Avanti Conversion!

[mfg]

A friend who owns a very nice '81 Avanti ll called saying his engine is running poorly due to carb/computer related issues. (His Avanti has the early computer controlled carb & distributor system))

I suggested converting to an Edelbrock square bore carb, using their 'thin' adapter plate on his spread bore manifold...also changing to an aftermarket vacuum advance type distributor.....

Was this good advice?

 

 

[Gunslinger]

Yes.  I would have suggested an Edelbrock Performer EPS intake as well if there was hood clearance.  The EPS is designed specifically for their square-bore carbs and posts somewhat better numbers than a stock intake or Edelbrock’s Performer intake.  

[mfg]

9 minutes ago, Gunslinger said:

Yes.  I would have suggested an Edelbrock Performer EPS intake as well if there was hood clearance.  The EPS is designed specifically for their square-bore carbs and posts somewhat better numbers than a stock intake or Edelbrock’s Performer intake.  

Agree...however this fellow basically wants dependability, which his Avsnti is not giving him now....A manifold change would be nice but probably not in the cards.

Too bad they never produced a spread bore Carter AFB/Edelbrock!!

[Avanti83]

12 hours ago, mfg said:

A friend who owns a very nice '81 Avanti ll called saying his engine is running poorly due to carb/computer related issues. (His Avanti has the early computer controlled carb & distributor system))

I suggested converting to an Edelbrock square bore carb, using their 'thin' adapter plate on his spread bore manifold...also changing to an aftermarket vacuum advance type distributor.....

Was this good advice?

 

 

Yes as it's the most straight forward route. Like Bruce, I'd generally replace the intake and cam but that's not in the cards here. Generally places like Summit Racing have brand name and also lower cost distributors. The brand names can cost a bit but they are usually good quality. I've run a couple lower cost distributors from Summit and others with good results if price is an issue.

 

[wildfelr]

RQB3263/81/305/700r4   Well I did exactly that on RQB3263  some 6 or 7 yrs ago..... I have bored you all with thoes details here before .... BUT.... the change is simple ... install a non-electronic Q-Jet less than $200  DIRECT  bolt on to existing manifold  /one wire ....remove all the wires/components computers ect  associated with it... I installed a quality after mkt.  distributor/wires,  MSD I think ....and havent touched it in years.... I also did the cam for a Crane RV Torque cam/lifters/springs but thats another story for another day... BTW the 305 needs all the help it can get especially it you have an OD trans (700R4).... keep in touch ....BILL

[mfg]

2 hours ago, Avanti83 said:

Yes as it's the most straight forward route. Like Bruce, I'd generally replace the intake and cam but that's not in the cards here. Generally places like Summit Racing have brand name and also lower cost distributors. The brand names can cost a bit but they are usually good quality. I've run a couple lower cost distributors from Summit and others with good results if price is an issue.

 

Yes, Summit  does have the needed parts...My friend Wayne's Avanti is a real nice car with under 70K original miles...however, the electronic Quadrajet has developed a mind of its own!

[mfg]

The problem with the original system is that the electronic Quadrajet carb can be overhauled perfectly, but if the computer, or a sensor, is out of whack the car still isn't going to run right.

[Avanti83]

15 minutes ago, mfg said:

The problem with the original system is that the electronic Quadrajet carb can be overhauled perfectly, but if the computer, or a sensor, is out of whack the car still isn't going to run right.

Correct. Be sure he knows the timing both initial and final before he pulls the original distributor. That will give him a starting point when he replaces it. During the 70 and 80's GM did some funny things particularly with initial timing on emissions engines. I suspect he will end up with a bit more initial advance than the computer is running but it's not hard to sort out when he gets the new dissy installed.

Let us know how it turns out.

BTW, welcome back and I also miss Gary on the forum.  

Edited October 8, 2022 by Avanti83

[Gunslinger]

Edelbrock used to sell their version of the Quadrajet which was and is an outstanding carburetor.  The molds/castings for the carburetor were accidentally destroyed some years back so they had to stop selling them.  Too bad...it would solve a lot of problems today without resorting to different carbs and intake manifolds for best performance.  

 

Summit is a a great place for parts.  Tell their techs what you want out of an engine and what kind of driving it will receive and they will give solid recommendations for the right mix of parts to achieve that regardless of name brand or house brand.  I'm a big fan of Edlelbrock carbs and intakes and Lunati Voodoo asymmetric cams...gives good power and idle without the lope of a standard high lift design.  But there's a lot of great products out there by many makers.  

[mfg]

Well said.....all!

[mfg]

Well, I went for a ride in this '81 Avanti this morning...it runs OK while at speed, but when idling in 'drive' it seems to load up (floods) and eventually stalls..Then it's hard to re-start.

This sounds like an internal mechanical problem inside carb....(sinking float, bad needle & seat, etc.)

So, although it could be a waste of time and $$, we are going to clean out and overhaul electronic carb and install new composite float.

After that, if the situation doesn't improve,.....HELLO SUMMIT!!

 

[mfg]

On 10/7/2022 at 8:15 PM, mfg said:

 

Too bad they never produced a spread bore Carter AFB/Edelbrock!!

CORRECTION...They did! (sort of)...The Carter THERMO-QUAD!

(I never liked them)

[mfg]

Well, my friend Wayne got lucky, the problem with the carb turned out to be a saturated (heavy) float!

A new float along with a new fuel needle & seat, plus a new accelerator pump plunger, and new fuel filter seems to have corrected the issue......

I put about 20 miles on the car yesterday, and it ran/ idled quite nice!