Performance vs. emissions in 1973

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Trevor B

Trevor B

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Hi All,

I only recently found Mopar religion so please excuse me if this topic has been covered and I just can't find it but...

After doing some online reading/research, it appears to me that the stock 318 in my "new" 1973 Duster underwent some changes to make it conform to emissions restrictions in the early 1970s. As in, a 1970 318 probably had more kick to it than my 1973 318. For example, the timing on my distributor is "supposed" to be top dead center (according to the emissions sticker under the hood!) but my gut tells me it would rather be advanced.

What changes were made and can I, uh, unmake them?

Thanks!
 
Can the "book" timing" numbers. Fix the mechanical advance so you can boost initial/idle timing and not have your total number be out of bounds.

A stockish 318 will like 10-14 initial timing and maybe in the 34-36 range for total. Both of those numbers are with vacuum advance disconnected and plugged.

It will run like an entirely different car with more initial timing.
 
Indeed so! Apply all hot rodded tricks and as power. The MoPar engines book is excellent. Put base the book for your current engine. Summit, Jegs, Manciniracing all carry these books.

The engine series you have is a small block "LA" series. The Magnum engines are easy to spot by way of vertical attaching bolts for the intake. FWIW....
 
In 1970 the 318 was 8.8:1 compression.

In 1973 it was 8.6:1.

Not a terrible difference.

My bone stock (except for dual exhaust) 73 318 pings like hell on any more than 0* advance running 87 octane. 89 does not help, and I ain't putting 93 in a 73 318-2 motor.

Chrysler claims that dual exhaust was good for 20HP. I'd do that first.

After I get my rear freeze plugs replaced, I'm going to start base lining 1/8 mile times, and then start some mods. My goal is to keep or increase my 15 MPG and 87/89 octane requirement, while adding some useable power/torque and increasing the "fun factor".

Stage I- Eddy 600 CFM and performer intake
Stage II- comp "256" cam
Stage III- change 2.76 open to 2.94 SG (and rear ISO elimination)
Stage IV- Dakota exhaust manifolds
Stage V- "302" heads
Stage VI- "Magnum" Heads
Stage VII- 3.23 SG gears

Not necessarily in that order.
 
YY1 said:
In 1970 the 318 was 8.8:1 compression.

In 1973 it was 8.6:1.

Not a terrible difference.

My bone stock (except for dual exhaust) 73 318 pings like hell on any more than 0* advance running 87 octane. 89 does not help, and I ain't putting 93 in a 73 318-2 motor.

Chrysler claims that dual exhaust was good for 20HP. I'd do that first.

After I get my rear freeze plugs replaced, I'm going to start base lining 1/8 mile times, and then start some mods. My goal is to keep or increase my 15 MPG and 87/89 octane requirement, while adding some useable power/torque and increasing the "fun factor".

Stage I- Eddy 600 CFM and performer intake
Stage II- comp "256" cam
Stage III- change 2.76 open to 2.94 SG (and rear ISO elimination)
Stage IV- Dakota exhaust manifolds
Stage V- "302" heads
Stage VI- "Magnum" Heads
Stage VII- 3.23 SG gears

Not necessarily in that order.
Click to expand...

See post #2, same problem, distributor with too much mechanical advance in it
 
I've got some studying to do. What book in particular? I've found two that seem similar - any preferences?
1) How to Rebuild Small-Block Mopar, by William Burt
2) How to Rebuild Small-Block Mopar Engine, by Don Taylor

I have to learn how to set total timing, how to deal with mechanical vs. vacuum, etc.
 
two biggest problems with smog engines, other than cam, is distributor advance curve, timing, and lean carburetion
 
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