# 1970 400 Carb Change



## LCplOsborne (Aug 6, 2009)

I'm running in what used to be a fully-stock 1970 400 block. What's changed is that I'd been running a Rochester Quadrajet, and am now running an Edelbock 1407 (squarebore with adaptor). The reason I switched was that the secondary cam in the Qjet broke in half, leaving me surging down the road with fully open secondaries and no fuel in them. I'm nowhere near any store with appropriate kits, but am considering ordering a full kit from Cliff to restore the Qjet (it comes with a new cam).

My question is that while I'd been running the Qjet I had a great deal of power at the low range, I was ALWAYS able to squeal tires at takeoff and the tires would also chirp at shifts from 1-2 and 2-3 (Automatic tranny). 

However, running the Edelbrock I dont have the squealing or chirping, and dont seem to have the same raw power at takeoff. On the plus side overall accelleration from 1-80 is MUCH smoother than with the Qjet. No hesitation during shifts at all. With the Qjet there would be a slight stall and then the tires would chirp and I'd take off again on each shift. I'm wondering if this is a tradeoff in carburetor types (spreadbore vs squarebore) or perhaps I can attain the same power with the Edelbrock with proper tuning.

Should I get the $90 kit and fix up my Qjet? Or keep messing with the Edelbrock?


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## xcmac26 (Dec 1, 2008)

fix the q-jet, sell me the edelbrock at discount:cheers

My understanding is edelbrocks are very street worthy carburators, made to run smooth but you sacrifice some outright performance in the process. You just need to ask yourself if you want that smoothness or if you want the car to be a little rough and wild.


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## LCplOsborne (Aug 6, 2009)

Well I'll work on ordering the kit, but in the meantime I had another question about this Edelbrock 1407. On the Qjet I had a manifold vacuum port on the rear that I was using for the brake booster hose. On the Edelbrock there was also this port, but no nozzle provided for the port, only a plug. Instead, I attached the brake booster to a large central PCV port on the front of the carb that the Qjet didn't have. After doing some research as to what that port is actually for, I figured it wasn't appropriate for the brake booster, so I got a nozzle and switched it to the back, leaving the PCV port open. After determining that this plug always pulls vacuum anyway, I plugged it with a short length of hose and a big screw. Did I end up changing anything at all? Is there a difference in vacuum pressure between these two ports?


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## xcmac26 (Dec 1, 2008)

:confused

I have no idea. Anyone else want to field this one?


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## geeteeohguy (Feb 2, 2008)

Depends on if the port is above or below the throttle plates. You want the brake booster, and the pcv, to be hooked up to direct manifold vacuum. Below the throttle plates. BTW, I vote for the Q-Jet. Economy AND raw power.


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## LCplOsborne (Aug 6, 2009)

Switched to a remanned QJet yesterday and very pleased.


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## 68greengoat (Sep 15, 2005)

Good choice.....


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