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 Post subject: Holley pump cams
 Post Posted: Tue May 08, 2012 11:33 pm 
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Are the secondary pump cams different than the primary cams. More specifically I am trying to tune in a Holley 800 spreadbore. It shoots a little after the butterfly opens. The large brown cam reads 664. None of my selection of cams even come close to the large stretched out ramp that this one has. I don't see how to place it any other way except on the #1 setting. I think that I may have it adjusted now, but it seems to me that I should have other options as far as cams and settings. 664 cannot be flipped either, has a lip on one side. I need it to ramp up fast, hard and leave the arm pressed below level. Is there a cam called "flushing a toilet".

just primer


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 Post subject: Re: Holley pump cams
 Post Posted: Wed May 09, 2012 5:02 am 
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i thought the cams were universal,you can also adjust timing with nozzle....small nozzle less fuel,longer duration.....larger nozzle more fuel less duration


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 Post subject: Re: Holley pump cams
 Post Posted: Wed May 09, 2012 7:19 am 
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If I remember correctly, you're trying to get a stumble out at the hit?

The pump shot can be manipulated somewhat by slightly bending the pump cam lever where it contacts the cam. What you don't want is for the pump to bottom out at full stroke though. You should have "some" clearance left to prevent this at WFO.

One of our members has been playing with Domninator pump cams trying to even out his AFRs at the hit and from what I understand, he filed some pump cams to make the shot what he wanted. I probably wouldn't try this unless you have a spare though and then only if you can't get full stroke on the pump any other way.

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 Post subject: Re: Holley pump cams
 Post Posted: Wed May 09, 2012 8:11 am 
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That cam is for a 50cc pump on a 4150. Similar to the Yellow Dominator 50cc pump the hole/slot for the shaft is smaller.


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 Post subject: Re: Holley pump cams
 Post Posted: Wed May 09, 2012 8:41 am 
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How much travel is to much on the pump? Will it tear the pump? I have a 38 squirter which is the stock size, and I have a 40 I have tried, don't notice much difference. Other than that all I have on stock are 25's and 27's. Would a power valve block off on the secondary side ruin all the progress I have made. I am so close, I have had this carb in and out for a least two years when I would get a bright idea. I normally run a 650 spread bore.

Just primer


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 Post subject: Re: Holley pump cams
 Post Posted: Wed May 09, 2012 12:01 pm 
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Rule of thumb is NEVER run a PV in the secondary side of a Holley carb as under acceleration Gs fuel is forced to the rear of the fuel bowl, which will uncover the PV circuit and cause a lean condition. Also should have push on jet extensions for the same reason.

RE: Pump shot. You don't want the pump diaphragm to bottom out inside the housing.

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 Post subject: Re: Holley pump cams
 Post Posted: Wed May 09, 2012 1:53 pm 
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Yes, it seems like if I work the secondary side slow and at 3/4 throttle it will scream healthy, but if I go into full throttle in drive it acts like its running out of gas no black smoke, clear. Last weekend I replaced my rubber line from the block to the carb with 3/8 steel. Idles better but no change. I am thinking that a block off might help, though on my 650 I ran a 4.5 in the secondary side and it worked great. When I start out in 1st and gun it from a stop it will scream healthy though every gear, at least for a short while. Does seem like it is out of gas in drive, almost like it runs out of pump shot, but I will go in and check the o-ring, (it's the older style with an o-ring to transfer the fuel, main body to metering plate. (no provision on the gasket) it does not have a tube with the two o-rings going inside the main body. I do not have any extensions, hot rod shop will likely have them. Can I make my own? Not to be cheesy but I love to fabricate as much as possible.

Just primer


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 Post subject: Re: Holley pump cams
 Post Posted: Wed May 09, 2012 2:02 pm 
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True Value hardware stores has some thin wall brass tubing that's mostly used for hobby stuff that some ppl make them out of. Take a jet to the store with you to see but I believe it's 5/16" brass tube that fits.

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 Post subject: Re: Holley pump cams
 Post Posted: Wed May 09, 2012 7:56 pm 
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if the car launches good the accelerator pump circut is doing its job correctly,if its laying over at the top end the pump cam is out of the equation,also if it goes to high gear good jet extensions wont help either will they?the g-forces have greatly diminished by then,and if it got to high gear good the rear jets werent uncovered.....could it be too little pump or a plugged vent in the tank??or plugged up bowl vents


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 Post subject: Re: Holley pump cams
 Post Posted: Wed May 09, 2012 9:11 pm 
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One thing you didn't mention that would help diagnose fuel related problems is a pressure gauge mounted up on the cowl where you can see it? Do you have a gauge on there?

This is a stock block mounted fuel pump also, correct? :-k

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 Post subject: Re: Holley pump cams
 Post Posted: Sat May 12, 2012 11:51 pm 
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This is a stock mount fuel pump it has a return line as well. My 650 spreadbore screams without any hesitation, in any gear, any speed, even on the highway. The 800 just has a better Idle and a much stronger launch even though they are supposedly the same size primaries. Also in gear from a stop if I shift manual (B@m z-gate) it goes into the secondaries stronger than the 650, my shift light is set early, (it's behind the air vent) and it goes off much faster. (3.90 gears) It may just be too much carb for me. I just see signs of life and bursts of power that I never had with the 650 and it makes me want to continue looking. If you look up LunA4318 you can see that my cam should be able to support this carb. I also have roller rockers with the 1.7 ratio If i recall correctly. Aluminum heads and intake. So recently I added some extensions and blocked off the powervalve in the back and went up from 85 to 90 on the back jets. and It was not any better, maybe a little worse. The block off seemed to make my Idle rougher and the jets seem more rich, less responsive, though I realize a PV equals 8 to 10 sizes. I believe that I will put the PV back in ,go back to the 85's, leave the extensions in and investigate if the pump diaphragm has a hidden hole. I did not see any signs of if but I should probably fill it with gas and leak check it. I should clean up my spark plugs. This would probably be easier if my Ram air was isolated and functional. I used to use it with one of those cheap foam air cleaners and now that I have a freshly machined engine I am afraid to go back to It. The hot rod shop told me that they let in fine dust for your engine to chew on. The biggest problem is that its hard to tell if I need to go lean of rich, i mean is there a larger squirter than a 40, seems huge to me, and jetting over 90 for a street car seem silly too. The stock jet size for the back is 85 with a 10 power valve, but stock for what, maybe they set these things up for an old Cadillac they used 800 easy. Olds used some large Quadrajets, but this is my third 455 and I have never found them to like a big Carb. I am still experimenting trying to figure the 800 out, I am not frustrated, its like an ongoing test, just am not sure where to go from here. When it works it works better than any carb I've had. May have some time on Sunday, but for the next two weeks I am going to be working on the exterior of a cabin in the mountains for my company. The wife and kids are coming with me because Its a second home right now and we are going to stay there while I Stain the wood siding and Decks.

Just primer


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 Post subject: Re: Holley pump cams
 Post Posted: Sat May 12, 2012 11:54 pm 
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I do not have a pressure gauge, not even for testing. I have an electric fuel pump that I have never used. It was free, was used with a regulator.

Just primer


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 Post subject: Re: Holley pump cams
 Post Posted: Sat May 12, 2012 11:58 pm 
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The 800 was cleaned and a new kit installed (blue plate gaskets) when I first started working on this. Will double check the vent tubes.

Just primer


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 Post subject: Re: Holley pump cams
 Post Posted: Sun May 13, 2012 7:20 am 
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IF THE CAR LEAVES GOOD THE ACCELERATOR CIRCUT HAS DONE ITS JOB AND CHANGING SQUIRTERS WILL BE COUNTERPRODUCTIVE,but with that said the squirters in my carb are 55's so yes they make them bigger

instead of cleaning the plugs you may want to replace them so that you can visually check the mixture of the carb,if the new plugs are
tan-mixture is pretty good
white-mixture is lean
black-mixture is rich
try to make a hard run on them close to the house so you are not idling around much on them afterwords or go somewhere that you can make a hard run on them then shut the car off in a parking lot maybe and pull a plug before you drive home to check the color of the tip

one other thing you may want to try is to add a degree or two of timing to the engine and see if that makes the car happier,i did not check your cam specs but i would think a 455 could live with an 800,what are your torque converter specs?


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 Post subject: Re: Holley pump cams
 Post Posted: Sun May 13, 2012 8:53 am 
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I have and antique champion plug cleaner. A sandblaster that I would like to get working and try out. I seems to work, I added the wrong size sand and I need to pull it out and add finer sand. I am kind of old school in a lot of ways. So for a converter I have a jetaway converter on a TH400 switch pitch trans. I does stall stronger than the 12 converter that it came with, but I have not tested the exact stall speed. Supposed to be in the 3000 to 3500 range. I really do not want to raise my initial timing any more than 14, because my distributor was tested and I was told that 14 was the limit. I run 91 octane and I am afraid of a silent detonation with the aluminum heads. My last engine lasted me 9 years but at the end I kept creeping the timing up and I ended up with a hole in the #1 piston.

Just primer


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