Edelbrock AVS-2 carb connections

Message Topic Search Topic Options Post Reply Create New Topic Printable Version Translate Topic

   I just recently began the process of replacing my Holley 4150 with a new Edelbrock AVS-2.  It is being installed on a 1973 429.  I am also replacing a Carter fuel pump with the Edelbrock Performer fuel pump. I am not overly knowledgeable with carbs and need some advice on the connections on the carb.  Here are a few pics of how I have it set up at the present time.  

First, the carb has 3/8ths vacuum ports at both the front and rear of the carb.  Edelbrock says the rear is for brakes and the front is for PCV.  My brake vacuum is coming from the intake.  Is there an issue with running the PCV to the rear port?
Second, there are two3/16th ports on the front of the carb for distributor advance, one for emissions controlled vehicles and one for non emissions controlled vehicles.  Mine being a 1973 was at the beginning of any pollution controls but not sure if it is considered emissions controlled.  The Holley I replaced had the distributor vacuum advance capped off.  Do either of these ports have to run to the distributor?
After installing everything as pictured along with the Edelbrock fuel pump upon going on a test ride it ran really well until about 5 minutes into the run.  I was maintaining a steady 40-45 mph and the engine died.  After pulling to the side of the road I started the engine without any problem.  This scenario repeated itself a few times until I got back home.  
The fuel pump literature states it produces 6 psi and doesn't require a regulator for Edelbrock carbs.  However, upon getting back home the engine was putting out around 7psi.  Any suggestions are appreciated.  

Edited by 1973gts - 04-August-2024 at 1:57PM

Author	Message Topic Search Topic Options Post Reply Create New Topic Printable Version Translate Topic
1973gts Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 05-March-2018 Location: Grand Rapids Mi Status: Offline Points: 720	Post Options Post Reply Quote 1973gts Report Post Thanks(0) Quote Reply Topic: Edelbrock AVS-2 carb connections Posted: 04-August-2024 at 1:50PM
	I just recently began the process of replacing my Holley 4150 with a new Edelbrock AVS-2. It is being installed on a 1973 429. I am also replacing a Carter fuel pump with the Edelbrock Performer fuel pump. I am not overly knowledgeable with carbs and need some advice on the connections on the carb. Here are a few pics of how I have it set up at the present time. First, the carb has 3/8ths vacuum ports at both the front and rear of the carb. Edelbrock says the rear is for brakes and the front is for PCV. My brake vacuum is coming from the intake. Is there an issue with running the PCV to the rear port? Second, there are two3/16th ports on the front of the carb for distributor advance, one for emissions controlled vehicles and one for non emissions controlled vehicles. Mine being a 1973 was at the beginning of any pollution controls but not sure if it is considered emissions controlled. The Holley I replaced had the distributor vacuum advance capped off. Do either of these ports have to run to the distributor? After installing everything as pictured along with the Edelbrock fuel pump upon going on a test ride it ran really well until about 5 minutes into the run. I was maintaining a steady 40-45 mph and the engine died. After pulling to the side of the road I started the engine without any problem. This scenario repeated itself a few times until I got back home. The fuel pump literature states it produces 6 psi and doesn't require a regulator for Edelbrock carbs. However, upon getting back home the engine was putting out around 7psi. Any suggestions are appreciated. Edited by 1973gts - 04-August-2024 at 1:57PM
	Dave - 1973 GTS N code

1973gts Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 05-March-2018 Location: Grand Rapids Mi Status: Offline Points: 720	Post Options Post Reply Quote 1973gts Report Post Thanks(0) Quote Reply Posted: 05-August-2024 at 8:23AM
	Also one other question, if the pump is putting out more pressure than the carb is designed for, does it damage the carb or just flood it out?
	Dave - 1973 GTS N code

72 RS 351 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 04-September-2014 Location: Knoxville TN Status: Offline Points: 3445	Post Options Post Reply Quote 72 RS 351 Report Post Thanks(0) Quote Reply Posted: 05-August-2024 at 9:14AM
	Extra pressure does raise the float level some, the 7psi might not be enough to cause too much trouble. But if it's higher than that sometimes and you don't know it, then it might be flooding the engine. What kind of fuel pump is it, it might not be a trustworthy pressure unit? If you aren't sure about the pump's pressure to be reliable, a regulator might be a good idea.
	*Don* 73 Ranchero "Sport 72 front end", floor shift/console, planning EFI 7000 rpm 351 stroker 73 Ranchero GT 351C-4V &4R70W for sale later. 92 Lincoln Mark VII SE GTC, OBDII 347/4R70W

1973gts Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 05-March-2018 Location: Grand Rapids Mi Status: Offline Points: 720	Post Options Post Reply Quote 1973gts Report Post Thanks(0) Quote Reply Posted: 05-August-2024 at 10:44AM
	The pump is an Edelbrock Performer RPM and I bought it because Edelbrock says 6psi and it doesn't require a regulator. I'll be contacting them tomorrow and see what they say.
	Dave - 1973 GTS N code

Rockatansky Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 30-July-2010 Location: On The Road Status: Offline Points: 6398	Post Options Post Reply Quote Rockatansky Report Post Thanks(0) Quote Reply Posted: 05-August-2024 at 1:17PM
	i don't care for the vacuum tap off the single runner, you have the brake booster and what else connected there? i wouldn't connect anything of consequence to a single runner tap, maybe the climate control reservoir and that's about it. IMO the brake booster and the transmission vacuum modulator need to be direct to the intake plenum to pull from the benefit of the entire intake rather than a pulsing single runner
	72 GT Ute

1973gts Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 05-March-2018 Location: Grand Rapids Mi Status: Offline Points: 720	Post Options Post Reply Quote 1973gts Report Post Thanks(0) Quote Reply Posted: 06-August-2024 at 9:21AM
	Rock, glad you caught that, wasn't aware that couldn't be used for the brakes, will rectify it asap.
	Dave - 1973 GTS N code

1973gts Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 05-March-2018 Location: Grand Rapids Mi Status: Offline Points: 720	Post Options Post Reply Quote 1973gts Report Post Thanks(0) Quote Reply Posted: 06-August-2024 at 1:09PM
	Response I got from Edelbrock tech support states that their fuel pump does not require a fuel regulator and stated there could be other reasons the pressure is too high such as changing fuel line size. The fuel line is 3/8 which is what the fitting on the carb is and the same as the previous line. Any reason anything else would affect fuel pressure besides the pump?
	Dave - 1973 GTS N code

72 RS 351 Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 04-September-2014 Location: Knoxville TN Status: Offline Points: 3445	Post Options Post Reply Quote 72 RS 351 Report Post Thanks(0) Quote Reply Posted: 06-August-2024 at 2:59PM
	You might need a pressure gauge to first confirm it's not running within the proper range of pressure. Is the float level easy to adjust, try to play with it a little.
	*Don* 73 Ranchero "Sport 72 front end", floor shift/console, planning EFI 7000 rpm 351 stroker 73 Ranchero GT 351C-4V &4R70W for sale later. 92 Lincoln Mark VII SE GTC, OBDII 347/4R70W

1973gts Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 05-March-2018 Location: Grand Rapids Mi Status: Offline Points: 720	Post Options Post Reply Quote 1973gts Report Post Thanks(0) Quote Reply Posted: 07-August-2024 at 1:56AM
	There is a pressure gauge on it just before the carb connection, it was consistently reading 7 to a little above 7.
	Dave - 1973 GTS N code

72FordGTS Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group GTS.org Admin Joined: 06-September-2005 Location: Ontario, Canada Status: Offline Points: 6780	Post Options Post Reply Quote 72FordGTS Report Post Thanks(0) Quote Reply Posted: 07-August-2024 at 2:04AM
	FWIW, Ford connected the brake booster and transmission modulator to a single intake runner from the factory on these cars. I don't think it would be an issue for a engine with lots of vacuum. A brake booster is just a reservoir. What kind of cam are you running in the engine? As for the fuel pressure, mechanical pumps are not always the most steady at supplying pressure and Edlebrock's are very sensitive to pressure. Have you checked the pressure under various conditions? How steady is it? It might be worthwhile to look at some sort of pressure regulator. How is the response on the AVS2? What size did you run?
	Vince 1972 Ford GTS Sportsroof - Survivor, One Family car GTS.org Admin

1973gts Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 05-March-2018 Location: Grand Rapids Mi Status: Offline Points: 720	Post Options Post Reply Quote 1973gts Report Post Thanks(0) Quote Reply Posted: 07-August-2024 at 2:53AM
	Vince, the cam is an Edelbrock Performer RPM cam. The issue I have is that Edelbrock states this fuel pump makes it so you don't need a regulator and that is the whole reason I bought it (it's not cheap). I've only taken the one test drive with it so far because I wanted to see what all the possibilities were for it acting this way. I will be trying different sustained rpm runs in the garage and see what the results are. The carb is a 650 cfm, the response was very good, better than the Holley I had on it. Edited by 1973gts - 07-August-2024 at 3:13AM
	Dave - 1973 GTS N code

Eliteman76 Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: 20-March-2006 Location: Nebraska, USA Status: Offline Points: 5450	Post Options Post Reply Quote Eliteman76 Report Post Thanks(0) Quote Reply Posted: 07-August-2024 at 6:42PM
	What AVS2 model are you running, just seen it's a 650CFM. I went with the 1913 800CFM vac secondary, but I am running deeper gears, a TKX 5 speed, and I can tell you on my Q code 351C, with the RPM air gap intake, Performer RPM heads, my '72 is a rocket ship now. But I have no issues laying into things. As far as hookups: Front port is meant for the PCV valve off the front left valve cover PCV valve. Hose off the right rear valve cover goes to the air cleaner. Back of the intake or the back of the carb, I have an AN to NPT fitting screwed into the intake/carb and going to the "tee" block on the firewall. Should really upgrade that block to a piece of billet aluminum or a brass block, but using stock Torino. That block feeds to my brake booster and the HVAC system. As far as fuel PSI, I've been told the Edelbrock should be no more than at 6.5-7PSI otherwise it can lead to issues. I am running a RobbMC 550 mechanical pump, and one of their regulators. I need to revisit my PSI, I was getting too much and dialed it back. Have some tuning I need to do and double check my fuel system. I may have dialed the PSI back too much. Still want to swap my frame hardline to my 1/2" line I had Inline make for me, and the new tank sending unit, but that's going to have to wait a while.
	Andrew:GTS.ORG admin, '72 Q code 5 speed Restomod Pondering: #99Problems

72FordGTS Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group GTS.org Admin Joined: 06-September-2005 Location: Ontario, Canada Status: Offline Points: 6780	Post Options Post Reply Quote 72FordGTS Report Post Thanks(0) Quote Reply Posted: 10-August-2024 at 1:59AM
	Dave how is the carb coming? Any results on the fuel pressure? It's possible if your pump is putting out 7 or slightly more this could be causing issue. You could contact Edlebrock to see if you pump is within spec of the carb or exchange the pump to see if you can get a lower pressure output. How is the float level on the carb? With a performer cam, I would think your engine should still have pretty strong vacuum, so I don't think using the intake port on the manifold should cause issue, but maybe Rock or somebody else might have info to the contrary. I use the intake port on my engine for brakes and trans modulator and I have about 16" of idle at vacuum with my cam, but as much as 20" at light cruise. Doesn't seem to be any issues with my car. I missed your first question on the distributor. Typically, a ported vaccum port is used for a distributor canister, although some prefer to use full vaccuum. Your instructions should show you which port is which. Otherwise, use a vacuum gauge. A ported vacuum port will have no vacuum at idle, but when revved up will open up. What distributor are you running? Some factory distributors from this era used dual diaphragm canisters, which use both ported and full vaccuum.
	Vince 1972 Ford GTS Sportsroof - Survivor, One Family car GTS.org Admin

1973gts Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 05-March-2018 Location: Grand Rapids Mi Status: Offline Points: 720	Post Options Post Reply Quote 1973gts Report Post Thanks(0) Quote Reply Posted: 10-August-2024 at 5:03AM
	For both Andy and Vince, the carb is a 1906, 650 cfm with an electric choke. The info with the carb says psi should be 5.5-6 psi and the fuel pump info says it puts out 6 psi and no regulator is needed with Edelbrock carbs. I've touched base with Edelbrock tech and they agreed too high a fuel pressure can cause my problem but stated it must be something other than the fuel pump. They wondered if I had changed fuel line size, I advised them that it's the same (3/8) which is what the pump and carb call for. I am in the process of installing a QFT fuel regulator and will dial it in to 5.5 at first and see how it goes. I have a feeling Edelbrock is not going to be much help in solving this. Is there anything else that would increase fuel pressure after the pump? Also when I was running it I had it hooked up to the ported (passenger side) connection as per Edelbrock. As far as any vacuum canisters the car had none when I purchased it from P/O. As far as valve cover hose hook ups, presently have an oil breather cap on driver front valve cover and pcv valve on pass rear. Does it matter where the pcv valve goes? And do I need a breather hose to air cleaner from the other valve cover? One last thing, the air cleaner I have is a stock Ford 429 but not sure from a Torino. Due to the AVS needing a throttle linkage/kickdown adapter for a Ford the carb throttle system sticks out to where the air cleaner bottom causes interference unless it is rotated counter clockwise to where the snorkel is pointing to the driver front corner of the engine compartment. There is a large cut out on the under side of the air cleaner base which allows the throttle linkage free movement in this position but if one wants a purely stock look the AVS may not be the right choice unless my air cleaner is not from a Torino and the correct one has the cleaner cut out on the drivers side. Again thanks for any more info/suggestions. Edited by 1973gts - 10-August-2024 at 5:11AM
	Dave - 1973 GTS N code