Hey guys, I was wondering if it would be worth putting any money/work into an LB9 (305 TPI) engine. Is it possible to squeeze any more horses out of it without a total rebuild? I'm talking cams, different intakes, blowers, etc. I have a 91 T/A 'vert with that engine coupled to a 700r4 and I was wondering if it would be possible to have it put out around 250 hp (stock is around 205 right?) and over 310 lb ft? I don't have any plans right now but I was just wondering if it is worth dumping money into these engines. And any idea how much fuel mileage would suffer? If I do pull this off someday I don't care about it sipping fuel since this is by no means a daily driver, but it would have to pass CT emissions. Obviously I don't want a ripped engine, just a mildly built one.

Oh and what are your thoughts on those programmers/chips? Any good companies?

Flat top pistons vortech heads comp cam headers = SLP stuff for the tune port should have you well over 300 hp

if you figured that the majority of parts are transferable for a 350 then it would make since to upgrade, exhaust headers, add some runners, do some port work, and then eventually get a 350 and all the parts will transfer over. but again i figure suspension is one of the biggest and first mods you should make. even a 305 has plenty of torque down low and im sure you have plenty of slipping in first, second, might want to eliminate that before you go adding more power and creating less traction.

Thanks for the tips so far guys. As for the pistons, that's a bit too much work for me at least for now. I'd like to do something where I can keep the engine in the car. Would it be possible to shave 1 second (or more) off of the 0-60 time with that kind of work? What are your thoughts on chips/programmers? What about cams? Ram air intakes? etc etc.
What I thought would be really cool would be to make the hood vents/scoops on my stock 91 T/A functional. Did anybody try that?

Hehehe yup! I remember one time I was going down a fairly steep hill in my Trans Am so I threw it into first gear to let the engine slow it down and the thing chirped the tires! GOD I'm such a noob!

So... Check it! I have 90 Iroc and have already put around 7K in suspension and engine mods. I can tell you that for around $2000.-$3500. you can have a LB9 put out around 300-330HP with minor chip programming, or unplugged sensors and a check eng light(which ever you choose) I chose to do the same thing (even when everybody said a LB9 was a dog) because mine only has 26K original miles and I want to keep the stock block as long as possible. It will get frustrating especially when it comes time to tune air/fuel and overcome the OEM ECM settings for emissions B.S. but, remember you can only go so far with a LB9. So if your looking to have a street screamer at 400+HP later on...save your money and move on to the 5.7 block. If you can live with a modest HP number and just want a 5.0 that will raise eyebrows then here is a list of what I did to get to the 300HP+ range The LB9 already has good low end performance, this will help it breathe better in the higher RPM range and extend the performance up the RPM range as well The stock heads will work pretty good with this set up for a modest performer. Again...there is a limit to what you can do with an LB9, so you need to make the decision now as to what your end result to be after the project is done.

58MM ported Plenum
58MM throtte body (BBK)
SLP Runners Ported Out
Accel HI-Flo manifold
1"5/8 Headers
Complete 3" Exhaust front to rear
Comp Cam kit (complete kit) 266HR-14 (part#)Ko8-304-8
MSD 6AL

Yea I just want something fairly modest that'll "raise eyebrows" like you said. Even though I'd hate to admit it, I think some "serious" ricers are faster than my stock LB9. So eventually I'd like something to hand it to em. Any idea how much those things on that list go for?

yeah! your right there are some rice burners out there that will spank your LB9 as well a mine but there are also some out there that will spank a big block in a quarter mile run but, think about it any one can dump 3K plus a 70mm turbo on a 2200-2500LB car and go fast. It takes brains and and commitment to push a 3600LB to 4400LB car down that track at 12 sec or better on all motor. Which would you rather be know for! Me...I'll take a good old fashioned small block over a 1.8 turbie any day. OK now for the info you wanted. Sorry to take so long to get back to you, I went to the beach for awhile. I live in Miami.

58MM ported Plenum(speed density) $125.00 EBAY
58MM Throttle body(BBK) $325.00 Local speed shop
SLP Runners $450.00(Year One) Porting Svc $85.00 local machine shop
Accel Hi-Flo Manifold Base$450.00 (Year One)
1"5/8 Headers $445.00 SLP (Year One)
3'' complete exhaust w/custom made 3" Y pipe ($500.00) local speed shop
Comp Cam Kit 266HR-14 ($790.00) Comp directly
MSD 6AL ($350.00) Year One
GRAND TOTAL $3520.00

Hey, before you swap to a 350 block, awitch your 305 heads to the 350 block. This sounds dumb but you will increase compression which will give you more horses or torque. This is true because the 305 heads have a small diameter right (less than 4" across), so when bolting on the 305 heads to the 350 block, there will be more space "used up" in the combustion chamber, a plus would be using flat piston.

Would knocking/detonation or something be a problem with that? Would it require higher octane?

And thanks for the tips guys, now I know what I'm dealing with.

Good question. I was givin that advice from Summit racing before I found out that my engine was actually a 350. This would be a quick way to boost compression. Can anybody answer this question for this gentleman? Will knocking or detonation occur doing this free swap ?

I've seen it done before (considering buying a late 80's Z28 with a 350 engine/305 head combo) I was just wondering if it needs higher octane or if the engine's life is shortened and prone to problems, etc etc etc.

personally, I dont know bro.

A 58mm throttle body is not needed a 305 TPI at all. Unless you're running a big blower or something. Its not even needed on a 350 for the same reason. And dont bother spending the extra money on a new Accel base, you'll just spend more money on the same Edelbrock base you can get for cheaper.

305 heads might have a smaller combustion chamber for more compression on a 350 block, but they also have smaller intake valves and smaller intake runners than 350 heads. Any gain you might get from higher compression you will lose in reduced airflow, as well as increased potential for knocking and pinging. Its not worth it.

Kevin91Z JUST SCHOOLED ME!!!!!!!!! I didnt even know that. You see, even the techs at Summit probably didnt know about the potential problems from switching heads. Good deal Kevin91Z. I learned something today.

musclecar70sfan, I think it would be better just off and buying a used 350 block. I bought mine at a junkyard for 75 bucks with the heads. If you buy the 350 and switch everything from the 305, youll have to get better injectors because the 305 injectors are i think are something like 22 psi and the 350 injectors are higher. Im not quit sure if there is any other mods to be done but I was running a 305 block with a 350 ECM which had a Hypertech chip and I never ran into problems until I threw a rod during a street race back in 2002.

305 TPI injectors are 19lbs/hour and 350 TPI injectors are 22lbs/hour.

I recently tried to dyno tune a 350 TPI engine with 19lbs/hr injectors, and it went lean above 4000 rpms.

BBBBAAANNNNGGGG!!!!!!! Kevin91Z just schooled me agian!! I knew one or the other injectors where 22 lbs, I just wasnt sure which one. musclecar70sfan, obiously Kevin91Z has some good knowledge of the 3rd gen F-Body. You the man Kevin91Z. So the 19 lbs injectors act the same way for all 350's? This would obiously cause a failing smog test right Kevin91Z? musclecar70sfan, I wish you luck with your car bro. Ill try to help you all that I can depending on my knowledge. Peace.

Lets start at the rear.....

3.42 gears
auburn diff.
TA diff cover
4th gen alum. driveshaft (to reduce rotating mass)
Tranny - shift kit, vette servos, etc.
FIRST intake
ZZ4 cam
Com CM pushrods and full roller rockers (self align)
Trick Flow 305 heads (this will bump the compression to around 9.5)
AFPR set to around 55-60 psi
Hooker or Dyno don headers
3" Borla cat back (dual cats)
Tune

Should give you 270-290 hp at the wheel (and I'm being consertative)

NOICE... well for the winter I might put in 3.42 gears with a posi/LSD along with disc brakes since I think my current (stock) one is a posi but with drums and higher gearing. What's the stock gearing? And would the car still be comfortable to cruise at 75 mph on the highway with the 3.42 gears?

And does a rear drum-to-disc conversion involve a lot of work? I'd probably buy a whole new axle that's used with discs on the back.

i agree with most of whats above ,but i would use zz4 aluminum heads or 113 casting heads instead which are much cheaper and the same cc...... cost about 1/4 the price used as the trick flows do new, they also work fairly good on a 350 engine to obviously.

no need for a first intake though... semi siamese your runners and plenum and thats more than enough for a 305 revving less than 6,000 rpms could ever need...

although he is being conservative i could see an easy 300 at the wheels off the above...

personally i have a fully ported/siamesed intake for my lb9, edelbrock headers, ported 416 heads, msd stuff, crane 2032 cam, afpr, k&ns, aluminum ds, airflow divider deal for the throttle body. i hope to make 300 fwhp and i only paid 125$ for a used cam, everything else i had lieing around the garage other than 150$ for the intake which i plan to sell my original to recoup my money there.

basically all i need to do is take the heads to the machine shop and get some bigger springs, screw in studs, mill the guides so they will clear with my 1.6 ratio roller rockers and im ready to throw mine together.

with just full bolt ons mine runs a very low 14 quarter to a high 13..... should run an easy mid to low 13s with the cam heads and ported intake on.

And that's all motor with a 305 tpi huh? not bad!
How do these things react to blowers? anybody try em?

Most autos had 2.73 gears while the 5 speeds got 3.08 and 3.27.

My 3.42 with the 700R4 spins around 2400 at 55mph.

Converting to disc is not that expensive. You could get what you need from the classifieds. You would need a proportioning valve.

I had an '89 with a 350/305 head combo, but the heads were the HO better flowing heads and I already had them on the 305 that was supposed to be a 350 in the car when I bought it. Basically the only reason I did it was because the car came to me with what was supposed to be a 350...well when I found a spun main bearing on the 305, I got a 4 bolt main block, but kept the 305 heads since the cast numbers verified at least it was better flowing. I had issue after issue getting that car to run right, programming/idle control, ping issues...yes it did need higher octane fuel and I got very little if any power for the trouble. The 19 lb. injectors were a problem eventually too and had to be swapped out...figuring out which sensors and how to program for a mutt engine was more complicated than expected...ESC unit was different between motors, injectors, knock sensor I believe, and a couple other things that made it a bit more difficult to get running smooth/right after the build due to the nature of it being a 350 with 305 heads and deciding which of the two sensor choices worked best. That was just my experience though and could have been just my build...maybe I had unusual issues that no one else had. Just putting that out there.

That seems way off. 2400 RPM in over drive should be more like 75 MPH.

I found this site when I was trying to find out the same thing as you. I just didn't see the need to get rid of my LB9 when I knew it could put out decent numbers. Check out this link: http://www.popularhotrodding.com/eng...cks/index.html. These guys put some really decent street power, that would have no problem smoking a rice burner, into a 305 for not too much money. Also, like someone else said, the parts would transfer over to a 350 nicely if you upgraded in the future.

I have 3.42s in my car with a 700R4. In overdrive at 70 mph I'm taching about 2400 or 2500.

Expect pretty decent mileage out of the 3.42s as well. I drove my car from Cleveland to Orlando and back and averaged 28 miles per gallon believe it or not. Mine is a LO3 TBI at the moment though. I would assume similar from a 305 TPI.

That seems way off. 2400 RPM in over drive should be more like 75 MPH.Thats funny. 2400 RPM... 75 mph sounds better.

Not that it matters, but come drive my car and I'll show ya at 70 its about 2500

No insult intended. Its just that it sounds funny the way its typed. On the serious note, 2500 rpms while hitting 75 mph? my wifes little 4 banger (Mercury Mystique) hits 3,200 rpms at 75 mph. Seems odd bro. Is your Tach working correctly?

Do the math and you'll see,

3200 rpm @ 75 mph in a 4 banger makes sense. The 4 banger needs the higher rpm to carry the car no matter what speed it is traveling. Which is why v6's and v8's will rock your world when you can get them to rev high efficiently.

Ahhhh. I learn new things everyday.

My 91 5 Speed TPI has 3.42 gears with the G92 option...

I would start bolting on things that you can use regardless of your engine, Panhard bar, rear lower control arms, sub frame connectors, strut tower brace, wonder / steering bar, etc...

Engine wise, the same, headers, 3" Mandrel bent exhaust, high flow cat, etc...

As for engine it'self, to take advantage of high flow base / runners, etc, new heads / cam would be in order & if you're gonna do that, might as well get a new 350...

Get a NOS TPI system & that should be plenty until you decide to get a new 350... For the 305's it says to only run a 100HP shot, but many here have run 150 shots with their 305's...

Rafael