Hey there everyone,
I have a 72 Vette that I got from my Dad. He mainly drove it on the highway, and just wanted it to be quick, and sound good. He took good care of it, but wanted things to run, and not require tuning. For years, he ran a 600 Edelbrock, and that was what came with the car. I felt it was underpowered, and tried to swap a Holley 750 onto it, but the carb was poorly rebuild (by yours truly) and I just stuck the spare Edelbrock 800 I also had onto it. Currently, the 800 works, but it is not the right carb for what I want to do. I'm slowly building it into an autocross car, and hopping around to projects that are either necessary, or convenient without the plan of a standard race-car build. I also plan to be able to drive it to and from work regularly (once a week?) Recently had some rod bearings fail, so the engine got a pretty good workover, and I think I'm going to need to start looking into a more effective carb for my engine. The 800 is fine, but doesn't run as well as it did with the 750, or even the 600. It gets better fuel than the 600, but is slower to start and bogs (probably tuning issue). This car is mishmash of projects. Car is in the shop, so can't get pics of existing setup ATM.

Anyway, I'm running a 406 small block, 2.05 aluminum trickflow heads, and around 10:1 compression on 91 octane. The cam is specced to 6500 as solid roller, so I'm guessing I need about a 750CFM carb. (406*6000/3456 = 705CFM, 406*6500/3456 = 764CFM). The carb I have will give me the fuel I need to run, but it's not exactly the bees knees of carbs. Intake is a edelbrock performer (don't remember if RPM version or not), square bore, and dual plane. Previous engine build was to 7000RPM.

My question: Which carb should I be looking at? I'm not stoked about EFI, think a carb should get me where I'm going just fine, and for a lot cheaper.
Stock Quadrajet - I believe the old man still has it sitting in his shop, likely needs rebuilt.
Holley 4160 - 750 CFM? - would have to buy, but seems to have the 'easiest' tune-ability. I've had some offers for free parts, but I don't trust myself to rebuild this. Too much detail I'm not great at.
Edelbrock 800 CFM - what I have now, but maybe tune it better?

 

Use the stock Quadrajet and have it rebuilt by Lars. You're welcome.

 

If you have a square-bore manifold, you can't run a Q-Jet, so you are limited to the Holley-based platforms...

 

You are flowing some volume, ditch the performer and if you have hood clearance; put in rpm performer air-gap. The rpm performer air gap fits under my hood, but I have a 76 so the hood is higher up than some years. I would look at Quick Fuel SS series.

 

You mention 6k and 6.5k rpm numbers but your intake, Performer, is designed for idle to 5.5k.

 

What kind of driving do you mostly do with this car?

 

Autocross stuff can be low speed or high speed...but response out of the corners is vital....and depending on gearing....you might be pulling pretty low on RPM...so a good Performer RPM or Air Gap (better) would do well I think. A 750 street HP Holley has always done well for me out of the box.

I've posted before...but here's a 400 I did with Dart 200cc as cast heads, 248* solid roller with some intake/carb tests. The dual plane was a Dart (air gap style) and the single plane was a Weiand. The carb- was an out of the box HP Street 750 DP. The other was a heavily ported 283/270 intake with two WCFB carbs. Gives you an idea of TQ curves to match with your gearing.

JIM

 

You can get a Performer RPM manifold that you can put your Qjet on which would be a good way to go. if your set on the Holley style carb then i would recomend AED.

Pat

 

The Street 750HP or Classic 750HP is the way to go on these 400inch engine....I run a Classic 750HP on my own 406......you cannot do any better.....as mentioned, AED builds Holley's and does a 750HP version.......
Your intake manifold is probably a 2101 Performer......for hood clearance.....which will support about 430-440 horsepower on a 406.......so this is going to be the cork......the divider can be miller 3" across and 1" to help upstairs....but you really need an intake that moves some air with your CI/Cam/Cylinder head combo......which if you have the stock base model hood.....is a problem......I run a 7530 Team G single plane with an L-88 hood....1/2" four hole spacer......this will support 500hp easy......and that is about where I am at.....I like a single plane intake on a 400ci engine......a 406 pulls plenty vacuum to signal a carb with a single plane but the Air Gap intakes work extremely well too.....

I don't recommend a Q-Jet at this level as it would require more modification than it is worth to use one.....and they need a very good fuel supply to keep the small float bowl filled at these power levels....

Jebby

 

If you are lazy try allstate carburetor in new York they are pretty good at specific out and building a carb for you. There are others..I agree no q jet at this level.

 

I have dealt with Allstate and they are great.......Also look at Patrick @ Pro Systems in Michigan........he has thousands of files dating back over 20 years on every combo he has ever worked with.......just a little more than Holley gets for an HP too.....

Jebby

 

Brawler 750 manual secondary's best bang for the buck. Easier to tune then Holley nicer carb better feature's. I have run them right out of box with zero issues. Maybe adjust the air bleed

 

$575.00 (by far the lowest price) is a lot of Buck for the Bang. (Demon level)

 

I bought one 3 years ago from the local parts store it was 389 just looked at summit holy crap they have went up. But same Holley is 200 more and not as nice

 

I mix my driving up quite a bit, probably 40% highway, 40% around town, 20% autocross. In regards to performance, I am solely looking to improve the autocross driving experience, so will aim my carb/intake toward that. For autocross specific driving, I can either run entirely in first gear, and wind up from 3500-6500RPM, or jump to 2nd, and run between 2800-6000. I've been running in second more often to get into the torque more than just HP, but haven't really raced it in a year due to the rod-bearings and the time it took to get a new camshaft.
I got looking at some pictures I have on my phone, and it does look like I have the base performer 2101, like Jebby guessed. The Hood clearance shouldn't be an issue, as I have an aftermarket 'cowl induction' hood. I can remove my carb spacer and get a taller intake without causing too much havoc under the hood. Now I just need to get a actual vent/cowl induction so I can get nice cool air under the hood.

I'll start looking more specifally into Holley 4150 or similar carbs. Haven't done much reading on the brawler vs HP.

 

You can ck on Holley re-man carbs from Summit or Holley. They are warranty returns and then they are gone through one by one by hand to make sure they are good. 9 times out of 10 it's someone who bought wrong carb or had other issues. If they can see it was bolted on something it has to be torn down and gone through. I've been in the factory several times and seen the process and the extra ck's they go through to make sure they flow properly.

One of the best bargains there is.

JIM

 

Who is Lars?

 

Google the name Lars Grimsrud, ex-GM, probably best Quadrajet expert in the country along with Cliff Ruggles. He can be directly contacted at v8fastcars@msn.com