Help for Edelbrock Carb and Eaton True Track differential wanted

[Lazerwolf]

Hoping to get a little help out there or maybe educated a bit. I recently purchased a 74 Charger SE with only 61K miles. I thought it would fry the tires off the car but actually doesn't, it just accelerates quickly. I'm currently playing with carb tuning and this may be the key but the rear differential may be the answer as well. Sorry about the length here, but everyone always asks for more information so I'm trying to provide as much as possible.

The guy I purchased the car from knew little to nothing about the car, and I believe the owner prior to him did most of the work. Here is what I do know about the car after tearing it apart to fix wrong parts and leaks everywhere. The block is the original 400 HP block with a street cam, not race cam it in. I have no clue which one. The heads have been replaced with Edelbrock E-Street aluminum ones. I changed out the Edelbrock Performer RPM intake for a Performer one, following Edelbrock's tech advice to better match the RPM range of the components. The water pump and radiator appear original, and it has a 195 thermostat. The AC components have been removed. The mechanical fuel pump may be an aftermarker HP one, but really looks original. The original 727 tranny has a B&M shift kit in it I believe since I found the documentation in the glove compartment. The last two components are where my question are based. The 8 3/4 rear axle has green bearings and an Eaton True Track differential with 3.55 gears. Maybe these are designed to hook up immediately without any tire spin. The carb is the last question. It's an Edelbrock 1406, 600 CFM carb. I would rather spend $50 tuning this than needlessly wasting way more on a Holley, so please don’t suggest that. I know this is a fuel economy carb but I'm following the 1405 performance carb tuning chart. Idle is set at 900 RPMs by the way, which is what a factory sticker under the hood said it should be. Initially, the car hestitated and struggled from 900-2500 RPMs, but then pulled really strong. After contacting Edelbrock carb techs, I did the following. The idle mixture screws are out 1 1/2 turns. The primary jets are .098 and secondary jets are .095, which is standard on these carbs. The step up springs were changed from the standard yellow ones (4" Hg) to the pink ones (7" Hg). The metering rods were changed from 1459 (.075 x .047) to 1455 (.073 x .042). The accelerator pump linkage was moved from the middle hole to the one closest to the carb to give it the biggest shot of fuel. All of these changes did pretty much eliminate the lack of fuel issue from 900-2500 rpms. I'm a carb tuning novice and don't want to flood the carb with more gas than needed. Edelbrock did say for street driving, the 600 CFM carb should be fine and there should be no need to go with a 750 CFM one.

This is a street car that I occasionally drive to work about 30 miles each way so I don't want a race car. I just thought with all these nice components, this car would be explosive, especially off the line, but have been disappointed so far. Any help or suggestions would be very much appreciated.

 

[benno440]

I would check your cam was installed properly and not a tooth out.
check your timing and definetly tuning on the carb.

the eaton true trac is a helical gear and is always loose until you apply power and torque is when the gears match up and spin both wheels. best unit in the world imo
should be bagging the tires

 

[62 Dart Convertible]

For sure you should be smoking the tyres. True Track with 3.55's isn't your problem, it's your lack of torque.

The hesitation you corrected sounds like it was caused by lean mixture which should come as no surprise considering the 1406 OOTB is calibrated for economy.

Pity you know nothing about the cam. You don't mention CR either, do you know what it is? An idle vacuum measurement would help make an educated guess as to how big the cam is, and what to expect.

You haven't mentioned ignition at all. Timing is critical and you need to be sure the condition, advance curve and rate and timing settings/total advance are correct for your engine. Stock factory settings count for nil in a modified engine. If not right, it can be the difference between explosive and lazy. This must be sorted before playing with carb.

None of this is rocket science, but takes time to learn, some tools (like an AFR meter to dial in the carb really well) and patience to complete.

If you just want it done to enjoy asap, I would recommend you take the car in to a Mopar friendly chassis dyno tuner and have them dial it all in.

If you plan to DIY, say so and I'll post some links to some resources rather than re-write the Gettysburg address.

 

[YY1]

I agree about timing.

I had a stock 77 400 in a 70 Super Bee for a while. Stock 727 and factory 3.55 SG.

That car would spin whenever you wanted it to, and ran nearly as good as the higher compression 383 that came out of it.

I'm currently running an Eddy 600 on a 69 440, and it works just fine until about 3800 RPM, then I can tell it's not getting enough fuel. I didn't change anything internally, and it's a $65 swap meet carb.

With respect to timing, both my previous B block motors wanted a heap of timing.

I also set my timing by ear- advance until it pings under hard load (in gear), and then back off slightly until the ping goes away. If you can't get a happy medium between bog, and hard starting, then perhaps the vacuum is not working or the springs need adjusted.

Knowing the cam sure would help, as it could be totally wrong for the rest of the build or installed incorrectly.
Everyone told me a 284/484 was wrong for my 383, and it probably would have been if it was installed "straight up".
I degreed it following the MP video and that motor screamed.

For what it's worth, going forward quickly is usually more desirable than smoking the tires

 

[Lazerwolf]

Thanks for all the information so far! I agree with you YY1, going forward quickly is usually more desirable than smoking the tires. It's not a question of wanting to fry the tires with me, but could I if I wanted to. Right now, that answer is no. I'm too old and cheap to just fry several hundred dollars worth of tires. That was fun back in the early 80's with the 440 in my Chrysler New Yorker when Dad was paying for the tires! The guy I bought this from originally had it for sale for $9500, and over a month or so, dropped the price down to $5900. I walked away from the deal because I was looking for a fun cruiser/hot rod, not a street racer. He called me the next day and said he would take $5,100 for it if I bought it that day. At that price with a solid car and several thousand dollars worth of parts, my wife actually told me not to refuse.

Here's what I can answer. The distributor is a Davis Unitied Ignition (D.U.I) street/strip version, which I know nothing about. My timing light is old and cheap but appears 10-12. I would guess the compression ratio (and pistons) are stock at 8.2 since the bottom of engine appears to not have been opened. It will this winter since both the rear main seal and oil pan gasket are leaking. The vacuum at idle is 15-15.5 at 900 RPM. Edelbrock was guessing this was their Performer cam and probably bought as a package with their heads, intake and carb. They did not think with that high of vacuum, it was the Performer RPM cam since vacuum with that should be around 10-12 at idle.

One last thing I forgot to mention is that is has the stock manifolds and exhaust for the most part with some type of turbo mufflers. There is a leak somewhere on passenger side near manifold but I have not checked that out yet.

 

[Lazerwolf]

Although I am not sure exactly how to set the timing with the D.U.I. distributor, I think the issue is the lean setting on the carbs. The distributor does not have the vacuum advance and when I first checked it tonight, I would guess it was in the 20-25 before range, since it was well off the timing mark range by an inch or so. I left the timing set where it was and altered the carb a bit. I put the accelerator linkage back to the middle hole, so it got less gas per squirt and put in a richer metering rod. I chose the next step up .070 x .037 (1449) and gave it a test. I hammered it off the line and the rear tires talked to me for a few seconds. It also pulled strong all the way from idle to about 3500, which is as far as I took it. I will drive it next week to see if this is a happy medium of performance and fuel economy (yes, I know, good joke there). Any one have any suggestions on how they set up the 1405/1406 carbs for a good balance? Not looking for a burn out king.

 

[62 Dart Convertible]

Any one have any suggestions on how they set up the 1405/1406 carbs for a good balance? Not looking for a burn out king.

What jets/rods anybody else is using is irrelevant as it's not your particular engine. Edelbrock explain the procedure all here -

http://www.edelbrock.com/automotive/misc/tech-center/install/1000/1404_manual.pdf

Before playing with the carb, you need to be sure ignition timing setting and curve is correct.
You say initial timing is 10-12 BTC. The big question is what is your total advance and at what RPM is that reached? General consensus is total should be 35-38 all in by 2500RPM.
If you can't check as you don't have a timing tape on the damper, I'd suggest you get one on asap.

 

[benno440]

thats decent vacuum am i right, if cam is installed incorrectly i am aware that you will have really low vacuum (correct me please) so your cam might be right it must just be a timing and carb tune issue. 8.5 compression is also very low, whach a turbo on it with that compression haha.

 

[62 Dart Convertible]

thats decent vacuum am i right, if cam is installed incorrectly i am aware that you will have really low vacuum (correct me please) so your cam might be right it must just be a timing and carb tune issue. 8.5 compression is also very low, whach a turbo on it with that compression haha.

Yep, that vacuum level indicates very mild cam, a good choice with such low CR.

A large percentage of perceived carb problems are actually ignition problems and why one should always ensure ignition is 100% right first.

 

[Lazerwolf]

Thanks for the responses and I appreciate the feedback. 62 Dart, I've been over that Edelbrock manual a dozen times and especially the 1405 and 1406 charts. I definitely understand the comment that no one else's engine is the still as mine. Here's where I was going on the metering rods and jets. The Edelbrock tech told me to just change to the 1455 metering rods, which is moving from the #1 to #23 on the 1406 chart. That's really helped the idle to 2500 RPM range, but didn't feel like it solved the issue. However, looking at the charts for the 1405 and 1406 carbs, the 1406 #23 is the exact same as the 1405 #29. According to the 1405 chart, that is still extremely lean on the cruise side. So, I stepped up to the 1406 #19 tonight which is the same as the 1405 #26. I definitely saw improvement and feel it found several of the missing ponies. The #19 is as about as rich as you can get on Edelbrock's chart for the 1406 carb, but not even close on the 1405 carb. This being my first experience with these 1405/1406 carbs, I was looking to see how rich people were making these without issues. Trying to find all the HP my engine was built for and having it streetable without just dumping gas out the exhaust.

I would also appreciate any info/links you can supply on setting the timing on those D.U.I. distributors. Their online info is pretty useless.

 

[62 Dart Convertible]

As you know, the 1406 is jetted for economy and recommended for a stock engine. Putting it on a non stock engine I would expect it would need to be richened up by quite some margin. How much, I have no idea, but it is ascertained by the procedures outlined in the manual, or better still by an AFR meter in the exhaust, either while driving or on a chassis dyno.

Before playing with the carb, you need to be sure ignition timing setting and curve is correct.
You say initial timing is 10-12 BTC. The big question is what is your total advance and at what RPM is that reached? General consensus is total should be 35-38 all in by 2500RPM.
If you can't check as you don't have a timing tape on the damper, I'd suggest you get one on asap.
It's possible your distributor curve and timing is perfect, but you need to know it is.

Incidently, the weakest link in realising the full potential of this engine is your stock exhaust manifiolds. Not that I want to cloud the issue here, just pointing out that these will severely limit the horsepower in the mid to top end. It's baffling to me why one would spend $$ on cam, aluminium heads, intake and carb and not put headers on it. It should be the first thing on the list.

 

[charger360]

rule of thumb always do your timing first you just can't set a carb properly till you get that done. dui ignitions are top notch units you time them the same as any other unit I would say you are wasting your time if you can't set the timing either with timing tape or a dial back timing light. as for the carb it is a 1406 I don't care what the guy at edelbrock told you it is not the best carb for a 440 with some cam. at least a 1405 has slightly richer internal calibrations which would help you out with your tuning. some folks find the 750 eddy is even to lean! with the amount of vacuum you have I would say you have a small cam upgrade at most. I would find a way to be sure of my timing setting before wasting my time with the carb. the reason for this is if your timing is off your idle speed will be affected which will throw off most of the carb adjustments you are doing as the transfer slots could be bypassed in the idle circuit. as for me I have run 600 eddy's 750 eddy's and holley's they are all good carbs but if you were to find a 750 eddy with the manual choke to be sure you get the performance one I think you would see a big improvement overall and no big change in economy. I have done this on a few big blocks I know it works. 62 dart is on the money about the timing events in the previous post

 

[Lazerwolf]

Looks like I will concentrate on the timing first. I just verified with my cheap timing light it was at idle (900 RPM) approximately 12 BTC like the information on the D.U.I. website said. There is no timing tape on the engine so I will get that next. Then back to the carb and maybe a 750 like you suggested. Edelbrock seems to have a rule of thumb that anything below a 402 c.i. is fine with a 600 CFM.

62 Dart, I did laugh at your comment "Incidentally, the weakest link in realizing the full potential of this engine is your stock exhaust manifolds". When I bought the car, there was an exhaust leak somewhere near the bottom portion of the right manifold and the left tailpipe rattles against the body above the rear axle. Oddly enough, he had a brand new set of Hedman headers in the trunk he never installed. I set them on the bench and forgot about them, concentrating first on oil, coolant, brake fluid and transmission leaks. I've had nightmares before with headers, but they were Hooker.

 

[62 Dart Convertible]

It's quite likely DUI (Driving Under the Influence?!) recommend idle at 12 BTC as their mech advance is likely 24 deg = 36 total. It is prudent to check though, cos if their mech adv is less than 24 deg, I'd advance it at idle to bring total to 36 deg. With your low compression, pinging certainly should not be a problem.

I am in your boat too with exhaust manifolds. I can't run headers as I have to keep my car factory original. (Law here where I live in order to drive a LHD drive car.) I could however put on some Max Wedge exhaust manifolds as they were a factory option. It's just the $$ that is stopping me atm.

There is no arguing headers will make more power. Folks will argue about how much more, but there are plenty of engine builders out there that have dyno'd back to back and have published results...

If you plan to put the headers on, don't bother playing with carb until exhaust is sorted.