Warped Holley carburetor body repair and carb rebuild questions

[Clark Coe]

Today, Ross ( my427mustang ) warned me to make sure the faces of my Holley C8OF-9510-D 600 cfm  carburetor were flat. Went home and disassembled the carb and found that the Primary was .009” warped and the Secondary was .008”. This carb/Mustang has not been used since 1997 and it is time to get it back on the road. 



It took 30 minutes with a new file to cut the Secondary surface flat. Tomorrow I will file down the Primary side. I found that the more material to be removed, the slower the progress was. This would not be complex operation for a machine shop, but I want to get this carb rebuild quickly and move on to other tasks.



Question 1: Is the .009” warped mating surface enough to make trouble with how this carb would perform? Seems like the Holley gaskets would easily make up this difference. Am I fixing something that is not bad enough to be messing with?

Question 2: What is the recommended product to soak and clean out the dried / stinky gasoline film from the inside of the carburetor? Decades ago I used caustic carb cleaner that would burn your skin, but did it cut through the crud. That stuff worked so good, I am sure it has been outlawed. Would soaking in lacquer thinner, followed with carb cleaner aerosol spray and compressed air blow out be adequate?

[My427stang]

Clark, I'll answer with more of my own advice LOL

First, with no torque on the 4 bolts, you were warped .009   Now, add heat and bolt torque, some vacuum here and there and use a non-stick gasket instead of the old shellac gaskets that used to adhere to both sides and likely use nylon washers instead of the old soft ones.  Finally, let's add a fuel that has alcohol in it and likes to creep around a bit.  Yes I think that combination could cross channel

Second, I haven't found a need to boil, soak, or otherwise go crazy on a Holley.  Good carb clean, (Gunk or others, not Autozone brand that smells oily) blown through the passages, and occasionally air if you have a fussy air bleed, usually does all you will ever need.  Especially with something that looks relatively clean

Finally, although I do use a file in a pinch, you'll find a machinist can cut less and cut far straighter.  It's cheap money in my book

[thatdarncat]

You are correct that the old Methylene Chloride based carb cleaners worked great but seem to have been pulled from the market. It's the same main chemical in most paint strippers though, but they are usually gel based and wouldn't get into the small passages. They will work to clean the black sooty stuff from Venturi's if needed. I would avoid lacquer thinner, it will clean the carb but will also remove all the gold plating leaving the carb dull grey unprotected zinc.

[Clark Coe]

Thanks for the replies and advice. The picture of the filed surface does not correctly show the filed finish. It is not as crude as the picture would suggest. To set the record straight, Ross DID strongly recommend having a machine shop perform the milling operation.

This car is a driver and not a show car. I like the idea of using an original Holley-Ford C8OF carburetor. After 18 years of setting around it is externally reasonably clean.  I will forget about the lacquer thinner and use spray carb cleaner. Hopefully the spray stuff will dissolve the honey colored/stinky residue in the bottom of the fuel bowls.  Thanks again, guys.......you are always helpful.

[jayb]

+1 on getting those surfaces flat; even a small amount of warpage can cause trouble.  And I think filing the surface is just fine.  The machine shop has to fixture the carb so that an even amount is taken off top to bottom, and front to back, and that is not always an easy task.  To do it properly would take some time and make it expensive, at $75 an hour or so.  I've filed lots of those carbs just like you did, Clark, with no problems afterwards.  Good luck on the project!

[jimeast]

Getting Flat.

If you have a small surface plate, float glass or just counter-top granite.  you can put down some fine sandpaper on it and get a very flat and well finished surface by rubbing the carb back and forth.  One thing to watch out for is if the middle is the convex side, you can get into a rocking motion where things get worse not better.  You can use wet or dry or whatever seems most appropriate.  I've never done this with a carburetor, but I have flattened a number of cast iron hand tools this way.

The upper part of the surface close to the air cleaner area might be a little tough to make consistent with the rest of the surface. 

[RJP]

.008-.009" is not bad. I've done many 4 bbls that needed a .015-.018" just to clean up. 2 bbls are much worse due to less mass. I've had several 2 bbls that needed as much as .030-.032" just to get flat. I do almost all of my Holley machine work using a Bridgeport mill, carb fixture and a flycutter. I only take .0015-.002" per pass so it can be somewhat time consuming. Do not forget to check the base of the main body, they can get wonky too. If the base is bad enough the carb will leak fuel when the engine is shut off.

[chris401]

Thanks for the tip. I ran that carb for a few years and now its for sale. Didn't leak but it may be somthing the next person may want to know.

[Clark Coe]

Dear Friends, Got more Holley carburetor questions.  Power Valves  and  Gasket Material and Power Valve Check Ball Kit.

Q1: What is the best sealing gaskets for bowl and metering blocks ?......not going to do much disassembly for tuning. Do not want puddles of fuel in the intake. I am using Holley Renew Kit #3-422 that came with black gaskets. Many years ago, the rebuild kit I used contained tan colored gaskets that are sort of waxy. The used, tan gaskets actually came off better than I remember the softer black gaskets used to.



Q2: What would be an appropriate power valve for 600 CFM? Motor is cammed with a standard 428CJ hydraulic. I cannot make out the power valve vacuum value on the new power valve that is supplied in the kit, the small, small, small stamped characters are incomplete and do not make much sense. Old power valve is stamped "6" "5". Original 1968 Ford Mustang repair manual specifies a 85 power valve.

Q3: Because I already have it, I am installing Holley Power Valve Check Ball Kit 125-500. I have never ruptured a power valve with a backfire, but it does not seem like a bad idea. Is there any down side to installing the Check Ball Kit ?

Big thanks for everyone's input, ideas and shared experience and wisdom.   Clark Coe

[Nightmist66]

For the gaskets, I like to use the blue "non-stick". If you use the other ones you mentioned, either should be ok. One thing we always did to the gaskets before the days of "non-stick" is apply a thin layer of chap stick to prevent them from sticking.

You will probably be just fine with that 6-5 power valve. If you didn't know, that stands for 6.5" of vacuum to actuate the valve. A good baseline is check the idle vacuum, and divide that number in half and that is your starting point for the power valve. So, if you had 15 inches of vacuum at idle, you should need roughly a 7.5 power valve.

I can not see any downside to installing the check ball kit. We do it on every one of our carbs. Just added assurance.

[Ford428CJ]

I see that kind of problem with a ton of carbs. Some are better then others. But after doing 25~30 carbs a year for people. Its not shocking at all. I use ultrasonic cleaners and so on. The cleaner, flatter, the better! It helps a lot....

[Clark Coe]

Got my Ford 600 CFM carb assembled but things are not going well. Poor idle quality, will not idle lower than 1300 - 1500 RPM.

Last weekend, the Mustang did cruise great at 60 mph for several miles without any fuss, but setting at traffic lights was a real challenge....needed three legs and feet.

Distributor is pointed straight forward and timing is 10 BTDC at 1300-1400 RPM....difficult to tell of sure, keeps dying.
Points - Condenser ignition system is completely stock. Coil is stock. Ignition works well enough for good crisp starting and running at 60 mph.
Manifold vacuum at the 1300-1500 rpm range is 15" but vacuum fluctuates/floats 16" to 18".....not jerky, just "hunts".
Have disconnected and plugged vacuum line to power brake booster.

Fuel level is just below bowl plugs.
Idle mixture screws are 1 and a quarter turns out.
Manual hand choke conversion and have plugged the hot air vacuum port on right side of carb body.

Unmodified Streetmaster intake with a 3/8" composite, four hole insulator. Installed carb, insulator and manifold with thin gaskets, without sealer. Victor Reinz intake manifold gaskets installed with a little smear of Motorcraft gray RTV diesel sealant.

Engine is not burning oil, no black smoke or blue smoke. After sitting for eighteen years, I was afraid there would be stuck rings or valves.
Exhaust has no harsh odors.

Hydraulic lifters with adjustable rockers. Adjusted cold to top of lifter travel, then turned down half turn-full turn, I forget exactly. Valve train is quiet.

Pulled the new Autolite 45 ( .035" gap ) plugs and they were super clean.

With all of the plugs out, tried to check compression on warmed up engine. 9.5 Badger pistons. Unknown, mild hydraulic cam, #5=152 psi, #8=148 psi, then the hose from the compression gage is spinning in the 18mm threaded fitting and will not unthread out of the head. . Everything was too hot to try to retrieve the gage hose....so it was time for a bag of micro wave popcorn.

Need some ideas to try tomorrow. I want to be driving my Mustang before the Nebraska winter sets in.

[Drew Pojedinec]

Some folks like to talk badly about the light tan gaskets, but I've been using them forever with no issues.
I buy the ten packs for dirt cheap from Summit.  They are AED brand.  I get a ten pack of bowl gaskets and a ten pack of metering gaskets.

I smear a little dielectric grease into the gasket prior to install.
I take my carbs apart every year or two just to check/clean everything out, never a problem.
I run pump gas E10 so it seems wise to check out the carbs every once in awhile.

Good luck

[My427stang]

Clark, if you can get to Papillion, I'd be happy to take a look at it.

Email me,  too bad I didn't see this yesterday, I was bored enough to take a 1984 6.2 diesel job I put off, which I have to finish up today.  Would have paid someone yesterday to be doing something else.

I will be in Plattsmouth until about 11AM and free until about 2PM. 

[Clark Coe]

Thanks Ross for the offer. We will see how the day goes. Got church and afternoon birthday party for grandson to do first. I will be in touch.

Clark Coe