Carburetor Assistance Please, L79
 

Here's what I'm giving some thought to doing. My car is a '66 327/300 that still has its born with Holley carburetor...

http://i171.photobucket.com/albums/u...ps1caa5eb2.jpg

...seen on the right. I happen to own a practically new Holley (just can't quite remember the number of it off hand), seen on the left which I've run from time to time on a stock '66 Chevy II, equipped with an 327/350 L79.

http://i171.photobucket.com/albums/u...psdbadb99e.jpg

The only difference I can see from the original, shown above...

http://i171.photobucket.com/albums/u...psef76bcb1.jpg

...and my new carb pictured here, is the metering block on the rear which L79's have.

http://i171.photobucket.com/albums/u...ps2a91c5a7.jpg

Here's the original from the other side seen above and...

http://i171.photobucket.com/albums/u...ps075ad2bc.jpg

...the new one with the rear metering block. The casting number on the main body is the same on both so I'll guess the CFM's are the same.

The original has who knows how many miles on it, while the new one is, well.....new. I have no need for the new at present and I thought why not put it to use and put the original away for safe keeping. The car came with the original carb in a box, rebuilt but I have no idea of the quality of that rebuild. The carb that's on the engine at present is in need of a rebuild so that's why I thought about using my extra L79 carb. That way I'll have a practically new carb on the engine which is always a plus. Anyone think of why that will be a problem? Off hand, if I do install the new one, any idea of jet sizes for a 300 h/p engine or should I just experiment and re-jet the new carb as needed?

As always my thanks in advance for any assistance/insight you can provide.

Thomas

Although carbs seem "plug and play" there are many subtle differences in them. I would look at the service manual for your year and engine combo to determine a good starting point for the jet size if you use the other carb.

I may have missed it in your post, but the carb with the rear metering block uses screw in jets, just like the front. The carb without uses a metering plate.

If you have a stock engine, my advice would be to get the carb that belongs (part number) on that year/engine. Sell your other carbs. There are many good carb shops out there that can return you a like new carb. This way, your service manual has some value with regards to tuning.

- Mark

Find the "LIST" numbers for each carb on the air horn and post them. The LIST number tells all.

I'm guessing the carb with the metering plate is a list 3810 BUT it appears to have external adjustable floats. However you can use a metering block with jets in place of the metering plate. Look on the front air horn, should be clearly stamped.

Go to (or search) for Holley's carb specifications (http://www.holley.com/TechService/Library.asp) and look up what your carb should have. Rebuild it, if necessary, starting with the stock configuration. Nothing is really magic here; but new gaskets are important; I'd use the stock carb, but either will work.

Also notice that the primary bowl vent is backwards on one of the carbs.

Is this the LIST number?...

http://i171.photobucket.com/albums/u...psc0325baf.jpg

...6R 2747 B if so it is the same for both. This is the original carb...

http://i171.photobucket.com/albums/u...psbdfa6b14.jpg

...and this is the proposed replacement, # 6R 2747 B. The B on the right end is very faint but visible.

http://i171.photobucket.com/albums/u...ps8856122a.jpg

This is the box the replacement came in showing it to be Holley #4160. As I recall now I couldn't find a suitable L79 carb so Holley told me this carb with a metering block installed on the rear would be the same, modern day replacement for the original so that's what I did. My thought is the new, #4160 would be the modern day replacement for the one on my engine with a metering plate. I do have the metering plate it came with so I could swap that back on or just leave the existing metering block on as this makes jet replacement very easy. Any thoughts on this new information? Thanks again for taking the time to help out.

Thomas

Tom,


the rear metering block is plug and play... you can swap between the willy nilly and have jets or not.

the carb will fit under the stock air clearner with the added metering block (trust me on this)

I can't see the pics at work, but I think it will work our just fine for you.

No, you are looking into the carb in your photos. the numbers are on the outside of vertical choke portion, facing forward as installed.

The LIST number, part number (and the date code) are stamped into the driver's side front of the choke air horn, like the photo below. :thumbs:

Thank you John, It's been a 18 hour long day for me so I'll go to the shop and take a look tomorrow and report back. Thank you again everyone for all the help thus far. I'm learning all the time.

Thomas

http://i171.photobucket.com/albums/u...psef39220d.jpg

Here then is the LIST # for the original carburetor, 3884505 DA, LIST-3367, 5A4 and here...


http://i171.photobucket.com/albums/u...ps09caae7e.jpg

...is the identical LIST# for the replacement, 3884505 DA , 3367. Am I correct there is no manufacture date on this new carb? Am I also correct that from an application standpoint, these are identical carburetors and the new one just has the rear metering block installed? With this being the case, I have no present need for the new one so I may as well go ahead and use it on the car. Can someone provide correct jet sizes for front and rear so I can get it set up for 300 h/p engine before I install in on the car?

Also Larry Walk mentioned in post #5 "..... notice that the primary bowl vent is backwards on one of the carbs." Could you elaborate on that?

Grateful thanks to everyone.

Thomas

http://holley.com/data/TechService/T...%20Listing.pdf

Should have 65 in the front, if using the metering block maybe something like 73-75 in the rear.

Nope - the L79's used exactly the same carburetor as the base 300hp engine (3367 in '66, 3810 in '67), with only a primary metering block - the secondary side used a metering plate inside the float bowl. :thumbs:

My comment about the bowl vent actuation refers to the arrangement of the linkage from the throttle bellcrank lever which moves the link to the bowl vent (a top the fuel bowl). This bowl vent is normally open with throttle off, and closes as the throttle is opened. With the 4160 carb, as shown, the link is on the wrong side of that lever (IIRC).

:thumbs:Tom has a 66 Nova it has the rear metering block

Donny, thanks for pointing that out. John, I apologize to you sir for confusing you about the rear metering block on L79 engines. Here's the 1966 L79 engine I'm most familiar with...

http://i171.photobucket.com/albums/u...ps91e597db.jpg

http://i171.photobucket.com/albums/u...psf46211b8.jpg

... in my 1966 Chevy II. When those cars were equipped with L79 engines in 1966, they came with Holley carburetors that had rear metering blocks installed from the factory as seen above. I'm still fairly new here and thought Corvette L79 engines were like those in Chevy II's but I was mistaken. I didn't make clear what I was referring to but since Donny has some personal knowledge of that car and has seen its rear bumper in his windshield when crossing the finish line (:D :eek: )....... on numerous occasions....... he knew what I was referring to.

I have now learned that Corvette base 300 h/p and L79 350 h/p engines used the very same 3367 carburetor, both configured the same. Not all 1966 Chevrolet L79 engines were alike as seen in the Chevy II applications. I am learning all the time. Thank you everyone.

Thomas

I would not say 'numerous'................ :toetap:









:D

So are the two metering block 3367 carbs for Nova/Passenger car only?

I don't have the non-Corvette charts, but I doubt if there's such a thing as two different 3367's (one with a secondary metering plate, and another one with a secondary metering block); that carburetor carried GM part number 3884505, which defined a single configuration (secondary metering plate).

If a similar carburetor was used on the Chevy II L-79 application with a secondary metering block, I'd expect it carried a different LIST number and a different GM part number on the choke air horn than the 3367 used on the Corvette. GM didn't describe or release different things with the same part number. :thumbs:

'66 L79 Nova came with a Holley list#3245.Much harder carb to find then the #3367