LedZep

iTrader: (22)

Ok so I have a pretty much stock 305 TBI w/ Cold Air Induction Box for the Power Bulge Hood. I have read some articles/blogs on increasing performance on a stock 305 TBI and it seemed like replacing the intake was the best first step. My question is if I go after one in Classifieds, what should I be looking for and out of curiosity does having the air box make any difference in what the intake will gain or what I should pick?

The only other real upgrades on the car is a high flow cat + 3" I Pipe to an 80 Series Flowmaster. I also upgraded it from a 2.73 open to a 3.23 SLP Posi.

So basically I am looking for advice on what type of intake I should be looking for in Classifieds. I would be willing to spend up to $150 if the part mattered that much between the higher cost one and a lower cost one.

Also what type of HP do you think swapping the intake would make? Would doing the "Ultimate Throttle Body Mod" also increase the benefits of a new intake?




Here are some old pictures I dug up randomly:

LedZep

iTrader: (22)

Nobody has any input?

skirkland1980

iTrader: (2)

Maybe because this is such an old subject. Any mods you make to a FI engine may present demands that may actually hurt performance. A good thing to do is install a wideband make sure it doesn't.

LedZep

iTrader: (22)

I realize asking any questions about upgrading any third gen is an old subject, but isn't that the point of these boards? To ask questions about our cars and if interested in doing upgrades and want specific opinions rather than following a thread, you make a thread

All I wanted to know is what type of intake to look for, as I know it is one of the easiest upgrades to increase HP. I was also curious if having a functional power bulge hood CAI would play a role in anything.

You are suggesting installing a wide band air/fuel (O2) gauge if I even touch the motor? Changing just the intake is going to throw off something that badly to need to change it?

86firebird350

The next big upgrade for you shouldn't be an intake manifold as they aren't a big restriction on a mostly stock 305 TBI. Your next upgrade should be a set of headers to go with your hi flow cat and cat-back exhaust. That will really open up the car and maximize what you've already invested in. You should also consider getting some sort of tuning software (i would recommend EBL) to get everything out of the motor thats possible. I would almost go so far as to say you should do this first before anything else.

krazeefewl

iTrader: (1)

If i remember correctly there are 3 options for an intake manifold. Holley makes one, Edelbrock makes another, and I forget who makes the other one. I've heard the Edelbrock Performer TBI is the easiest one to install with the least modifications. IMO if you're going to spend the money on an intake getting an open element air filter will be another good/cheap upgrade as these things don't breath very well to begin with. I've been looking into doing the Ultimate TBI Mod myself, just haven't gotten around to it, and don't really know if I want to spend the time to do it as a different engine will be going in the car eventually. Hope this helps

skirkland1980

iTrader: (2)

I was answering your question about lack of input...Yes. The wideband will allow you to monitor your mods. If your intake causes your engine to go too rich then you will need to tune it. Or you could swap to a carb while you're changing the intake.

LedZep

iTrader: (22)

Thanks for the input and I'd like to get a set of headers, but the cost for a good set is too high for my budget. I'd also need to get a larger Y-Pipe too if I was going to invest in a set of headers. I guess I could look for a set in Classifieds to save some money. My problem with headers is two things, heat and they always seem to get loose.

My next step is going to be the Ultimate TBI Mod and I can't decide if I should go with a dual snorkel setup or not with my CAI from the hood. What do you think about that? I considered completely sealing off the air cleaner and doing away with the snorkel, but I don't think the air box is big enough to deliver the air I need solely from the hood.

Anyway you gave me some good things to think about and I will hold off on an intake, although I still think it might provide more gain for the cash than headers + y-pipe.


I used to run an open element and I prefer the CAI from my functional power bulge hood. If anything I would go with a dual snorkel air cleaner, but then I would just pull in less cold air from the hood as I talked about above.

Do you guys think the air box pictured above is large enough to deliver 100% of my air intake or do I need the snorkel? If you think I need the snorkel, should I go with duals? Also how much gain do you think I would get from a filtered lid to pull air in from the top too.


Thanks for everyone's input.

86firebird350

Some headers come with a y-pipe, though I can't remember which ones do and which ones don't. You'll definitely want to save up for a decent set. Don't skimp on headers. As far as heat, there's little difference between cast iron manifolds and steel headers. If you're really concerned about the increased temps, you can have the headers coated and/or wrapped. And making sure the bolts are tight is part of the job. The headers (and consequently the bolts) will require several heat cycles to break in and "settle" so to speak. After a couple heat cycles and tightening you should be good to go.

If you're looking for a good bang for the buck, seat of the pants type mod, underdrive pullies are a good investment. They're really cheap, easy to install and you'll notice a nice bump in throttle response. A lower temp thermostat is also another one that you can do. I recommend a 180 stat. Also play with your timing a bit. Most of these L03s like a little more timing than stock. 6* was a good spot for me.

The ultimate tbi mods are a good idea as well. the more air you can get in the motor the better.

krazeefewl

iTrader: (1)

I'm not too familiar with the power buldge hood, or the functionality so I can't give any advice on that. As for the filtered cover, any increase of surface area where air can I get in would be of a benefit, as for how much I do not know as I haven't looked at any data numbers. If you're looking for a dual snorkel set up, this is what the PO of my vehicle put on

It looks nice, but I don't like what he did to get it to fit. (Hacked up A/C Bracket and cut up the A/C box/evaporator in the process) None of this was necessary, just being lazy and making it look like a 10 year old did the work.

I agree with 86Firebird350. The more air you can get into the motor, the better.

86firebird350

With that said, I would like to point out (and maybe I sound like a broken record here) that if you can't get that spent combustion mixture OUT of the engine any faster/more efficiently (headers) it won't matter how much air you push into it (intake manifold, air intake) because you'll hit a bottle neck. That's not to say you won't see any difference if you do these things first, you just won't see as much gain with them until you take care of the primary restriction in your drivetrain.

LedZep

iTrader: (22)

Any advice on my questions about what to do with air intake from the hood vs. using 1 or 2 snorkels or closing the air cleaner assembly off all together and only pull from the hood?

I'd like to figure that out and I have found a K&N XStream Lid for $40 + SH, so that will help with pulling in air.

I realize the restriction of the stock exhaust manifolds and I would like to change them to match my high flow cat + 3" I Pipe + 80 Series Flowmaster, but I don't see it in the budget right now. For the Y Pipe and Headers I am looking at at least $350, even in the classified ads I have seen. Going ceramic coating will run another $100 or more, so you can say all day headers, headers, headers, but to do it properly is going to cost a pretty penny. I think I will just keep an eye on the classifieds and maybe stumble across a good deal.

Thanks for the advice and I'd really like to hear some opinions on what to do about running a functional power bulge hood with snorkels or without.

86firebird350

Your air intake setup is really a matter of personal preference. If your hood opening is functional, i would definitely try to use it. Due to its size, I wouldnt use it exclusively but it's always good to get fresh air directly into the air charge when you can.

LedZep

iTrader: (22)

What if I modded the air box so the outlet hole was larger and in turn modded the inlet hole on the air cleaner larger?

zenish

let me throw this in for discussion.what about 305 vortec heads and duel plane intake and adapter OR gm tbi vortec intake.i didn't suggest the 350 heads since the compression would drop and the valves would be too close to the cylinder walls.

lozantius82

iTrader: (1)

If i was you bro id bump up the base timing or purchase ebl and tune your combo right!
GM left a lot of improvement and the swirl port heads build tons of torque when matched with the right camshaft. I would also do all of the ultamate tbi mods and headers too. TBI gets no reaspect buddy, but when you mod it right the look you get when you say its TBI is priceless!!!! lol

LedZep

iTrader: (22)

Well I just ordered this Injector Spacer (http://www.jegs.com/i/JEGS+Performan...15410/10002/-1) Except I got the exact same part new off Ebay for $12.27 w/ Free Shipping.

and today after pulling some parts I am going to perform the Ultimate TBI Mod

Does anyone know of a good alternate to the K&N XStream Flow lids? I know other companies make them, as I have seen ones that are blue before. Is our size 14" to fit the stock air cleaner (not an open element)? The reason I ask is because a guy was trying to sell me a used one he claimed fit the stock assembly that was 14", but I know the outer diameter on our filters is 12". I guess since I want it to fit on top of the air filter instead of cover the entire top, it confuses some people.

Assuming all of those changes, how much HP gain do you think I should get? 5-10? Will the CAI from the functional power bulge hood make even better use of these changes?

LedZep

iTrader: (22)

Here are some shots of my throttle body after removing the throttle bore ridge:








Like I said earlier I have the injector spacer ordered and on the way, but I really don't think I am going to shave the throttle shafts. This seems like way too much trouble for very little difference. Does anyone have a strong opinion on doing or not doing the throttle shaft mod?

While waiting for the spacer to arrive I am going to send off the throttle body to be cleaned by a buddy who works on carbs almost exclusively (he owns a performance car garage) and then I will bring it to a polish after it is cleaned.

LedZep

iTrader: (22)

Does my modification job on the throttle body look good or should I make more of a curve? Also can I take out more material to make the overall inlet of the venturi bigger without screwing up anything?

I'd really like opinions on if it is worth shaving the throttle shafts or not. It seems really risky for the slight difference it would make. Can anyone give me their opinion on that part of the Ultimate TBI Mod:

thomas1976

What you did with the TB is ok, but you could take all the ridges off. Here a pic of what it would look like. https://www.thirdgen.org/forums/atta...s-dsc08618.jpg
Do not waste your time with the trottle shaft, stock TB flow around 440 CFM http://www.summitracing.com/expertad...cfm-calculator as you can se it is nowhere close to maxed out.

Concerning the stock intake manifold, if the engine is making less then 270 hp then it is not restricting.

On a side note, my 360ci TBI kills stock LS1 4thgens and GTO's and it has only a 46mm TB and 48mm bore TBI performer intake manifold.

The air cleaner on your car is a cool piece, the dowside is the design of the base, the inlet pipe in front of the thermac is also really small. An upgraded version would be awesome, but it is a DIY way.
Here is what I did with the basic air cleaner https://www.thirdgen.org/forums/tbi/...l-diy-tbi.html

For hp gains you would be better of by start looking at cam, heads and what goes with it.

LedZep

iTrader: (22)

So you can take off all ridges without any issues with mounting the stock hardware back on?

I was basing my cutting/grinding/sanding on this picture by NEEDforSPEED

(https://www.thirdgen.org/forums/tbi/...owing-tbi.html)

https://www.thirdgen.org/forums/atta...g-tbi-end1.jpg


I'm trying to get the most out of the motor without having to get into internal components. I'm saving that for when I pull my 89k mile 305 TBI out of my wrecked parts car that I've been selling parts off (https://www.thirdgen.org/forums/inte...ula-305-a.html).

I'm going to put that motor in my 160k mile Formula 305 that I am running right now. I'm trying to get as much sold as possible before pulling the motor/tranny and I have got a decent amount sold. I hope to do the swap when it warms up again and while I have the motor pulled I will probably swap the cam/intake/heads and hopefully put headers on it to complete my cat back setup.

In terms of the sport hood air box, I know it is not the absolute best in terms of air intake (it is a stock part), but pulling cold air directly in has to be better than having a dual snorkel setup. I'd like to know if I could close off the assembly completely with no snorkel and get enough air from the air box. However the only way to truly test that is to put it on a dyno and that isn't an option for me.

I could make the inlet hole to the air cleaner larger and make the hole to the air box larger, but then the part is modded and if I ever wanted to sell it, it would bring much less money. It is a rare part to find, especially the TBI one (vs. the CF one) that isn't damaged.

I appreciate your input, please elaborate on taking off more material from the throttle body. If possible provide pictures of yours or a throttle body removed from the car without it assembled showing exactly what you are referring to. Although I am pretty sure by your picture what you are talking about, I want to be sure. I also want to be sure it won't effect anything negatively, be that performance or mounting the stock parts back.

I'm assuming you are talking about these ridges:



Don't these serve some purpose with assembling the TBI?


Thanks.

thomas1976

I bough my TB from Tom Miller at Turbo City, a while ago, you can se the pics of his ported unit in the attached link, supposed to flow 620 CFM with the spacer.
http://www.chevyhiperformance.com/te.../photo_05.html

(The ridges, was probably GM's "innovation" to keep the dirt out in poor maintenance situations.)

LedZep

iTrader: (22)

But those ridges I marked are the ones you are talking about correct?

thomas1976

Yes, the ones you marked included.

krazeefewl

iTrader: (1)

I like the progress you've made, makes me want to take mine apart and do the mod this weekend. Good work.

LedZep

iTrader: (22)

Thanks, I'll post more pics up after I take off the ridges marked in red.

LedZep

iTrader: (22)

Ok, that is done







and the injector spacer just happened to come today

LedZep

iTrader: (22)

Guys when I was looking over the throttle body for cleaning, I noticed a problem inside on the interior wall of the venturi.

(this picture is obviously from before I did the second part of the cutting/grinding/sanding)




Two questions:

1. Was this a casting mistake when it was made or was this done over time by usage.

2. What is the best way to go about fixing it or should I just leave it alone. I had one person suggest to fill it with a material and sand it smooth, but I think if anything I should have both venturis ported slightly bigger.

What do yall think?

thomas1976

Oh boy! You are asking the same question twice on the same bord

I gave you my opinion in your other post here https://www.thirdgen.org/forums/tbi/...-wall-tbi.html

Probably casting imperfection, that part is not machined.

But your porting work looks good!

Now it is time to build that 305 to make power up to around 6000 rpm, to take advantage of the potential of the ported TB

LedZep

iTrader: (22)

Yea I made a second thread about something having nothing to do with anything intake related. People aren't looking in an intake manifold thread to give opinions on throttle body venturi damage.

I didn't know it was a big deal.

Thanks for the compliment on the mod though!

edited

LedZep

iTrader: (22)

edited

not getting non A.I.R. equipped headers

LedZep

iTrader: (22)

I decided to pass on that set of headers and Y-Pipe to look for a set that is A.I.R. equipped and like I said, I wasn't very fond of the locally made Y-Pipe.

nando5

Did you put the TB back on?
If so did you notice any gains?
If it has noticeable gains i might be thinking of doing this mod to my T.B.

LedZep

iTrader: (22)

I haven't had time yet to put it back on and I still need to clean the entire throttle body, but I suspect it will have a noticeable gain with an estimated 15% more air.

Right now I am too busy pulling parts for people to sell.