When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Not completely true....Quads do have vacuum secondaries, however, the throttle blades in the baseplates are opened mechanically by throttle position. The vacuum portion is controlled via the upper valves (secondary side) that you can push open with a finger. If you have a sensitive foot, you can feel the "tip-in" point where the secondaries are mechanically actuated. That's why you get that whoosh, and behavior I'm describing that is not from improper tuning...
The air doors are not vacuum actuated or lack of vacuum actuated, nor do they have anything to do with vacuum. If you really want to know about the Q-jet I found this book to be very informative. It's a great read. Rebuilt and modified mine from the information in this book. Have spent many many hours tweaking and tuning. I knew nothing about the Q-jet prior to this book and rebulding mine. It's really a very very good carb properly tuned.
There is no use in us arguing about it. They are flow sensitive. How much air is on demand from the engine. Mass air flow.
edit: I do want to mention it is recommended for a street car to not use Air-Gap, as it makes tuning a bit harder.
Never heard that one. In fact, I would think its more for street because of the constant hot temps.
Drag racing engines are seldom warmed up. or hot.
The Air Gap Intake is really nothing new. Ford Edsel had them back in the 50s on those "Y" blocks. Its design was to allow cooler air to pass through under the carb.
I have never heard of the Eddy Air Gap causing tuning issues. But those Tunnel Rams were a different story.
I am up in the cold country. I have no tuning issues with my Eddy Air Gap.
My fuel no longer boils out of the carbs bowl vents.
I am using the same jet sizes as with my earlier Eddy 2101.
I am using the same timing as the 2101.
No tuning issues.
And as far as the heated cross over built into some Intake manifolds, a set of aluminum heads blocks that off anyway.
I wouldnt be surprised if the weiand is the same height as the professional products / assault intake im running as they are all cast in china possibly at the same foundry. I know my polished rpm clone is slightly shorter than the rpm I had compared it too and sold. I know these magazines and businesss do often fudge numbers to make sponsors products look better.
Last edited by augiedoggy; Dec 25, 2022 at 03:01 PM.
I wouldnt be surprised if the weiand is the same height as the professional products / assault intake im running as they are all cast in china possibly at the same foundry. I know my polished rpm clone is slightly shorter than the rpm I had compared it too and sold. I know these magazines and businesss do often fudge numbers to make sponsors products look better.
Some of the stats/details are a bit fudged as well, since many are basically the same and they need to seem different. Summits sbc dual planes are Weiand clones and some of the overseas ebay generics clones of those, all prob cast in the same place since Weiand is part of the Holley parts group and they have been overseas cast for awhile. I think the PP intake is a RPM clone tho. But Dart claims the RPM copied their intake the koolcan(now SHP)
Also if you factor a basic clean-up of of the ports/plenum/runners, I'd bet the power spread on all those intakes in that article test would be Less. A guy on another forum use to say, all the intake does is hold the carb up! Maybe for dual planes but I still think single planes it's worth doing some homework to find one that best suits your use.
Sucks that intake prices have doubled for some. I plan to buy a Summit stage 3 vortec intake and it'll cost me more than the SHP or either RPM air gap I all bought new. And $10 more than the new Motown single plane I still have in the box. Seems the ebay generic copies choices are dwindling as well, use to be more of a variety. SBC was king of the parts market for awhile in my opinion, with all the variety offered but now it seems to be starting to fade.
When I broke in and dynoed my 71's motor. ( forged steel crank - roller) The engine builder's dyno showed only a 2 to 3 HP difference between the Elde, the air gap and the Weiand.
He was amazed that the Weiand Street had a lot more Torque down low , which I wanted for a street motor. No other noticeable differences, he now is using them. I stated laughing. Holley now owns Weiand. (?)
Just as a note as a former Pontiac Guy, the Pontiac motors had "air Gap" manifolds from the factory with a valley pan.
When I broke in and dynoed my 71's motor. ( forged steel crank - roller) The engine builder's dyno showed only a 2 to 3 HP difference between the Elde, the air gap and the Weiand.
He was amazed that the Weiand Street had a lot more Torque down low , which I wanted for a street motor. No other noticeable differences, he now is using them. I stated laughing. Holley now owns Weiand. (?)
Just as a note as a former Pontiac Guy, the Pontiac motors had "air Gap" manifolds from the factory with a valley pan.
It's because the Weiand keeps the divider intact and RPM air gap has the notch/cut-out. Why I want a Summit stage 3 for my truck project, when I have two RPM air-gaps and a few other air gap dual plane intakes. All mine have the cut divider.
alot to read, with all that said, which one will fit under stock big block hood and utilize a q/jet carb? or did I miss it?
thanks for the input
Edelbrock 2101 ( pictured below ) includes 8901 cover plate for divorced choke. You can reuse the divorced choke thermostat from your manifold. You will need to modify the choke rod length or purchase this https://www.edelbrock.com/automatic-...etor-9171.html
When I broke in and dynoed my 71's motor. ( forged steel crank - roller) The engine builder's dyno showed only a 2 to 3 HP difference between the Elde, the air gap and the Weiand.
He was amazed that the Weiand Street had a lot more Torque down low , which I wanted for a street motor. No other noticeable differences, he now is using them. I stated laughing. Holley now owns Weiand. (?)
Just as a note as a former Pontiac Guy, the Pontiac motors had "air Gap" manifolds from the factory with a valley pan.
when I bought my 74 the previous owner put that 2101 performaer intake on it. They also gave up on the qjet and put a spreadbore/squarbore adapter and an edel/carter clone carb. There was a lot of spare room but I have an aftermarket high rise hood. I swapped in the assualt non air gap version intake which is definitely higher (I recall 4.65).. the article above intentionally fudged some of the numbers to make it less obvious which ones are rebanded marked up generic chinese intakes. I cleaned mine up by porting to match the heads but the runners were good on mine and I have no complaints for a $150 polished intake
Last edited by augiedoggy; Dec 26, 2022 at 11:28 AM.
alot to read, with all that said, which one will fit under stock big block hood and utilize a q/jet carb? or did I miss it?
thanks for the input
There have been numerous threads asking the same question over the years, and the discussions usually become just like this one, talking about performance and design.
In a couple of the older threads the members used straight edges laid across the hood lips in the engine bay and made measurements from the top of the oem intake carburetor pad to the straight edge to determine how much room they had to play with and then could determine how much higher the new intake carburetor pad could be.
If you plan to keep the QJet, it will limit your choice of intake models you’ll have to choose from.
If you want it to fit under an oem big block hood, purchase the intake with the lowest carburetor pad height, install your QJet and if needed find a drop base air filter to get it all under the hood.
If you want the best performing intake, for your QJet, that will fit under your hood, then ask someone like Jebby or Lars who work on C3’s, run QJet’s and could recommend the best combination.
You can also compare carburetor heights.
They are usually found on the manufacturer’s website.
A Holley or other brand name carburetor may give you more clearance do to a lower profile design and changing to a square bore carburetor would open up your choices of intakes.
You can always just built the engine for max performance and then plan to modify or replace the hood to fit everything underneath.
For example: My big block with an Air Gap, 1” spacer, flat base air filter and 3” element, may fit under my tall L88 aftermarket hood which is built 4” taller for clearance.
If not, I’ll have to run a drop base filter.
If I remember correctly, there is one model Edelbrock intake listed on their website that says it will fit a C3 Corvette.
If it says it will fit, then that could be the intake you need.
Probably any of the air gap intakes
weiands newer air gap may have bigger csa than edel. Idk. Holley list the exit size
Here is afr's on my flow bench.
I was kinda disappointed how the csa at the exit was all over the place out of the box.
unused ports are either taped up or foamed.
My cam lift is about 530 after figuring in some deflection.
It went 255cfm ported to a trimmed up 1205 that matches head exactly, at 530 lift on that runner. No intake 274 cfm or something. Not ported idk.
Csa from afr at exit was about 1.85ish
Heads are afr enforcers. Testing only the port, That one port in pic was high 250s max. before porting the head. Some ports where 270ish from afr. Now there all mid 280s
that how it goes. Especially with china heads. Obviously you want them all close to the same
These parts are going on my c3.
use to build bikes, so just using my tools I have for myself now
