I plan on porting some 305 TPI heads but while im having them ported what else should i have done to them?

Example, what size valves should i upgrade to? What kind of screw in rocker arm studs should i replace my pressed in studs with? What kind of springs should i get when im still running my stock cam?

Anything you can think of that i can tell the machine shop to do is appreciated. Thanks!

Ok, here's the deal... Porting the stock 081 heads is a great idea, but what are you using for your TPI set-up?? The stock base, plenum and runners are in need of porting/replacement as well.
On to your question, the ports in the heads should be MATCHED to the valve size, you can do this by making the runner's 165-170cfm intake, and running 1.84 valves with a good valve job (3 angle or more) or 1.94 valves. The stock bore is 3.736" and to help un-shroud the valves I WOULD stay 1.84, with a bass ad valve job. Rocker studs can be 3/8". As for valve springs all arent created equal. NOT even close. I like Manley Nextec's but im sure that would require some machining. Use any STOCK style size spring. I havent measured but im guessing they are 1.250" and you need about 120 - 135lbs of seat pressure for most cams with 240* duration or less and .525 lift or less. Roller tipped rocker arms (with roller fulcrum) that are SELF aligning and just for good measure get some new valve seals. You CAN use guide plates... thats up to you. I think they are over rated for anything that see's a RED LINE @ 6250rpm or less (shifting at about 5500). BTW: With ALL this work, get a NEW cam kit, or if your roller, just a cam. I would use a XE249 (flat tappet) - XE262 (roller) depending on how *good* your heads are. Of course, cam SHOULD be based on your cyl. head flow data!!! Get a print out, call comp...match it up. ALso, GET a throttle body and headers ASAP. This SHOULD be good for 230-250RWHP or 280-300HP@the flywheel.

Just looked at your cardomain and saw your tBi.... Go carb, or make the TBI regulator adjustable, get a spacer, and a tune when your done. Carb will make more power... even more than TPI (but less TQ than TPI)

a carb won't make any more or less power than TBI, on a simlar intake, thats been proven many times, as long as the mixture is right, the engine doesn't care about whats on top giving it fuel.

BS? I want you to take your hand and choke yourself! Now can you breath very well!?? Just because your some die hard TBI junkie, dont give out false info! If TBI made as much HP as carb, then EVERYONE would be using it. You can forget it! During my stint at UTI I did an 89 5.0L 305 firebird, with nothing but a cam change we picked up 18hp and 4 ftlbs from TBI to carb. Not to mention NO MORE PROM TUNING. I also have 10 years building experience locally here in austin. TBI is ok for stock, NOT going to feed his combo the best with mods. I have TPI and it still gains from carb. Oh and BTW, read my second post. READ before you post and make sure the info you give out is accurate!

No point to change FI for 300fwhp, BTW the stock TBI TB is good for 280fwhp.

For a proper running 300fwhp TBI engine, the fuel pressure regulator will have to be Vacuum referenced.

Large majority of 250rwhp up, TBI engines described on TGO have no spacer.

Correct. For a 300fwhp TBI with a VAFPR, EBL is the way to go.

It appers so on an engine dyno, but the real world is a whole different story. You can try to swap a carb on a LO3 to find out.

Yeah, and im sure you have put many cars on the dyno. It's not worth arguing about, I know what WE saw (that be about 30 of us) and I am aware of tbi's 280hp capability. Think about it, heads, cam, exhaust, intake...more than 280 at the flywheel... spacer does good on ANY TBI -Fact... now, if you still want to waste time arguing, go ahead. Original Poster, listen to me, I have worked building Hot Rods for 10 years in Performance Shops in Austin, TX. A carb WILL make more power than TBI - with the mods mentioned.

Well 2 more years experience tuning the TBI with EBL flash, and you will be telling us different experiences.

As long as your TPI set up isent restricting the engine's power potential, it is the exact opposite of what you are stating.

Hey, IF you had read what I told him when I found out he was TBI then I dont know why you are trying to prove something thats already been said?? Also, carb is better, for power. This hold's true until RECENT EFI systems. I didnt say there was anything wrong with TBI, just it has its limits. TBI IS NOT the best induction method, hate me then get over it.

As long as a TBI system is set up correctly, tuned correctly and is not restricting the engine's power potential, a correctly set up and tuned carb is worse.

and i dont think you'll get the same fuel mileage from a carb as a tbi

EFI is better for Mileage... I just dont understand why someone would take the time to sit on there pc, and tell someone TBI IS better when, a) IT DOESNT flow as much CFM b) THROWS A FIT at any cam too "wild" for the ECU c) Is used as a MILD performance application IN EVERY car it has been offered in. d) Needs someone to spend lots of time to get tuned properly ultimately costing MORE than a carb for the average person. THIS IS WHY it often gets swapped for a carb. Ask anyone who ISNT biased towards TBI what makes better power, you get answered with carb. Sorry man, but just because YOUR camaro uses it, and it's not someone's top choice for performance; you get mad like I am saying something to someone the MAJORITY of the performance WORLD doesnt already know! Tune all you want, TBI has limitations, parts wise, cfm wise... SO WHAT! SO does TPI, its restricted with the long runner configuration which is DEAD after a certain HP level. I just told them I made more power and a little more TQ switching over to an Edelbrock 1406 (of all carbs, lol) with a performer intake and a stock vacuum advance dizzy.. Thats NOT even a performance carb!! Its for reliability, driveability, and economy. I even told him what to do with the TBI!!! lol You know, im done with school today, this thread couldnt look any worse because someone took GOOD advise and made it personnel. Thats the internet for ya!

You pointed out 300fwhp, so, no need for a carb.

As for saving $ with a carb, only if you do not drive that car.
The upgrade of the LO3 TBI to support 300fwhp is not going to cost much more then a carb swap.

And no, you cannot swap just the cam in a EFI car, then for comparison, slap on a carb, tune it and come here and say the carb is better.

Look fellas, I am saying, a carb will make more power than a STOCK TUNED STOCK TBI unit. thats it. Most people who build can understand a few mixture screws better than an entire prom reprogramming process.... Can we just drop it? You arent telling me anything I dont already know. I have had 3 TBI third gens, I researched adding power to them VERY thoroughly. There really is NO argument here. Sorry for the misunderstanding... I couldn't be more clear this time. See ya.

there are bigger throttle bodies out there, cheap too, I picked up a 454 TB for $50, and I'm sure there are many out there for less.

I'm not a "Die hard TBI junkie", (hence me putting an LT1 in my L03 Camaro) and it's not false, not even close.

HSR makes as much power as a carb, is everyone using one, with better drivability, is everyone using one??? nope.


first, 18 hp and 4 ft lbs, really wow, that's a ton OMG! , to me that sounds like someone got close with a tune, but not spot on.


oh wait you said it, maybe you should heed your own advice.

he was refering to a ulitimate mod TBI having the 300 FWHP limit, you can get 454 TBIs that support much more.


FALSE WRONG DO NOT LISTEN TO THIS!!!!!!!!!!!!!!!!!!

The TBI injectors spray fuel in a conical pattern at the cylinder walls to help with fuel atomization. with a 454 TBI unit, it's not hard to move the injector spray pattern to high. if you were referring to a plenum spacer, you're still wrong, high velocity makes better power and torque than flow alone. too much plenum volume and fuel will fall out of suspension resulting in a loss of power.

you should really read the stickies on this board, power is all in the tune.


TBI will net you better fuel econ, esp with EBL and it's lean cruise mode.

CFM is not always the answer, also, EBL supports 2 throttle bodies, and if you can't feed your motor with 2 454 TBIs, then it's probably not a street car.


https://www.thirdgen.org/forums/tbi/...i-buildup.html

that's fast355's budget TBI build thread, running an LT4 cam, I know it's not all that wild of a cam, but it's no slouch either, esp for a street car.



WRONG AGAIN!!!

Haven't you ever heard of crossfire fuel injection??? yep TBI, it was factory on many corvettes, and some Z-28's and Trans Ams.

I believe it was RPO code LU5 IIRC


so does a properly tuned carb! just because it's running doesn't mean its right!



I'm not mad, just frustrated with ignorance.




so does a carb! yeah you can get a bigger or better one, but not in usable (I mean bolt on and go, not rebuild and then go) condition for less than $100.

a well set up TBI will make just as much power as a well set up carb on a comparable motor. thats fact.


School has just begun, you're not giving good advice, and I haven't made any of it personal. in the long run, it's his car, and it doesn't matter for me what he does to it, but I've owned enough Carb cars to know I don't want another unless it goes 7's in the 1/4.

you don't say, really?


They think they understand, but like I said in my last post, just because it's running doesn't mean it's correct.

I could argue against that. judging by your posts.

Ok, so you say i'm wrong for suggesting a carb when, what you say a stock TBI system can only support 280HP, but were talking 300 or more?? Then i'm wrong for saying TO USE a spacer when there's nothing wrong that? Then you guys say, that im wrong for saying a carb will out perform a stock TBI system?? THEN you dont believe I have owned a 92 RS 305 TBI, a 89 RS 305 TBI and an 89 Firebird 5 speed TBI all 305's?? Get a life already. Post what you want, I am officially done arguing over nothing.

You need to read this thread before you continue to make an *** out of yourself:

https://www.thirdgen.org/forums/tbi/...ferrerid=35855

423fwhp & 423fwtq out of a 305 with pretty much garage and budget mods. And thats with a throttle body that will flow about 700cfm.

The limit of a stock 2" bore 454 TBI unit is OVER 500 HP on a single plane manifold.....A taller injector spacer than what is used on a stock 454 TBI is not needed.

The factory TBI Marine engines ranged from 280-310 HP from the small blocks and Mercury Marine had a single TBI 405 HP big block that was designed for heavy boats...AKA low-end and midrange grunt not a race engine.

I mostly play with my 2006 Quad Cab Hemi Ram (getting a custom Crower ground 268 cam and Flex-a-lite 183 E-fan kit next weekend) now, but I still have the TPI Van and still play with it on occasion.....I have it torn apart and am porting the intake base and installing SLP runners.
Its sad that my moded hemi Ram is just now passing what my 305 TBI van did in the 1/8 mile.

http://www.youtube.com/watch?v=HUFeRMCb244

I was looking for that thread,

Not on a stock LO3.


If you do not know what needs to be done to TBI and the TBI tune to support some moods, do not come here and say carb makes more power on a engine combination, were a correctly set up TBI is wery capable of handling it.

As many times as I have used that thread for reference or showed it to someone about TBI, it should really be a sticky IMO.

I have it saved as a favorite. Reading more about Fast's TBI build and all the others, I have since decided to stick with TBI. It's like a carb with fuel injection...best of both worlds as I see it. Can't deny the potential of TBI.

I've saved it too. Been wonder about buying a 350 crate engine and sticking my TBI on it with some mods to make it better for a 350.

Ok, you can think im ignorant all you want. I am NOT making an *** of myself. I simply said a carb will make more power than TBI (meaning a stock TBI system). Next, your going to tell me that the tune wasnt spot on.. How do you know? Did you see the a/f chart? Houston summer heat with houston humidity kills HP and TQ. BTW: Tuning was done via UTI instuctor, tell him from the internet his tuning is off, im sure he will agree . What Else? Oh yeah, CROSS FIRE INJECTION. Its capable, just not in stock form the intake manifold needs major porting to remove the restrictions (the ones that are about a half a port wide). When you do make a high HP X fire, it usually ends up being X-RAM! I have spent a lot of time at the crossfire injection vault back when I had one.
FYI - I swapped the cam, then we tested with a MODIFIED TBI system (fuel pressure mod was done with a dremel and drill) and it was too lean. So the instructor sold me a carb/intake for $50.00 bucks. I got the dist. from another student for like $60.00. I never mentioned ANYTHING about a modded TBI not working, so mentioning "454 that" or "this thread" goes against NOTHING.
Bottom line, your school session advice has been basic info thats been available on this board since the 90's, so it's in fact useless to argue with someone who knows already! I have been on here since 1995 just in-case you didn't know. Oh yeah, carb BEAT the stock TBI system in my case. Get over it will ya? There's nothing you can do to change it, it was 9 years ago!

The stock TBI tune is almost incapable of running the stock 305 TBI engine. Do any change, no matter how minor, the engine is going to suck green donkey dick 24/7/365. And the tuning required to make the mod work is almost damn near impossible without the EBL. There is a great thread over in the DFI forum about how people would expose the PROM chip to UV light to erase it, then rewrite it with a PROM burner and the tuning was literally done by best guess. And that thread is a sticky and most of the posts were from 9 years ago.

Fast forward to today where we have realtime readouts of how the engine is working with almost instantaneous feedback of what parts of the tune worked and what parts didn't through the EBL. Back in your day, tuning required the patience of Job and the wisdom of Solomon in order to be anywhere near close. Erase, burn, dyno and repeating those steps until you got your desired results. Today its flash, drive about, log the data, review the data and repeat until you get desired results. Its no longer a blind shot in the dark.

And if you think TBI is no good, TBI was developed in the 1940's for large fighter aircraft piston engines. Those engines were rated at operational altitude for well over 1000hp and in most case the engines were supercharged to produce over 2000hp. Its all in what you do and how you do it.

did I read this wrong?

its not about whether it's capable or not, it was a stock TBI hi po, yes it's laughable by today's standards,but it was a high performance option.

typically bone stock Gen 1 third gen parts don't perform optimally. I didn't think that was rocket science. and if you've got a dremel, all you need is a couple of carbides and a gasket kit and you can do it yourself for cheaper than most intakes would cost.

the fuel pressure reg mod does nothing if your pump doesn't put out more pressure than your reg is set to, if it's the stock pump, you're prob over that threshold.

I agree....Back when I did work for CCS Tuning in Pflugerville working for Jim P. And Real R. Jim made me a chip for my TBI Camaro. Bone stock I think it gained like 9hp?? Sound right? Maybe it was 6... anyway it wasnt anything to write home about but the area under the curve was better and ran smoother and cooler. This was about three tries into it, which everyone knows it takes at least twice that amount of data. Nevertheless it was tuned on a mustang dyno and made 160 something HP at the wheels..... My point is this was 2005, and that was the last I have heard about running TBI beyond the point of keeping up with it. I consider TBI to be VERY reliable, great for economy and it has a nice sound to it when it's got an open air cleaner element. Back in world war 2 the planes were supercharged, mainly the P51, which actually had a Rolls Royce Merlin V12 for power (P51) and the Corsair had 1800+HP with a Pratt and Whitney "Double Wasp" Radial engine. YES these planes were pressure injected, a variant of TBI... Albeit a nice one because as far as I know a TBI equipped camaro can't fly upside down like a P51 can. All tho Im sure there's an ex-m u l l e t sportin Hagar fan who says otherwise...... (I use m u l l e t in the sense of style back then, not a put down) Anyway, war planes are my other love! Off topic,, Wiki has all this info under fuel injection BTW. Later.

Well see, mild performance application in the terms of an auto...Im sure there's something out there that used it effectively with more HP than our beloved camaros... Lets talk about Xfire performance numbers... For their day they were NOT good. After the 60's and 70's people said WTF is this SH!7! It would be like us getting 200HP vettes in a couple years after the ones we have now... without the understanding of programming the thing!
Hi-po option offered yes, hipo performance?? Not by a long shot! See where i'm going??? The fuel pressure mod helped out a little from what I remember.

He hasn't quit yet???
Bring yer 650cfm brick with a hole in it up here.
Well see how it stands up to my e-licktric brick. Might wanna check yerself, I gotta EBL.

Quit already you are wrong.
It can be done.. maybe not by you, or those you know..

Is this the type of "tech" these "schools" put out?
Your "stint" at UTI was a waste of time & money.
Sadly, yes, and the bike "schools" are worse. A graduate of MMI could not diagnose primary ignition failure. Another "trained expert".

goin for a quotie mark record here..

Not exactly that bad, wenn you upgrade the exhaust and get a little better air cleaner, even on the stock tune the LO3 makes more power.

A stock LO3 with a nice EBL tune is not going to make huge powergains, it will be more accurate resulting in better overall efficiency.

Lets not forget the multiple (expensive) restrictions of our LO3, exhaust, 2.73 gears, cam and cylinder heads, that make it a simple cruiser. Its not about what fuel injection is used.

If these components, would have been matched to our stock TBI capacety with matched fueling and tune, from the factory, the "LO3" thirgens would have probably been a healty 280hp car.

Though 280hp and affordable fuel efficient v8 would not have fit in the same category anymore.

Sry got off topic

Quality valve-springs that fit come from K-Motion, K700 under .480 lift K750 over.

Have the upper guide/seal boss cut to allow .580 lift..trust me.

I use 7/16 studs, 3/8 pushrods & guideplates, no BS on valvetrain. I flog my mice.

3/8 screw studs will be great, money is tight for most, but if you can, do it.

I think the pressed-in hold OK under .480" lift and less than 350# open spring pressure.

Swirl & neck cut stainless valves are worth their weight..Manley or TRW.

Those heads will benefit from pocket porting, most shops have the cutter..but sensitive to ramp & intake port-side, guide work..best left to a pro.

Port match to intake gasket & intake.
Get happy (smooth, not a lot bigger) with the exhaust ports.

I like the big TBI cuz it's like a tiny, 2bbl, electronic Ron's toilet.

The bird catcher solved the bug catcher problem..

I am wrong about what exactly?? Why dont you mind your own business? and - Actually, I went to UTI via Firestone to get a raise when I was done, it paid off and fwiw, I knew most of it before I went.....UTI knows how to tune EFI. I wouldnt talk about stuff you dont know, like the nitro in your screen name, im sure you know all about it. dont cha?

I cannot believe so much **** over a carb swap. No wonder people think white trash when they see a third gen, who gives a **** it was MY car??? Nitro, when you are in the pits working on TFH or Top Fuel (actually working on one) not standing there like an idiot telling your buddy dumb **** like most of them do....then let me know. Your right about one thing though, UTI was a waste of cash, all $2800 I had to pay back!! I learned how to work on diesels and got any job I wanted when I was done.....but as I said, most of it was already known so your probably right... anyway....I am done with this thread.... It seems almost every post I look up on TGO its got someone acting like an ***. No one knows everything about every aspect of performance, theres too many styles and classes.... also .... Ch3, like my PM says, if your in Texas, let me know, otherwise shut the fk up. No one wants to read this internet BS. Grow up already and drop it.

It was meant more as a figure of speech. Although, my IAC somedays has a mind of its own.

I 100% agree that the EBL by itself won't make huge gains, but it does allow the engine mods to be maximized more than they would be with the stock ECU.

Some TGO members have experienced and reported valve spring failure (broken) using that brand of valve springs.

Thanks for the posts that were on topic. I asked Bruce at HAWKS if he could do those modifications to some LB9 heads and he said they could for $1200 (which includes the price of the heads which are $150). Is that what i should expect to pay for this type of work on stock heads?

$1200 is too much. I would seriously consider Vortechs before that. Also, you can look at TFS aluminums, or maybe this Brodix head thats in another post
http://www.pa305sprints.com/2009Rules.pdf
FWIW my machinist can get 220's out of 416's for $700.00, which is an early LB9 head.
Sorry for the off topic BS - later.

roger that, if anything ill just buy the heads from HAWKS and have someone locally do the work for cheaper. The whole point of porting stock heads is the budget factor for me, like you said with $1200 i could buy some alum. aftermarkets. Thanks!

Roger that? What branch? What unit? I was 11B infantry with the 25th i.d. scofield barracks, HI. Stryker Brigade. (Not to hi-jack the thread) Also, I have a member on Maliburacing.com who is interested in some Sprint Car 305 Brodix aluminums. So...maybe we can get enough interest to get a discount if vortec's dont end up being significantly cheaper.

Depends on how they do it. If this is something they don't get very often, that would explain why it costs more. Or it might be that they get this request fairly regularly and have a machine that they have to pay for like this:

http://www.centroidcnc.com/cncvideo/...d_porting.html

That machine is junk! I have one in my garage!

I highly doubt that. An entry level 5-axis Haas will run you $100k. Thats a highly specialized tool and I'd be willing to bet that its at least that much. I also doubt that machine is a piece of junk, I'm betting its more like operator error or incompetence.

I learned how to CNC machine on a Fryer MB-15 4-axis vertical mill with an ANILAM M1400 controller. When it takes 2 CNC operators 4hrs to setup a mill, you'll know you've got a touchy mill. I was making intake runner molds for someone and it took 2hrs to send the program to the machine and then another 2hrs to reboot the mill and get it running again.

Although, I must say, when it was a small program (under 10k lines of code), that thing was absolutely great to work with.

That was a joke...hence the Anyway, the machine is sweet! If hawks uses that I will be surprised.

There is a lot to be done to have a nice set of 081, its probably only cost effective if you DIY.

In the end http://www.summitracing.com/parts/TFS-30300005/ may end up being a better option.

Why not the EQ vortecs? Given the chambers are all bigger than the cylinder, I am leaning towards those. Also, the Brodix head looks fine, I am getting some pics of the heads to post up so we can look at them but im tired for today. later

The flow numbers of the TFS 175 on a 305 bore are still impressing, out of the box.

The vortec intake manifold, the EGR plumbing adapting the brake boster vacuum line and trottle linkage add expenses.

What does brodix have for 305's?

Look up the 305 Racesaver engine post in General Tech, I just started a topic on it this morning. 435hp+ 305ci in Sprint Racesaver Series. All specs and parts are there. Even a pic... I am trying to get some more tech data for us 305 guys who have a desire to use what we have.