Hi, I know this has been covered to some extent, but I never found anything that said what the best thickness would be.
I'll be making one at work out of aluminum, unless there is a more suitable material.
I'm going to do the Ultimate mods at the same time.

I have an LO5 in my truck. I have a cold air intake setup, and a 24" glasspack. I'll probably get a carb intake, or headers next, with more mods to come with the money.

I understand that more then 1/2" will cause trouble with the cables.
What aboue the fuel lines?

I'm looking for mileage mainly, but a lower rpm for my max hp and Tq numbers wouldn't be bad.

I have looked at anything from 1 1/8" to 1/4".
I don't want to go too far because I don't want to mod the bracket more then nessicary, but I don't want to make it too small and get no gains outta all this work.

I'll be making my decission based on what you guys think, so if you have any opinion please feel free to express it.

Thanks

 

I ran a 1" spacer on my 92 GMC truck with the L05 and didn't have any cable issues. I did have to tweak my fuel lines a little.

 

here is a site that covers tbi spacer thickness:
http://members.aol.com/j007golden/modeval.html
it says 1/2 thick max due to breather/hood clearance.

I guess I should have read your question better, this article is for 305tbi birds not trucks. sorry

 

Don't go any higher then .5 or you will have to modify your cable bracket like I did on my LO3. But if a 1 inch works for the LO5 then go for it.

 

I guess there isn't a way to know how much spacer you need otherwise I would have gotten more responces.

Anyone know how I should find out the best thickness?

 

It really doesn't matter. Just go with .5" inches and you won't have any problems.

 

Well I'm sure it makes a difference. If it didn't then why add one?

If your a spacer nay-sayer then thats fine, tell me not to add it.

I'm atleast doing 1" now. Thanks bharris
I want to remove the collar that goes between the aircleaner housing and the TBI.

Thanks

 

It seems you don't like yhe answers your getting here, Maybe you should go to www.offroad.com or www.4x4wire.com and talk to those guys. They might be able to tell you what you want to hear.

 

I've run both 1" and 1/2" spacers in my car and did not notice any difference between them.

I started out with 1/2" which did produce a noticable difference in throttle response. Since I could make them myself, I went to 1" because my Caprice had the hood clearance. I didn't notice any further gains from the 1". I changed my airbox this year and had to go back to the 1/2" to gain some clearance and, again, did not notice any difference in switching back to the thinner spacer.

This is just my personnal experience. As there are lots of combos out there, someone else may have different results.

 

LoL, ok do what u want. I never said it was a bad mod, I told you to go with the .5" spacer because I went with the 1" and I had to modify my cable brackets cause it was to high. Thats what I said and thats what I am saying now. How is that not the anwser your looking for?

 

I thought that IS what you said LOL

 

Thanks Paul

Maybe you don't care about the details on your car, or getting something right the first time

If you mean answer my question. I'll look into that.
You might look at www.chevytalk.com they always come up with good ideas. Maybe even the high and mighty can learn something too.

All's I'm saying is that I don't want do this twice. So I asked a question. Just because I drive a truck doesn’t mean anything. I'm just glad Low1500 is getting some good times. To prove to some that trucks have an internal-combustion engine too.

Will someone please close this thread?

 

Well it's like 91Bird305 said; 1/2 is what you need, and you did'nt like his answer. Or maybe you just did'nt read it. Either way no need to reply, I'm sure this thread will end; Unless of course, you have somthing else to say. And I don't think anybody said, bacause you have a truck you shouldn't be here. Just said you should probably check out those other sites since you did'nt like the answer you got here. So all I got to say to you is GOOD LUCK in your quest for the answer to your question.

 

i have a 91 firebird and a had a custom one built out of phenolic 1 1/8 and since the fuel lines are routed different than that of the trucks i never had any probs with the lines or cables or hood clearance either .and i do feel a big difference in my 350. i average about 24 mpg with this as a daily driver and thats with headers also.

 

Yeah, I am telling you your not gonna notice a difference between a .5 spacer and a 1" spacer. If you do, its all in your head and u should go get in dynoed and see your real anweser. Its a spacer, your not gonna notice a difference at the seat of your pance. Go run it in the 1/4 mile before and after and post your results. It adds a little bit but nothing dramatic or amazing. So when I say it doesn't matter, I stick to that. Get a .5" to avoid problems with modifing your brackets (atleast in the firebird/camaro 305 TBI's u have to with 1" spacers) or do whatever u want.

 

Thanks jlbolin


It sound's like your thinking I'm going for track times(you know who you are). I'm looking for economy. You've proven you don't know the answer ,so quit posting.
Thanks

 

If you can make it out of a glass reinforced plastic (like G10), then it will work better than aluminum. Keeping the TBI cool will help reduce the heat soak to the airflow, and using aluminum will only transfer the manifold heat extremely well to the TBI body... which is not what you want to do. There may be other composite materials you could use, but make sure that whatever you use is impervious to gasoline.

I doubt the spacer will help that much for fuel economy purposes, but if you can make one for zero dollars and minimal effort, then it can't hurt to try it.

BTW is your stock intake manifold divided into two plenums (each plenum pulling from only one TBI bore), or is there only one big single plenum? (plenum is a term for big volume)

The only benefit I could see to reduce friction, or enhance resonance filling (both which can increase fuel economy) is that a short spacer with the bores open and connected to each other would allow a dual plenum design to pull from BOTH bores of the TBI. This was mentioned to me once by a non-3rd gen TBI owner and it does make some sense, but I would think it would have the best gain at the highest engine speeds. So I really don't think it will help much in the fuel economy dept.

FWIW. - Ken

 

Once again, ur not gonna notice a difference in your fuel economy either. You want better fuel economy, take out your cat, upgrade your ignition to either MSD or Accel and do a full tune up. My LO3 made 17mpg city and now it makes 20mpg city.

 

Again thanks kdrolt

Sooo... Mr Bird your saying I shouldn't do it? Are you saying that you don't think this will help? What your saying is that I'm not going to notice any gains. Ok so I shouldn't do this mod, even if its free. Gee thanks what whould I do w/o your post whoring.

I'll just do 1 5/32" that should be just perfect.
Thanks for helping me make my decision

 

listen im not trying to be a pain but my car has no cat, has a 97' z-28 exhaust that i needed because old rusted clean through, this car had 196,000 when i bought it from my sister, by then it was losing cmpression andsoking as soon as you start it up. with in 6 months i pulled out the 305 and put in a 350 from a 94 silverado, now this motor has a slightly bigger cam and just barely.but i have been drivving for 1 month and got about 23. i dont get there to ripp up the the pavement. maybe once a week if in a descent mood. after i bought the headers and made the spacer i averaged 24mpg. i dont know how far you drive to work but it 1hr and 45 mins to work for me one. and that cruse set on 55 cant afford to set at 60 on the road i travel on . the state patrol will swarm yu . like i said dont mean to make anyone upset.and my throttle cabels were not modified any whatsoever and my spacer is 1 1/8 inch and the only thing needed modded was my fuel lines and all i did was that the bolt onthe intake next to the throttle body that holds the fuel lines down, i loosened this bolt completely and raised this where i needed it and thats it. later.gotta help a butty do his 89 formula in the morning.by the way my car does have a 5 speed dont know if that waould make a difference but guess ill find out in the morning. hope this helps!

 

Jesus dude, I am not saying that at all, I am just saying, there are better fuel economy mods out there then just adding a spacer. Do the g o d d damn spacer at 5 f-cking inches, I don't care. Just giving u some other options too, ur not gonna notice that much fuel economy from just a spacer though. G o d damn ur a f-cking dick head.


He said it wouldn't help either, jump his bones too and call him a post *****.

 

HOT DAMN you go 91bird305..
I think he should understand that. Well maybe

 

Thanks jlbolin.

What? I don't get it.
You don't know your a post *****? It has to suck to be in the dark. You should come out of the closet. You haven't added a single positive letter to this post. I knew from the start that cables would be an issue. That is the only reason you have given to make it a set height. Go back and read the opening thread. You should read your posts too, they are... something. Real creative with the whold spaces and - you used. Impressive.

:hail: :lala:

 

The ultimate mods are agood idea.

For better gas milage and increased HP, I would lose the EGR.

 

Nope, doesn't help either. EGR does not effect performance (turns off instantly when going WOT or in PE mode) and it increases gas milage by letting in less oxygen into the intake = a cooler combustion (less o2 burning) and you can pump up the timing (highway mode) resulting in good gas milage.

 

Without getting into tuning parameters...


I'm pretty sure the EGR only feeds the right bank of the motor (ie: the side without the O2 sensor) So Emissions would be lower (the whole point of EGR) but since the same amount of fuel would be going into that bank (which now has less oxygen) , the motor will have to be under a little more load, because of the lack of clean air to burn all the gas. WHich means more gas going in to sustain a given vehicle speed, beasue of the increase in load. I say all this because when I looked at my old stock intake it looked like the EGR only fed the one side.

Now even if it fed both sides, I still feel fuel consumption would be higher:

1) Your heating the already burnt air again, which is an increased loss of heat out the exhaust (ie: decrease in thermal eff)

2) Your motor will make less power because of the decrease in fresh air coming in, so an increase in load will have to happen.

Edit: Its pretty late right now so I'm not thinking too straight, I know that the prom has VE correction tables for EGR %, so It must flow to the wole engine, but even still I don't see any way it could increase fuel milage. Now changing the commanded air to fuel ratio will change milage, and you can add hiway spark just as easy without EGR.

 

I can only respond against your second statement because I don't understand what you're trying to say with the first one.
I stand corrected after looking through some stuff Grumpy did with EGR. EGR will effect performance a little if you have a crappy exhaust setup that is too small for your motor. Built up backpressure can cause the valve to open so yes, EGR can be a problem but only if there is a major exhaust restriction. Now about the loss of power and increase in engine load, yes, that can also happen. The difficulty with this is you can't over generalize something as being good or bad without knowing the WHOLE picture. From what I've gathered the loss in power from EGR is still nothing compared to the increase in engine load, fuel consumption that is. Think about a 3600lb vehicle and think about the hp needed to accelerate or better yet sustain a specific mph. When you work out the physics you'll see that it doesn't take much if any power to do either. Now if you look at an engine's design you can pick up lots of power, just look at vortec heads for a prime example. They can make more power with less fuel just by the design of the chamber. Doing little things to make an engine more efficient is the name of the game for gas milage. Without EGR my car now gets the same gas mileage as the stock motor mostly because of tuning but also because it's just that more efficient.
As far as hot exhaust gas, it's next to nil but dramatically effects the potential of the intake charge. In the next few examples it's presumed that air and fuel are proportional to keep a specific AFR.
Running normal amounts of oxygen you can run normal timing. Increase in oxygen like with no EGR, N2o, super/turbo charging you need to remove timing. Consequently replacing oxygen "fresh" air with exhaust fumes and crank gas vapors will allow more timing than normal to keep performance from really suffering. The other effects are air fuel ratios (AFR). Under normal daily driver conditions a ~14.7 is a target AFR for the ecm. Running leaner AFRs allows you to run more timing (hence highway mode and increase in gas mileage) but at a risk of engine damage, higher emissions, and performance. Rich AFRs are for max torque and result in better performance but require less timing. Power adder engines are a perfect example of this. They require timing to be pulled or they'll do internal damage.
If you want me to go on about how and why AFRs are so important I can or if you don't understand why an AFR needs to be richer than 14.7 to make peak performance then let me know and I'll go on.

 

No need to exagerate. I apprecieate all the info I have gotten from this thread and Thirdgen in general.
I will be doing the Ultimate TBI mods and my EGR is long gone. I have winaldl running already and I'm in the process of making a chip burner. If that works out then I'll be adding the Hiway mode for sure. Also I think getting the perfect chip would add the best power and mileage. I'm a perfectionist, if you couldn't already tell. So it will be the perfect chip.

Again thanks to EVERYONE.

 

I re-read my last post and changed a couple things in the 1st paragraph, maybe It makes sense now.

Jon,

Good point about EGR having a lot of other varibles invovled, I agree.

Could they make an egr system for major fuel economy? YES

Could they make an EGR system for lower emissions? Yes

I do think the heat loss from heating up that extra CO2 and H2O is somthing to bring into account. When at cruise your butterflys are barely open, and since the egr orfice is about 3/8", I think there is a decent flow there.

One thing about the vortec heads over stock one is:
My motor uses about the same fuel from 1000rpm to 2500rpm as my old cam'd up stock motor, but It makes alot more power now. I always have thoughth this was do to the Vortec CC's too.

 

EGR isn't just on or off, it's a pulsed signal just like a sub woofer if you can imagine. What it does is pulse depending on the need for EGR. With a large cam EGR is not needed at idle or low rpm because there is already a LOT of self-EGR happening, anymore and it's overkill.
The major issue seems to be exhaust backpressure. If you've got a free flowing exhaust system then don't worry about the EGR opening up, if you have stock stuff then it could definatly be an issue even on a stock motor.
Vortec heads kick serious ***. The intake ports and combustion chamber make serious power by creating "swirl." I haven't taken much of the fluid dynamics classes to understand exactly how the flame swirling has an effect on power but it obviously does. Vortec = good mild motor if you're looking to get into the low 13's and pass the sniff test without EGR.

 

The EGR valve is still opened by manifold vaccum, The computer just attemps to throttle the flow to the diaphragm. The ECM can pulse as fast as it wants to but there is still a large lag in the air line..... but this isn't really relative to anyhting at all.

I have taken a few fliud dynamic courses, but trying to explain or figure out what goes on a cylinder heads ports or combustion chambers would be next to impossible (nothing is close to linear). But I think the combustion chamber's swirl makes more power because the fuel concentration is closer to the spark plug (@ TDC), and since the mixture would still be swirling when ignited, I think the burn would be a little more uniform (for the most part happening at the same time), than that of a tradtional head.

I agree about exhaust back pressure being a big factor. After all this talk of EGR all I can say is let the jap cars use it, me I'm happy without it.

 

The flame-front speed is pretty poor in an IC engine, so having swirl helps to mix fuel with air and it helps to convect the flame front into areas of the chamber that might not get full combustion. So it helps power and fuel economy, as well as reducing HC.

You won't get much help in Fluids I & II to see how swirl helps. For that you'll have to do outside reading. - Ken