Hey, I have a 91 formula WS6, 305 tpi, 5-speed. I am thinking about switching to a carburetor. This is what I've come up with so far:

reasons to switch:
1)Free up top end of rpm range--cheaper than miniram.
2)I can use computers quite well, but I don't really like them; I would rather adjust a carb than burn chips.
3)Cheaper to tune?--TIME (I'm in college)+ about $300 to start burning chips vs. cost of setting up carb and tuning. Also, as in 1), include cost of miniram/super ram to really free up FI. As for the time of swapping to carb, I could do this over Christmas or spring break.
4)Power gain right off the bat from taking TPI restriction out of the intake (from what I can gather reading on this board and talking to people)
5)Wouldn't consider this if I had an LT1 or LS1, but TPI is not the greatest FI setup.

reasons not to switch:
1)Aside from how to set it up and just get it running, I don't know anything about carburetors (except how to spell the word, so I am ahead of some people on this board )
2)Loss of gas mileage? I drive about 200 miles/week of stop light and light freeway driving.
3)Can I pass emissions?/What kind of carb, intake (cc or not) do I need to pass emissions? If cc, am I back to where I started as far as having to burn chips?
4)I have a perfectly good TPI setup, although I'm not sure I like it that much--4500 power redline is not my favorite on a small block.

What else is involved here? What do you guys think. If I had my way, I would have a non-computer-controlled, perfectly tuned carb controlling my air and fuel. I will be using two catylitic converters (and EGR on the carb if I need to) either way, so emissions shouldn't increase a whole lot going to carb, right. I'm by no means a tree hugger, but don't think my car should should spew emissions just because I want a simpler setup.

What do you guys think? I'm sure there are other people on here considering this, so let's get a good ol' fashioned dee-scussion going

I originally posted this on the carb board, but I also want to know what you guys think.

 

Let's just put it this way. My friend switched to carb on his car and I've heard him do nothing but complain about it since then. He says he'll NEVER switch to a carb again. He's got a nice setup but he's constantly having problems with it. I would say that he spends 2 to 3 times the amount of time working on his carbed 360 as I do working on my TPI 355. The benefits sounded good to him too... until he did it. Needless to say, right now he's saving up to put FI back on his engine.

------------------
1986 Trans AM
355 TPI
4 Wheel Disc Brakes
9 bolt Borg Warner Rear (2.77's....oh joy) :P
6" rods, approx. 9.7:1 Compression, Stock TPI (soon to be ported), 24#/hr LTI injectors (cleaned and flowmatched by Cruizin Performance), Hedman Shorty Headers, 3" exhaust with 80 series flowmaster, SBC 993 heads completely redone and modified for 1.6 RR, 1.52 RR (for now), Comp Cams XE262-14 TPI Cam, Holley AFPR, TPIS airfoil, MSD wires, MSD 6-AL Ignition, Hypertech 53,000 volt coil.

Track times to come.

 

I agree, don't switch to a carb. If youre dirving alot keep the tpi. The carb will just kill you in gas. My brother has a Monte Carlo SS with a 305 Ho and he gets like 8.5 miles a gallon. And a Carb isnt gonna boost power that much. Plus if youre in school you need to save your money for chicks.

 

LOL @ 87irocz350 save your money for chicks. hahaha, but seriously if you are in school and do not have time to be messsing with your car i wouldn't. tpi will give you better mileage than a carburetor (ie highway mode). a PROPERLY tuned carb can ALMOST give the same mileage as FI. my friend took the CCC carb, CC distributor, and comp harness out of his firebird and regretted it. he just couldn't get it to work the way HE wanted. he is going to put it all back in next weeekend.

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86',88',89' IROC-Z, 350 TPI, 700-R4

94' Formula, LT1, 6spd



[This message has been edited by mystikkal_69 (edited November 24, 2001).]

 

Don't get me wrong: I have time to work on the car. I look at all the boards here every day and sometimes a couple times a day. I don't, however, have the large blocks of time that would be required for the swap over until a break from school, that's all.

mystikkal_69, it seems like you have a preference for computer-controlled carbs, if it must be carbs. Is this correct? What all does the computer control--just the spark curve or more?

I'm also kind of thinking maybe I'll just get into burning chips.

It sure seems weird, though, for a sbc to be limited to 4500-5000 rpm. Maybe it's just because all the other small blocks I've driven go much higher (making power).

Anyone on this board favor the swap?

One last thing--I would rather spend my money on my car than other stuff

 

Just as a reality check.
A stock 305 isn't a big breather to begin with. What makes you think there are going to be any gains going to a carb?.
Learning how do chips will long term pay for itself.
If they ever enact any smog laws where you live, you'll have to reinstall all the stock stuff anyway.
1/2 the magic with EFI is the ignition. You'll never get close to what an ecm managed distributor can do.
Don't forget dropping the gas tank and changing to a TBI pump and getting a pressure regulator, suitable for use with a carb.

 

With "properly breathing" TPI parts you can get a SBC 350 to easily run over 5,000rpms. I ran my stock 305 up to 5k all the time and it seemed to still make decent power too. I know I could have gotten it to rev higher if not for the stock cam and stock ignition. I don't have but about 100 miles on my new 355 but when the rings finally seat and I can rev it high I'm hoping to hit 5500-6k. Siamese the TPI intake and with a properly balanced rotating assembly I'm sure you could get it to rev over 6k easy. Nothing is impossible. Just when you think it'll never happen, someone does it just to proove you wrong.

Actually, my friend ran a mechanical pump on his when he did the swap and just left his TBI pump in the tank of the car and just unhooked the electricals. Of course he got rid of all the computer stuff and after about 3 years it did finally get clogged to the point that he had to take the tank down and remove the pump all together.

------------------
1986 Trans AM
355 TPI
4 Wheel Disc Brakes
9 bolt Borg Warner Rear (2.77's....oh joy) :P
6" rods, approx. 9.7:1 Compression, Stock TPI (soon to be ported), 24#/hr LTI injectors (cleaned and flowmatched by Cruizin Performance), Hedman Shorty Headers, 3" exhaust with 80 series flowmaster, SBC 993 heads completely redone and modified for 1.6 RR, 1.52 RR (for now), Comp Cams XE262-14 TPI Cam, Holley AFPR, TPIS airfoil, MSD wires, MSD 6-AL Ignition, Hypertech 53,000 volt coil.

Track times to come.

[This message has been edited by 86TpiTransAm (edited November 24, 2001).]

 

Ever since I got my computer replaced, without the performance chip, it seems to pull strong all the way up to 5000RPM... And I am happy with the TPI because it has nice low end torque... I love "torqey" cars. I'll never get away from TPI... I love it, the looks and the design. It just needs tweaking. I think the cam and heads on a factory L98 have a lot to do with the power range as well.

Carbs are a pain... espicially when you live in the great white north, and need that dreaded choke that never seems to work right.

My $0.02

------------------
1988 Pontiac Trans Am GTA L98 5.7L, Black on Black with 114,000kms.

Best ET 14.559 @ 95.25MPH
Custom 3" Stainless Exhaust Y-Pipe back (High flow Cat and Flowmaster Mufler)

 

what carburetor did he use?



------------------
1986 Iroc 305 small block chevy: ported heads, 1 3/4 slp headers, rpm intake, 1.6 roller rockers. looking for carb and cam.

 

What you should prolly consider doing is
getting rid of your car for an older HO 305
with the quadrajet, rather than ruining a good TPI car. Someone else will make a better home for it.

Once you have the quadrajet car, and you've
enjoyed a solid week of getting it to start
in the morning (assuming its at least 50 degrees out), get yourself a holley 600 CFM
carb. Don't bother with anything bigger
than a 600, cuz it won't help, but rather
will hurt.

Get a carb spacer, that might help get some
of your lost torque back that you were used
to on your TPI car.

Then call up summit, and get a holley nitrous
kit, and buy a electric inline fuel pump.

Remove your factory pump with a block off plate, and adjust your fuel pressure a little
for the nitrous. Run 150 shots, and take it to the track.

At this point, you'll have about 1/2 the power as I do, on a naturally aspirated 355
TPI motor.

Good luck.

-- Joe

------------------
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
1989 Formula 350 4-bolt mains, Forged .030 TRW pistons, SLP 51010 Roller Cam, Comp-cams roller lifters,
Summit 1.5 roller rockers, World Products Sportsman II 2.02/1.60 heads, Edelbrock TPI Intake,
Cloyes Double Roller, timing chain, Mellings oil pump: 13.5 @ 100.23 MPH

Since close of track : Ported SLP runners, Ported Plenum, AFPR, Autometer 100lbs gauge, A/F ratio gauge.

http://www.joesperformance.com

 

He started out with a QuadraJUNK, then switched to a Holley which went up in flames, then switched back to the QuadraJUNK, and finally got a 600cfm Edelbrock which he still uses. They don't call them QuadraJUNKs for nothing and Holleys are harder to tune than Edelbrocks. He works on the Edelbrock ALOT less than he did with the other carbs but still works on his ALOT more than I do my TPI engine.



------------------
1986 Trans AM
355 TPI
4 Wheel Disc Brakes
9 bolt Borg Warner Rear (2.77's....oh joy) :P
6" rods, approx. 9.7:1 Compression, Stock TPI (soon to be ported), 24#/hr LTI injectors (cleaned and flowmatched by Cruizin Performance), Hedman Shorty Headers, 3" exhaust with 80 series flowmaster, SBC 993 heads completely redone and modified for 1.6 RR, 1.52 RR (for now), Comp Cams XE262-14 TPI Cam, Holley AFPR, TPIS airfoil, MSD wires, MSD 6-AL Ignition, Hypertech 53,000 volt coil.

Track times to come.

 

yes actually i like the CC carbs better than non-CC carbs(atleast as far as carbs go). there is a wealth of knowledge on the carb board how to tune the q-jets for performance. the computer on the CCC system is by far simpler than a TPI system. The computer on this system controls the spark curve, attemps to maintain a proper A/F mixture, EGR operation, TCC lockup, and the idle to some extent. I am currently in the process of installating the CCC system on my project 355. everything looks good so far.... (i had no luck with the edelbrock, holley, or the vacuum advance crap). so out goes all that junk.

[This message has been edited by mystikkal_69 (edited November 25, 2001).]

 

I'd stay with the TPI. if you plan on junking the computer control equipment altogether you will get sh*t gas mileage and you won't pass emissions with any carb, be it a q-jet or a holley. You will have to change the computer, wiring harness, and totally re-route a TON of vacuum hoses for the emisssions equipment if you want the computer-control setup. IF you can get the CCC setup to work properly after the swap, there will not be any performance gain, if not performance loss, over the TPI setup. I've found the CCC setup to be very unreliable as you have all the mechanical problems heir to a carburetor, along with all the problems of electronically controlled engine and emissions management.

------------------
Red '87Formula Firebird
-mostly stock 5.0L LG4 w/cowl induction setup borrowed from '83 TA and T5 tranny.

My newest Ride:

'85 Silver L98 Corvette w/4+3 manual tranny. not bad for $3500.

 

This is your daily driver, stick with TPI. The only good reason to switch to carb is if you're making a track-only car.

------------------
1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH (2.10 60')
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
-=ICON Motorsports=-

 

As an example, I'm switching to TPI from Carb. The reasons:

#1. It's all about driveability. When I start my car up, it won't idle for 5 minutes. After that, it takes bout 15 minutes to warm up the manifold so the thing won't fall flat on it's face.

#2. Your car is tuned optimally at all times. Let's say you live in california. You drive up to lake tahoe, and you tune your carb. Then you drive down to LA along the beach. Two completely different altitudes and tuning requirements. FI, no problem, it can compensate ... or you could get out and re-adjust your carb for every 50 ft altitude drop.

#3. I get like 8 mpg with a holley double pumper. The strip that I drive to is 40 miles away ... the round trip adds up. Plus, you have a limited gas capacity. If you get 8 mpg and you are trying to cross the desert in Nevada ... you can pretty much just forget the idea.

#4. Torque and throttle response. Chicks like it when you blaze up two fat 245's.

#5. Computers are idiot proof. The sensors make it harder for you to screw stuff up.

Think about this ... Port fuel injection allows the air to move faster from initial point of intake into the cylinder head. Carbed manifolds are wet flow, so fuel is suspended in them at all times, meaning the air moves more slowly ... some say this provides better atomization ... but the slower the air moves, the less it gets in the cylinder to blow stuff up

------------------
355 c.i.
Dart 180 Heads
Lunati 224/224 cam
Harland Sharp 1.5 rockers
Performer RPM Manifold
Holley 600 cfm double pumper
Hooker Super Competition Headers
Flowmaster Exhaust
Competition Engineering Sub-frame connectors
Tremec TKO
Pro 5.0 Shifter
GM posi 3.42 rear
Hurst Roll Control
13.9@102
http://www.geocities.com/thetpiguy/index.html
chemjoker@aol.com

 

Instead of switching to a carb, why dont you do this:

http://members.home.net/millicanga/s...into_a_1st.htm

Its a helluva lot cheaper than a miniram or SuperRam setup, plus you get to learn how to burn your own chips (which would be reccomended if you got a SuperRam or Miniram anyway). I am personally switching from TBI to TPI w/ the LT1 intake for my 406. I'll have plenty of Torque down low no matter what intake I use, and the LT1 intake will definately breathe enough for me to rev over 5 grand. It may be a liitle different on the 305, though. You might lose a bit of low-end torque, but you'd probably make some more power high up.

 

OK, you guys win (for now ). I think I'll stay with tpi. The real reason is that it's going to cost about $700 for SFCs, wonderbar, and a suspension upgrade. I don't really mind tpi that much, it's just not ideal.

Thanks for the lt1 intake recommendation.

Maybe someone will try an ls1 swap next. Before you jump all over me, I haven't even looked at an ls1 closely to know if it's even possible.

I think you guys are seriously mistaken about carburetors being so bad. Every car ever produced (except some like the fuelly vettes) used carbs until not that long ago. Well, it has been a while, but not that long. Anyway, excluding the later 70s and the early 80s, where american cars were not that great, carbed engines have a decent track record.

I think it's a little extreme to say that if you go to a carb setup (:eek you would have to readjust it every time you change your altitude by 50 ft. I think that your 8 mpg is either on a car setup purely for performance, or that the guy doesn't know a thing about carburetors. Carbs are simple (relatively speaking) and you can work on them easily.

It costs what, like $300 just to get setup to burn chips? I'm not saying that that's not the route I will take, but man!

Yeah, I admit it--FI is superior in really every way, but you really have to pay $$$$$ for that superiority.

Also, anethes, I'm giving my car a great home. I baby that formula like few other people would.

Anyway, thanks for all your input, information, opinions, etc.

Now to see what the carb board had to say...

Y'all won, though.

 

If your keeping the 305 Keep it tuned port.
If your going to put a hot 350 or bigger in there, ditch the tuned port.
easy as that

 

I'm interested in the take here, my instance is I have a tpi long block I put in place of my 305(1987 carb option). Asked mountain man to setup the carb for my engine and he said the tpi motors don't like carbs till the cam is swapped out.. anyways I have headers and full exhaust, open air cleaner and it runs and idles ok but it's overloaded with fuel, either I rebuild the carb or get a different carb, this is strictly a weekend cruiser maybe a few times a month(ideally) I like the idea of messing with a carb a little...

 

This is an old dead thread . A tpi will run fine with a carb swap but do you have a ccc and have to pass emissions? Might not have a fp pushrods hole in the lb9.

 

It's still here though, and I am curious on input, the car as stated is a 305 carb car from factory, and I swapped a good running tpi LONG BLOCK as a replacement, so intake, carb electronics from car have been retained. Not a tpi swapping to carb. I feel a lot of people will be biased and have an attachment to the car and factory features, but they are out dated and everything plastic or seal wise is going to need replacement or soon will. I seen the car and fell in love with its physics, not it's drivetrain.

 

No emissions here to worry about (MN) and it was there, did a bunch of research on that first. Actually I was worried the crank wouldn't have the lobe for the fp and researched that, they have a block off plate when in tpi.

 

I’m not following the point or what you’re question is ?