84z5350

hey guy's it's been a while since i posted but i have been dreaming about a dual tbi set up on a 350 in my 92 rs. but im not sure if it's gonna work or not.and i would like some input before i get started and to involved .

so far i have picked up a edelbrock tunnel ram.i have numerous sets of heads both old style and new,tbi units,

what im not sure on is what mods i have to do?
pcm, what cam to run on somthing like this

ok what set of heads should i use on this?
14101083
14102191
14102193
14014416
3998993

im gonna check my pistons today so ill post what i find there

and i have a set of heads from a gm replacement block that do not have a casting # does anyone know how to i dentify these?
now i know that these heads are junk but its what i have and cant afford to purchase new ones at this time.

if any of you have any input please post

Ronny

iTrader: (1)

Search threads by simpson36. He developed a dual TB setup(net 4 barrel).

Are you doing due to need or just for WOW factor?

Do you need a 1000 CFM capacity? It may prove to be a tuning nightmare....

84z5350

nah im looking for some wow but mostly holy ****!!!!

i am looking to use 220 tbi units
dont have a need for 1000 cfm just want to c if i can make it work
thanx for the tip ill see if i can search it

Ronny

iTrader: (1)

220 are single bore?

84z5350

oh ok i was on cfm and must have mis read i thought stock 350 tbi was a 220. if they are not what are they? i have some from a 4.3 some from 305 and 350's the bore size is the same right just the injector size is different right or am i wrong on that two?

92RS_Ttop

iTrader: (3)

Sounds like you're looking at truck TBI units? I have a couple of them laying around as I was thinking of doing the same thing in my 92 someday. The "220" is cast on the throttle bodies themselves, and I believe its more of a model number than anything related to CFM measurements.

A few thought from the little bit of research I have on this idea:

2 TBI's can feed a 350, check out the link below. Its from a Chevy/GMC truck forum where a member did this to his truck.

You will DEFINITELY need a way to tune the ECM, or go aftermarket. I will probably go Megasuirt on mine if I do this

You need a way to drive both IAC's

IIRC, in the link I have below, he had to turn one of the TBIs around to get them both to fit on his manifold

You'll need a new fuel pump to handle the demands of the 4 injectors

Different truck engines used injectors with different flow rates. You should really get yours tested to find 4 that are very very close to flow rate. Otherwise tuning may be difficult.

http://www.fullsizechevy.com/forum/g...bi-mockup.html

Ronny

iTrader: (1)

I think the TB on the 305-350 flows 530 or 550. Not sure. Yes the injector(s) vary.

https://www.thirdgen.org/forums/tbi/...tbis-dual.html

92RS_Ttop

iTrader: (3)

AFAIK, bore size is the same on all but the ones used on the trucks with a 454.

Stock CFM I believe is around 450. I know I have the actual number around here somewhere, just can't find it right now. It very well might be 220 per bore.

Edit: Just remembered where I found that CFM number. According to TBI Chips.com the stock TBI bores flow 450CFM:

http://www.tbichips.com/truckmods.htm

84z5350

i am just wondering if anyone can help me with choosing witch heads to use from what i listed above and maybe a cam sugestion thank you keep in mind that if the tbi idea dont work out than im gonna have to go carb so i dont want a cam thats too radical

92RS_Ttop

iTrader: (3)

As far as which heads to use, it will depend. I am assuming the intake manifold you bought will fit all the heads you have available.

The 14014416 heads(416 commonly) are 305 heads but will work on a 350. In fact, I'm running them on my 350 right now. They work well with a carb and can flow pretty good with some decent port and bowl work. There is a great tutorial on here with lots of pics by Sitting Bull on how to port these heads. Only problem you may run into is they will raise you compression ratio and depending on what pistons you have may be unusable due to this. I have stock dished pistons and am running around 9.2:1.

The 14101083 heads are stock 350 TPI heads IIRC. They use center-bolt valve covers and will not work with same intake manifold as the 416s.

The 3998993 heads are old 70's smogger heads. I believe they are commonly referred to as "boat anchors" around here. They will work, but if you have ANYTHING better, use them. These will fit the same intake manifold as the 416s.

The 14102191 heads are also stock center-bolt style heads. Same manifold problem as the 14101083.

The 14102193 heads are basically the same as the 14102191 heads. They are truck TBI heads and good for low-end torque, but bad for top-end horsepower. They can't flow much past about 4k RPMs or so. No better than the 993 boat anchors.

84z5350

so my choice than would be the 416
the pistons that im running are the mahle flat top 4 valve relief
not sure about the compression tryed to run # from them today but found nothing the 416 are a 59 cc head arent they? will they work or am i gonna have to run airplane fuel? hah hah

84z5350

i was told that the 65 were they way to go (tpi heads)
i have modified the 4 center intake holes in the past to fit the older intake to the newer heads

92RS_Ttop

iTrader: (3)

The 416s are 58cc.

Yes, the center bolt holes can be ovalled out to fit, but getting the gaskets to seal right can be tricky. I have the same situation on my truck - PO swapped in an older engine but kept the original TBI manifold. It never sealed right for him and he had all kinds of vac leaks because of it. I've swapped gaskets twice already and still can't get it to seal right. I bought a pair of correct heads and will swap them in this summer to finally take care of it.

What are your goals for the engine? Do you want a drag racer, or a corner-carver, or a stoplight-to-stoplight machine?

I'm not sure which heads you mean by the "65 heads"? You mean the 083s?

Compression ratio will definitely be a problem for you. Even with figuring a .030" overbore, and a thick .040 head gasket you will be at almost 12:1 compression ratio. I'm assuming .020" on the piston height. Here is the calculator I use:

http://www.csgnetwork.com/compcalc.html

Assuming the TPI heads are 64cc chambers, which I believe they are, your compression ratio will be around 11:1 using the same measurements as above. That's still really high for iron heads.

84z5350

yes i was told that the tpi (083) would be my best choice but im not to thrilled about that high of a compression.im just looking for a week end runner that i can drive into town maybe twist the tires and get home before the cops catch me haha no really just want to build somthing that no one in this area has. thats why i would like to run the dual tbi 2 barrel's but even though it will look good it still needs to run. i dont have access to a drag strip in my area so that is not needed.witch ones would you put on if this was your choice. im not to good with the mathmatical stuff but i will tak a look at your link

84z5350

this is what i found about my pistons that i have in my block
MAHLE

1.5, 1.5, 3.0mm File Fit Performance Ring Set included

362 4.060 492 11.4 10.6 9.9 SBC550060F4V

not to sure if this helps but from what this says if i run the 58cc heads with these pistons i will have 11.3:1
and with the 64cc i will have 10.5:1
and the 72 cc i will have 9.8

http://www.mahlemotorsports.com/C125...20complete.pdf
if this makes any sense please someone say somthing

92RS_Ttop

iTrader: (3)

Yep, those numbers pretty much match up with what I got. The site I linked above doesn't require any math. Just need to know some basic measurements.

I would go with the 191 or 083 heads. If you don't mind swapping out the pistons for something with a dished top, the 416s would work nicely. With the pistons you have though, they will be useless for you.

84z5350

you kinda confused me on that last one. are you saying that my pistons are useless or the 416 heads are useless in this combo / the tpi's are what were on this block when i got the car it ran great i was not sure if they would run good with this intake and the dual tbi setup and if i should swap out the cam for somthing different

84z5350

ok not to keep going on this and agervate any one but if this tbi idea dont work out and i have to run carb does anyone have an idea on a carb size and posibly a compression ratio i should shoot for

92RS_Ttop

iTrader: (3)

Sorry about that. What I was trying to say is that your pistons and the 416 heads will not work together. The compression ratio will be too high. You can either swap the pistons out for dished ones and use the 416 heads, or you can keep your pistons and not use the 416 heads.


As far as using a carb:

Compression ratio requirements will not change. The carb does not determine what compression ratio you can run. If you aren't planning any kind of forced induction(turbo/supercharger) then you can run anything from 10:1 and lower. If you will use some type of forced induction on the engine, then you will want to stay below 8.8:1. Your flattop pistons will make it very difficult to get the compression ratio that low however. (I don't get the impression your planning on running any kind of boost, but thought I would include the info just to be complete).

The camshaft requirements for running a carb are less strict than for running any type of EFI system. EFI systems need lots of vacuum signal, so lobe separation is usually 112 or more, IIRC. Carbs can run on less lobe separation to provide more overlap and better exhaust scavenging.

Carb size will be dependent somewhat on the heads and cam you use, but as a general guideline I would stay around 650-750 CFM.

84z5350

ok got it now, so if i use the tpi heads at 64cc and the flat tops it will be respectivly at 10.5:1.now i still have the tpi cam witch ran great with a edelbrock 1406 last year should i leave that in the block or is the tbi cam different? remember i want to start with the tbi setup first than if it dont work go with two small 4 barrel carbs (like 390'sor 400's)

92RS_Ttop

iTrader: (3)

The TBI cam is definitely different than the TPI cam. However, it is also a "weaker" cam in that it will not produce as much power as the TPI cam. If you don't want to purchase a new cam and lifters, then stick with the TPI cam. If you plan on purchasing a new cam and lifters, then there are much better cams out there. While I understand the basics of cams and how they function, I'm not really qualified to recommend one beyond what I mentioned about the lobe separation above. I'll leave that to members that are more qualified.

As for the 10.5:1 compression ratio, you should be fine there as long as you don't mind paying for premium at the pump.

84z5350

just got of the phone with edelbrock they dont have a cam to match up with aything that i have and dont recomend using the gm tbi stuff they say its crap and wont make big power.he just wasent understanding that it is only gonna be a to the car show and home kinda car.he want to sell me a multi port set up to change the intake to 8 seterate injectors wit 2 tbi units just fore the air. oh my head now hurts and so will the rest of me when i tell my old lady that the intake i just spent 300 on is worthless to me!!!!

Ronny

iTrader: (1)

1992 Camaro RS? 1228746 ECU. It will not drive 4 TBI injectors. you would need to go aftermarket. dynamicefi or megasquirt for ECU. We are talking a bit of a chalenging project here. Edelbrock may have given you good advice. Port fuel may be the best idea. Use two TBI units without injectors/pods and have that manifold drilled for 8 injectors. Power it with aftermarket ECU.

84z5350

ok than lets say we go that way do you have any links to sites to get me started. do you maybe have any $ figures on that type of system?

Ronny

iTrader: (1)

1. dynamicefi.com ECU with optional port mod
2. machinest will need to drill your manifold for injectors(summit) or buy an Edel Vic EFI small block or Pro Products at less cost. Fuel rails too. Adapter plate for mount of TB to manifold
3. you will need a variable fuel pressure reg. Kirban?
4. IAC? You may be able to get by with one and cap/plug the other TB.
5. linkage will need custom fab. See simpson36 thread
6. Earls or Aeroquip plumbing
7. custom air filter assembly.

84z5350

im sorry to say it but i think this is gonna have to go carb.as much as i want to be different i just cant do this with what i have.any one want to buy any parts?

KC51

Maybe a dumb question but what about trying this with the crossfire tbi's??

thomas1976

What about a simple, fast and strong 350 TBI, how common is that.

With the heads and cams you listed, 450-500 CFM is about all you could need.

http://www.4secondsflat.com/Carb_CFM_Calculator.html

Ronny

iTrader: (1)

500 cfm? I have a 7.4L TBI. I have a restriction. 1000 ft .sea level.

I am at 90MAP WOT. there is the rub.

Holley rates theirs(mine is GM) at 670. But with the pod i will say is more like 570.

edel RPM heads 64 cc rated for 7000 rpms I think. CC 224/230 @.05 114 LSA rated for 5800 rpms. Holley projection TBI manifold rated for 6500 rpms. Roller rockers. Huge canister KN AF.

My fueling per EBL utility supports 373HP yet I am running 100%DC 2nd gear pull of 4. Now I am at 3.5 lbs higher FP and have not checked DC. 80 lbs now at 26 lbs FP. TPI pump.

So I say a 500 cfm TB is way too small. My engine builder agrees on my restriction.

It appears the TB is the restriction

thomas1976

Ronny, not sure what you are trying to say, none of your parts are on the OP's build list.

Ronny

iTrader: (1)

Just a response to comment on "all you need". With heads and induction(which OP is considering) need OMO is in excess of 570 or so. A reflecton on my experience with TBI(crossfire xram and 7.4L TBI) ...

thomas1976

Hmm... maybe I missread somewhere, my understanding is the 083 + TPI cam are the best head + cam combo he could come up with.

Ronny

iTrader: (1)

I see your point. I did not see the TPI cam. My error.

Ported TPI heads and a larger cam may well exceed CFM of a 2.00 TB be it CF or a 7.4L TB.

gregs78cam

I have done it.

http://www.gearhead-efi.com/Fuel-Inj...164-My-project

Lots of details, but surely do-able. And can be pretty cheap too.
Done with factory '7427 PCM Injector Driver upgraded by Rbob.
One IAC, One TPS, adjustable regulator. It really isn't that hard. And if you don't go too wild with the cam it won't be that hard to tune.



some other details from my set up:
using a MPFI fuel pump from a '94+ sunfire
running 4 61lb 350 injectors and have more than enough fuel at 13psi.
could actually run 2 61 and 2 55lb for better idle fuel control
on a dual carb intake things would be much easier
I think I have less into the "DUAL" part of it than getting one rebuilt BBC TB.

What else would you like to know?