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From: At my Bar drinking and wrenching in Lafayette Colorado
The low speed air bleeds (IABs) on the L82 carb are different to allow good idle fuel flow response with the slightly bigger cam (less manifold vacuum). Since the IABs are slightly smaller, a fatter primary rod was used to prevent the cruise mixture from going rich.
Additionally, the L82 carb is 800 cfm, and the L48 carb is 750.
Basically, they're two completely different carbs. I get questions from people about what they need to do to the jetting on an L48 carb to "turn it into" an L82 carb. The simple answer is, "you can't." On the other hand, the non-L82 carbs can be modified, with some work, to reduce the IAB sizes and make the carb more responsive on the idle fuel circuit to an engine with a bigger cam, thus making the L48, and other carbs, very responsive on a performance engine.
Lars
My baseplate on the original L48 card has a crack in the lower base plate on the choke shaft. So I either need a new baseplate, jb weld?, or another carb. A guy at my work has a q-jet from his 74 he is going to give me. So, hopefully between the the 2 I can get a functioning q-jet for now until I can get a real rebuild on it for performance purposes when I do the engine over. Not sure if this is salvageable or not. My current carb is an Ebrock 1406.
But, is the 74 q-jet better on my 78 with no emission stuff, or is the 74 a smog carb too. If the 74 is a better carb I will freshen that one up and use it. Don’t have it yet.
From: At my Bar drinking and wrenching in Lafayette Colorado
The '74 carb is a 4MV carb. Your '78 is an M4M. You cannot interchange any parts between the two carbs - they are completely different model-series carbs. The '74 4MV carb also cannot be used on your '78 engine/manifold and still make the choke work. You need a complete M4M carb or a replacement 1978 throttle plate off of a like-numbered carb.
That's not the choke shaft - it's the primary shaft in the throttle plate. No, you cannot fix that with JBWeld.
The '74 carb is a 4MV carb. Your '78 is an M4M. You cannot interchange any parts between the two carbs - they are completely different model-series carbs. The '74 4MV carb also cannot be used on your '78 engine/manifold and still make the choke work. You need a complete M4M carb or a replacement 1978 throttle plate off of a like-numbered carb.
That's not the choke shaft - it's the primary shaft in the throttle plate. No, you cannot fix that with JBWeld.
Lars
Could I add and electric choke to the 74 and then use it? I have an Edelbrock performer 2101 intake and the 1406 is electric choke.
From: At my Bar drinking and wrenching in Lafayette Colorado
Nope. The 4MV carbs are divorced choke carbs that do not have the choke as part of the carb. The 1975+ M4M carbs are integral choke carbs and can be converted to electric choke. Not the '74.
Also, not sure what your concern is with an "emissions" carb. Carbs built 1974 and after have an additional provision for ported vacuum to provide EGR signal, and some post-'75 carbs have bowl vent provision to allow the EVAP system to capture vent fumes off the carb. None of this has any effect on the operation of the carb. Most of the post-'71 carbs are set up with low speed air bleeds that assume operation with a very mild cam (pulling good manifold vacuum), so they can run out of idle mixture screw adjustment when used with an aggressive aftermarket cam. But that can be rectified. There is no advantage of the '74 carb over the '78 from a performance standpoint., and you're going to run into choke, linkage, and hookup issues trying to swap those two carbs.
Nope. The 4MV carbs are divorced choke carbs that do not have the choke as part of the carb. The 1975+ M4M carbs are integral choke carbs and can be converted to electric choke. Not the '74.
Also, not sure what your concern is with an "emissions" carb. Carbs built 1974 and after have an additional provision for ported vacuum to provide EGR signal, and some post-'75 carbs have bowl vent provision to allow the EVAP system to capture vent fumes off the carb. None of this has any effect on the operation of the carb. Most of the post-'71 carbs are set up with low speed air bleeds that assume operation with a very mild cam (pulling good manifold vacuum), so they can run out of idle mixture screw adjustment when used with an aggressive aftermarket cam. But that can be rectified. There is no advantage of the '74 carb over the '78 from a performance standpoint., and you're going to run into choke, linkage, and hookup issues trying to swap those two carbs.
ok. Thanks. I have what I have and trying to make use of what’s best for my car. I will be doing flat top pistons, aluminum heads and mild cam in the future with my 2102 intake. I will also get a better ignition setup as well. After your hate comments on the ebrock carbs, I am looking to get a decent q-jet to run with my setup. With the 2101 intake, all egr and emissions are gone except pcv. Unfortunately the original carb has that cracked base plate. So, if the 74 carb will not adapt I will need to find one that will fit/work.
Lars, what’s year/model will work for my needs? Carb id numbers etc? If I need to find a q-jet to work for me, you would know. I have a 4 speed as well, so auto brackets are not needed if it matters.
From: At my Bar drinking and wrenching in Lafayette Colorado
I consider my "hate comments" about the old, obsolete Edelbrock reproduction carbs to be "factual observations that may be offensive to some people at the Edelbrock Marketing Department."
The carb to look for and use, if you'd like to stay with a Q-Jet, depends on the choke system you want to use. If you're going to use a manifold with divorced choke provision, you will be looking for a 1969 - 1974 Chevy passenger car Q-Jet. Of these, the hands-down most versatile and easiest-to-use carb is the 1969 350/350 carb, part number 7029207. Original, unmolested versions are still popping up at reasonable prices, but the prices are going up sharply, and there are a bunch of "fake" ones out there that are complete junk (judgmental hate speech, again). Otherwise, the most refined carbs in this vintage model/series are the '73-'74 Chevy passenger car carbs. The choke system on these works very well, and these carbs can be set up to run well with a big-cammed engine as long as some attention is paid to the air bleeds.
If you want an electric choke for use on a non-divorced-choke manifold, start looking for M4M carbs. Avoid the 1975 carbs - they have a grossly inferior APT system that is pure junk (hate-speech again - get your kids away from the computer). '76 - '79 Chevy passenger car carbs (NOT truck carbs) are all very usable when correctly set up , and all can be converted to electric choke. The L82's and many of the Monte Carlo carbs are 800 cfm carbs, and make very good performance units when set up right.
Lars
I consider my "hate comments" about the old, obsolete Edelbrock reproduction carbs to be "factual observations that may be offensive to some people at the Edelbrock Marketing Department."
The carb to look for and use, if you'd like to stay with a Q-Jet, depends on the choke system you want to use. If you're going to use a manifold with divorced choke provision, you will be looking for a 1969 - 1974 Chevy passenger car Q-Jet. Of these, the hands-down most versatile and easiest-to-use carb is the 1969 350/350 carb, part number 7029207. Original, unmolested versions are still popping up at reasonable prices, but the prices are going up sharply, and there are a bunch of "fake" ones out there that are complete junk (judgmental hate speech, again). Otherwise, the most refined carbs in this vintage model/series are the '73-'74 Chevy passenger car carbs. The choke system on these works very well, and these carbs can be set up to run well with a big-cammed engine as long as some attention is paid to the air bleeds.
If you want an electric choke for use on a non-divorced-choke manifold, start looking for M4M carbs. Avoid the 1975 carbs - they have a grossly inferior APT system that is pure junk (hate-speech again - get your kids away from the computer). '76 - '79 Chevy passenger car carbs (NOT truck carbs) are all very usable when correctly set up , and all can be converted to electric choke. The L82's and many of the Monte Carlo carbs are 800 cfm carbs, and make very good performance units when set up right.
Lars
