Intake Manifold Choice for EFI - Pontiac

[Dave]

(long time reader, first time poster)

I've been reading this fuel injection forum a lot and really appreciate all the information every body has posted. It has helped a lot!

I'm looking at converting my '68 Firebird's 455 to EFI from Carb. Edelbrock offers two intakes: Victor EFI (really a Torker II) and Super Victor EFI (really a non-EFI Victor).

Both will fit under my hood (due to the fact that the thottle body is much shorter than my carb, so I'm saving some height there).

My local speed shop that's helping me with the conversion is recommending the Super Victor. Since I'm not building a race car and would like it to have good manners aroud town I asked them to explain their reasoning. They explained that since the injector is located immediately before the intake valve all the standard arguments about intakes for carbs don't apply in the same way. Ex. You don't need long runners to help the fuel to atomize.

They say for EFI systems the air flow of the intake is the main factor, and that's why they recommend the Super Victor.

However, I look at Edelbrock's "3500-7500 RPM" quote and get scared.

Any thoughts?

Thanks!
Dave.
PS: Both the intakes in question are single plane, correct?

[68Formula]

Well it's true the fuel injectors do the atomization, however runner length and cross-sectional area still determine optimum rpm range for cylinder filling even for EFI. As a matter of fact OEMs often use electronics to vary the runner length. How does the shop explain that?

Maybe they are confused with the fact that the engine is less sensitive to the throttlebody size than a carbed because the pressure drop does not impact the fuel curve at low rpm?

I wouldn't spend too much time argueing about it, just tell them you want the Torker style and that's that. And yes both are single plane intakes.

BTW, if that's their level of knowledge, you might want to shop around for someone else's help.

It'll be nice to see a EFI'd Pontiac motor (not too many of them). Good luck with your project.

[64duece]

I agree with the above and will add, carburated intakes are also designed to carry fuel through the runners as well. The typical low RPM 455 would probably be better with the Torker intake. Your hood will also thank you for it!

[Skip Fix]

If you measure the runner length the Torker II and the Victor are almost the same. The Victor runners have a bigger cross sectional area though. But the Torker II has a bigger plenum. The EFI real Victor allows "normal" injectors. The Torker II EFI uses the shorter PICO injectors so the fuel rail clears the TB since the intake is shorter.

My Torker II is feeding 550+ hp with a carb, unless you have some big flowing heads it should be good enough, but the PICOs limit choices of picking up used injectors.

[Karch]

You must consider the airflow capability of the heads, as the torker II, on a 455, will lose to the larger intake starting around 4000-4500, IF the heads support 280cfm+ airflow. These number are approx.

There are other options as far as intakes, but those require work (not setup for efi out of the box).

Tomahawks are used by some for their efi's as well.

Just my opinion (I personally like the super victor as it gives more potential).

[Hammered]

I converted my Pontiac to EFI and am using the Torker EFI intake on a motor that makes 550+ HP. The Pontiac guys talk a lot about keeping port velocity up so big passages are not always best. Plenum volume on the other hand can be helpful so run the Torker and use a spacer to add plenum volume. Another difference between the two is that the injectors on the Torker spray the back of the valve while the Super Victor injectors spray the port floor. Ask the shop which one is better now? Finally, don't forget that you need to run Edelbrock's pico injectors with the Torker. I have a bunch of info on my conversion here: http://john.my67.net/efi.htm

John

[Hammered]

Wow - two additional posts in the time it took to write mine. My heads are ported to flow in the 310 range and I'm running a custom roller that allows for a relatively smooth idle at about 800 rpm. There is a stock application for the picos, but I don't know what it is. Once someone figures that out, there will be a supply of rebuilts. Anyway, they're available up to 44lb/hr which should support HP in the high 600s unless you're running a blower or nitrous where extra fuel is required. I believe Edelbrock is working on a larger flowing version. You can also port match the Torker to your heads if desired. It took me a few hours to do mine.

[Dave]

I probably should have given more details in my original post. The heads in question are out-of-the-box Edelbrock heads. I'm currently running a Performer RPM intake with a Holley double-pumper. My hydraulic roller cam gives me a slightly-loppy idle around ~800 RPM currently. The engine dyno'd at ~515HP, ~580ft-lb when built. I don't plan in going beyond 6000 RPM (its rev limited there).

Looking at the specs up on SummitRacing.com, both of the intakes in question are rated from 1500 and up (The Victor going to 6500, the Super Victor going to 7500). That 1500 low end is very different than the RPM range given for the non-EFI versions.

I guess my main question is: How different will these intakes REALLY be? A ~15 HP difference at 5000 RPM really isn't going to make my knuckles go any whiter than they already get But if the Super Victor is going to be misbehaved at ~2000 RPM then I have my answer. Conjection is welcome

Also: I currently run a dropped-base air filter to clear the hood. Running the Victor EFI(aka Torker II) would let me use a normal air filter. I'd need to keep running the dropped-based air filter with the Super Victor EFI. There is something appealing about getting rid of that stupid air-filter... throttle linkages often bang into it...

John: I know all about your website, I've been studying it for weeks Thanks! I hope to build something similar one I'm done, since examples of complete systems are very very useful to people just starting out.

[68Formula]

The smaller runner cross-section and larger plenum in the Torker will improve cylinder filling at lower rpms (especially at part throttle for driveability).

Regarding the Tomahawk: I don't recall exact numbers but there was an article Pontiac Enthusiast that showed some really good numbers for a single plane intake as far as torque in the lower ranges.

Note: There is an exhaust crossover in the heads. I believe the standard Edels have them too (no doubt someone will correct me if I'm wrong). Just on the backside of the center exhaust valves is a passage-way. It is feed by both center ports up through the heads into the intake and to the other center ports. This makes the intake charger hotter. I also cannot imagine the pairing and all this dead volume does much for keeping cylinder to cylinder charge the same across all eight. The exhaust crossover was for aide in atomization. Since you don't need that now, you can fill it in with aluminum to pick up some additional power. Blocking it off at the intake face only partially addresses the problem.

Once you get the engine running decent on the EFI, trying setting more ignition timing at idle speed to smooth it out. For cranking 12-14° is good, but then set the controller (I'm assuming you're using the EFI for fuel and ignition) to 20° for idle speed and then keep increasing it in 1° until you get the smoothness you want. Experiment, but the key is getting it as smooth as possible with the minimum advance to achieve that smoothness.

[Hammered]

I'm glad to be of help Dave. Let me know if you ever need more details on my system.

Everything you're thinking about the air filter is correct. Another advantage of the Torker is that you can run a RA system if you so desire. I would advise against the Kinsler TB that I used and go with a Holley TB or something that is more common. Running a shorter TB will also reduce the restriction of the TB and allow you to increase plenum volume.

The E heads like lots of timing. On the dyno, mine wanted 38 total for max power. 34 - 36 total is average for these heads. I backed mine down to 35 to be safe on the street with pump gas.

The exhaust crossover is not of concern with the E heads and EFI intake. The E heads can be tapped for a pipe plug, but even this is not necessary because the EFI intakes don't have the crossover. In other words, the EFI intakes block the crossover. It was mostly for cold start atomization of the fuel which of course is not necessary with EFI.

John

[Skip Fix]

My heads flow in the 320 @28" range and the HP peak is at 6200 with the T2. no flat spots in the curve anywhere. Pushes the car to 10.99 @ 124 weighing 3750. I did weld and opne up the top of the runners to match my taller head ports. Teh EFi manifold looks like it has a little more meat up there.

The Tomahawk has pads to drill for EFI but the very front runners #1&2 are much narrower and need ALOT of massaging to flow the same as the rest.

[Dave]

John: Did I remember you mentioning someting about having fuel rail <-> throttle body linkage clearance issues?

I'm planning on going with the Accel 1200 CFM throttle body (not sure who the original manufacturer is).

Thanks!

[Hammered]

Yes, I had some problems but solved them by modifying the original mechanical linkage. The Kinsler TB is not compatible with any of the aftermarket cable brackets. The Kinsler TB linkage is rather bulky and sticks out too far. They also sit the TPS switch outboard further than it has to be.

For 515ish HP, you should do fine with a 1000cfm TB. A too large TB will make your throttle overly sensitive. Mine is 1000cfm and is slightly more sensitive then I would like it to be.

[Karch]

Also, there have been multiple posts on the Performance Years forums on the topics of efi and the above mentioned intakes.

Regarding the question in post #8 by Dave...I don't think you would have any streetability issues with either intake. Tuning will be the key with anything you get, but in the end, it's probably a toss-up. The torker II based intake is, I think, about $100 less than the victor based one (why they had to call them victor and super victor is beyond me, but that's another topic).

I haven't got my car on the dyno yet, but I think I am in the 520-540 range with my HR and 11:1 compression eheads. I have 42# injectors for a late model Ford Lightning, and plan on using the walbro 255 hi pressure pump.

[andrewb70]

For what its worth, I like the fact that the Torker II has the fuel rail attachment bosses cast into the manifold. While the Pico style injectors may limit you in terms of flow selection, their small size make it a nice package. It also allows the injector to be leaned over more so the fuel is sprayed at the back of the intake valve.

Andrew

[68Formula]

I should also note with fuel injection, usually a minimum 112° lobe seperation is required otherwise the MAP reading flucutates too much to calibrate at idle (114° is better).

[andrewb70]

I should also note with fuel injection, usually a minimum 112° lobe seperation is required otherwise the MAP reading flucutates too much to calibrate at idle (114° is better).

This is very true and very important. THe more vacuum at idle, the better. Pontiacs a low end torque monsters, so a milder cam is not a problem in most street applications.

Andrew

[EFI69Cam]

For what its worth, I like the fact that the Torker II has the fuel rail attachment bosses cast into the manifold. While the Pico style injectors may limit you in terms of flow selection, their small size make it a nice package. It also allows the injector to be leaned over more so the fuel is sprayed at the back of the intake valve.

Andrew

How cruicial do you see the injector aiming to be? I know its big for emissions, but most guys are running batch fire and spraying onto a closed valve 7/8ths of the time anyways.

[andrewb70]

How cruicial do you see the injector aiming to be? I know its big for emissions, but most guys are running batch fire and spraying onto a closed valve 7/8ths of the time anyways.

In this application I don't think it would matter a bit. I mostly like the cast boss for the fuel rail attaching point. The short injectors allow the height of the manifold to be shorter and the throttle body mounting pad to be lower. Makes for easier packaging, especially in Trans Ams.

Andrew

[Dave]

About Camshafts: Mine has a 110 degree lobe seperation (Comp Cams XR288HR-10). How much of a problem is this going to be?

(perhaps this should be on a different thread...)