If I can get the old L48 Q-jet, who here can rebuild it so it works right? I can check with the guy I got the car from.

All I would need is pcv and vacuum advance ports, can all the rest be plugged? And maybe an electric choke if it does not have one.

 

Lars is the Q-jet carb guru.

 

I'm paying attention to this thread as we are installing my new 383 this w/e. I purchased a 2601, Ed Performer Air Gap (to go along with my Lars built QJ), and after reading this post, and not wanting to mess with not having enough hood clearance, and the carb to top of the air cleaner clearance Lars was referring to, planned to go pick up a 2101, the standard performer intake (that was copied from GM's L82 intake).
However, the Edelbrock site shows the 2101 is only .27" shorter than the 2601, that's not going too make much of a difference.
Then, I read on a oost here there is a Ed Performer RPM Air Gap, that one is .70" shorter, maybe I bought the incorrect intake to begin with.
Is .27 of an inch going to make a big enough difference to run around and do some exchanges?

 

My Air Gap on Vortec heads wouldn't fit under the hood of my '74. Pretty sure the '77 is the same hood.

 

I have a Performer RPM Air Gap on my 406, on the 77...with stock hood. I use a 1" inch drop air cleaner , 14" x 3" tall K&N filter, on the Holley SA 750 double pumper. It fits and works just fine. The hoods are all the same height from 73-79. The small block hoods 68-69 are WAY lower in height than 73-79. I really don't know about 80-82, but they also appear low.

As for the distance between air cleaner gasket and lid being under 3".....I would not know. I guess I can measure it. BUT.........not to dispute Lars and his testing, .....my question is, at what RPM does the minimum 2" distance hurt power? If its at 5000 RPM, its irrelevant to me, and frankly to anyone who does not rev to 5000. If you do, if you race it.....yes, it could mean a loss. If not, its irrelevant. Unless it affects HP and torque and much lower RPM numbers.....or does it hurt HP and torque at ALL RPMS? And at what point does a stock low rise manifold restrict flow enough compared to an RPM high rise manifold that its still a better choice. This is what matters to know.

I am interested in hearing Lars response to these questions..

 

I have a 2101 w. Q-jet and stock air cleaner on my '76. I have 3/4" clearance to my hood.

 

If it was me Id put an EPS or the equivalent from Weiand.
SMI (Sean Murphy Induction) also builds a decent Qjet

 

[QUOTE=lars;1605694652]No, it's not. Ditching the 1950's carb and getting a 1970's 750 cfm Q-Jet is. If you find a '78 L82 carb, it's 800 cfm. Your manifold is not your limiting issue.[/QUOTE. Is the ZZ4 intake any better than the L82 intake?

 

I put a Baldwin motion hood on mine and put a 5" tall filter on it and it did pick up power noticeably.
Not to disagree with Lars but I see no difference in the cast iron factory intake and the aluminum version. Looking at the carburetor mounting pad there is a huge difference between the factory intake and the performer. That said all 3 are garbage.
If you have stock heads and factory exhaust manifolds you likely won't see much difference . In my case however the air gap with a spacer made a worthwhile improvement..

 

[QUOTE=wilcar;1605702723]The ZZ4 is a better intake but it is .5" taller than the L-82 intake. You just need to measure what you have now. I didn't want to risk the paint job on my '80 with only 1/8" hood clearance left after the swap.

 

Not sure why the topic of hood clearance is so mysterious, and so all over the place, because there are only so many combinations of intake/carb setups, but it is, in general. I did a bunch of research before making my selection of airgap intake and carb (Eddy AVS2) combo for my '69 (which I have not yet installed) and 385 stroker (.040 over) - there are quite a few threads from various forums on the internet that discuss this, and sometimes you end up being more confused than you were before starting the research.

I ended up buying a LT1/BB hood, as most everything I read at the time indicated that a 14"x3" with a .6" drop base would fit, with between 1/2" to 1" clearance in small block configuration with that setup, and not to forget that the LT1 also had a high rise intake from the factory. I guess I'll find out for myself when I install it. Lots of other stuff to do before I get to that. I will create a new thread after I have done this, and will include specifics.

There are probably other variables that are equally important, like motor mounts, that depending on age (or if they were replaced by aftermarket ones that could affect the height), or other small variations in frame configuration from chassis to chassis that could add to these variables that make for less than an exact science.

I'll use the high tech measuring technique that others have used - silly putty, then gently close the hood, and then measure. I can always try to find a 2.5" filter (not easy) if I need more clearance. I just love the looks of that Airgap.

What would not work is if I kept the stock hood, and I quite like the looks of the LT1/BB hood anyway. I'm pretty sure that I read it somewhere, and I'm not sure what the height difference between the early C3s and the 74+ C3s are, but I believe they as tall, (or maybe even taller) than the LT1/BB hoods - But not as tall as the L-88 hoods.
From what I've read for early/chrome bumper C3's:

For a SBC-equipped Vette with a high rise manifold, you need a BB/LT1 hood
For a BBC-equipped Vette with a high-rise manifold, you need a L-88/ZL1 hood

Again, seems to me that the 74+ hoods are at least as tall as the BB/LT1 hoods on the 68-72 cars, but I'm sure someone here will correct me if that is not accurate.

 

I can't testify that they are as tall or taller, but the Airgap on my small block with Vortec heads would not fit my '74 even with a drop base air cleaner.

 

Do you have pictures ov this mod? I have an old Performer in my 73 that i'll probably keep a little while longer. Would you dare doing that mod with the intake on the engine? Plug the runners, etc? I wont be removing mine until i find a nice single plane.


Also, are all you guys with 74-79 hoods and clearance issues keeping the cowl structure in place? Are you pushing your AC's through the hole? Or are you cutting the whole structure out? If your AC wont go through that cowl hole, there is an easy inch to be gained cutting that inner structure out. Thats what i'd do, but i'm not keeping the stock hood, nor do i run an air cleaner.

There might be a niche to fill here. A lot ov people seem to like that stock hood, but just need another 1-2" inches. A stock-looking 74-9 cowl hood with just a small gain in height would sell well i think.... I personally love the look ov the stock cowl. I just wish it was 5" taller...

 

 

Back when I ran a small block, I used the Performer RPM Q-Jet manifold (same height as most of the RPMs). Stock hood with Moroso drop base air cleaner. Air cleaner has a 1” drop, 3” filter and a dome so was probably getting 2.25” to 2.5” above the carb. Worked well enough for my 350 and fit under stock hood. Just had to dimple the base for the Q-Jet pump arm.

Old post: https://www.corvetteforum.com/forums...post1601757056

Pics:

 

I have a 78 with an Performer RPM Air Gap and Fitech EFI on a 383. Air cleaner is a 3” X 14” K&N X-Stream Air Flow filter assembly (filter element in the lid) with a 1” drop base mount. No clearance issues and no noticeable power restriction. I agree that if power restriction is at 5000 rpm or above it is a non-issue for a street car.

 

The 73 and up C3 hoods are 3/4" taller then the 68-72. Is the fitech the same height as a q-jet? I disagree that over 5000 for a street car is a non-issue

 

Yup. I dont get this 'street' engines have to be low-RPM mindset. The magazines have been pushing that bullshit forever. Yet, go to the track, and its horsepower winning races. On the street, you're either cruising, or trying to school someone. If its the latter, then why aren't you driving it like you're at the track?

 

I can’t speak to the Q-Jet but the FiTech is the same height as the Edel. (Old Carter AFB style). As for Over 5000 rpm being a non-issue for a street car, how many “street” cars ever turn 5000? The vast majority of street driven C3s with stock Gen1 SBCs will never see 5000. Those that do will likely see them nose over not because of a restricted air cleaner but because of a multitude of other things that limit the torque curve. Things like cam lift & timing, head intake/exhaust runners, roller or flat lifters, roller rockers, valve size, headers or stock manifolds, etc. Without putting the engine on a dyno and doing a sanitized test there is no way you can rightfully tell what is causing the engine to nose over. Certainly not the “seat of your pants”. All that said, for the “average” guy that has a driver with a stock or near stock engine 5000 rpm is not an issue. If you have a "built" SBC that can stand to turn 5000 on a regular basis then good for you. FYI, it's TORQUE that wins races.

 

Where do people come up with this stuff 🤣