hey guys i going to buy the zz4 chevy crate motor now i wanna stay with the tbi system.i read the holley 670 holds 275 hp?how can that be when there are 305 tbi flowing like 400cfm running almost 13 flat with stock everything ,what is the true deadline of the holley 670 tbi?and i saw in a catalog holley manke a 700 cfm tbi any clue were i can get that or if its any good?

check with holley... i think the 670 dual TBI will support all of 275 HP and more. The 700 TBI I believe is their "system" which includes the ECU and tuning instructions to retro a older carbed vehicle to EFI. 13.0 flat ? 400 cfms? that may defy physics? there is a certain amount of HP/TQ required to propel a certain (heavy) weight to 1/4 mile in 13 sec. will require a lot of air + fuel or an air substitute/ enhancer like blower/NOS.

The Holley TBI is rated at 670 CFM @ 1.5"/Hg

That's enough to support about ~400 HP at 6,500 RPM at 85% VE. Not too shaby, right?

The problem comes with delivering the fuel.

Based on a few calculations that are floating around in the world, 112.5 lb/hr at 80% Duty Cycle would be required.

Good luck finding those.

Uh Oh! Another "future" ZZ4 owner! lol

will the stock 670 tbi hold the zz4 power? while adding offcourse a fuel pump on my car?

largest injectors i believe are 90 lbs GM. At 80% duty cycle at 12 lbs FP I think they are good for 300 HP(give/take) if i read correctly on forum. At 15 lbs of course higher. not sure what the A/F ratio would be at WOT with that engine at higher RPMS. Might go way lean. On crossfire forum someone is building an intake with 4 injectors in top plate. that would take care of fuel delivery issues.

yeah i think it will be fine i wont be abusing it so much so most of the times it wont pass 3k rpms so i think the holley 670 will be fine now at the track i see first what happens on the dyno that a next summer project

just felt like saying the Green RS in that sign picture above is my car

Is it really a fact that its flowed at 1.5 inHg? Ive always heard 2 inHg.

I posted this a while ago and asked the mods to make it a sticky so everyone would see it.

I guess they felt the need to move it to this post so less people would see it.

http://www.thirdgen.org/techbb2/show...hreadid=205713

I just got my car back from the shop last weekend after destroying the clutch at the track late october. Long story, moved to illinois, car was in missouri etc. Anyways, had it worked on at vamp auto in Grain Valley, MO maybe 15 minutes from KCIR. These guys were the first and only shop in missouri that had a clue about my project, fuel injection, and the need for speed.

Anyways, they estimated the car at 400 fwhp good for high 11's low 12's. This is from guys that run mainly mustangs (I know..) ranging from 11.5 to high 9's. I have already promised traps of over 110mph this coming spring at Route 66 outside chicago. Times should be much improved as well, as my pinion angle was at a +2, and now properly set at -2.

There are, in my opinion, only a couple things needed to make the 670 work to it's full potential.
1) Intake! most important supporting piece. Peronally, I think a single plain is the way to go, or at least something with good plenum and an rpm range to 6,500rpm.
I went from the performer to the rpm air gap and got massive gains. and I was running traps at 105+ with the performer. The reason I believe I gained so much however, isn't so much the change of intake, though that had an obvious effect. More so however, the adapter plate I use is open, thus allowing each cylinder access to both bores, and more plenum in that my new adapter plate is a half inch taller than the one I had on the performer.

2) Inexpensive and free mods. An injector spacer, rounding the bore openings, shaving the throttle shaft, and grinding obstructions such as the pegs for the aircleaner. A good cleanup on the cast and polish will help as well. I have did all to mine, and all I can say is, it is smoooooth...literally.

3) Ignition. Stock ignition is fine if you never plan on seeing past 5,000 rpm, but anything past that and you will need to upgrade. This is personal and professional experiance. Some people will argue, but whatever.

Also, the biggest misconseption is that TBI cannot pull high rpms and is only good for low torque, as someone tried stating in one of the links. How about this? 95 mph outta 3rd with a t-56 and 3.73s and still pulling. Haven't gone past it as I still need chip work, and am iffy about doing anything too crazy with the current one.

Nice to see this post...I was about to ask the same question. In reading this, I see very mixed opinions on the Holley 670 TB. I had the Holley ProJection system that was supposed to support up to 275hp at 670cfm of flow. Honestly, their claims about that system were accurate in terms of hp. The TB supplied with that system is quite different from what is probably used by most guys on this board. The immediate and most obvious difference is the lack of an IAC...and of course the 2.00" diameter bores. The TB is obviously a GM derivative of some sort....maybe a 2.8L S-10 or the like. The reliability of that system left a great deal to be desired, however. If I had it to do over again, I would have spent the extra $$ and gone with a Howell system in the first place.
As for the 670cfm Holley TB, I have been looking at it for my own project for quite some time now. After reading this post and the sticky thread, I am starting to wonder if it is all that great of an idea. For the $$, it seems like it would be compatible right outta the box, but from what I have just read, it isn't a bolt-on affair...there may be a good bit of tuning involved. What is the general consensus on that? Would it work right outta the box with a 1228746 ECM and the ANLU (cop car) bin? (Engine is an AMC 360, +0.030", race cylinder head job with full port/polish/gasket match and radius exhaust valve job, full Accel 300+ ignition, Performer AMC intake) I know it sounds kinda bastardized...'cause it is. You'd have to see it to believe it.

See my post on the sticky RE 670 TBI injection. Its at the end and no one has answered it.

All the other issues notwithstanding re TBI, I don't think we know for sure the 2" units really flow 670 @1.5"hg with the pod ON.
Re-read the source of information that was posted supporting the 670 flow rate and let me know. Thanks..............bob

I keep hearing how the 670 is flowed at 1.5 hg, but my curiousity got the best of me and I had to know for sure. I emailed holley and they assured me all of their 2 barrel tbi's were flowed at 3hg. What gives?

Wouldn't flow-testing them at 3" Hg give numbers that would be unrealistic on a real world engine?

Your attitude needs adjusting. Why would any moderator want to help anybody on this site if all they do is bitch and complain about something so absurd. Is the post not a sticky? lol, where is your problem with us moderators?
Now for the 670 TBI technical info, it'll support 300rwhp in stock form with a LOT of fuel pressure and/or some really efficient heads, roller cam, roller rockers, etc. An efficient motor will have a lower BSFC so it all depends on the big picture.
Anything requiring more air (and fuel) would benifit from a 4 barrel TBI or enlarged TB. Look at the power those 454ss guys are making with the 2.2" bore TBs and the crossfire TBI's can be sleeved out for the same effect.... less vacuum at high engine speeds w/lots of load.
I'm looking into using a zz4 cam with these vortec heads. I'm hoping for a big jump in power from the roller, more intake lift. I have yet to simulate it but I think the 2" bore TB will flow enough to not drop more than a few kpa. If not, I'll bore it out and do some flow simulations to try and increase the air flow. If it's too much work I'll just do port injection. You might be better off with port injection too. The prices for injectors and parts to convert carb intakes to port injection have dropped a LOT. Run a 730 or 165 ecm, depending on your preference, and never worry about your hp support. Just get big enough injectors to support your range with room for improvement . Face it, TBI is good for certain applications but it isn't for everybody and it definatly not easy to tune when you're talking about going to a zz4 or something even hotter. I would keep 2 barrel TBI to a mild 350 or super mild 383 and bigger.

I don't have a problem with "us moderators" at all. At least not today.

It's just this has been a "did the chicken or egg come first" type of discussion for quite some time.

I finally found SOMETHING IT WRITING that said what flow rate was used. I felt it deserved it's own sticky, if only for a couple of weeks.

The problem with old stickys is just that; they're old. People tend to overlook them after a week or two regardless of how many new posts have been added.

If you think this is considered "bitch and complain", and "so absurd", you haven't a clue. If I said you had a
HUGE ***!!!, that would be absurd.