BPA

I currently have a LO5 caprice 350 in my 91 Rs. My question is this.. Would i be better off going with the 454truck tbi or the holley 670 tbi. What modifications besides the afpr on the truck tbi, and the changing of injectors on the holley will need to be made?right now i have the stock 470 or what ever the exact cfm is tbi and intake manifold. Im going to upgrade the manifold to a performer erg in the future. will eather of these tbi's work on the stock manifold or are the manifolds ports to small? Its good to see the boards back up.

badbird88

I would buy the Holley unit and the injectors that come on it will support 300hp and more easily (see my sig) which is more than the caprice 350 is putting out now. I've been using mine for 4 years and had no problems other than modifying the throttle bracket slightly to accept my throttle cables since the Holley is setup for a truck throttle linkage. I would definetly get a new intake but as to which one, everyone has their opinions. I just got my Holley projecion intake in yesterday so I havent gotten into the install to see what problems await me. A carb intake will work great also but you need the adapter for the TBI to bolt to the carb intake. My Holley fits on my stock intake fine...but why it will on the stock but not on the Edlebrock (so Edlebrock claims due the the intake openings being less than 2") is beyond me. The stock intake has less than 2" throttle bores but the Holley fits perfect and the throttle blades open all the way. The Holley manifold has 2" throttle bores. The stock intake is killing my hp so definetly get a new intake.

Here is a picture of how I modded my linkage, not the best but it works. You have to grind a piece of the linkage and put a bolt in it's place. Mine is a manual car so it may work fine on a auto how it is. Ignore the ugly oxidized look of the manifold, black paint was coming off at the time!
http://www.geocities.com/badbird88/t...linkagemod.jpg

The fuel pressure regulator screw is covered by a metal cap that you need to knock out to be able to access the allan headed screw so you can adjust your fuel pressure. Mine is sitting around 14 psi.
http://www.geocities.com/badbird88/t...ssurescrew.jpg

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1988 TA 300+hp 350 w/ TBI and Holley TB unit,
WC T-5, 3.42 gears w/ Auburn posi. MSD 6A, edelbrock TES headers, dynomax 3" cat and cat-back system, ACCEL coil, polyurethane bushings all around, aluminum driveshaft, Mr. Gasket open air cleaner.

1993 S-10 w/ 4.3L V6 TBI, slightly bigger cam, Mild polish job and 3 angle valve job on heads, Edlebrock TES headers, Dynomax cat back, MSD 6A, ADS chip
(bought from my dad)

2000 GMC Sierra Regular Cab Stepside
285hp 5.3L w/ 3.42 gears and locking diff. (sold to my dad..no!!)

FastBroker

Have you guys had trouble with the Holley injectors on those 670 cfm units??? I have put several Projection units on vehicles and I think about 50% of them had injector problems. ie, leaking or sticking open or sticking closed... I really need a 670 cfm unit and I swear by the Rochester (OEM) units. Maybe the Projection (system/ECU/harness?) is the problem and not the TBI unit itself???????

The 5.7 liter 670 Holley piece has 80pph injectors, right? What about the 5.0 liter??? What size injectors? Oh, also, is the IAC EXACTLY the same as OEM? ie, can you buy OEM IAC motor and install it if/when the Holley supplied IAC breaks?


[This message has been edited by FastBroker (edited September 19, 2000).]

Dan W

BPA and FastBrokers... I think I can answer almost all your questions...

Yes, I've had problems with the holley TBI injectors, they are actually dodge type injectors. I had one that was bad and as far as I can tell it was bad when it was shipped. The injector worked normally when cold and spuddered when hot. No matter what I do, I cant get the replacement injector to stop leaking. The Dodge type TBI injector is an inferior design anyway... They are not suited to high pressures and may begin to have issues after 17 or 18 psi... not so with the GM units, I've heard of people pushing those things to over 30 psi. So there is the reason I dont like the holley 670. BTW, I'm running a 700cfm 4bbl TBI on my car.

I would definatly go with a used 2" truck unit if given the choice... but if that is not an option, I've heard of people mounting their stock injector pods on the holley 670 TBI unit with very minimal modification required (elongation of a couple of screw holes I beleive)

I've heard a couple of bad things about the Edelbrock TBI manifold and would shy away from it. My first choice for a tbi car would be a low rise single plane with an adaptor plate. If you insist on a low rise dual, go with a carbed style, again with the adaptor plate.

Some people complain of a bog when they upgrade to the bigger TBI unit w/o a custom chip. This is due to the fact that the new TBI unit flows more air and the computer is not compensating with a large enough pump shot.

This leads me to the injector issue with the GM unit, someone correct me if I'm wrong but these are 90# injectors right? Rated at what psi? Pablo, I know you know this off the top of your head. Anyway, these are a bit big for a mild 350 with FP adjustment alone and the stock prom... but if your getting a chip made anyway for the larger pump shot, they can cut the Base pulse width down while they are at it and compensate for the too large injectors... or you could just run your stock (probably slightly small) injectors in it with more fuel pressure.

The stock manifold will work or so I've heard but the bores are smaller than the TBI unit... its the equivilant of running a restrictor plate. You negate any potential HP gain by using it, replace it, its one of the worst intakes known to man anyway.

I have a '98 holley catalog that says the 305 units have 57# injectors, the 350 units use 80# units, thse are rated at 15 psi and yes your stock pump can handle that if its in good shape.

All the pictures I can find of the 2bbl holley units use the same type of square 4-pin connector IAC that was on my original 2bbl. The 4bbl units use an inline 4-pin connector and require a different plug.

FastBroker

Yeah, the problems I have had w/the Holley injectors are making me shy away from their units... No fun w/bad injector when you are far form home and it's 20 degrees below in the Winter... Guess I'll wait for a Rochester big 2bbl off of truck. but, waiting sucks

badbird88

I did have a problem with the injectors when I first bought my unit...they were #80 injectors which they were only suppose to be the #67 or something close to that. No matter how low I turned the pressure down I couldn't get it leaned out and that is on my 300hp 350! We finally called and they were reluctant to admit that they shipped it with the wrong injectors and sent me the smaller injectors (the ones in the 60's) I did have one of those stick open with me but that was the first couple of times it was running. We took it apart and put it back together and I haven't had a problem with it since (4 years ago).

The other problem was the injector wire cap (where it snaps on to the top of the injector) wasn't connecting very tight so I had a injector that kept cutting off for a couple weeks until I realized the female prongs in the cap need to be squeezed together so it would snap on to the male injector prongs tighter. Not really a problem just a fluke I think.

Kind of curious why Holley says their units come with #80 injectors now. Is that for the replacement 670 unit or the TB unit that comes with the computer as a kit to retrofit a previously carb'd vehicle. I believe the 2 units are diferent when it comes to injector size. These are suppose to replace the original TB's on 88-92 Trucks which only had 205hp. #80 injectors is way to big for that low of hp especially if they were to big for my 300hp motor. Call Holley or e-mail them to be sure.

You can get a new set of matched injectors from Turbo City to match your engine hp so you can use the 454 TB unit. Go for it if you have a 454 TB available.

Overall, my Holley has been pretty much trouble free. Plus I like the fact that I was getting all new sensors (IAC, TPS) and not ones that had been used for 7-8 years.

FastBroker

I've had problems with those injector pinch connectors, too. Holley admitted to a problem and said that they were going to do a redesign, but that was over 6 years ago. Shows you how much they care about our problems...

badbird88

I must say I did put the poor injectors through some rough times during those few weeks the connectors were screwing up. I noticed if I tapped on the top of the injector it would come back on so there were a few mornings I got so aggravated I beat on the poor helpless things ..lol! They are still flowing perfectly after all the beatings!

Pablo

iTrader: (1)

I agree with dan in that if given the choice, i would run the GM unit or at least the holley unit with the GM injector pod. GM injectors respond really well to increased pressure, in fact, thats the only way to squeeze out LOTS of hp from them. Ive run mine at 50 psi before with no problems, this helps with atomization and really makes the spray cone open up so less fuel is hitting the blades at part throttle. Im currently running 20 psi on stock 305 tbi injectors and the car is running great

The GM unit came with 90 lb injectors initially and the later models came with 80lb injectors i believe. Both injectors that are rated at 10 psi and can be pushed up to probably 70 psi which would support ungodly amounts of horsepower.

I also agree with Dan on the single plane issue, I have a single plane, and my car runs great, the torque is fantastic and the top end is killer

Pablo

BPA

Thanks for the info guys it was very informative.. ive heard that the edelbrock tbi manifold is bad it has the smaller bore openings i think right?just wanted to clear this up in my head. Ok thinking about it hear if i decide to go with a 670 holley or 700 4barrel holley and a performer egr or the single plane like a few of you guys are using and get the custom chip burned what do you think a resnable power gain would be form this. The engine i believe was rated somewere between 190hp and 225 depending on the chip used. This would be with slp 1 5/8 headers and a cat back. Im just trying to see my hp/to dollar ratio.
anyways thanks again for all the replys i really apreciate all the insight.

Dan W

The TBI unit isnt what makes power, your head / intake / cam / displacement combination are what make power. The TBI unit or whatever you choose to meter your fuel and air must only support this power... it doesnt really make power, just supports it.

So with that said, the GM unit with 90# injectors can support over 400 hp. Even though I am now running a 4bbl, the GM 2bbl would be my first choice if I were to start over. The holley 2bbl with the GM injector pod would be my second choice next the 4bbl holley and last the holley 2bbl with the holley injectors.

But Before I specificly suggest a TBI unit for you, I have a question. Are you done with your performance modifications? If not, how much power do you eventually plan on making.

Yes the edelbrock TBI intake is bad for use on a 2" 2bbl application because its bore is said to be smaller than that of the TBI unit creating a flow restriction, this could be opened up easily though. I think the real problem is that (and this is something you should look up in the archives if you want more detail) dual plane intakes are best for carbs... hot street TBI setups will do better on a well designed single plane intake w/o the fuel metering problems that carbs suffer from on this type of intake. One source from an old hot rod article (90 timeframe) cited that the edelbrock TBI intake suffered from fuel distribution issues... the company (Traco Engineering now out of business as far as I can tell) designed their own adaptor plate and used it on a carb type Edelbrock Performer intake to solve these distribution problems.



[This message has been edited by Dan W (edited September 20, 2000).]

Pablo

iTrader: (1)

Yep, that was oct. nov. and dec. of 89, F Notes

they had a two week dyno thrash and used all sorts of combos and found the edelbrock manifold provided good low end torque gains but that was it, it couldnt hack it in the upper rpm range

btw they ran a 13.8 on slicks and like a 14.1 or .2 on street tires

BPA

Dan, my mods are far from done. I would like to be making about 300 hp when done. I have no idea if the heads on the engine are any good, im guessing that they are similar to the 305's , if they are like the 305's i will probably end up getting some ported al. L98 heads or some other good flowing head. Aslo in the future i know that i well want a better cam (smog leagal), i believe but dont have the numbers on me right now, the cam in this engine is a little milder than the L98's. Im having a little trouble finding info on certian things about this engine but i think it will be a good foundation for power. Oh ya , im planning on getting some gears and a posi., probably 3.42's. Do you guys think 300 hp is atainable?

rsilver

sorry to butt in, but when you guys talk about the GM unit are you talking about the 454 unit or can you use the stock unit off a 305 if you are doing a mild 350 swap? Is it worth it to have the GM unit Bored out to 2"?
I heard this can be done. Thanks......

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91 camaro RS convert
t-5
open element air cleaner
TBI spacer
Flowmaster muffler

FT-LBS

RSSilver...

Did you notice any difference with the TBI spacer? Was it difficult to install?

...Matt

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1992 Camaro RS 5.0 TBI A/T
Most of the Bolt-On Mods