Attention MoparHeads ! 72 Dodge B300 Carb/ 360 cid

[P. Vallerie]

It,s a balmy 3 degrees!! Time to start doing the heavy mechanic's on the "Queen". She's a Class C, 1 ton duelly, all butt 20' bumper to bumper @ 8,000 lbs. Carburetion on this olde gal... I am ready to yank this Holley H2 2210 and throw it against the wall!! We knew when we bought her that the carb needed work. The right carb & it's settings are the heart of any engine. Here's my dilemma. Do I rebuild or replace with new and improved. I would really like an electric choke - cold starts suck. Fuel economy, ease of tune ability, settings; that will hold. 2 barrel 500 cfm square bore vs a 4 barrel spread bore @ 600 cfm. She has a 3 speed automatic transmission. Here's another thing to put in our bonnets. We live @ an altitude of 5,500 ft. above sea level. We do a lot of mountain camping typically @ 9'000 ft. above sea level & would like to take her along. It's the age old fight between Holley vs Carter (Edelbrock now a days). It's all about air or lack of it.
Mmmmmm.. Do I keep the old and rebuild/remanufactured? OR Do I replace with a new Holley 500 cfm - electric choke (bypass the heat/vacuum auto business). OR Change the input manifold to a spread bore configuration add a 600 cfm Edelbrock electric choke. I really would like to keep a cast iron manifold..........
What do....What to do? Any suggestions? Do and don'ts from experience?

[John Demarrais]

This is in reply to the private message you sent me.

I believe you messed around with the accelerator pump and got it working. I just don't believe the "cause-and-effect" relates to spraying carb cleaner in there. The accelerator pump works pretty much just like a kid's water pistol. It is powered either . . . by a round rubber or leather seal (in the old days) that goes up and down in a round cylinder . . . or a flat diaphram made out of a soft rubber like material. The carbs used OEM on Mopars (if not Holley) use the round type (Carter, Ball, or Rochester). If the vehicle sits for a while without being started that round seal dries out and stops working. Once started and run again - sometimes the seal swells up and works again and sometimes it won't. It is the #1 wear item on those carbs and when it dries out - the engine is hard to start and once running - it bogs something awful cold or warm (but worse cold). It's not just for starting. It is also for warm running. Anytime you attempt to accelerate and push on the gas-pedal - a lean situation is caused because the carb is opening but the engine RPM has not caught up. It is referred to as "lag." The accelerator pump is there to eliminate that lag and richen the mixture anytime there is ANY forward movement on the throttle linkage. When you let off the gas and the linkage goes backwards, it does NOT engage.

Note that the accelerator pump is a "forced fuel" hydraulic system. It uses a piston or diaphram to force fuel under pressure out those two little jets (on a two barrel) or one jet (one a one barrel). Like a said, like a water pistol and pretty hard to plug. On four-barrel carbs - some come with only two jets for the accelerator pump and some come with four. The ones with four are often called "double pumpers." Usually only used in hot rods and racing. Most street four-barrels run on just two barrels for normal driving. When you stomp on the gas, the second pair of barrels open but do so very slowly and gradually so not to cause a huge "bog" since they lack an accelerator pump. That is the way the OEM four-barrels like a Rochester Quadrajet work, a Mopar Thermoquad, or a Holley "vacuum advance."

From the overly rich symptoms you described - I'd make sure that choke-break vacuum-diaphram isn't bad (easy to check with a hand-held vacuum tool). Even if it IS working- it must be adjusted properly. If it pulls the choke open too much -the engine bogs until it warms up. If it does not open the choke enough -the engine runs way too rich and can flood.

John Demarrais

[Matthew Tritt]

My Dodge-based class C Hall GTC came with the original Holley 2 barrel on cast iron intake with divorced choke. It was gutless in the mountains, had poor cold start problems and used way too much fuel under all driving conditions. Prev owners had replaced exhaust manifolds with stainless headers but left a crappy dual exhaust with no crossover pipe in place. I changed over to a huge freeflow muff, a resonator with 3" all the way from the "Y" and single pipe exiting ahead of the left rear wheels.  Prior to a total engine and transmission replacement, which I did for reliability and fuel economy reasons, I installed an Edelbrock Performer intake (spreadbore), squarebore adaptor, Edelbrock 1400 with electric choke. I had to design and install a modified throttle linkage, run new 12 volt circuit to power the choke, find an appropos Mopar air cleaner that fit the limited space under the doghouse* (aftermarket air cleaners do nothing to quiet the tremendous air inrush noise generated by all gasoline engines at full throttle) and do a fair amount of other tweaks. I also rebuilt the carb prior to installation.

One benefit of doing all this stuff includes reducing the sprung weight over the front axle, since that lovely old iron intake weighs a ton! The aluminum replacement is a far more efficient part and is well worth the money.

Another goal was to reduce emissions by going with a better carb design (not personally a Holley fan) and to have improved performance on mountain grades........ however. After all the work I've done to make my ride fuel efficient and mountain capable, I can say for certain that the ONLY way to really accomplish this goal is to convert over to a throttle body EFI system. This is because the jets installed in your carburetor have a fixed orifice size that can only provide optimum performance within a pretty narrow range of altitude variation, If it works great at sea level it will positively suck at 7,000', let alone 9,000! There will be too little power and too much wasted fuel exiting the tailpipe in the form of unburned hydrocarbons, and it will be hard to start. I know of no way to get around the laws of physics that have to do with fuel/oxygen combustion as related to air pressure/specific gravity other than with the aid of computerized air-fuel mixture and spark timing provided by EFI. 

[Dave Creu]

I guess I'm late too this conversation, although I'll throw in my 2 cents! :)

I have a 1976 Dodge Sportsman Tioga class C with 360 and 2 bbl Holley 2210. I have the heads pulled right now to replace a burnt exhaust valve on #7 cylinder (was like this when I bought it). When I get to installing the intake manifold, I'll be going with an Edelbrock 2176 performer, and an Edelbrock 1801 500cfm AVS carb with electric choke. 

While the Holley "can" be tuned correctly, to me they just aren't worth the trouble. The 4 bbl will get better mileage, have better throttle response, and Carter/Edelbrocks hold a rock solid tune. I disagree with anyone who says they aren't as tunable as a Holley, and tuning them does NOT void the warranty. Fact is, they are much easier to tune than just about any other carb, and there are plenty of tuning bits and pieces to get the job done, BUT, it doesn't take but a few tweaks to get them right if you have a wide-band O2 sensor in the exhaust stream. This and exhaust gas temperature are the only real ways to get the perfect tune, especially in high altitude environments.

Unless you are adept at tuning carbs (and that should begin with tuning the ignition curve FIRST), then EFI would be the better way to go. EFI will  keep the air/fuel ratios correct, but of course you are going to loose power the higher the elevation, and the best way to keep the power pumping in those situations is to install a turbocharger system. I know... that's waaay more involved than what most folks are willing to do, but it is the correct solution for everyday high altitude driving.

My experience with these engines and 727 trannys is that they are indeed as close to bulletproof as you can get, although, proper and precise tuning of the spark and fuel curves makes ALL the difference.

Dave

[P. Vallerie]

Thanks Dave. No your not to late. This has been a really interesting discussion. I am sure it will go on for awhile. I just got back from our garage project. We are going to baseline with what was on there to start. Our focus right at this point in time is to get the front end/suspension rebuilt. Then a simply carb clean up, dial it in to get it running well.
I am very interested with the final results of your eddy carb/intake configuration!! It is one of the options that I am considering. Same carb/intake. Please share the results with us once you got her put together and your test drives. What improvements have you experienced etc. The other is to hold off for a tad and go full blown EFI in a year or two. The altitude driving is the trickiest to work through. What altitude are you at?

[John Demarrais]

If you decide you want an Edelbrock Performer intake - I've got one on a truck I'm going to junk this spring.  It's on a 1969 Dodge 318 V8 with a Rochester Quadrajet on it .   I tried many different carbs years back and the Rochester gave the best MPGs (in two-barrel mode).  Anybody who wants it can have it for $50 if they want to go take it off. (in Central NY).  I was never impressed with it - but my disappointment with the engine cannot be fairly just blamed on the intake.  The engine also has 10 to 1 pistons in it, a Crane "RV" cam, headers, etc.   It's in a 1969 Dodge Power Wagon, not an RV so it's easy to get to.

[P. Vallerie]

Gosh John I wish we were closer. Colorado it a bit of a distance. But maybe some one else would like it. It's a great classic set up and would work nicely with the right engine. You should post it on the for sale forum. Might get some bites. P

[John Demarrais]

I'm 800 miles away from that truck right now, thus the reason why I'm not presently pulling parts.   I was stripping and scrapping trucks and RVs all fall.

On the subject of altitude, power and fuel mileage. The general rule is a 1% loss for every 333 feet above sea-level.  When I was fooling with my two Dodge RVs I was living at 1800 feet. 6-8 MPG is what they got.   I took both on trips through Canada and Michigan and tested both at near zero altitude (600 feet).  They still got 6-8 MPG.  I.e., no difference big enough for me to detect.

I had a 1987 Chevy diesel 4WD Suburban fixed up for camping.  In NY at 1800 feet it could get 18 MPG.  When my son took it to Colorado at 6000 feet - it got 13 MPG and ran so bad, he could not pass the smoke-inspection test.  He later had to install a turbocharger kit to make it pass.  Note that the drop in MPGs is not exactly "science." I'm sure my son had a heavier throttle-foot then I did.

[P. Vallerie]

John your wealth of knowledge & experience is worth it's weight in gold. The amount of information shared by all has helped me rethink my approach to this olde gal. Slow it down, take the time and get the old school technology working at its best. Then slowly methodically add the bells & whistles that will give us the best bang for our buck. Thank god we have several fantastic high performance shops in Ft. Collins. One in particular that I really like working with for future modifications especially with the high altitude we live & drive in. He has been around for ever & has won all kinds of awards. Trust me I will be asking some more questions in hopes that you will help guide us fixing this olde gal. Bringing her back to life in her full glory and some kick. I will keep you posted as we progress. Thinking of starting a blog. More journal like. P

[Dave Creu]

I certainly understand the need to focus on the most important fixes first. Seems like there's always something, but really, that's just part of the fun!

I'll remember to keep you posted as I progress, and hope that you will be able to get the ole gal running like a top in those high places you frequent. I'm down south, so my elevation at any given time is usually between 300-600 ft. above sea level. No real tuning challenges here except for harder winters (and this with a carb).

Best,

Dave

[P. Vallerie]

Thanks Dave. I'll need all the support I can get. It is certainly an interesting challenge. I have not attempted something like this before. I always dreamed of restoring a 42 Chevy panel truck since I was a kid. How I ended up with a Dodge....RV.....I just could not pass up a great deal & opportunity. My background is working on those big Diesel marine engines with my father in my younger years. Finally I have the time & a little extra $$ to spend on grown up toys. This is a small land yacht.
The intake-carb combination that you are about ready to do to your rig. I am really interested in how that is going to work on your 360.
Keep me posted with you progress would love to see some pic's of your completed modified engine. P