Anybody know any fairly cheap things that can be done to a TBI 350 that will add some hp to the car? I've got the l05, which I believe is low to mid 200 hp.. not a huge jump from the 170 hp 305.. Decent but not wonderful.. Anyone know what the exact horse power of the l05 is because I can't seem to find it.. Anyway any cheap power adders would be welcome here..
Thanks Guys
-Justin

 

That's a truck motor, so a different cam should help a lot.

 

I thought the l05 is a caprice motor.

Anyway, while on the subject of cam shafts.. If I buy an lt-1 camshaft to throw in the car, A) will it work ok and B) Are putting in new camshafts difficult and finally C) how terrible will my gas mileage become by doing this? I'm trying to have a happy medium between gas mileage and power at least until I'm done with school..

 

I think youd get a lot more power if you dropped the tbi and went to carb. Changde the intake and put a non computer hei dist. with the carb and you be much happier. A cam could come later if you don't want to play with that right now.

 

why would I be happier with a carbed engine as opposed to the TBI? Isn't the carbed engine a pain in the butt when weather changes? I know the corvette is a pain to make work properly at varying times of the season.. If it's not a huge pain, then how much can I pick up a new intake and carb for approximately?

 

I would just stick with TBI for now. If you get a carb, that will eliminate the computer, meaning you'll need a new distributor, and if you have an auto, you'll have to take care of the TC LU.

My car isn't that much of a pain when the weather changes. And I live in MD 100* in summer, 20* in winter at times. As long as the choke is properly working.

 

The earlier ones had 180hp..the later ones had 200. Get one of those pick up truck magazines, they have a lot of performance parts for that engine..since most chevy trucks from 88-95 have that motor.

 

The easiest things would be a chip, a throttle body spacer, or an injector spacer. I think turbo city sells the later two. Im not sure about your exhaust, but a fcree flowing one is a definent must.

 

I'd say don't fool with the induction for now. I don't know about your car, but when I hit WOT from rest, my tires just spin in place. At the track I had to go from rest to half throttle, then gradually to WOT so they wouldn't slip, and I got like a 2.5 60'. I suggest you make sure that all of the power and torque that your engine is making makes it to the ground before you start trying to pull more out of it. Also I've heard that 3.73's work well with this engine, you might try getting new gears. Besides, you just got your engine running right, why fool with it so soon? You'll void the warranty if you do anyway.

By the way, if you got P/N 12513151, it is indeed the Caprice engine. I'm pretty sure that with TBI it's rated at 205 hp and about 295 lb.-ft.

 

See:

https://www.thirdgen.org/techbb2/sho...hreadid=128005

The LO5 has also been discussed elsewhere on the TBI forum, as well as at the Impala SS website,

http://www.impalassforum.com/cgi-bin/ultimatebb.cgi

under the Caprice forum topic.

I assume that you used to have an LO3, so that means you have the smallest injectors. The throttle body from the 305 is the same used on the 350s, so what you have is fine, and it is adequate air-flow wise in stock form for up to around 300 fwhp. That said, doing the so-called Ultimate TBI mods (per the ThirdGen Tech Articles, and especially as seen on the TBI topic by Snuf) will raise the airflow a bit more.

What you need is the copcar (Caprice 9C1) 350 fuel injectors (65 or 68 lb/hr depending on the year) and the ECM that drove them. That's just for a decent starting point. And it will put you at the 190 to 205 fwhp factory rating (depending on the year, 1989-1993) of the LO5, or higher, depending on what you have for air intake and exhaust. BTW, the 205 fwhp rating (1992-1993 LO5 9C1) also had 300 fw ftlbs torque, so that should feel a LOT better than your 305. But you are probably using the 305 injectors right now, so you are not feeling the full effects of the engine you bought.

So you NEED the larger injectors, and the ECM.

AND keep in mind that any further engine mods you do, beyond where you are now, will require even more fuel; a cam swap will definitely require more fuel.

The vacuum-compensated FPR is something that LB9/L98/L99/LT1/LT4/LS1 engine owners automatically get, but the only TBIs that got them were the marine 502. BUT the marine 502 vFPR is a bolt on for the TBI throttle body. There is a very long thread discussing it at the TBI forum. Find it and read it. You could use it.

An LT1 cam will wake up the LO5, and it won't affect your mpgs very much (but your foot will), but it will also void your warranty (if you have a new engine). So if your engine is still in warranty, keep the existing cam because it's the same cam as in the L98.

You can get the LO5 up to 225-235 fwhp and 320+ fwftlbs while retaining the stock cam, by doing a handful of easy/cheap mods:

Adding a good cold air intake, a good exhaust, TBI mods, slight changes to the base timing, and a static change to the fuel pressure (quarter mod is one way to do it) is enough to get to 225-230 hp, as evidenced by the 4400 lb Caprice 9C1 cars with these mods running 15.5 to 15.7 in the quarter. That translates to 14.7 to 14.9 range in a Fcar weighing 600 to 800 lbs less, with no other changes.

An aftermarket intake manifold would also add more power (but I can't suggest one offhand, because I don't know what the hood clearance issues are). 1.6 rocker arms would also help because the stock cam lift is 0.410 I think, so you should gain 3 to 5% more torque everywhere from even using the $70 SLP-1023R rockers from Summit (self-aligning stamped 1.6 steel from Sealed Power). With the intake manifold and rocker swap (stamped 1.6 all the way up to the full rollers) I'd expect 20-30 hp total, which gets you into the 250-260 hp range, and that would put you even (or faster) than the best (stock) L98 Fcars.

Note well: your stock fuel pump probably won't provide enough volume to keep up with the stock LO5 above 4000 rpm; with any extra mods, the rpm for going too lean will get even lower than 4000. So replacing the fuel pump with a higher volume pump is almost required for even what you have now.

HTH.

 

It sounds like kdrolt has this pretty well covered, but I want to jump in and educate Mark about how computer controlled carbs DO exist

You'd see a nice gain in power with an LT1 cam, but you'd probably have to do some head work to bring those factory heads up to spec so they don't fall apart on you. You would not sacrifice much gas mileage with the swap, and it's pretty straight forward.

If you're on a tight budget I'd just do minimal mods in case something breaks.

 

True, but they're rather pricey, but then again, I guess by the time you add in a new dist it equals out.

 

Well one if your biggest issue, i ebeliev has to be the TB! which one doyou have ont hat motor? is it the 305 TB? if it is, you have a very large cork in your system... an upgrade to the holley TB would likely give you a pretty good gain.

As for the motor, it needs a mild cam, a free exhuast and something done on the intake side...

Steve

 

Thanks guys, you've all been a HUGE help.
This is what I've planned so far....


I'm going to pick up some Long pipe headers to replace the ever so restricting 305 exhaust manifolds..
I'm going to look into the TBI because mine is indeed the tbi from the 305 (with the the newly added cop caprice jets and a prom for the 305 camaro that is the cop car setting (no speed limiter etc))
I'll change the camshaft after my waranty is gone (I never even thought about that) I was debating replacing my current open element air filter with I think it was an slp dual cold air induction system. I think overall that would benefit my car more than the open element.

AS was stated somewhere in this article, I DID just get the car working and I'd hate to screw with it to the point that it stops, so limited things willb e what I work on for now.
THANKS SO MUCH guys,
-Justin

 

Oh man, I didn't realize you still had those crummy stock manifolds. Good choice on replacing them. Getting the correct injectors and ecm/prom is a great idea as well.

 

Unbolt everything from the intake and up and throw it in the trash. And then get a carb, TPI, or someother port injection setup. TBI and performance just don't mix. Seems like a lot of work to get 230-250 hp................

 

TBIs don't have jets. They have injectors. That's probably what you meant. The 305 PROM may be useful as something which could be reprogrammed, but it is NOT going to be correct in trying to feed a 350 with an L98 (LO5 9C1) cam. At the bare minimum you need the copcar (9C1) version of the LO5 injectors and the ECM that goes with them. The 91-93 Caprice 9C1 (whale style body) with LO5 reached 130, 133, and 132 mph during testing by the Michigan State police when tested with V-rated tires. So the copcar limiter, for that car/engine, is probably 147 mph even though the LO5 could only get it just above 130. So the copcar ECM will have a speed limit that is plenty enough for you to lose your license. So don't worry about the speed limiter. Instead, worry about getting that 350 the fuel it needs because it's probably running lean right now. And running lean is exactly how you punch a hole in a piston.

Repeat after me: copcar TBI injectors, copcar ECM, new fuel pump.

Then you can tweak the fuel pressure, and timing. And you will need to tweak them after you mod the exhaust, and perhaps less so when you do the cold air intake.



IMO the open air elements are easy to do, and cheap. And they make a lot of noise. But they are not as good as a decent cold air intake. You should read the tech article on DIY dual-snorkle air filter intake. It's cheap, and it works well. You did say in your post that you wanted cheap mods, right? Besides, you will be spending some money on the exhaust, so you need to stay cheap elsewhere.

FWIW, TBI has it's limits (as does TPI), but tossing it all in the trash only to replace it with something else offers a host of other problems. Keep it simple, stay with what you have, and do only the items listed above for now. Your car will wind up being just as fast (or slow depending on how you view things) as a similarly equipped TPI Fcar. 230 hp and 320 ftlbs should be enough to get you through life in the happy valley.

 

Quote:

Originally posted by kdrolt


At the bare minimum you need the copcar (9C1) version of the LO5 injectors and the ECM that goes with them.

I already have the injectors for the L05, and I have the Prom that goes in my ECU that have the cop car settings. The stock prom is gone now. So the car seems to be running normal now (except a high idle until I can get home to fix it). The only thing I need is a bigger fuel pump, I didn't think about that.

Quote:

IMO the open air elements are easy to do, and cheap. And they make a lot of noise. But they are not as good as a decent cold air intake. You should read the tech article on DIY dual-snorkle air filter intake. It's cheap, and it works well. You did say in your post that you wanted cheap mods, right?

I already have the open element, but I want to do better. I'll have to read the article on the DIY dual-snorkle intake. I've been trying to pick one of them up for quite some time. When I say cheap mods, I am looking for something that I can save for a couple weeks and then pick it up. What I'm trying to avoid is something that's going to be an expensive piece and a time consuming project.
The TBI I was looking at is something I'll look into, but probably not until christmas or summer rolls around (when I'm home to install such ideas)

Quote:

Besides, you will be spending some money on the exhaust, so you need to stay cheap elsewhere.

The only thing I need to do to the exhaust at this point, is to get the constrictive exhaust manifolds off and put some headers on. I've already got an edelbrock 3" catback sysem going out the car.

 

i have a l05 I can rebuild an put in the 86, but after some serious thought I figured i wouldn't be happy till I could easy crush mustangs and new f-bodies....so a 454 it is!!!!! in a gutted 86!!!

 

You can easily get 500+ horses out of a 383 without power adders or extremly high dollar parts. That is without all the added bull**** of cramming a bbc in our engine bay. If you want a thirdgen with a bbc (it is cool) then go ahead. If you just want to be fast, stick with a sbc.

 

I still think you guys are missing a big restriction here- that TB is WAYYYYY to small for that engine... 430 cfm will not make power on that motor.

I would say stick with the TBI- holley has TBI units that will support well over 400 horse.

Steve

 

Interesting how my topic has gone from cheap hp adders to adding 454's and 396's..
I think that come this summer I will be picking up that holley TBI and a new intake manifold, it seems like a great idea. (maybe I can con it out of the girlfriend and parents for christmas.. lol) and in the immediate future comes the long tube headers, because that exhaust is just so damn constricted.
One more question.. When I change to long tube headers, should I just get a new cat too? Would a better cat help my cause any? (personally I'd love to have no cat, but I don't know anyone to pass my car in emissions)
-Justin

 

Get a high flow cat.

You might be able to save some cash by using a GM TBI from a 454, if you can find one in the wrecking yard. I think they flow a lot more than a 350 unit and will support good hp

 

Definanatly spend the cash and get a hi flow cat...engines need some back pressure, and hiflo cats really flow quite well.

As for thr TB, maybe someone could confirm that a BBC TBI unit flows how much more. That would definately be a budget way out!

Steve

 

500 cfm 2 barrel carbs (i.e. 2 venturi carb) can flow enough air to support over 350 fwhp, based on engine dyno tests (example: see article in HRM on a mid60s Mustang set up with a 289 and 2v carb for a race in Mexico). Yes, a 4 barrel carb will flow more air, and therefore make more power but that's not the issue. The issue is whether a 2 v carb, or 2 v TBI can make decent power. The answer is yes, so long as over 300 fwhp is enough. Another example: at least one TBI forum member has dyno'd 310 crank hp on a 350 engine test while using the small 2v TBI.

The small 2 v TBI unit, a Rochester 220 TBI as used on GM 305 and 350s, has 1 & 11/16 inch diameter bores and is rated, AFAIK, at around 500 cfm. The TBI used (previously) on 454 engines has 2 inch diam bores, and is rated at 670 cfm. The Holley large TBI has the same size bores and is also rated at 670, if memory serves.

Based on bore diameters, the area ratio of the small to large TBI is 1.40, so the larger TBIs have 40% more flow area. Sanity checking the small TBI flow rating times the area ratio, or 1.40*500 = 700 cfm, so the area and flow ratings are fairly consistent with each other.

Summary: if you are on a budget, and having a ceiling of around 300 fwhp is acceptable along with retaining good throttle response for street driving, then the 305/350 TBI unit is fine. If you want more power than 300, then you will need to modify the small TBI (least expensive choice), or step up to the GM 454 TBI or Holley 670 large 2v TBI, or bite the bullet and go with a Holley 4 v TBI and manifold.

And yes, you could always opt for the carb, or a TPI, as so many have pointed out -- but there are costs and compromises with those as well.

Red_Demon said he was on a budget, so that's what these series of replies were intended to address. FWIW.

 

Well i was under the impression that actual flow tests rated the 305/350 TB at 430-450 cfm. Moot point really.

The fact of the matter is, to make that much power on a street motor with a restricted intake takes some fancy cam tuning.

Example? race motor in our latemodel stock car, had to use a stock unmodified, holley 2bbl 500 cfm carb... 430 fwhp.... it can be done, but only with seriously tuned cams and other stuff.

Fact of the matter is, a 350 needs over 600 cfm at 6k plus, meaning that TB is maxing out at around say 5200... probably out of your power band if you do any sort of cam swap.

I still think, in my own opinion, your TB should be on the top of your upgrade list-

Steve

 

You are still arguing about a lot more power than I am. Reread the posts.

I am using a ceiling of approx 300 fwhp. You are talking about 400+. The owner who started this thread is on a budget, and he's not likely to do anything but cheap stuff to his car/engine in the next few years (he's probably still in college given his location in State College PA). And he has no idea what 230 hp will feel like in his car, because his engine is being strangled with LO3 305 fuel delivery. 230 fwhp will feel great, and 300 would put him close to LT1 and LS1 cars.

I agree (and agreed previously) that for significantly more than 300 fwhp, ANY larger injection method (larger 2v TBI, 4 v TBI, modified TPI, LT1 SEFI etc) is required.

For the example you gave:

350 cid * 6000 rpm = 2100000 in^3 /min

now convert to cubic feet: 2100000/(12*12*12) = 1215 cfm

1215 cfm / 2 = 607 cfm

where the division by two is need to account for one intake stroke for every two crank revolutions. So I agree with your math but not with the answer.

The problem with your answer (600 cfm) is that you assumed that the VE (volumetric efficiency) is 100%. And it isn't. It's more like 90-105% at the rpm for peak torque, and thereafter the VE drops, as rpms increase, to 80 to 85%.

In a race motor, you might get a larger VE at high rpms, but the trend will always be that VE peaks at the rpm for peak torque and VE drops as rpms climbs. This happens in both street cars and race cars. The VE doesn't drop enough to overcome the increase in rpm, so that is exactly why power (which is really a measure of the rate of airflow through the engine) peaks in the 5000 - 7000+ rpm range (for decent street cars -to- race cars, with v8s).

If the VE was 85% at the 6000 rpm you furnished in your example, then the cfm is 600*0.85 = 516 cfm. And I made my arguments based on a nominal 500 cfm TBI.

FWIW VE is the ratio of actual cylinder filling, on each intake stroke, to the theoretical cylinder filling.

IN the race car you mentioned, you said you used a 500 cfm carb and made 430 hp. What that says to me is that you did a lot of work to the full induction tract, incl the carb, because 500 cfm isn't going to make 430 hp. 600 cfm will however, so the 500 cfm carb (and intake) probably flowed 600 cfm when you guys got done. And I believe that it took a lot of work.

So a 500 cfm carb/TBI is appropriate, even for your own example, and your own example dovetails with the HRM article I mentioned. They used a 500 cfm 2v carb and made 350+ fwhp at 6700 rpm, on a .030-over (IIRC) 289 v8. Could they have made more power with a larger carb? Yes, slightly more because the viscous losses in a larger carb would have been less at 6700 rpm. But it wouldn't make much sense to use a significantly larger carb, on that engine, because the low speed driveability would get a lot worse and there would be little point in using a large carb on a small v8, especially one running under 7000 rpm. And here we are talking about a street car, not a race car.

The 350 in question in this thread is not going to run anywhere near 7000 rpm, and it probably redlines (in the ECM) at 5000 rpm. The rpm ratio (5000/7000) more than makes up for the ratio of the displacements (350/289), so the nominal 500 cfm TBI is adequate for street purposes.

You can look in almost any serious book/paper dealing with engine design (C.F. Taylor books for example at the high end, Lingenfelter for more popular reading, Yunick, etc) and you'll find curves for VE vs rpm, and they *all* have the trend I described above. The modern improvement, which overcomes this deficiency, is where the intake uses runner lengths/plenums that vary length/size with changes in engine rpm --- this is equivalent to having TPI where the runners get shorter as rpm increases.

For the BMW and Mercedes engines (among others) that use variable induction schemes, they can get the VE to stay above 90% in a wide zone from 3000-5000+ rpm.

In summary, I don't agree that a TBI swap should be at the top of the list... but we can agree to disagree and leave it at that.

IMO the TBI unit (a Rochester 220) on the car is adequate for now, and perhaps for a few years. The fuel delivery is, however, inadequate because it's an LO3 (170 hp) fuel system (pump, injectors, ECM) trying to feed a minimum 205 hp engine. FWIW.

 

Yeah, i'm not argueing, just offering my onpinion i respect your opinion and reasoning too!

My reasoning is only takinng into respect that the 305/350 tb is closer to 400 than it is to 500. support 300 hp? yeah i could probably agree with that. especially on a healthy 305.

an lo5 with an appropriet cam in it should be able to make power right to 6-6200, and like you said, when you get into the higher rpm, you loose effeciency.


As for the race motor, there was nothing done to increase the flow of the carb, they had teching tool and they checked them when we placed in the top 5. The heads were stock chevy 202 castings, aside from the obvious valve/valvetrain and valve job upgrades. The intake was an edlebrock performer (not the rpm) All this was rule mandated. What we did have done was a cam that worked very well with a very restricted intake, it can be done, and if i told you the specs, i'd have my head hung by the engine guy, but if your well versed in cams, and how changing different values can help it overcome an intake or exhaust restriction, you could figuer it out i will say however, it was a 10.5:1 motor.

 

2x post

 

actually, while my budget IS limited, I am more so using this post for thoughts of what I should save for. at the top of my list is the headers and the cat, and followed shortly there after (when I get more money) the TBI and intake.. I'm also still going to look into the injectors.

While I have no idea what 230 hp from my car will feel like, I sure as heck know what 400+ hp from my corvette or 345 hp out of my dad's ls1 is.. Much better than mine.. That's all I can say