Holley Tech Answers to '67 3810 Carb Problems

**Carl Rose (30187)** · February 8, 1999, 08:07 PM

The evil #3810 Holley

Hi Mr. Jewett!

I just noticed you are posting about the infamous #3810 Holley and would like to add my two cents/commiserate...

If your #3810 behaves anything like mine, exorcism may be required. The shop manual isn't very specific on this point. Mine was a new (date code replacement) unit purchased in 1985 for my 327/300. Initially it lulled me into submission by working quite well, and would actually respond to turning those little screws for idle mixture and idle speed. Over the years, it's true personality has emerged - I have honestly had the carb apart on at least twenty-five occasions. Rarely would I find a truly identifiable problem, but often after such a "therapeutic diassembly" demonstrating my affection it would function quite well. After a particularly frustrating experience several years back, I purchased (ransomed, if you have priced this model lately) a new #3810 to replace it...but after that "last chance" rebuild it worked acceptably well once again. I think I scared it. And now when I drive it occasionally it refuses to idle at one stoplight and functions perfectly at the next (suspect worn throttle shaft bores). A friend of mine has an L-79 similar to yours and has had difficulties with gas leakage through the primary fuel bowl upper plug. So in case this doesn't solve your problem...you are not alone...!

(smile) Carl

P.S. Highly reccomend the Holley Carburetor and Manifold Book if you do not already own.

**Craig Jewett** · February 8, 1999, 10:49 PM

Re: The evil #3810 Holley

Hi Carl,

Thanks for your response. As I mentioned in a previous posting, the 6239 Holley I had on my '72 LT-1 was such a good carb compared to this 3810 disaster. I am tempted to do the following to fix the 3810 once and for all : 1) Replace both bowls with the externally adjustable float type. 2) Add a secondary metering block and extended fuel transfer tube. This would essentially convert it into a 4150 from a 4160 (which is a cheaper version..I guess GM wanted to save a buck or two). I'm convinced that would definitely be an improvement. Now I know that the purists out there would frown upon such a conversion, and I would most likely be ex-communicated, but I'm at the point where the problem must be solved, otherwise it's just not fun anymore. When I bought my car a few years back, the previous owner gave me a care package which included among other parts, an extra Holley. Since I found the engine had the correct carb on it, I did the smart thing..I sold the other carb (!!) Now I wish I had the darn thing to try on the engine....live and learn.

**Jeff Cheney (29688)** · February 9, 1999, 01:26 AM

Re: Holley Tech Answers to '67 3810 Carb Problems

I have the same problems with a 67 3811 carb on a L36. It leaks in both the primary and the secondary, some times starts hard when its cold and sometimes when it hot and leaks fuel from the carb base onto the manifold after I shut it down. I rebuilt it twice to no avail. I am now considering sending it to ether Holley or Chicago Corvette to get it rebuilt. Does anyone have experience with ether place for carb rebuilding?

Thanks

**Carl Rose (30187)** · February 9, 1999, 01:36 AM

Re: The evil #3810 Holley Saga continues

Hi again Mr. Jewett!

Don't go to the externally adjustable fuel bowls just yet. The more moving parts, the more things that can fail. Here's my thoughts on your (possible) solution:

1. Purchase the Holley rebuild kit and a new fuel filter, diassemble, and fully rebuild your current carb. The #3810 kit is about $30. Leave the throttle bores in the shafts and the choke plate staked, don't adjust the secondary stop, but disassemble pretty much everything else. The clutch-head screws on the secondary metering plate can be removed with an appropriate-sized flat-head screwdriver (been doing it for years). Would also reccomend replacing your vaccum seconday diaphragm (about $7). Secret to installation is to push it in when tightening the cover screws to obtain a good seal.

2. Shake the fuel bowls to ensure they haven't "taken on fuel" and sink in the bowl. Rare with the older metal versions but occasionally if water in the gas they can rust. Now the rebuild kit and the Chevrolet manual list different float settings for the secondary bowl as I remember; I used the Chevrolet. Drill bits measured out with a caliper work well for me.

3. Perhaps I'm a cynic but I fail to see how a warped secondary metering plate would cause excessive fuel leakage onto the manifold. now if the carb body was warped and not sealing against the bowl...but that would be relatively obvious. Reassemble the carb, noting that not all the holes in the bottom require screws. There was an article in the Restorer some years back by a gentleman who tapped the extra holes and installed screws and apparently the carb functioned much better - I haven't resorted to this yet so I cannot comment.

4. Use a Fel-pro gasket (cannot remember the number (#60124?), but it is specific to 1966-7 327 engines)and then the SS heat shield on the manifold. Make sure the manifold is clean (I wipe with carb cleaner or alcohol). Spray out your PCV valve with carb cleaner. Suck in on the distributor hose to make sure you don't have a vacuum advance leak. I usually set my carb on the studs, hand-tighten the fuel line, and then install the carb nuts. Beware using too think a gasket for danger of putting uneven torque on the throttle plate, warping it and causing the shaft to bind. Work both primary and secondary shafts with your hands to make sure they move freely.

5. Run the idle fuel mixture screws in (gently) until they seat, tehn back out 1 1/2 turns. (My 327/300 usually likes about 0.75 turns out from seated)Uncrew the idle speed screw until the throttle tang no longer touches, then screw in 1 1/2 turns. Start the infernal beast and warm to operating temperature. Assuming timing, dwell, etc. set correctly, work with the idle screws to obtain the highest smoothest idle. Then set the idle speed. My beastie never seems to want to run at the factory 500 rpm and likes about 700 better.

6. After running the car, re-tighten the bowl-to-body screws. Check for fuel leaks, especially at the inlet fitting.

Changing the configuration to a 4150 is tempting (why didn't Chevrolet in the first place...! as with the 427/390) but I am one of those excommunicating purists. If all else fails (and it well may!) a new #3810 is about $550. A #3367 (the 1966 version - functional but not identical) is about $350. On a driving car I probably would opt for "new" versus "rebuilt". If showing you might consider purchasing an extra date-coded carb for shows.

Feel free to email me directly at crose@adclinic.com if you need more help/advice/moral support. I'm convinced black magic must be involved to make these run correctly.

Carl

P.S. and if it makes you feel any better...I got a "spare but incorrect" Holley when I purchased my car in 1986...that I subsequently gave away....!!!

**Joe Peplinski** · February 9, 1999, 08:33 AM

Evil Holley's

Ah, so my tri-power Holley fuel leaks do infect 4-BBL Holley's as well. I was wondering if the fuel leakage was a tri-power only problem. It is worse when three carbs leak, though. The leaking fuel fouled my oil in only a couple hundred miles of intermittant driving.

Actually, I am sorry to hear that you have the same problem as I. I will be watching to see if there is a common solution.

I have been fighting the fuel leakage problem down the throttle bores down into the intake manifold since I purchased my car over a year ago, to no avail. Recently on the Corvette Restoration and Preservation List I got the advice that a warped metering plate or metering block is probably the root of my problem. So let me offer this experience before you perform a conversion. My primary carb with the metering block leaks worse that the secondaries that have metering plates, so the conversion might not solve your problem. I was advised to carefully follow all torque specs upon reassembly of the carbs to avoid warping them and to check the metering plate/block/throttle body surfaces with a machinists straight edge and have then machined back to true if they are warped. I probably won't be getting to these steps until spring. so I cannot say that they did solve my problem. Then again, maybe I should just spring for some new carbs and put the numbers matching ones in storage for a future show. Good Luck.

Joe Peplinski '69 L68 4-spd Conv. NCRS #29918

**G A Bramlett (135)** · February 9, 1999, 09:39 AM

I've tried both - don't do it.

Holley's guarantee: "Your rebuilt carburetor will leak at every pressed-in plug, and if it doesn't, you can send it back". Actually, I think Chicago Vette uses Holley for their rebuilding work.

Jerry Luck is the way to go for carburetor rebuilding. He test runs them on real engines with real gasoline. This is very important, but I don't know any other rebuilder who does it. The others let you be the test monkey. Holley claims to test them, but they must not use gasoline under pressure.

**Tom Buddie** · February 9, 1999, 10:37 AM

Worn Throttle Shaft Bore- The fix

FYI- a little background information...

All carbs with soft metal throttle SHAFT bores (not throttle bores) and relatively hard throttle shafts will wear over time to the point that, at idle, air is drawn INTERMITTENTLY past the shaft instead of past the throttle valve (disc). Some Holleys had teflon type inserts wrapped around the shaft, inside the throttle shaft bores to lessen this problem. As the clearance becomes more excessive, in order to keep the engine from stalling from an over-lean condition, the idle screws are turned out to provide more fuel. The idle MIXTURE screws only have a limited scope, so this eventually fails to keep things smooth, and the idle SET screw is turned out to move the discs off the IDLE ports and onward toward the TRANSFER (slotted) port. Thus, you now have the car that only will "idle" at 700 or higher (and won't pass emissions testing).

Frustrated owners will sometimes add a real stiff carb return spring to try to get some relief from the "erratic" idle, but this only accelerates the throttle shaft bore wear.

A shiny new carb will solve all of these problems. But, the original can be repaired. I have been repairing these for many years. Yes, it does require a big investment in machine shop type equipment, but here's how it's done: The throttle shaft screws are VERY CAREFULLY (like a surgeon) ground off for removal. They are turned out very slowly to take note of any possible thread damage to the shaft. Further grinding may be necessary. When they are originally "staked", the tips also tend to spread. I will sometimes try to squeeze them back a little before I grind. If you damage the throttle shaft threads, you are SOL. You don't need anyone looking over your shoulder while you're doing this step- you need to concentrate 100%. Next, mark the discs with a permanent marker for re-assembly, and remove them from the shaft. Remove the nut/lever & shaft from the throttle body. The throttle shaft bore is then reamed oversize, and a bushing is prepared (cut to length) for each end of the bore. The bushings are pressed in, and if necessary, flex-honed for proper clearance. The bushings are designed to initially fit tight on the shaft, but I almost never have to hone the bushings to size because the shaft also has some wear on it. Then the carb is re-assembled using new disc screws, which vary and are specific to the particular carb you are working on. I use a heavy dose of thread-lock on the screws. I have found Holley carbs to be missing the teflon inserts on occasion. These were only used in certain applications, not all. On those applications, the shaft is "ringed" to accept these seals. These small parts are still available from Holley, but vary by carb & must be ordered via LIST number & part number from the Holley Master parts/spec catalog.

One final note: many OEM carb setups have the carb return spring on the same side of the shaft as the throttle cable/rod. Functioning as a "pivot", this places a lot of friction & stress on the surfaces of the shaft & the shaft bore, which in turn severely limits the useful life of the carb. On my vehicles, I always re-engineer this arrangement so that the carb return spring pulls directly on the cable/rod, and does not use the carb shaft as a pivot. I also set it up so it can be easily converted back to "OEM" if/when necessary.

Hope this sheds a little light on the erratic & finicky worn-out carb.

**James B. West** · February 9, 1999, 12:51 PM

Re: Holley Tech Answers to '67 3810 Carb Problems

The 3810 Holley on our '67 327/350 car leaked so bad that I gave up trying to re-adjust the float and after countless regasketing was forced to send it directly to the Holley's Custom Shop in Bowling Green Ky. For $220 they completely restored the carburetor back to factory specifications, including dichromating of the carb castings to the original gold-tone finish. The carburetor was rebuilt and returned in 6 weeks. They are very careful to log in each carb, which includes pictures, and all the correct date codes to ensure the owner receives his original carb back. This was the best money I have ever spent! All I had to do was reinstall the carb back on the car, start it up and set the correct idle speed. The carb performs flawlessly and does not leak one drop. I highly recommend this to anyone who is experiencing problems with their Holley carbs. Holley's number is 1-502-843-8630. There is a good article in the August 1996 issue of Corvette Fever Magazine.

Regards,

James West

Holley Tech Answers to '67 3810 Carb Problems

Holley Tech Answers to '67 3810 Carb Problems

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