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Author Topic: Build thread - 1979 Dodge Diplomat - AKA - "The Duplomat"  (Read 4946 times)

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DobaMark

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Re: Build thread - 1979 Dodge Diplomat - AKA - "The Duplomat"
« Reply #15 on: June 26, 2015, 19:21:04 »

I hear ya.  Long term will get an aggressive 360, but for the time being, I am looking to wake the 318 up a bit.  I didn't go stupid on cam, intake and carb (454 lift / 272 duration), torker intake, and vacuum secondary carb.  I believe the ignition upgrade alone should be helpful.  I can't fathom the logic that said "let's drop the voltage down with a resister".   
There is plenty of spark power with the stock system, only real issue is timing advance can be lazy.
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Backtobasics

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Re: Build thread - 1979 Dodge Diplomat - AKA - "The Duplomat"
« Reply #16 on: June 29, 2015, 09:47:44 »

Weekend progress:


Adhesive removed, roof sanded, primed, painted.


Rustoleum paint, local hardware store, thinned to 60/40 and shot with Sharpe HVLP gun. 


It could be better, but the roof is secure, will not decay, and the car is a bit more presentable.   The only thing I would do different is the tape.  Harbor Freight tape started to lift with sun and warmth.












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Backtobasics

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Re: Build thread - 1979 Dodge Diplomat - AKA - "The Duplomat"
« Reply #17 on: June 29, 2015, 09:50:44 »

There is plenty of spark power with the stock system, only real issue is timing advance can be lazy.


That may be so, but I have never loved the idea of the ballast resistor.  There is a huge business in the aftermarket making more and better spark, yet Mopar decided to bring the energy down?


I have a vacuum advance distributor, that I am combining with an MSD HEI module and coil.  Short of a CDI box, this should get the spark up, and with a better curve, to go with the intake, carb, and cam kit.  Install is scheduled for July 25th unless it happens sooner.

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80 Lebaron Coupe

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Re: Build thread - 1979 Dodge Diplomat - AKA - "The Duplomat"
« Reply #18 on: June 29, 2015, 09:53:15 »

Nice Job! :thumb:
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270SE

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Re: Build thread - 1979 Dodge Diplomat - AKA - "The Duplomat"
« Reply #19 on: June 29, 2015, 13:47:13 »

It will not go faster until you change the pumpkin.  The engine mods will not really make you go with these cars.

There's a big change, but there also develops a lot of compromise. There's little to miss of the poor drivability and weak power most of them came with, but the low RPMs on the highway's not something hard to miss. 4+ hours at 70 can get old at 3000RPM in most any vehicle.



That may be so, but I have never loved the idea of the ballast resistor.  There is a huge business in the aftermarket making more and better spark, yet Mopar decided to bring the energy down?

I have a vacuum advance distributor, that I am combining with an MSD HEI module and coil.  Short of a CDI box, this should get the spark up, and with a better curve, to go with the intake, carb, and cam kit.  Install is scheduled for July 25th unless it happens sooner.

It might have to do with reliability, they're actually really good systems- even if you rob everything used off a 360 it's worth doing to have as backup for if/when the CDI burns out- the lifespans tend to be much smaller than the factory boxes. All of MoPar's performance vehicles including the Hemis, RRs, 340 cars and the E58s that ran strong stock had the voltage stepped down with ballasts.


I hear ya, Gents.
This is my daily driver, and needs to be able to go 65 on the highway.

Surely a performance cam, intake, carb, and ignition will help, a lot.  I am sure this engine is so smogged, that the camshaft might not even have lobes.

Yeah, even the trucks of the era could do with more intake and cam.
« Last Edit: June 29, 2015, 13:48:08 by 270SE »
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fifthcrunch

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Re: Build thread - 1979 Dodge Diplomat - AKA - "The Duplomat"
« Reply #20 on: June 30, 2015, 05:03:39 »

They found that the less power the less smog.  Just don't burn as much gas that way.  Who needs lobes on a cam anyway?  That only opens the valves.  If you don't open the valves, you don't burn any gas.  Saves the environment.  Similar situation with horses: don't feed 'em and you get less emissions, which equals less flies and less stink.
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Backtobasics

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Re: Build thread - 1979 Dodge Diplomat - AKA - "The Duplomat"
« Reply #21 on: July 01, 2015, 15:09:59 »

It is without a doubt the slowest small block Mopar I have had, slower than many of the 2 barrel cars in my past.  Feels like it would run well into the hundred + range, but would take ions to get there.


The stock ignition was a compromise I am sure, with reliability, cost and performance all in the game.   I am willing to throw in a set of plugs and a cap and rotor from time to time for a full 12V spark, with a more aggressive timing curve. 


I will take some caliper measurements of before and after on the camshaft lobes minus the base circle.  It should be interesting to see the difference.
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fifthcrunch

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Re: Build thread - 1979 Dodge Diplomat - AKA - "The Duplomat"
« Reply #22 on: July 01, 2015, 17:36:29 »

It's not the ballast resistor that's robbing you of power.  It's the cam, the distributor, and most definitely the compression ratio and rear axle.
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brotherGood

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Re: Build thread - 1979 Dodge Diplomat - AKA - "The Duplomat"
« Reply #23 on: July 01, 2015, 21:34:45 »

It's not the ballast resistor that's robbing you of power.  It's the cam, the distributor, and most definitely the compression ratio and rear axle.

This
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Backtobasics

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Re: Build thread - 1979 Dodge Diplomat - AKA - "The Duplomat"
« Reply #24 on: July 02, 2015, 13:11:52 »

I get it, I get it, the ballast resistor ignition is not the entire reason why the car is slow.  It's one of the steps that I am going to take to try to get the power up, in addition to distributor, camshaft kit, and dual exhaust.


I am not changing the rear axle, this is a highway daily driver.
I am not changing the compression ratio, too much time, money, and hassle.

Eventually a higher compression motor with headers, OD trans + gear change will fix all the ails, but for the time being the goal is a power increase, efficiency, and reliability. 
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MarkM

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Re: Build thread - 1979 Dodge Diplomat - AKA - "The Duplomat"
« Reply #25 on: July 09, 2015, 10:45:06 »

Two things that I see with this combo: that single plan intake is going to kill your bottom end, and if you're unwilling to change to a steeper gear then you need a torque converter.


These recommendations are taking into consideration you are using a 2.2x rear gear ratio.  This is a total limiting factor, but I understand it since this car is a highway cruiser.



That intake has an advertised range of 2500-6500 RPM and is a total mismatch for that cam and gear; the RPM Performer would be a far better choice at 1500-6000 RPM and could be used on the new motor, or better yet the original Performer at idle to 5500 RPM.  Just whatever you do, don't run that Torker!


That cam is going to push the torque curve farther up in the RPM range; which is going to create a big issue with 2.2x gears.  You need all the torque you can muster to be as low in the RPM range as possible.  There is a way to mitigate this though.  You need a converter that has a high stall to let the engine build R's to get you off of the line, but still has lockup for your highway cruising.  You can get a Mopar converter that fits this bill for $200 and I would not skip this!
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Backtobasics

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Re: Build thread - 1979 Dodge Diplomat - AKA - "The Duplomat"
« Reply #26 on: July 10, 2015, 09:43:32 »

Your logic is sound, but I have a few reason why I am going to buck the trend.


The Torker is a single plane, yes.  However, the runners are quite modest and are actually smaller than modern Performer RPM sizing (from experience, I make my living in the speed and aftermarket industry), so I do believe that port velocity will be reasonable.  This coupled with the price (40.00) is the reason for the use.  Long LONG way down the road might include a turbo build, where the single plane will be preferred.


The cam will move things higher, but I honestly believe that the weakness of the OEM cam is the lift.  I am going to give my best detailed math on both the aftermarket and OEM cam, to try to put into perspective just how little the stock camshaft is.  This unit was chosen for a compromise between all out performance, and TQ.  I did not make the rookie mistake of going to the bottom of the camshaft book page, and picking the largest thing available.  454 / 272 is pretty mild in the grand scheme of things.  I chose the lowest cost option here that had a performance flavor.


Ideally, as suggested, a converter would help.  However, that is going to wait for Stage 2, so that I only spend the bigger money, one time.


Regardless of what I do, with the existing rear gear set and converter, this car is never going to blow the tires off at stop light.  That isn't how it's used and not what I am looking for. I am more concerned about middle range performance, and passing gear power, where the car is used.  So I don't mind the combination of the cam / single plane when I want to move on the highway, where the car is already cruising at 2K+.  My information says I should be in the sweet spot of the cam, and the intake at that point.
« Last Edit: July 10, 2015, 09:50:30 by Backtobasics »
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Backtobasics

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Re: Build thread - 1979 Dodge Diplomat - AKA - "The Duplomat"
« Reply #27 on: July 10, 2015, 09:49:40 »

This is a budget oriented build of a 1979 Diplomat.


The ONLY place where I spent premium money so far is the Demon 1904BK carb, and while it might be a bit big for a smog 318, it is effectively a vacuum secondary and will flow what the engine needs. It will support the Stage 2 (360 and OD trans) down the road.  With my cost through work, it was less than what the average person pays for an Edelbrock 600cfm carb, so I went up. 

The cam, timing set are on the cheap end of parts, for budget.  The HEI parts, intake, carb, and cam will all swap over to the 360 at a later date.  The goal is to add a little HP now, until the 360 / OD trans will allow for a gear change.
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Darth-Car

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Re: Build thread - 1979 Dodge Diplomat - AKA - "The Duplomat"
« Reply #28 on: July 10, 2015, 16:06:49 »

Since this is your pay-check area, you may prove to be an advisory sounding board for us all on engine mods.  The more folks we have that bring quality knowledge to the table, the better this forum is for all.
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Backtobasics

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Re: Build thread - 1979 Dodge Diplomat - AKA - "The Duplomat"
« Reply #29 on: July 13, 2015, 09:00:40 »

I will contribute any where I can.  I have honestly been in the speed and aftermarket industry for 15 years, from warehouse to inside sales for two large wholesale distributors.  I have even been known to sell the wife car parts in my sleep.  She finally figured out if she agrees to buy whatever it is I am selling, I will shut up and go back to sleep. Last round had me convincing her she need a new performance exhaust on her minivan.  (it may sprout it down the road, for the hell of it.
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