Hey guys, I'm a new member here. Just a short bit about me (or more to the point, my cars) - I have a 1973 Corvette, along with a 1982 Corvette (yes, the one with the fabled CrossFire Injection!) I've been working for about 3 years now gathering people together to work on getting the CrossFire some deserved recognition that it CAN produce power. (A *BIG* thanks goes out to Bruce Plecan, who started figuring it out on his own, and has shared some of his info with me and others in the past.) Our website can be found at http://www.crossfire.homeip.net if anyone is interested in looking at it.

Since I have started learning what the CrossFire can do, and it's incredible streetablity, I have found I really like TBI a lot. I read with great interest about Badbrd383's Vortec/TBI setup and strangely enough, I'm highly interested in duplicating the results in my '73 Corvette. I currently have a 350, with some junky heads (don't ask) in it and a Performer intake with the old Q-jet on top. Needless to say, power is "okay" but fuel economy and tune-ability are much higher on my list than originality. I'd like to go with the TBI setup described (Vortec heads, Performer for Vortec, 2" 2bbl TBI) and a '7747 (I have all the stuff to program them.)

The good news is that the entire motor has less than 2000 miles on it (it's been sitting for a while, but gets run every so often) so the bottom end is pretty strong. I plan on taking the entire engine out; swapping in a new cam as well. I do understand that with a MAP system you need to run at least 112 LCA for reasonable idle, so I've been looking at cams with that as my prime concern. I'm also aware that that Vortec springs (stock) are only good up to .450" lift. Bearing these two items in mind, I played with several cams and came up with the Crower 239 cam. Duration is 254/265, and lift is .431" for both. Dropping a set of lightly modded Vortecs (per David Vizard's specs) on top and some extremely free-flowing exhaust (since the car is from '73, I no longer have emissions concerns) with the TBI/Performer combo, DesktopDyno shows around 350-375hp (possibly more.) I set the TBI at 600CFM, assuming that would be sufficient for a 2" 2bbl TBI.

Since I have made several friends in the CrossFire region, I might be able to get a TBI bored out to 2". (I have a friend that does CrossFire TBI's to 2", but they are single barrel ones and probably easier for him to do.) I'd rather pick a TBI up at the junkyard and have it cleaned up rather than spend $400 on a 454(SS?) TBI.

Part of the reason I'm going with this setup is it would retain a fairly stock-appearing setup (I can use my old aircleaner.)

What do you guys think?

Ken

 

dude no smog? I should dig out the dual 4barrel carbed 427 with custom intake pan in my old Corvette fever mag.

------------------
-Tas
'89 Formula WS-6
[soon to be Torch Red with black hood and headlights =) ]

305, TBI, auto, 14x3 chrome flat based open element with K&N, functional Formula hood, cross-flow Flowmaster, '99z28 rear pipes and tips....

Super GRK_Taz World
EFI & Intake Options
AOL IM: superGRtaz
ICQ 82881207

 

Nope, no smog equipment. No AIR pump, no EGR, no EFE (well, when I put headers on there won't be) - and get this - no THERMAC (from the factory!) Technicians at the inspection place are clueless about it, and it doesn't have to pass any emissions anyway. No cats, nothing! PCV valve and vapor cannister are the only emissions pieces on there.

Exhaust will be headers out to 2.5" pipes, back to an "X" pipe to smooth things out and tone things down a bit, then back out to two high-flowing mufflers. (I'm open to suggestions, but am eyeing the Ravin mufflers.)

Ken

 

Hey dude

Marck

 

Wow, never thought I would hear someone say "Swapping from Carb to TBI" Correct me if I am wrong guys, but isn't the highest TBI unit made a 670cfm? So if u don't plan on having an engine that needs anything over that cfm I guess u can swap out the carb for that tb unit. But if u plan on making 385-400+ hp then I wouldn't suggest it. Easier to just throw on a higher cfm carb then changing the entire injection system. Just my thoughts.

 

Ken, sounds like youve already got your feet wet in the cross fire world. Thats good and I'll save the standard "how much work your in for with tuning speech". At peak flow, those vortecs flow about 240 cfm. Make sure the intake you choose is up to it... Preferably single plane if available. Remember, vortecs dont use a standard intake. Since your going to pull the valves on those heads to pocket port, why dont you install some springs that can handle more lift and a matching cam? I like the stock look also... very clean. Consider the Holley TBI unit for your application... the one with the 85# injectors would suit your application. Last I knew, they were going for about $270. You should not run the dodge style injectors that come in these units beyond 18psi… this will support about 370 horse on your vortec 350. You can swap a GM injector pod on to the Holley unit if you want and use the better GM injectors.

Now, let me deal with something else...

Actually there is a whole industry built around this... see Howell-EFI, Turbo City, Holley and Accell.


If you are talking about 2bbls as far as I know, yes. Holley makes a 4bbl 700 cfm with 65# injectors and 900 cfm unit with 85# injectors. I'm running the 700.
The 2" bore TBI units flow ~ 670 cfm. On a hot street 350ci motor running at 90% VE, it will feed the motor to about 7400 rpm. Exactly how fast do you think he is gonna spin that small cam motor?


Why? On a motor with great heads like the vortecs, a 2bbl with a pair of 90# GM injectors will support 460 horse @ 20 psi and 90% duty cycle and they can be run at higher pressures for more horse power... besides didnt he just say his projected power was 350-375?


Perhaps, but did you read what his question was, what he was trying to accomplish and his experience?

I've noticed your posts lately and could share some thoughts but I think I'll reframe.

 

Well thanks Dan! Dude, do u have to be an a$$hole when u correct people. How bought, actually Eric, they make this and that instead of smart a$$ remarks. I am sorry my knowledge of TBI is not superior to u. I said "Correct me if I am wrong" Not be an a$$hole about it.

[This message has been edited by 91Bird305 (edited January 18, 2001).]

 

Well thanks Dan! Dude, do u have to be an a$$hole when u correct people. How bought, actually Eric, they make this and that instead of smart a$$ remarks. I am sorry my knowledge of TBI is not superior to u. I said "Correct me if I am wrong" Not be an a$$hole about it.

eric man u do need to chill a little bit. I have also noticed everytime u find out some bit of info u share it with the world and act as if u know it all. Like how u said earlier how TBI can only go up to 700 cfm and how carb is good to 1000 CFM. ONce u found that out u where saying it all over the place but now he just said that there is a TBI unit that will put out 900 cfm. is that gonna be what i read about in ur next 5 posts? look man i am honestly not trying to be an *** but u need to do a little more research if u plan to win these debates. I mean if u are gonna support carb so much and thrash TBI all the time(and i do mean ALL THE TIME) than switch the an equal CFM carb and tell us how it runs. Dont forget to run ur car b4 u do the swap, u will need a timeslip to remember when ur car had *****.

------------------
1989 pontiac firebird
bright red exterior(just repainted)
grey interior
5 spd
305 TBI (stock)
WS.6 formula wheels
3.73 posi rear end
http://members.aol.com/j007golden/Mikey89.html
-------------------------
1985 trans am
factory bright yellow
4 wheel disks
16 inch wheels
305 TPI
power antenna and mirrors
t tops

 

with all this carb to TBI talk and vice versa, the test subjects always seem to be hoped up with full exaust and intake at least. what if someone tuned the TBI for ALL this added air before the carb swap on the same intake. I bet the change will be ZERO.

If you run a stock TBI orignaly tuned for **** exaust and a 1" x 2" intake snorkel on a car with full exasust and open element of course a carbed car will have an improvement.

------------------
-Tas
'89 Formula WS-6
[soon to be Torch Red with black hood and headlights =) ]

305, TBI, auto, 14x3 chrome flat based open element with K&N, functional Formula hood, cross-flow Flowmaster, '99z28 rear pipes and tips....

Super GRK_Taz World
EFI & Intake Options
AOL IM: superGRtaz
ICQ 82881207

[This message has been edited by Tas (edited January 18, 2001).]

 

Hey guys, didn't mean to incite a riot here! I appreciate all the comments so far!

Dan, I wouldn't even say I have my feet wet; I'd say I'm soaking from head to toe! I was going to reverse-engineer the original 1225550 ECM, but gave up after several friends convinced me to move over to the '7747. (Although I still have them in the garage, I haven't done anything yet.) I have since sent all my spare ECM's to a friend in Sweden who is going to reverse-engineer them instead. I've managed to pick up two '7747s to work with and I'm probably going to get a 3rd for my truck. (One for my '73, one for my '82, and one for the truck.)

I actually plan on moving to a CrossFire in my '78 GMC Jimmy for some hefty down-low torque, as well. The truck doesn't rev past 4500, so I will probably pick a cam suitable for it soon. (It has a crate motor in it.)

With the Crower 239 Compu-cam I was talking about, which would you go with - the Performer or Performer RPM? The cam doesn't really rev past 5500, so I was considering the Performer instead. (I do realize the Vortec heads have a different bolt pattern and ports; I saw the post a while back from Scoggin-Dickey and have those pictures saved.) I will be getting the Vortec-specific intake for either of which I choose.

As for the injectors; can you get the Holley 2" unit, then pick up an injector set (tower) from the junkyard and slap it in?

Ken

 

See that? That means I am unsure. That doesn't mean this is fact. I think you guys need to get off my f-cking back and maybe help me out and give me info instead of being total b-tches about it. I didn't proclaim any of that was fact. Thats why I said "correct me if I am wrong" Go ahead and correct me but don't dis me. Thats nothing a friend would do, would it Mike?

I don't see why u couldn't. Maybe even call and ask Holley and see if they maybe make one? Wouldn't hurt to try.

[This message has been edited by 91Bird305 (edited January 18, 2001).]

 

im thinkin, i did see some a*sholish comments, but i dont think they were intended to be that way. if they were, you need not comment to tell us that. ill be back on here more, and i appologize that i was offline for a while and let this happen, i see a few of these posts that i would have and will in the future ask you to edit, before i delete it.

remember on the internet, people automatically assume that the mood is not good, you have to try extra hard to make yourself not seem mean. think guys, and be nice. i do however think there was some good information in the posts above.

 

[quote] Originally posted by Ken73:
[Dan, I wouldn't even say I have my feet wet; I'd say I'm soaking from head to toe! /QUOTE]
LOL, I know the feeling.
At this point my first choice for TBI would be a single plane. Remember, the dual plane thing is a band aid for carbs to boost the signal to the venturi. With that said, I'm running an edelbrock performer right now on a standard head. My exhaust crossovers are blocked off and the engine lacks wot response at low rpm when cold. Its possible you may run into this same problem with the performer on the vortec heads. Grumpy offered an explanation for this not long ago... it seems that the lower plane on a dual plane can be slightly up hill allowing for puddling at low rpms with a cold intake. The only single planes I've seen for the Vortec have been Victor JR type... but its been almost a year since I've looked into it. I'd be scared to run a big intake like that on a low rpm motor but maybe thats not a reasonable fear. Maybe someone is making a low rise single plane for them now???

Otherwise btw, my performer works fine on my combo... I'm running a bigger cam but crappy heads and my motor pulls strong to nearly 6000 rpm. I'd do some checking to see how those performer intakes flow in comparison to the vortecs at the lifts you plan running them. Choosing an intake that flows less than your heads may limit your top end a bit.

Thats a whole lot of talking and now I'll answer your question by saying I dont like either of the choices and dont have enough info to necessarily give you the right answer. If you want a shot from the hip though, I'd guess the RPM intake but then again I have the Tim Allen complex... bigger is better ar-ar-arr.

Yes, it is possible but may be the expensive way about it as I doubt a junkyard will want to separate the injector pods from the TBI units. I think the larger injectors only came in the 2" bore big block units... you should check on this. Having a more common small block unit bored is probably the cheapest solution but you will still need injectors. Has this been done by anybody yet? Personally, I'd spend the extra buck up front and pick up the GM 2" unit... I wish I had gone this way in the first place... I really dont have a need for the extra fuel of the 4bbl holley and with a 2bbl, no one could tell it wasnt stock even with the air cleaner off.


------------------
1988 T/A,
9" Ford, 3.50 gears, Auburn posi, 700r4 -w- 2100 converter
350 .060 over with forged 1 pc rms crank, and forged TRW pistons, 9.5:1 cr
Factory GM heads Pocket ported, 2.02/1.60 valves, back cut
Lunati roller 219/227, .479/.480, 112 LSA
Holley 700cfm 4bbl on TBI truck 7747 computer and chip by Howell-EFI
Edelbrock Performer EGR intake, Edelbrock TES and 3" cat

[This message has been edited by Dan W (edited January 19, 2001).]

 

i thought i clearly said that i wasnt trying to be an *******. I was trying to say one friend to another and be kool about it. I get pissed off becouse of the smart *** tone ur comments seem to take on and thats when i becouse a little "rude" so to speak, but i never directly insulted u unless we where having an all out arguement or u really said something to get me. u need not assume all the time and do a little research b4 u go telling everyone that ur right.IMO

 

Dan, I think I might stick with the Performer, partially because I'm not sure I have the hood clearance. (I'm going to check on that though.) If I have clearance, I might go with the RPM. I understand about the venturi boosting concept; but I thought it was to keep air velocity up at lower speeds as well? I haven't seen any single-plane low-profile Vortec specific intakes yet. (Weiand makes some nice ones but none are for the Vortec heads.) For that matter, could you do a little "creative porting" on the RPM (remove the divider) and almost have a decent single-plane?

Which begs the question; how much shorter is a TBI unit than a Q-jet? I'll go measure my Q-jet sometime today and see how tall it is. (From mounting surface to air cleaner seal surface.)

The junkyard I go to is a Pick-A-Part and I can pretty much strip anything I want. I grabbed my '7747s with about 6" of pigtail on it; I just took some big clippers with me and chopped them off. They never even winced. Getting an injector tower wouldn't be a big deal, but I think I'll get the whole TBI and have it bored over. (I already have some 2" butterflies leftover from my CrossFire stuff, even.)

Injectors are, however, much more difficult to come across. I think I might buy new ones from the local auto parts store if I can't find any. (Suggestions on which ones to look for or buy?)

Ken

 

Yes it does... these two things are related. As you increase volume, velocity goes down right along with the signal to the Venturi... The Dual plane cuts the plenum volume in half.

I can better elaborate if I quote from a book on intake design:
"Single plenum manifolds used with TBI have performance characteristics very much like a carb. The vacuum requirements of TBI are less than a carb. A TBI uses force of fuel over atmosphere to mix it with air. Carb requires reduced vacuum in the Venturi to draw fuel into the air stream. (note from Dan W: as velocity through a venturi goes up so does the pressure differential to the outside of the venturi... as velocity increases pressure decreases)
The result of using a carb on a single plane is usually a poor mix of air and fuel at low speeds. Since TBI uses positive pressure on the fuel to create this mix a TBI system mounted on a single plane manifold will gain the benefits enjoyed by the car at high speeds without as significant a loss of smooth performance at low engine speeds."

Velocity is important to TBI (remember my cold stumble) but not as important as with a carbed car. The carb suffers from this and more importantly fuel metering difficulties at low RPM. A well designed intake should take care of almost all of the TBI fuel puddling issues. The more down hill the better. On a side note, one of the advantages of multi point is that there are far fewer considerations when designing a manifold.

I tried to do a little research on this but couldn't find anything. I know I've seen some small modifications to tune dual planes but cant remember how drastic they were. Sorry. In the absence of some literature or experience, I'd be afraid of ruining a $200 intake.

Help me guys... didnt Shane Buss use an rpm intake on his vortec motor in the beginning? I can't measure my stock TBI... no Idea where it is... you will be happy to know that I did venture into the garage to look but was promptly turned back by severe frost bite.

I'm not sure about stock part numbers. I've got a 1998 Holley catalog here that lists replacement injectors for their TBI units that appear to use GM style injectors.

57# 522-1
64# 522-2
69# 522-3
90# 522-40

90# will do it at its rated pressure... 64 or 69# will need to have the pressure increased to handle it. I'd go with 90# if choosing from that list.

Try to do a search. I seem to remember someone posting GM injector sizes per application a month or two back.

 

Thanks for the tutorial, Dan. I understood how carbs reacted to the manifold differences but didn't realize TBI's were less sensitive. That being said, I think it's safe to say I could probably cut the center section out of an RPM manifold and blend it smoothly to somewhat make a single-plane manifold. Or, at least drop it down a little and smooth it out so you can have some pull from both barrels. (That is, if I have the hood clearance for the RPM. Remember it's a Corvette!)

So, with a lower velocity due to a single plane, and you're now injecting the fuel under pressure - does the pressure become important? I mean, stock fuel pressure is around 9-13 PSI - should that be increased? (Of course it'll be tuned into the ECM, so pumping it up higher won't matter.) Or, am I going out on a limb here?

Ken

 

LOL, sorry about the tutorial.

Buddy has a '76 vette with a vortec 350, perf. rpm intake, edelbrock elec choke 750 cfm carb, 2 1/2" drop base... rubs the insulation slightly.

The injectors are situated in atmospheric pressure conditions so they are more or less immune to whats going on in the intake.

Why do you think that removing the divider will help you make more power?

 

Actually the tutorial was very helpful!

Since your friend is running a Edelbrock carb, I know almost for sure that it's taller than a TBI unit. TBI units that I've seen are VERY short. Do the TBI units require a spacer for the aircleaner to fit?

Removing the center divider will allow each plane of the plenum to pull from both barrels. Otherwise, you're dividing it into two seperately-fed ~300CFM single barrels that feed each plane. It'd give a little more top end. I would think it would also increase plenum size. (That's my theory and I'm sticking to it.. at least for 10 minutes.)

Ken

 

I think in order to run a drop base, yes... at least I did and used my stock spacer on my 4bbl. Not sure about the 2bbl. I'm running a flat base one now w/o the spacer and its a bit shorter but has to be on just right to not interfere with the linkage.

 

If it makes any difference, when I went from Edelbrock 1406 to Rochester 2V TBI in my 79, the air cleaner fit great. But I digress, I was also running a 9" x 2" non-drop open element in the first place.

A 14x3 drop-base *may* need a spacer ring to clear everything.

And if you were wondering, I yanked the TBI off, long story short, the thing ran like crap, I think it just needed a ignition module, but at any rate, I got tired of throwing money at it to get nowhere, thus the restoration process and a Carb

------------------
Shane McConnell
macgyver@nethirdgen.org [*]Webmaster of www.NEThirdgen.org[*]1991 RS 305 T5 15.6@88[*]1979 Z28 ZZ4/2004R (In the future.)
I'm the kinda guy you bring home to Mother.

 

Ken, in reply to your idea about grinding out the divider in the edelbrock performer rpm manifold, they actually sell an edelbrock rpm air-gap intake which is essentially the same at the edelbrock performance rpm intake but with the gap shaven off just like you said. If you look into the Jegs catalog, they have a picture of it and you will notice that they did not shave it off completely, therefore it still remains a dual plane. The only thing is that it costs almost twice as much as the performer rpm, so it might be a good idea to get the performer rpm and shave the gap off yourself.

------------------

Mods:Hooker Aerochamber 3" exhaust, gutted kitty,
March 2 piece underdrive pullies, smog pump gone,
14x4 K&N, 3.42 gears,
Eibach springs with KYB's all around.
Appearance: Harwood cowl hood, Z-28 wing, painted black(7/20/00)-original color was light blue
*All these mods were made this year
Stock Options:120,000 miles on motor, 5spd, TBI, 305, T-tops
Run a best of 16.7 @85mph before gears

 

the tbi is 2 and 1/4 inches tall with the bore ridges. 2 even without