Hello all. I have done a search for this, but it seems that most guys were having bogging issues at low rpm or at idle.

I have switched my '90 RS 305 TBI stock air filter with an Edelbrock open element 14x3. At any point below WOT, it feels much better than before. However, and 100% throttle, it bogs. When I hold back just a bit, it accelerates much harder.

The filter is the only aftermarket part on the car. Is it a fuel flow issue? Has anyone found a solution to a similar issue?

 

Yeah, sounds like its alittle lean. You'll have to get an adjustable fuel pressure regulator or make yours adjustable.
You can try the coin trick too, place a quater or nickle on where the spring sits, this adds alittle more psi.

 

Thanks for the tip. I was hoping that just an intake wouldn't require any extra work, but Lord knows that with an older, high-mileage car, everything may not be pumping at max pressure.

 

welcome to the forum

 

Thanks for the welcome.

This is the first Camaro I'll have owned for more than a month, and it feels nice to have such a cool sounding and looking car.

 

Do you really need more fuel for a stock engine with a new air filter? Mine seems to be doing this with my spectre filter, but I figured it's just cause TBI L03 engines suck ..

I've got a full 13PSI. Would making it adjustable and bumping the pressure up really help any? I don't want to run rich.

 

A 14"X3" open air element on a TBI can only help and should have nothing to do with bogging at WOT.If you beleave it is than switch back to the stock and see.(Im sure you plugged off the now open vacuum port with change,right)As far as my 5.0 is concerned bogging off the line at WOT was fixed by bumping my timing to 4* advanced,(helped allot just by itself and now has excellent throttle response off the line) and a gear ratio change from 2.73 trash gears to performance 3.42s with a Eaton Posi. Also installing a Corvette servo in my 700r4 helped tremendously with firm gear shifts.I can "bark" them shifting from 1st to second and "chirp" them from 2nd to third at WOT.Do all the basics with your TBI, 5.0,auto and than include the gear ratio change and you can have a car that's not only fun to drive but actually will push you back in the seat. Bump your timing and see if that helps. If not put it back.Including the timing bump and the upgrades listed in my signature have made a "very" nice improvement over a untouched 5.0,auto with stock gears.

 

did you block off the vacuum port from the lines that went to the stock air cleaner? did you check to make sure you didnt knock anymore loose?? have you put the stock one back on to try it? what did you do with the air temp sensor??

 

Well wait a second here. There cannot be any "vacuum" lines in the air cleaner assembly. There is only "vacuum" below the throttle blades ... Also when I built my car (I got it without an engine and trans) I did not receive the complete air cleaner assembly and subsequently have never used it. Currently I have a 9x2 non drop cleaner on there from spectre. It's a Spectre 47708 ... it was $30. I had no air cleaner. I had to run that same day, and it was in my hands already and I knew it'd work. As far as my air charge sensor, I got a 5/8 hole saw and did this:



Also don't look at my vacuum leak. I've already fixed that ..... I had timing at like 4 or 6 before, I can't remember, but it would knock under load. I have it at like 2 or 4 right now.

Just curious, but what is involved with swapping the diff? Will I need new axles? I have a non-posi 2.73 ... really kills a fast start, I'll say.

 

Yes, I have to run a mid grade 89 octane fuel in order to use a 4* setting .If I understand correctly you have the vacuum ports on the front of the TBI unit plugged off,right? There are 4 on the front and one on the rear.One of the front ports will be opened/unplugged when you take off the stock air cleaner assembly and need to be plugged. If its left open it will cause a major vacuum leek that can cause a variety of problems. As far as building a new differential there are a few different ways to go. I went the path less traveled and built everything from scratch with totally new parts that is shunned by most because of price.I have my reasons for doing it this way and saved a long time to have it done. Then there's the more common "swapping" to the 4th. gen rear,or finding a third gen at a wrecking yard that fits your needs. I'm not real familiar with the last two but can show you some photos of the build I had done.
My 10 bolt upgrade =
$700.00 for master bearing kit , axle bearings and seals, 28 spline axles, including 3.42 ring and pinion, and labor ,$535.00 for Eaton 28 spline Posi.,$169.00 for LPW Ultimate support cover.Total = $ 1,404.00 .Having to up grade to the 28 spline axles is what cost me a little more.

 

Well I bumped it up to 6 degrees just now when I gave her a bath. I guess if it starts knocking again I'll add some octane booster, considering I literally just filled up with 87 octane. Either way, I'm okay with going to a higher octane if it stars knocking. It isn't all that much more money IMO. From my initial test after setting the timing though, leaving the trans in 2nd and break torqueing will burnout ... so there's definitely more power to be had from a timing boost.

I'll post back with results, but again with my initial question: Do I need an adjustable FPR when I have 6 degrees of timing, open element air cleaner and headers?

Also I think I'd rather swap the whole rear end for a 4th gen or 3rd gen posi rear .... sounds like a way cheaper option.

 

Yes, that's the more popular option when it comes to rear ends.
"FPR" ?If that stands for Fuel Pressure Regulator than no it dose not need to be altered, I'm running 13 PSI with the advance,and open element, but still have the stock manifolds and Y into a Magnaflow cat and 3" American Thunder Cat back.CA smog is a little strict on exhaust tampering "cat and forward" limiting the header option for me,and I have chosen not to pursue it.
(These cars seem to act a little different with timing adjustment,some liking more.Some liking less.)Even with just a 4* advance mine with just a tap will lurch forward on the line.Once you get that rear done with at least 3.42s and posi/LSD your going to love it.A Corvette servo.upgrade for a 700r4 is a fairly simple procedure and made a "very" nice difference in shifts. Even when the trans down shifts you can feel it very well.=
http://sethirdgen.org/servo.htm
I bought mine at Pro-Built Automatics for $22.00.
After I did that swap IMO,a kit is not necessary .I decided not to let any one touch my trans. with a kit.(I have trust issues with mechanics) .

 

Well I think I figured out my bogging issue ... sounds like my cat exploded and went into my muffler ... It's a big quicker than before, with the 6 degrees of timing and throttle response is better, but I noticed it not only bogged at WOT, but it's also lacking in the high end speed.

Also yeah FPR ... sorry I meant fuel pressure regulator. I'm thinking I'll "fix" my cat. Then put a 3" cat back on it with a new muffler. I'll also do some porting work on my TBI. That servo sounds pretty easy to do .. I'll have to think about that one. This is a freshly rebuild trans, so I don't know if I want to get into it just yet. I think i'll focus on my exhaust and perhaps the rear end right now.

 

The only three pieces connected to my airbox were the sensor, the THERMAC, and a breather from the top end of the passenger side of the motor. I disconnected the THERMAC, moved the sensor to the firewall, and put a breather filter on the breather.

I've found that when the car is properly warmed up (120 degrees or more), it doesn't bog nearly as much.

 

Mine is almost the complete opposite of what you describe. Mine warms up in a matter of minutes, and ALWAYS runs its best RIGHT after you fire it up and when its cold.

Now .... here's a thought. My ECT has its plastic connector busted off the top ... so I have the pins standing up and the connector snugged up on the pins. What if ... the sensor is backwards? Don't ask, it was an engine install casualty.

 

I realize this may be a very rookie question, but is the AV adjustment only something to worry about on carb engines?

 

i also have a question about the open air element. i have the 305 tbi and installed the open air element. i plugged what needed to be plugged and the car ran terrible. it would rev up while i was stopped and then kinda sputter and feel like it wanted to stall out. i took it out and put the stock unit back in and now it runs good again. so what could the problem be?

 

AV = Audio-Video?
Depends on the adjustment of the TV cable from the transmission.

AV = Air valve?
TBI doesn't have an air valve. Quadrajets have an air valve.

GM has better engineers than the folks who make and sell open-element air cleaners?