. The only reason TBI cars are even around is because GM wanted fuel injection for emissions. Don't waste your time and your money.

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Drew
The lone Thirdgenner of the Apocalypse
predatorman@hotmail.com
My Website
87 Iroc
91 Formula 14.3@98mph
91 RS Convertible
91 Firebird V6Sold
92 S10FOR SALE!
98 Grand Am GT

 

ya and i guess thats why the l03 is rated 20 hp more and 5 ft/lbs of torque more becouse of that carbs better flowing

If ur gonna do n e kind of a swap just go out and do a TPI set up. Someone recently did that and made some very impressive HP #s with just the TPI swap. BEsides, as much as i luv my TBI, nothing looks kooler than those runners up under the hood. IMO no crome air cleaner can match that.

 

True,I was giving an example to help our friend to decide on what he wants to do.If he got a 350 universal,he needs to go to a carb because it is for 65-86 years.This used to be so and that may have changed.He needs to find out if so.I like both,TBI & carb.


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He could use TBI, CARB, or Tuneport. Whichever he wants. If he were to go with TBI the intake bolts won't quite matchup, he'd have to use a carb manifold(with adaptor).

 

WRONG, if he gets a TBI setup from a L03 then it will bolt right up no problem. Since it's a run of the mill 350 not like the 350ho or zz4 then a TBI system would work fine for his combo.
Drew, why are you so against TBI? You say that it's crap but you didn't answer the question, we're talking about putting the system on a mild 350. TPI is expensive so don't bring that into the picture. 8t9 says that is why the TBI made 20 more hp and more torque, the reason for that was because the L03 had 9.3:1 compared to LG4 8.6:1 and a few other factors BUT...TBI gets a lot better gas milage than any tuned carb just because of the better atomization of the fuel and the fact that it's electronically controlled. Then Drew makes the comment about a carb being cheaper to maintain. What kind of BS is that? Drew, sorry for going off on you but you obviously don't know much about TBI. There are TBI systems running 150+ miles with NO rebuilds. You always here people having to rebuild carbs and how hard it is to find a "good" carb for sale, they ALL need a rebuild. I've never read that about a TB unit, they seem to be tank. I know my system has run 147K miles and the intake has never been touched except for a 5.0ho air cleaner. I respect the fact that you're a moderator but your place isn't here talking about how a carb is better than TBI. Why did GM put TBI on do you think? Really do you think it was only to pass emissions? Maybe so but it did it better than carb and made more hp from factory so what is a waste of time and money now?
I'd say get a complete 350 intake system and you'll be set. A 454 TB unit would help in the upper rpm range. I'd like to see the cam specs to give you a better idea of what is needed to make __hp and __ft-lbs.
One note about the quadra-jet, it is a good carb if it's messed with. Car Craft did that build up with a 305 and they got to I think 280hp and they swapped on the holley double pumper and got 0 gain. I do think that the 280 was about where the quadra would have had trouble keeping up with the holley but still that was 280hp from a 305 with bolt ons.

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, Jon (91 RS too many mods to list)

[This message has been edited by JPrevost (edited March 06, 2001).]

 

Here's some more info about my engine:

Camshaft lift: 0.390"/0.410" Hydraulic
Compression Ratio: 8.5:1
Heads: Cast Iron 72cc
Valves: 1.940"/1.600"

If you need anything else, I can post it, or just go to www.scoggindickey.com. Under Parts and Crate Engines. 1969-85 GM 350. Thanks again for all your input guys, its helping me figure out what i want to do.

 

Mike why do u always compare to COMPUTER controlled carb on the LG4 to the TBI on the LO3? The word COMPUTER should tell u right there that the thing at real carb. You always use that as an excuse to dis on carbs. But it isn't even a carb at all. If anything its closer to TBI then it is carb since it is EFI.

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Eric Natzke
91 Firebird 305 TBI
"It Ain't Stock"
http://members.aol.com/j007golden/91firebird.html
For info on certain parts or mods go to the site below
http://members.aol.com/j007golden/modeval.html

 

Umm, moderator. He has the 350 universal replacment. It has '86 and back intake bolt patterns, and a '85 and back two piece rear main seal.

He could use the L03 intake if he wanted to modify those middle intake bolt holes, but why not just get a good flowing carb manifold and use an adapater?

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1989 Pontiac Firebird Formula LO3 Auto
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*****Possible summer '01 mods*****
Dual Snorkle, Auburn Posi, Keyless Entry, Wonder Bar from my IROC, 4th gen seats, T/A tail lights

http://www.geocities.com/krt80/

 

That was what I was getting at because of the 350 was a replacement.

 

Actually the one piece real main seal changed in 87 along with the intake bolts. I'm not sure if you ment to say 86' and 85' or what but whatever, doesn't matter. Also the intake can easily be modified for the center angle bolts, any shop could do it in a like 10 minutes if you don't feel like doing it yourself. I know local guys that don't even charge for that kind or work.
https://www.thirdgen.org/messgboard/...ML/000353.html
With that lift and I'm sure it's small duration, the L05 was rated at 210hp (300 ft/lbs) in the trucks with the 1 11/16" TB (same as 305) and same intake manifold. Since that cam isn't sporting much potential I'd do in order over time: Headers, cam swap, carb intake w/adaptor and larger TB unit (454 or holley 670). That is what I would do if I was in your shoes. If you aren't keeping it emissions "legal" then headers can be had for ~$350 and they'll wake that engine right up. Then anything else you do to the engine will end up with higher hp gains. It's good that you have a non roller cam because it's a LOT cheaper to do a cam swap than it is with roller (87+). $130 and you've got yourself a kit that'll wake that engine up. I have the 350ho right now and it's 330hp with 650cfm carb and headers. I've got a 670 cfm and edlebrock rpm intake so we'll see how that works out. With just a cam swap the 350ho makes 50 more hp and 25 more ft.lbs with JUST a cam swap. Same 650cfm carb and same headers, just cam and the RPM manifold were the difference. I hope this has cleared things up for you and keep the board posted with the swap whichever way you go.
By the way, it's funny to think about this but the TBI on a 305 made 170hp and on the 350 version it made 210hp. That's 40hp difference with same intake system (different injectors of course). The 305 TPI on a 350 made only 15 more hp from factory. Just something I would through out into the open for everybody to think about. Kind of like a fact of the day!

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, Jon (91 RS too many mods to list)

[This message has been edited by JPrevost (edited March 08, 2001).]

 

The one peice rear seal started in '86. The 350 universal replacment would probably make more power than an L05 with TBI.

[This message has been edited by Keith5 (edited March 08, 2001).]

 

That was my point, L05 is worse than the GM replacement and it still made 210hp from factory with the same TBI intake as the L03. Funny thing is that my 86 sport coupe had 2 piece rear seal, was that something strange? Then my dad's 87 suburban had the one piece and the 305 TBI. If it was 86 then please someone post a link to some kind of official info, thanks.

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, Jon (91 RS too many mods to list)

 

https://www.thirdgen.org/messgboard/...ML/001422.html go to edit/find(on this page) type in '86

https://www.thirdgen.org/messgboard/...ML/004702.html just read this one.

I'll get some "offical" links later tonight probably.

 

Cool, my 86 was a pos so I guess it probably had the engine replaced with an older one. The guy said he wasn't sure what was in it. I just took it because i needed a ride. Thanks for teaching me something. (dumb moderator )

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, Jon (91 RS too many mods to list)

 

Yeah, dumb moderator .

There is another possiblity, maybe some of the early '86s got the 2 piece seal's left over from '85.

 

Hey All-

Just wanted to let everyone know that over Spring Break I decided to rebuild the QJet. It ran worse when we were done than before we started. I went to a local salvage yard, bought a Qjet for $75 and now my car purrs like a kitten. Appreciate all the helpful info about TBI and such, but I think I will just stick with the carb for now.

 

Sounds good, you got lucky with a junkyard carb. You can almost never go wrong with a junkyard TBI setup since they're tank. Carb on the other hand usually needs rebuild.

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, Jon (in process of installing new engine)