SportZ2 Posted June 28, 2005 Share Posted June 28, 2005 Have a question for anyone that knows Holley vacuum secondary carbs. I put the carb on the car, started fine, idles fine, runs at any speed as long as I didn't get on it too hard. Realized that the secondaries weren't opening. So as a temporary fix I zip tied the linkage to bypass the vacuum. Took the car for a drive and what a difference. My question is, what causes the vacuum secondaries not to work? No vacuum leaks that we could find and from what I understand vacuum is very low with the secondaries open. Please correct me if I'm wrong. Thanks in advance. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted June 28, 2005 Share Posted June 28, 2005 You will need to install the lightest (weakest) possible spring in the secondary diaphram. In such a light car, there is not enough vacuum to overcome the spring tension. http://www.holley.com/HiOctn/TechServ/TechInfo/Trblsht.html http://www.holley.com/HiOctn/TechServ/TechInfo/f4010.html Quote Link to comment Share on other sites More sharing options...
SportZ2 Posted June 28, 2005 Author Share Posted June 28, 2005 Thanks Tim, I'm guessing the spring is way too strong since my secondaries don't open at all. The weird thing is I have used this carb on a V8 conversion before and didn't have this problem. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted June 28, 2005 Share Posted June 28, 2005 The diaphram may also be ruptured. If there was no work done on the carb in the time that it worked before, and now, I'd consider this as well (especially if it worked fine on another comparable V8). If indeed you were "oversized" on the carb to where there was not enough air flow to open the secondary, then by theory, the engine does not need the additonal flow, but if, as you say, the engine feels choked down by using only the primary metering, then it sounds like there should be plenty of vacuum drop to open the diaphram. Quote Link to comment Share on other sites More sharing options...
Pyro Posted June 28, 2005 Share Posted June 28, 2005 There could also be a bad seal on the lid of the vacuum advance canister. The diapham makes a seal with the lid and can tear or squeeze out if not installed right. I use the paper test on my car to see if the secondaries opens. Drop a small piece of paper in the secondaries and drive the car hard then look down the carb to see if it is still there. To check the seal of the vacuum canister, remove the canister and push up the rod. Then hold you finger over the port that goes into the carb and release the rod. If the rod springs back then the seal is bad. Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted June 29, 2005 Share Posted June 29, 2005 JEGS part numbers 510-135-4 Vacuum secondary daiphram. (Incase yours is leaking or has a hole) for 8.99 510-20-13 Assorted Springs (tuning) 9.99 510-20-59 Quick Chang kit (allows flip of a lever spring changing.) 11.99 For about $30.00 plus shiping you can fix your problem. Properly installed secondaries can not be felt when they "kick in" There should be a smooth transition as they open. The instructions said to drop down two spring sizes until you feel a lull or what others say is the secondaries kicking in. This is actualy the secondaries kicking in too soon and temporarily running too rich. Then go up one spring. Some idiot gear heads think that if you throw in the lightest spring and put a 50cc pump "it is basicaly a double pumper." Then they are amazed at it's horrible gas milage. More is not always better. A few final points Replacing these parts is very easy and takes a few minutes. Just read the instructions before messing with it. Forcing open the secondaries is dangerous. If Holley is your carb, buy a good manual on it. Quote Link to comment Share on other sites More sharing options...
orklc Posted June 29, 2005 Share Posted June 29, 2005 I once remove the check ball (#37 on the diagram) and that by itself caused the secondaries to open as the vacum increased. The check ball is a little ball bearing in the Diaphragm assembly. I am not sure if this mod will cause any other problems in your set up but in the v8 set up that I had 350 LT1 and a Holley 780CFM it made the car a lot more responsive. Good luck. Quote Link to comment Share on other sites More sharing options...
SportZ2 Posted June 30, 2005 Author Share Posted June 30, 2005 Thanks for the quick responses. I will buy the parts Tony78_280z listed. All the parts look fine on the carb, just guess it's been sitting too long between conversions. Someone also suggested I put in lighter springs in the distributor for better rsponse but is that really needed since I'm already running 30 degrees total? I know that the carb needs to be tuned better and will work on that next week (floats, jets, etc). Not sure about the check ball removal for better response. Will wait to see what others have to say. Quote Link to comment Share on other sites More sharing options...
jt1 Posted June 30, 2005 Share Posted June 30, 2005 Why only 30 deg total? Lots of times the best results are with 34 -35 deg total. You might play with that some and see what happens. John Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted July 2, 2005 Share Posted July 2, 2005 Don't just get the parts. Get a good book too. To tune a carb you need steady fuel pressure and it is advised that timing be acurate. Set floats first. Then primary jets. (then reset floats) Then worry about the secondaries. This is a great holley webpage http://www.bob2000.com/carb.htm Quote Link to comment Share on other sites More sharing options...
SportZ2 Posted July 17, 2005 Author Share Posted July 17, 2005 Ok guys I need your help. I rebuilt the carb (Holley 4011) put in the lighter spring, adjusted the floats, idle adjustment is right on giving me 14psi of vacuum (for 5000ft I'm told it's as good as it gets) and nothing is binding. Car runs fine, idles fine, cruises fine until I get on the gas and the secondaries don't open. Why is this happening? Everything has been replaced and the secondaries should be opening. Has anybody ever had this problem and if so what did you do to fix it. I hate to throw away what seems to be a perfectly good carb. I zip tied the linkage together to override the vacuum secondaries to see the difference and it was night and day. I cut the zip off right away since the carb doesn't like being forced to do it. Any suggestions would be helpful. Thanks PS: I did not remove the check ball since every book has said not to do that. PSS: Bought a good book on Holley carbs and it doesn't mention this particular problem. Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted July 18, 2005 Share Posted July 18, 2005 510-20-13 Assorted Springs (tuning) 9.99 I'd say you have yet to lighten your spring enough. As I said "The instructions said to drop down two spring sizes until you feel a lull or what others say is the secondaries kicking in. This is actualy the secondaries kicking in too soon and temporarily running too rich. Then go up one spring." Quote Link to comment Share on other sites More sharing options...
blueovalz Posted July 18, 2005 Share Posted July 18, 2005 Hard to help when we're not there. But, when you open the primaries, and then manually push up on the secondary diaphram rod, do you hear air being pushed out into the throttle bores (by pushing the diaphram up)? This at least tells you the path from the diaphram to your vacuum signal is intact (perhaps it got plugged up some how during the long sit). I cannot believe the spring is the problem here. Quote Link to comment Share on other sites More sharing options...
SportZ2 Posted July 18, 2005 Author Share Posted July 18, 2005 blueovalz, yes, you can hear the air rushing when the diaphram is pushed up. tony78_280z, I did put a lighter spring in (second tothe lightest in the kit) and still no response. When we were tuning the carb the other day some friends were just as baffled as I am as to why the secondaries aren't opening. This carb looks as new as the day it came out of the box, no deposits or rust buildup of any kind. I did a complete rebuild except for changing the jets, but that should have no baring on whether the secondaries open or not. I'm thinking of lifting the rearend and running the car so that it is under load to see what's happening. But I'm not sure that will tell me anything either. I'm starting to think that mechanical secondaries are in my future. Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted July 18, 2005 Share Posted July 18, 2005 so that it is under load to see what's happening. But I'm not sure that will tell me anything either. All-righty, I have read in one of my many holley books that the vacuum secondaries wont open unless the motor is under load. This is not completely correct as mine will open while in park in the driveway when I rev it way high for a few seconds. But they open just barely. (So the text that I read is slightly off) But this might explain your problem. You need to try the paper test (as mentioned by Pyro) but while the car is in motion. Also be sure you have tuned all other parts of the carb first. The secondaries should be the last thing you tune. Floats, then Idle, then primary jets, then secondaries. As the previous system effects the next system when it engages. Quote Link to comment Share on other sites More sharing options...
SportZ2 Posted July 18, 2005 Author Share Posted July 18, 2005 Did the paper test and the paper is still sitting there. So the secondaries are not opening under load. Is there anything else I can eliminate? Like i said the carb is running great. Idle seems to be dead on. Vacuum is at 14psi and at 5k alltitude I'm told that's great. I'm going to try calling Holley and see if i can get a hold of someone there. Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted July 19, 2005 Share Posted July 19, 2005 sounds like your not getting a vacuum signal to the secondary diaphram for whatever reason. I've never seen a v8 that couldn't open any of the lighter springs. 14 inches of vacuum indicates a pretty mild cam and coupled with a light car points towards the lighter springs, but, it is definately a vacuum signal problem. You say you hear the hiss when you manually open the secondaries, but where is the air escaping from? Likely that is the source of the problem. Also it would be a vacuum leak at wot so that would lean it out as well. It is either the vacuum cover over the diaphram or the seal between the whole diaphram canister and body of the carb. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted July 21, 2005 Share Posted July 21, 2005 You say you hear the hiss when you manually open the secondaries, but where is the air escaping from? Exactly! If it's not from the port in the main body (not sure where that should be but I thought it was a venturi) then the sound of air outside the main body would be trouble. I did have a Holley 950 cfm 3 barrel on my 302 that never opened the secondary (gee, I wonder why!) Quote Link to comment Share on other sites More sharing options...
SportZ2 Posted July 21, 2005 Author Share Posted July 21, 2005 I called Holley tech support yesterday and they said the only thing it could be is a clogged vacuum port. I'm going to pull the carb and try to clear all the passages. There is a test where you force air through a line in the primary section of the carb (not quite sure what he was talking about, but i'll figure it out) and it should open the secondaries. If it works then that part of the carb is fine and the only thing it could be is a clogged line. I just find it wierd that for as clean as this carb is something like this could be happening. I should know later today what's going on. Quote Link to comment Share on other sites More sharing options...
SportZ2 Posted July 23, 2005 Author Share Posted July 23, 2005 I think I finally figured it out. After be frustrated these past few weeks not being able to figure out why a perfectly good carb wasn't working right, I decided to take the carb apart agian (for the XXXXX time). I found out that the secondary vacuum port (I think that's what it's called) was not clogged. When I put everything back together and I tried to see if air was being forced out by the diaphram, I realized that the only sound I was hearing was the suction of the diaphram. At this point I was about to throw it across the room. Something in my head told me to turn the carb upside down and test it again. Low and behold it worked. So I thought to myself what is the only free moving part in this carb. The check ball. Since nothing to this point had worked I decided to use a smaller check ball (two came in the rebuild kit-one the same size as what was in my carb and the second one a little smaller) then the one originally in my carb. The carb works fine now. granted I had gone down to the second lightest spring and realized instantly that it wasn't the right one and changed it out for the purple one (next size up) and the car did what I've been expecting it to do-get up and go. I'm not sure that this was the way to fix this problem, but it works so I won't complain for now. I still have a lot of tuning to do and will probably be back soon asking more questions. Thanks for all the suggestions, it helped push me in the right direction. Quote Link to comment Share on other sites More sharing options...
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