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Discussion Starter · #1 ·
Ok guys here goes I've put on my new 750 holley the one that looks like it's chrome.Put in new plugs new fuel filter, new fuel pump, drained the oil put in new oil and filter.I guess it's now or never to see if it was the fuel pump that was fouling out my plugs.Mike from Savannah
(70 z/28 4 speed)
 

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Zgator - I am sorry I missed your posting about fouling. How is it that you think your pump was fouling your plugs? If fuel was being pushed past your carb and dumping it was you need and seats that were stuck. Or if you had an electric pump you needed a regulator...
 

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Discussion Starter · #3 ·
well, I already put on another new carb holley 750 that didn,t help, same thing so I bought a new 750 and put on the car because I figured it was messed up because I found alot of trash in my fuel tank.I have pretty much elimated the carb so I was told that my stock fuel pump might be pumping gas into my crankcase,which after insp.seemes to bare this out so I guess I'm ready to try it out this weekend.This whole think started with my old carb,so thats the first thing I changed,but the new carb was no better
 

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Discussion Starter · #5 ·
Yes it did that was what made me feel that what I was told about the pump to be true.I want this problem to go away soooo bad. I want to drive my car
 

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if you did smell gas in your oil then it would appear that the diaphragm is torn in the pump as you suspected. good luck with the fix!
 

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zgator,
Do you mind if I ask a couple of questions..Why did you think the fuel pump was fouling the plugs?? If you were dumping fuel from the pump it would 1)increase the level of the oil in the crankcase 2)Significantly lower the oil pressure by thinning the oil 3) Would not cause a rich fuel mixture because the fuel is being dumped in the crankcase not the combustion chamber 4) If you oil smells of fuel it could just be a rich mixture not necessarily from raw fuel in the oil..If you had fuel in the oil you would have noticed how thin it was when it was changed..If you do have raw fuel in the oil make sure you get it fixed fast,it will thin the oil to the point were it does no good at all,not to mention that the fuel in the oil will "wash out" the bearings...It sound to me like you have a rich mixture problem with the carb more than a fuel pump problem but I of course am guessing,however I feel pretty confident on that..I do not know the backround to what you are doing or exactly what the problem is but will be more than happy to lend advice if you need. Hope this helps a little!!
 

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her69 - hey, i want to drop the tranny tomorrow or this weekend. I NEED the gear reduction starter..... BTW, I talked to John and I will be putting the Pinkie in the Motorsport Nationals show with the Camaro Generations group. Look out your window and if my legs are sticking out from underneath the car, come on over!!!!!
 

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Discussion Starter · #9 ·
Her69. this is what I have done.It first started running rich with the old carb(holley 750)so I changed the power valve that didn't help so I figured that while it was broke I would pull the heads and have a valve job while the heads were off I bought a new performer rpm intake and a new holley 750 I put everything back together fired it up ,same thing my plugs were black and wet. so after two carbs I figured it wasn't carb related.I thought about mybe a weak coil so I changed that, no luck.I have since bought another holley 750 the one that looks like it's chrome.I've put that on,changed the plugs, oil, fuel filter,fuel pump I don't know what else to do. I have not fired it up since the above fixes.
 

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zgator,
If your plugs are black/drk brown and sooty that would be a rich plug..You say they are also wet! Are they wet with fuel?? If so you are not burning the fuel that is in the combustion chamber. That means either you 1)Are getting way to much fuel 2)Your ignition system is unable to burn the fuel 3)You do not have enough cylinder pressure(your rings are not sealing)to light the mixture....Have you run a compression test or leakdown test on the engine?? That will tell you if it is a problem with enough pressure...

You did not say what size engine you have so I will assume you are not over carbed,I am assuming a vac secondary 750 on at least a 350..If that is it and you have enough cranking pressure that carb should work in that combo.Also make sure the choke is open and not closed..Is this a stock engine otherwise??

If both those things check out next I would look at the ignition system. It could be from a weak spark. That could be from a bad cap,rotor,distributor,coil or plug wires etc..You did not say whether it was Hei or points either..

I might suggest you get a good service manual. You need to do some troubleshooting to see where the problem lies. It could be a worn out shortblock or maybe a bad coil wire(if points) or possible just a bad set of plugs(it happens).The bottom line is you need to do some diagnostic work and go from there. I would not be quick to blame the carb.. I have been doing this Hot Rod stuff for 20 years and seen only a handful of bad power valves in Holleys,they get blamed for other problems more often than not. On the other hand the great thing about a Holley is that it is tuneable but sometimes they need to be tuned to work correctly. Good luck...

[This message has been edited by her69 (edited 04-14-2000).]
 

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Discussion Starter · #11 ·
Her69,This is a #s matching z so it has the solid lifter 350 LT1.when this problem started and it had the old carb still on it it would foul one pulg,but after driving a short while it would clear up and run great.This condition was slow to develop due to the fact that the car is not driven very much.now all the plugs foul out,they are wet with fuel,and the smell comming out the tail pipes is so strong with gas fumes it will run you off and make your eyes water.I have replaced the coil.I don't have the tools to do a leak down test,however when it was running good it was real strong
 

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Start with the simple stuff. Even though lot's of guys run 750's on small blocks it's a lot of carb for that size engine. If you can borrow a 600 from a friend, try it out and see if the problem goes away.

Absent a swap to a smaller carb, try jetting the 750 down a couple of levels. My guess is that you are simply running way too rich in the main circuit. Talk to the local speed shop or carb shop guys and ask for a recommendation on jets for your location. Start there and run it with fresh plugs and take a reading. Adjust the jet sizes according to the color that shows. This may be all you need to do.

------------------
Scott
'69 400SB, Richmond 5-speed; '99 HD Road King Classic
www.geocities.com/sdenning1
 

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Once again, the elusive fuel-dumpin demon stinks up the neighborhood! I've got the same darn issue. The problem is, my holley 4175 doesn't have sight plugs! You've got to REMOVE :mad: the darn fuel bowls to adjust them. You're supposed to 'bend the tab til it looks straight' then put the bowl back on and start it up. My cylinders were so loaded with fuel after 10 seconds of running that she didn't want to turn over again til I took all the plugs out-which of course were black and damp. Maybe edelbrock is the way to go, I dunno. Again, I know this thread is old but the problem is definitely current.
 
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