i'm buying an IROC and wanna know the pros and cons of Carb Vs. TPI in the areas of driveablility, performance potential, cost of upgrading..

 

If you're getting an IROC, they only had carbs on the LG4 motors which is one of the worst performance engines. If you get TPI you'll get the LB9(305) or L98(350). Both of these will give you better mpg and performance. But you can still mod an LG4 to be fast, you just got to replace the weak stuff, which is a lot. But on all of these the stock exhaust from headers back is very restrictive, so should be among your first mods.

 

If you are considering a carb, I would presume you don't have to worry about emissions testing. A TPI can perform like a carb and get better fuel economy, but it will cost a lot more. On the same note, a properly tuned carb can get about the same fuel milage as a TPI setup would. I went to a carb b/c of the cost issue. I don't have the knowledge to burn my own PROMS, nor do I have a lot of time to learn. I wanted more power, and I wanted it now, not after I learn all the computer stuff. The intake, carb, and HEI needed to switch to a carb setup cost me $410. A new intake to match my Vortec heads, runners, TB, and chip burning equipment, would run about $1400. And then you would need to spend the time to tune everything in. I don't drive my car enough to worry about fuel economy. Just to make sure I don't upset anyone, I commend all those who do take the time to learn to make their own chips. I know its not easy, and it does take a lot of time.If this wasn't the case, I probably would have done it.

 

CC Q-Jets which came on LG4s were for emissions purposes, so you could still pass emissions with one. Now if they have visuals checks and you don't have the CC Q-Jet on there, you might fail.

ONe more thing to add, during '87 they changed some internals in the 700R4 making it better than previous years.

 

If its just a daily cruiser "look good" car that you just want to slap some exhaust and a few other bolt-ons then go with the TPI. Honestly I loved my TPI when my car was a stop light-to-stop light racer and daily driver. Now my car is aiming towards full 1/4 mile race car so I swapped to carb.

 

the 15k character limit made me leave out that i'm 17, a senior in HS, and have little experience in doing major car repairs. replies are as follows in other parts

 

it seems u can post over the 15k limit.. so here goes

Mark: i'm going for the 5sp trammy/305 combo so things about the 700R4 don't help. your other info is helpful tho. Will buying a TPI and switching to carb eliminate some of the "weak stuff"? what exactly is the "weak stuff"? carb engines are easier to modify, but generally ****ty engines.

Johnsjj2: your wisdom of coming b4 me is proving invaluable to me. After It gets current emissions, the carb will get the upgrade so I won't worry about emissions. but the LG4 engine is just plain weak, and that means taking into account other factors (damn this choice is hard!)

 

88IROC:that's what the car will most likely be.. a light-to light racer...I just fear hitting the barrier of cost when it comes to the TPI.. and the upgrades will be more than just bolt on... i'm gonna mildly do it up right.. thank you for your help

 

Switching from TPI to carb will not eliminate weak stuff. The weak parts of these motors are the heads, cam (especially in the LG4) and exhaust. However, TPIs stop breathing past 4500 rpms stock so switching to carb would help that, but I don't think it would cost a great deal to get the TPI to breathe better. The TPI will be just as easy to modify as a carb if you know what you're doing. The exhaust will be the same in the way it bolts up, along with the heads and cam. The only tricky part would be the induction system itself which confuses me.

 

A 305/5spd setup is ideal if you are a youngin searching for a nice car. The 5spd 305's got some better power (88 and up i believe) from having a better cam.

Here's my suggestion. Find a TPI car, and keep it. The TPI was really designed for the 305, so leaving the tpi alone while you do other mods, and won't hurt you as bad as it might on a 350 car.

First, lets address the weak points of these car's as far as power is concerned-

1 peanut cams, although the cams inthe 305/5spd's weren't as bad, and like i said, i think they started doing better cams in those combinations in 88. (305/5spd combos)

2 EXHUAST EXHAUST.... they sucked.. no getting around it. Best thing you can do is get some 1 5/8 headers, and a full 3 inch cat back with a high flow cat. Arguably the best single mod you can do- full exhuast. I think this is one of the few bolt on pieces that will net you the most power besides adding some juice.

3 cold air induction- your gonna want to open the intake up a little. SLP makes a good kit, add a k&n, maybe even experiment a little. check out some of the tech articles, i believe there is a cold ait induction one for tpi cars.

4 Although i said the tpi is somewhat sufficient for the 305, runners should be a priority, as well as getting the plenum ported. The throttle body isnt as much of a concern on a 305 as it is on a 350, since a 305 technically could run off 550 cfm at 6000rpm (in theory) i believe (anyone is welcome to correct me on this) that stock throttle bodies flow around 625m which is really enough, even for a healthy 305.

5 Gears- chances are your gonna find a car with 2.73's or 3.23's in it. While the 3.23's aren't so bad, 3.42's or 3.73's will suit you much better. They made an enourmous difference in my car, both in pickup and driveability. I upgraded to the 3.42's and i now wish i had done 3.73's. However, i use the car as daily transportation still.

6 to address and rehash what everyone else has said about TPI vs Carbs, this is how it is. Both have the abiulity to make the same power. TPI is more expensive, yet more economical. Carbs are cheaper, and make good power, but can't achieve the same economy. CLOSE, but not the same. I personally have a holley 670 sittin ontop of my motor, and i luv it. I still get 25mpg out of my car, with a mild cam, full exhaust and a performer intake.


7 Don't be scared that a 305 isn't going to be fast enough for you. I'll tell ya what, with not very much money in mods to my engine, i was able to almost double the output by replacing the cam, adding a full exhuast, and swapping to a NON computer controlled carb. The best part is, i am around 275 horse (dyno day comign soon to prove this) and i have yet to port the heads and try a cam of any decent size, and add roller rockers. To give you an idea of how quick 275 horse is in a 3600 lbs car, i am thought by many to be running high 13's.

Check out my sig for all my mods.

Steve

 

Check sig box

 

good.. we're on the same page here...the intake, the exhaust and the cam (especially the LG4 cam!) were the first three things I intend on doing to it. For me, that's not even an issue. Seeing as mark and you have told me that the intake/cam/exhaust are the major weak points on camaro engines, either way (TPI or carb) it's getting upgraded. That almost seals the LG4 as the engine going in my camaro. the last question will just make sure that i'm getting what I want:

the LG4 Vs. LB9: besides the cam and fuel induction system, did the LG4 and LB9 share most of the same parts? are the block, pistons, valves, heads,compression ratio and other important pieces the same? (for theoretical purposes, we'll use a 1986 IROC LG4 and LB9, sheerly for the purposes of availability) I don't wanna run into other suprises like the compression ratio being different, or having a different designed block or there not being a steady stream of parts availability for LG4s (hence the compatibility with LB9/L98 issue). If anything else major is vastly differnet, please let me know

BTW fb305SVS... i live about maybe a half hour away from u. WHEN i get my camaro, u can be my guide to the local f-body clubs and gatherings that happen in this yuppie state

 

Hey no problem man, i like workin on the cars, and feel i have a fairly strong knowledgte base in them.

As for differences between the lg4's and the lb9's (HO 305's), i think the biggest difference from 86 and beyond was a slightly better exuast (the lg4 one is 2 1/8, this i know lol) and a slighly better cam. Pre 86, there WAS a compression difference, 8.5:1 for the lg4 and 9:1 in the lb9. I know for a fact that my motor has the flat pistons, not the dished pistons, meaning i have the 9:1 compression. its an original 86 lg4 motor.

Also, if you live in CT, we have an fbody club here in the state. My advice for you is to check out www.ctfba.org . They are the local fbody club here. Also, check out www.thenortheastforum.com - This is a NE board for all of us racers/car luvers to chit chat and bull **** on etc. Great board, lots of great people.

Shoot me an IM sometime- fb305svs for aim.

Ok, and now to see if my SIG works... :-/

Steve