May have to send this Edelbrock packing

-
TylerW

TylerW

Well-Known Member
Joined
Feb 29, 2008
Messages
1,040
Reaction score
149
Location
Elkton, TN
Well, I've been running a 600 Edelbrock on my warmed-over 318 in the Dart. It's been a love-hate relationship to say the least.

My car doesn't get driven much since it's still under "renovation", and if I let it sit a month without running, one side of the idle circuit in that carb will plug up and I have to blow it out with an air gun.

It's also calibrated too lean since I had to fudge it with the stiffest springs there are, and still have a part-throttle surge. Add to it the electric choke which doesn't work well, blah blah blah...and I'm ready to put on a Thermoquad.

I happen to have a very nice 6518s T-Quad, which was original equipment on a 440 in a '73 motorhome. That incidently also makes it the 850cfm version. That would work perfect because it has the right ports for the charcoal canister, which OCD types like me must run lol.

My question is, can that Thermoquad simply be rejetted down to an appropriate calibration for the 318 irrespective of it being the large primary version? I rebuilt that thing but I don't remember much about it now.

I know Quadrajets intimately and those you can't recalibrate easily on the primary side. However, they DID run the larger 800 cfm version on small engines like the 307 Olds, and downrated the CFM from 800 to 525 by restricting the secondary air door opening to about 50 degrees, along with secondary metering rods which were very lean and had no power tip.

Thank you.
 
Not tough at all. There is no need to down jet a Thermoquad. On anything. They have very small primaries, even the 850. They can be tuned to run well on anything, that's why Chrysler chose them. The same carburetor worked well on a 318, 340, 360, 400 or 440. Even though the big blocks, 340 and 360 had the larger version, the 850 can be tuned for the 318 easily.

The primary piston is so adjustable that there is only a need to change jets or metering rods in only the most extreme of circumstances.
 
Oh one more thing. If you have a fairly radical cam with a low vacuum signal, you will have a tougher time with any carburetor that has metering rods on the primary side. The low vacuum signal confuses the rods and springs and tends to make them bounce at idle. This is very difficult to tune out, especially with the Thermoquad.
 
The hard part about tuning a TQ is getting rods and jets.
Since you have a Edelbrock carb, I'll assume you have the tuning kit that goes along with it.
(If not, your frustrations with tuning the Edelbrock have just become evident.)
Use the AFB rods clipped down 3/4 of an inch to fit the TQ.
 
Thanks very much for the info, that's what I needed to know.

I have the spring kit, that's it. The idle drifts some and it still has a lazy response to the pedal off-idle. Doesn't try to die, but there a 1-1000 2-1000 here we go type of reaction. The T-quad may not work with this cam so I'll get the actual tuning kit for the edelbrock and try that.
 
You'd be surprised what cam I can run with a TQ.
The 1-1000, 2-2000 is a tuning issue that could be in the distributor/ignition area as well as the carb. Have a good look over. ;)
 
Sounds like the primary piston needs lowering to lean it out some. Usually too lazy indicates a rich mixture.
 
RustyRatRod said:
Oh one more thing. If you have a fairly radical cam with a low vacuum signal, you will have a tougher time with any carburetor that has metering rods on the primary side. The low vacuum signal confuses the rods and springs and tends to make them bounce at idle. This is very difficult to tune out, especially with the Thermoquad.
Click to expand...

Hey I'm glad you mentioned that because I may be dealing with the springs as well pretty soon.
The A/F meter would have told me, but now I can keep in mind ahead of time.
 
If you cannot get the Edelbrock worked out, I might would be interested in it if you decide to turn it loose.
 
Is your Edelbrock a 1406? It should be if you have an electric choke.

First, check your fuel pressure and make sure it is under 6 psi. If you're getting trash in the idle circuit, make sure you have a good fuel filter. Second, buy a pair of 71x47 metering rods and give them a try. Use the pink or silver step up springs.
 
TylerW said:
Well, I've been running a 600 Edelbrock on my warmed-over 318 in the Dart. It's been a love-hate relationship to say the least.

My car doesn't get driven much since it's still under "renovation", and if I let it sit a month without running, one side of the idle circuit in that carb will plug up and I have to blow it out with an air gun.

It's also calibrated too lean since I had to fudge it with the stiffest springs there are, and still have a part-throttle surge. Add to it the electric choke which doesn't work well, blah blah blah...and I'm ready to put on a Thermoquad...
Click to expand...

That you let it sit a mounth without running is problably not the reason why one side plug up, I can't see why it should, you must have some dirt in your fuel line.

Edlebrock is so very simple to calibrate just changing the rods, you have about 4-5 different setting on each jet just changing rods, so if it was me I should try that before changing the carb to anything else.
 
Not a fan of the Edelbrock carbs..or the "thermo-bog"..get yourself a Holley 600 easy to tune and perfect for that 318..
 
You must log in or register to reply here.
-

Back
Top