New to me 73 duster 340

[t2ae]

Hey guys, Ive been lurking and trying to read up as much as i can for information. I recently acquired my grandfathers 1973 duster upon his passing. As you could expect i am trying to iron out all of the loose ends that he was not able to finish. The car has a 340 that has been bored .30 over, has a holley 600 carb, eledrock ld340 intake, headman headers, unknown cam but seems somewhat aggressive. 3 speed auto transmission with factory rear gears and stall. I have started with verifying the compression which is around 165psi on all 8. i Then moved onto the timing which is where i am getting a little lost and could use some help. car runs and drives ok it just seems to be beyond slow in my opinion. I adjusted the timing to see where it like it the best and at idle it seems to be happiest around 20 btdc. it doesn't seem to really like that set on acceleration though. When revved up watching the timing with the curve it ends up around 40 total timing. Any idea the specs i should be after?

 

[4mulas]

Beyond slow might mean the cam is retarded, seeing as you do t know much about the engine and it’s internals this could be a lot of things.

Sorry about your grandpa and congrats on the car

 

[t2ae]

What do you mean by cam being retarded? What other internals could have that big of a impact on power?

 

[Plymouth 65]

Typically, 12-16 initial 24-36 total. 65

 

[4mulas]

What do you mean by cam being retarded? What other internals could have that big of an impact on power?

The way the cam was installed into the engine. Read about cam degreeing, it can have a big impact on power

As for your timing question I run 18 initial and 37 total on my small block stroker. I just runs =what the engine likes. There is no one answer fits all applications

 

[Dart Frog]

Sorry about your loss. I'm sure that car meant a lot to your grandfather I hope you get enjoyment out of it. First of all almost all 340s that are anywhere near stock will never need more than 36 degrees of total timing. I would next be looking at fuel delivery. floor it does it backfire that will tell you it's leaning out. Another thing is you mentioned stock gears but does that mean exactly 323s 355 391s all were available if it is higher than a 355 and you say it's cammed it's probably not a good match. Especially on a low compression 73 340.

 

[t2ae]

Thanks for that! Stock gears are 323. It was an original 318 car that had the 340 put in. The engine was rebuilt about two years ago and had speed pro pistons put in that were 10.5:1. I only had it backfire through the carb once today when I was messing with the timing. Other than that no backfires

 

[t2ae]

 

[crackedback]

You might have to fix the distributor by limiting mechanical advance in order to get the idle timing where it needs to be and total number inbounds.

Nice car. Sorry about your Grandfathers passing.

 

[t2ae]

You might have to fix the distributor by limiting mechanical advance in order to get the idle timing where it needs to be and total number inbounds.

Nice car. Sorry about your Grandfathers passing.

I’ve read some on that and it seems a lot of ppl just lock the timing curve out? What’s the correct process or is it good to do a lockout

 

[RustyRatRod]

Thanks for that! Stock gears are 323. It was an original 318 car that had the 340 put in. The engine was rebuilt about two years ago and had speed pro pistons put in that were 10.5:1. I only had it backfire through the carb once today when I was messing with the timing. Other than that no backfires

Pistons are rated for compression with a given CC combustion chamber. Just because a piston is rated at "10.5:1" means nothing, unless you have the combustion chamber size that the piston is rated at that compression for. Chambers could be anywhere from 65cc to 72cc. Possibly a little more. So unless this was blueprinted and MEASURED, it's unlikely you just "lucked up" and landed on 10.5.

Condolences on the loss of your grandfather.

 

[t2ae]

Pistons are rated for compression with a given CC combustion chamber. Just because a piston is rated at "10.5:1" means nothing, unless you have the combustion chamber size that the piston is rated at that compression for. Chambers could be anywhere from 65cc to 72cc. POssibly a little more. So unless this was blueprinted and MEASURED, it's unlikely you just "lucked up" and landed on 10.5.

Condolences on the loss of your grandfather.

Completely agree that’s just what I was told the pistons were for

 

[RustyRatRod]

Completely agree that’s just what I was told the pistons were for

That means they "might" be the early high compression (68-early 72) 340 two eyebrow pistons. If you have a compression tester, run a compression test on it and post those numbers. That's give a good idea where you are.

 

[t2ae]

That means they "might" be the early high compression (68-early 72) 340 two eyebrow pistons. If you have a compression tester, run a compression test on it and post those numbers. That's give a good idea where you are.

I posted that in my op but that are at 165 across the board

 

[Dart Frog]

you said the compression test came out to 165 that's about where a factory high compression piston with a pretty good size duration camshaft would be with a factory cast j head. Does the engine pick up has the RPMs come up or is it pretty flat up top also.

 

[t2ae]

you said the compression test came out to 165 that's about where a factory high compression piston with a pretty good size duration camshaft would be with a factory cast j head. Does the engine pick up has the RPMs come up or is it pretty flat up top also.

I mean it picks up some but I would say more so flat. I don’t know what to expect power wise as I come from more modern turbo cars.

 

[Dart Frog]

Well that's apples to oranges but if it's running to its potential at all it should blaze through the tires when you mash it. Or hold you back in the seat under full throttle. I can tell you that 323s and a stock torque converter and a big cam Our recipe for mush. Or put a turbo on it and upgraded accordingly and you'll be smiling for sure. I think it needs higher ratio rear end 3000 to 4000 stall converter to start with.

 

[t2ae]

Well that's apples to oranges but if it's running to its potential at all it should blaze through the tires when you mash it. Or hold you back in the seat under full throttle. I can tell you that 323s and a stock torque converter and a big cam Our recipe for mush. Or put a turbo on it and upgraded accordingly and you'll be smiling for sure. I think it needs higher ratio rear end 3000 to 4000 stall converter to start with.

It definitely doesn’t spin a tire lol. Nor does it hold you back at all. I was just looking into both the 3.90 gears and a higher stall

 

[middleagecrisis]

I mean it picks up some but I would say more so flat. I don’t know what to expect power wise as I come from more modern turbo cars.

It’s not going to perform like a modern turbo charged engine. You should still feel the engine pulling harder and revving faster as the RPMs build with a high-performance cam. Does the car have fresh super unleaded fuel in it, or is the fuel old? Also, with the engine off and the air cleaner off, if you actuate the throttle lever on the carburetor, do you see it squirting gas into the primary side of the carburetor? The accelerator pump definitely needs to be working on the carburetor to get it moving. A carburetor that needs to be rebuilt definitely won’t do any favors for the way the engine runs.

 

[Dart Frog]

I would try to get any information I could about the camshaft you really need to know specs to maximize its potential as far as matching gears and stall etc. You should post some more pics we love pics. By the way that is a great looking duster your lucky man

 

[Demonracer]

Start with the basics, check the plugs to make sure they are the correct heart range, as mentioned set the initial timing 16-17* and around 37* total at about 2000 rpm. Get a vacuum gauge and hook it to the "manifold" vacuum port on the carburetor and tune the mixture screws for maximum vacuum reading. Take it out and drive it to see if those changes make any difference before tearing into the engine. Someone may have detuned it, "just because".

 

[ragtopfury]

Speaking of the throttle and carb.... does the throttle open all the way when the pedal is floored?

 

[RustyRatRod]

I posted that in my op but that are at 165 across the board

I'm sorry. I somehow missed it. I agree with those that the converter and rear gear ratio is probably the culprit. Is there any way you can post a video of the car running so we can get an idea of how "aggressive" the cam is? That would help.

 

[t2ae]

It’s not going to perform like a modern turbo charged engine. You should still feel the engine pulling harder and revving faster as the RPMs build with a high-performance cam. Does the car have fresh super unleaded fuel in it, or is the fuel old? Also, with the engine off and the air cleaner off, if you actuate the throttle lever on the carburetor, do you see it squirting gas into the primary side of the carburetor? The accelerator pump definitely needs to be working on the carburetor to get it moving. A carburetor that needs to be rebuilt definitely won’t do any favors for the way the engine runs.

Yes it always has and is running 93 gas. Yes the gas is squirting when the throttle is pushed by hand with the cleaner off.

 

[t2ae]

Speaking of the throttle and carb.... does the throttle open all the way when the pedal is floored?

You know I should verify that!