StingrayL82
Nampa, Idaho
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Griff in Fairbanks wrote:StingrayL82 wrote:My opinion is keep the ThermoQuad and rebuild it, it’ll give you more reliability than that Edelbrock ever could and, yes, ditch the EGR. I made my own with 1/4” steel.
Eric - this has been discussed extensively ... StingrayL82 is coming into the discussion late.
Ask ten people about carburetors. Three will say Carter AFB/Edelbrock is best. Three will say a ThermoQuad is the cat's meow. The remaining four will say chuck the four barrel and replace it with a two barrel.
Don't second guess yourself. You listened to various opinions and made your decision. You may find your decision doesn't work for you. However, in the vast majority of cases, you'll find your decision is right for you.
Lesson from decades of systems analysis and design: Only -- repeat only -- when you run into a cascade of steadily worsening problems is the only time you should back up and rethink your decisions.
I know opinions about carbs are like posteriors.. I’ve pulled 1406 Edelbrocks out of the box and they leaked like sieves, so that’s my experience with them, plus I’m a fan of putting OEM carbs on these engines. I know people hate the ThermoQuad, but my experience with them has been trouble-free.
As for the BBD, they are notorious for needing to be rebuilt on a yearly basis. The tubes clog up, requiring paper clips to be run through them. AMC/Jeep used them in ‘78-newer CJs and other models. Most Jeep guys throw them in the garbage and replace them with Weber’s. It’s just a urine-poor design.
Fred
Retired Army Guy
2005 Monaco LaPalma 37PST
Workhorse W24 chassis
8.1L Vortec
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Griff in Fairbanks
AK
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StingrayL82 wrote:I know opinions about carbs are like posteriors.. I’ve pulled 1406 Edelbrocks out of the box and they leaked like sieves, so that’s my experience with them, plus I’m a fan of putting OEM carbs on these engines. I know people hate the ThermoQuad, but my experience with them has been trouble-free.
As for the BBD, they are notorious for needing to be rebuilt on a yearly basis. The tubes clog up, requiring paper clips to be run through them. AMC/Jeep used them in ‘78-newer CJs and other models. Most Jeep guys throw them in the garbage and replace them with Weber’s. It’s just a urine-poor design.
Yes, there has been at least one period when Edelbrock was experiencing problems with quality control. Blame the pencil pushers and penny pinchers. Some of the problems were due to casting and machining problems, resulting in dimensional issues. Most of the problems were traced to using inferior gaskets and seals. I heard corporation overrode engineers, purchasing gaskets and seals that appeared or were certified to meet specifications but cost 75 percent less.
Interesting this is decades earlier Chrysler Corporation went through a period of identical problems with the Carter AFB. Descriptions of the problems and apparent causes were so identical it appeared someone had merely reprinted decades old text. (Or, someone had used a time machine to grab text from the future.)
In both cases, likely causes were:
1. Use of casting molds past accepted lifespan.
2. Use of tooling dulled through overuse.
3. Use of gaskets and seals that did not meet specifications.
Both companies tried to keep this under wraps but people talk and very capable mechanics can see things. (Gaskets that are little more than thick paper and seals that fall apart when you touch them are easy. Dimensional problems take a bit more work.)
I'm not familiar with the ThermoQuad so I have to rely on people's experiences described in this thread and elsewhere. Unless I'm confused most problem center around the phenolic plastic float bowls. Heat apparently causes the bowls to warp or occasionally crack. The bowls are no longer being made so the only option is to find a good one off another ThermoQuad.
The elevated temperatures inside engine doghouses aggravate this problem.
As for the Carter BBD ... I think I said clearly having to rebuild the one on my '77 B200 was my own fault, due to ignorance.
Our 1969/70 Explorer Class A had a BBD on the 318 engine. It work just fine when we bought the motorhome ... no leaks, no problems. It continued to work just fine for years. The only things I did to that motorhome was routine maintenance, new brakes, and advanced the timing a few degrees.
We left the motorhome sit unused for several years. One January evening with temperatures below -40 degrees F, Pat left work and couldn't get the van started. (Someone had turned off the outdoor outlets.) At home thirty miles away, I couldn't get the Bronco started. (Even after a hour of trying with a plugged in battery booster and starting fluid.)
In desperation, I turned to the motorhome. Because of how long it had sat unused, I had doubts. A splash of gasoline in the BBD and a fully charged battery. It started right up and was idling smoothly in less than a minute.
I know of only two vehicles, without a block heater, that would start right up at temperatures below -30 degrees F. One was driven daily ... the motorhome had been neglected for years and had been sitting, in the open, for over a month of seriously subzero temperatures.
(This is why Pat and I decided to use the motorhome as a basis for resuming pursuit of my lifelong dream.)
1970 Explorer Class A on a 1969 Dodge M300 chassis with 318 cu. in. (split year)
1972 Executive Class A on a Dodge M375 chassis with 413 cu. in.
1973 Explorer Class A on a Dodge RM350 (R4) chassis with 318 engine & tranny from 1970 Explorer Class A
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Leeann
Maryland
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The phenolic bowls do warp or crack, but not due to heat. You can hit one with a torch and it won’t get hot (told to me by my old parts guy who knows these old rigs - he said a salesman used to go around and do just that, then toss the bowl to someone after pretending it was a hot potato).
They warp or crack due to overtightening of the screws.
'73 Concord 20' Class A w/Dodge 440 - see profile for photo
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Griff in Fairbanks
AK
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Leeann wrote:The phenolic bowls do warp or crack, but not due to heat. You can hit one with a torch and it won’t get hot (told to me by my old parts guy who knows these old rigs - he said a salesman used to go around and do just that, then toss the bowl to someone after pretending it was a hot potato).
They warp or crack due to overtightening of the screws.
Oh, I stand corrected. So, people ruined them by trying to compensate for old or inferior gaskets.
Edit: You also answered a question that was bothering me. I know plastics and knew phenolic plastic was heat and electricity resistant. (It's usually thermosetting.)
Makes sense, I watch a young Army troop effectively destroy a two year old transmission while trying to stop a pan gasket leak. He stripped half the pan bolt holes before he decide he should ask someone.
* This post was
edited 04/18/18 08:30pm by Griff in Fairbanks *
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Leeann
Maryland
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Yup, damaged by ignorance.
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StingrayL82
Nampa, Idaho
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Damaged by overtightening of screws or not removing the two screws inside the primaries and then trying to pry the top off of the bowls with a flatblade.
The phenolic bowls, by the way, were proven to run 20 degrees cooler than metal bowl carburetors.
75-1966 needles and .104" jets are the perfect combo for the 800cfm (1-3/8" primaries) ThermoQuad on a 360cid at 2600ft elevation.
The bowls are still available new: New ThermoQuad Phenolic Bowls
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StingrayL82
Nampa, Idaho
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Eric Hysteric wrote:...
1. The carburaters have no fuel return line?...
Just a thought for you, Eric....if you're looking for a way to return the fuel to the tank, and the carb doesn't provide for that, get a fuel filter that has a single inlet and dual outlet, like the Jeep used. The top outlet is used for the return. Jeep Fuel Filter
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Griff in Fairbanks
AK
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StingrayL82 wrote:Damaged by overtightening of screws or not removing the two screws inside the primaries and then trying to pry the top off of the bowls with a flatblade.
The phenolic bowls, by the way, were proven to run 20 degrees cooler than metal bowl carburetors.
75-1966 needles and .104" jets are the perfect combo for the 800cfm (1-3/8" primaries) ThermoQuad on a 360cid at 2600ft elevation.
The bowls are still available new: New ThermoQuad Phenolic Bowls
Thank you. Last time people on this thread looked, they couldn't find new replacements. IIRC, one person knew of a source but when they looked again, the source had gone out of business or quit offering.
So, to paraphrase LotR, "Looks like ThermoQuads are back on the table, boys." (And, girls ... orcs can be sexist, we shouldn't.)
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StingrayL82
Nampa, Idaho
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Griff in Fairbanks wrote:Thank you. Last time people on this thread looked, they couldn't find new replacements. IIRC, one person knew of a source but when they looked again, the source had gone out of business or quit offering.
So, to paraphrase LotR, "Looks like ThermoQuads are back on the table, boys." (And, girls ... orcs can be sexist, we shouldn't.)
Well, you guys and gals have seen the video of mine running, and it's a scalded ape. They're easy to rebuild and, as long as you follow the directions and specs to the letter, it'll hum for you.
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Griff in Fairbanks
AK
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StingrayL82 -- yes, I knew phenolic bowls are cooler. A very strong argument in favor of ThermoQuads, in my mind.
With a ready source of new float bowls, I'm tempted. If I run into a problem rebuilding the Carter AFB sitting in my shop ... I may find a ThermoQuad, buy a new float bowl, rebuild and use it.
Eric -- pay attention, you can throw out a lot of what I've said up to now. (I still favor Carter AFB carburetors ... and Edelbrocks ...... but my position has softened.)
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