what my mechanic said...

[JohnZ]

I guess what I need is a reputable Holley guy to rebuild my carb and do it right. I don't mind trying it myslef, but if 3 experienced mechanics don't wanna play with it...I'm not sure if I could get it right myself...especially with no experiece. I don't want to spend $80 on a carb rebuild kit only to find out my problem returns or becomes worse...What could I expect to pay a pro for a rebuild?

Send your carb to Jerry MacNeish in Maryland (www.z28camaro.com) and it'll come back looking just like the one in the pic (my 100% factory-stock/original '69 Z/28), and it will work great and be leak-free. Depends on the condition of your carb, but will probably run around $275 for a complete, professional rebuild and cosmetic restoration (all parts re-plated, etc.). Jerry also does distributors, brake boosters, re-skins valve covers, intake and exhaust manifolds, etc - lots of info on his website.

 

[robert kirk]

JohnZ is right on the money. Have used Holley carbs for over 30 years with no problems that could not be fixed when done right. I have a pair of eld's on my bb now. I went with these for two reasons, No gaskets below fuel level, and tune ability. A holley built right is a pure joy to drive, built wrong and you will never be happy. This is true for any carb. robert

 

[tonyk72]

it's off...

I took the carb off today and will bring it to the local shop tomorrow for a rebuild. John, I'm very uneasy about sending it through the mail so that is not a good option for me...

As far as checking the #'s on my carb...the Corvette Black Book states that the corect carb is a Holley R6239A #3999263

The stamping on my carb reads:
3999263-GA
LIST - 6239- A
241

Is this close enough?
And how do I read the date code - 241 ?
If this is the day of the year, this would put me in August...
My cars VIN # indicates it was built in June of 1972
???

 

[JohnZ]

Numbers line up nicely - the List number and part number are correct, and "2" is the year (1972), "4" is the month (April), and "1" is the first week of the month. Sounds like the carb is original to the car.

 

[LIRacer]

I had the same problems

..with my LT-1. Hesitation, and leaking. I agree with most of the posts here, the Holley is the best and 30 year old equipment needs to be rebuilt.

In my case, I am lucky to have a great Vette hi-perf shop near by. The owner's specialty is carbs. He dyno tuned it and rejetted it after the rebuild. In all honesty, it runs like fuel injection now.

For anyone on Long Island, New York Vettetec in Great Neck is where to go. In my experience they are the best!


Bruce

 

[tonyk72]

I dropped the carb off this morning...anybody ever hear of Hobbs? Thats the name of the shop, they are supposed to be the best in the area...

I also left a list of every possible carb related problem I had:

1. hesitation on accel
2. backfire on sharp corner or low throttle (once in a great while)
3. fuel leak & smell when I park the car
4. carb would "whistle" if I had the (supposed correct) 1/4" gasket I got from Doc Rebuild.
5. won't start instantly, takes about 3-5 seconds of cranking to get it to turn over.

I hope it all gets fixed!

Also, when I pulled the carb off, there was a good amount of fuel sitting inside the intake...dunno if that is normal. I suspect this is part of my fuel smell/leak problem...

And the freakin' fuel line nut is startin' to get stripped again! What a PITA! It's brand new...I'll try to bend a new line myself.

 

[MoeJr]

I have heard of Hobbs. I hear his work is good. He is the only place around brave enough to rebuild the carb on a 2.6 Mitsubishi 4 cyl. Let us know how it goes.

Moe

 

[tonyk72]

progress report, its's back from the shop!

I'm glad my boss is a car guy! He let me leave work early to pick up my carb...

Accoding to Hobbs, my carb was in pretty good condition except for something wrong with the secondary diaphram. They told me something (I forget what) was put in wrong last time it was rebuilt...he said I should notice a nice performance increase.

So I bolt it back on, fire it up...it had a real rough/low idle. I let it idle for a about 5 minutes and took it for a 2 mile ride...I wasn't really impressed...(but my car wasn't warmed up yet) it stumbled worse than before...I wasn't happy. But by the time I got home I noticed the idle was nice and smooth and decided to take it for another spin...my car was fully warmed up by now. It ran MUCH better, no stumbling, no hesitation like before...great.

I park it, notice a fuel leak right away. A slow drip leaking down the rod going down from the secondary diaphram. WTF! Come on! So I let it sit...eat dinner and decide to take it for one more run before I pull it off and take it back to the shop tomorrow...

It still doesn't start up right away...takes 3-5 secs to start, other than that it ran real nice...no hesitation. I park it, start looking for leaks....hmmm, no leaks?? So I decide I'll drive it some more tomorrow & call the shop...let them know about the leak I saw earlier. Is it possible the carb was just working some kinks out from the rebuild?

I'll also check to see if the nasty fuel smell is in the garage in the AM.

 

[JohnZ]

The leak down the secondary diaphragm rod sounds fishy - the only connection between the diaphragm housing and the carb main body is a vacuum passage from the primary venturi that goes to the TOP of the housing, ABOVE the rubber diaphragm; if fuel is dribbling down the rod, it has to be coming THROUGH the diaphragm, which is not good.

Make sure you adjust the remote choke actuating rod per the Shop Manual specs - if it consistently takes 3-5 seconds of cranking to start, you're probably not getting full deployment of the choke.

 

[tonyk72]

some problems fixed, some not, some new...

OK, I'm back...I had some work issues to deal with...
but here is where the 'vette stands...
The choke plate...shold it be completely shut when the engine is cold & its like 60 + degrees outside? There is about a 1/8-1/4 inch opening...and what abou a hot engine? I assume the choke plate should be wide open right?

As far as the gas smell, it's still there...I put the sealed cas cap back on (I had a locking vented cap) to see if this would help...but no luck.

The obvious gas leaks are gone, but I will still find some gas on the intake manifold the following day...
I may bring it back to the rebuild shop...

How does it run? Very good...I changed the plugs, oil and adjusted the timing to 4 degrees before topdead center. The hesitation is gone...and it pulls strong to 5k, and thats where I let off...

Whats it doing now? blowing smoke out the exhaust...I'm positive it didn't smoke before...why now?

 

[JohnZ]

Choke sounds fine. What color is the smoke (blue, black or white) and when do you see it (morning startup, cruising, accelerating, after decelerating)?

 

[tonyk72]

smoke is bluish...I see it startup & at normal operating temp. I can't say I see it at accel or decel, but whenever I come to a stop...I can see it...

Here are some more details to help in troubleshooting...

I definatley did NOT have this problem before I started tinkering with all this stuff. The problem started to happen right AFTER I changed the oil and spark plugs. I am not 100% sure if I saw this after I put my rebuilt carb on. The time between rebuilt carb and the oil & spark plug change was about a week...or 20 miles.
I used 5 quarts of QuakerState 10W-30 for higher mileage engines...regular dino oil...and changed the oil filter with a FRAM...
I replaced the oil filter with the same one that was on there before. This is the 1st time I changed the oil since I had the car. I heard that if you use like a 30W oil, it could mask this type of oil burn, which I assume this is...
I used AC Delco R44T spark plugs (the old ones were the same type) & I gapped them at 0.035...I used one of the dial type gappers to measure. I noticed all the new plugs were gapped to like 0.045...I'm not 100% sure if the AC's were already pregapped to 0.035 (I heard they were)...

Any ideas?

 

[elseyj]

Sounds like a bad power valve.
I found an excellent book "Holley Rebuilding and Modifying"
'A guide to Holley Modular Carburetors' by Jeff Williams
S-A Design Books

Very helpful and it takes the mystery out of Holley carbs.
good luck!

 

[Jack]

Re: some problems fixed, some not, some new...

Whats it doing now? blowing smoke out the exhaust...I'm positive it didn't smoke before...why now?

I'm speculating here ... sounds like carb WAS dumping too much fuel ... has "gas-washed" the cylinders ... worn out the rings because their lube was gas-washed away. Why smoking only now? ... I dunno ... maybe before rebuild the carb was dumping so much fuel it was pushing raw fuel past the rings (so no oil got into cylinders (did your old drained oil seem thin & gassy-smelling?) ... I dunno ... but I still suspect the rings & cylinders have been gas-washed ... and suspect that's where the oil smoke is coming from now. Sounds like your motor warrants a close check of cylinder pressures ... there's often a step-by-step procedure found in back of many manuals ... helps determine if loss(es) are due to rings or guides. Pretty easy job to do by yourself if you rig up a remote starter button. G'Luck.
JACK:gap

 

[tonyk72]

So I called the place that rebuilt my carb...explained that I still get a fuel leak. He asked me to check and see if the seconday throttle plates are closed at idle & also to check the needle and seat to see if there is like a spec of dust stuck in there...I guess these two things could cause the fuel leak. I had the carb off this morn to bring to the shop, but now gotta put it back on to test this stuff out...He also said the choke should be completely shut when I go to start the car...This is frustrating!

 

[tonyk72]

I checked the needles and they were OK, found no evidence of any kind of particles stuck in them...I put them back & mounted the carb back on... I start the car...I had the air filter off so I could see the carb. I saw a good amount of fuel pumping out of what I think is the secondary air valve (its a verticle tube with like a 45 degree angle cut). I guess I found the source of the fuel leak now....the gas spilled onto all the areas where I always see the fuel...what could have cause this? The needle/seat was put back the same way I found it...

 

[tonyk72]

talkin' to myself...

I'll make this the worlds longest Holley thread...

Just spoke to the rebuild shop, they suggested I check the fuel pressure...it should be at 6...how do I do that?

 

[69_Dream]

You'd think they would test the carb on your car

If it isn't the carb, you could move on to the real issue, whatever that may be. If it is carb related, they find it/they fix it. Done.

I feel your pain, as mine is usually a case of fix something, something else blows up.

Sly

 

[tonyk72]

fuel pump OK

I ran down to Pep Boys, got a fuel/vac gague and tested the fuel pump...It seemed simple enough. The hose from the gague went into the fuel line (right before the Y Block). I cranked the engine over for a few seconds and the needle was at 6-7 while I cranked. So I assume this is OK. Tomorrow I bring the carb to the shop.
The attached pic shows how I hooked this stuff up...

 

[Redmanf1]

Either there is no gasket between the powervalve and metering block or the float is not adjusted correctly and or the needle/seat is letting fuel by and that is why your getting overflow of fuel. When you take the carb off drain the fuel so you can tip it on it's side. Look at the air slots and see if they look round. If you open the throttle plates or butterflies you will see the air slots they are about 1/4" long. When you close them they should look round in other words adjust the butterflies so the slots visually look round front and rear. If the car is stock it should just about idle right there. If you adjust the idle to far open it will take the butterflies out of the air slots and mess with the air screws which is your rich and lean idle adjustment and your ported vacuum. Your ported vacuum should be hooked to your distributor. Set the air screws at 1 1/2 to start with and then when car is running set them with a vacuum gauge. I would dump that quakerstate out. I am not a big fan of quakerstate as I usually say I would not run that in my lawn mower. I like mobile 1 but as a good backup I would use castrol GTX and then valvoline. On the blue smoke thing it could be a lot of things. Like some others said you could have washed down the rings and caused damage. You could also have future bearing damage this depends on how much fuel has washed down the motor and how long this has been going on. You can check your fuel content in your oil by taking a lighter to the end of the dip stick when you pull it out. If it lights quick you have fuel contaminated oil,change it immediately. The motor could also be trying to burn all that fuel and cause it to smoke. Also you could have bad valve guides or stem seals. Once you get the carb straightened out you can do a metalology test on the oil and it will tell you the amount of different metals or amount of wear. Sorry about the long post but I hope it helps some.