general info - differences between a smogged 318 and a non smogged?

[jasonmrenda]

i understand that the pre-smog 318s had much more power. is making a smog-era 318 the same as a "non-smogged" version a matter of simple parts exchange/removal/replacement? or are they 2 completely different motors?

just curious. thanks for any insight

 

[glockr]

Later cylinder heads have EGR ports (think that's what they're called) built into the exhaust ports. Would probably be a good idea to have them plugged.

 

[moper]

They didnt make much more or less power. The ratings changed in the early 70s. The only power lost to the later 318s was from runniing an air pump and catalytic convertor. They were all pretty much the same until the Magnums.

 

[2 Darts]

The waters of power ratings get a little muddied because while power was being reduced in the engines, the accepted method of measuring horsepower changed. This makes comparisons a little more difficult. In general, here's how the engines lost power in order to comply with increasing emissions restrictions.

Reduced compression ratio
Re-profiled camshaft
Changes to fuel/air ratio, ignition timing, and thermostat
EGR - valve located on intake manifold
Air pump - injected into exhaust manifold
Catalytic converter on exhaust

While this was going on, high octane leaded fuel was being phased out. There were competing methods for octane rating which made claims difficult to sort out. A "hot" batch of premium fuel in the early 70s might have an octane rating as high as 103. Early unleaded was 87 and it stayed that way a long time. I have no way of knowing how the change in fuels affected the results auto manufacturers could get in measuring the power output from their engines. It would seem reasonable that fuel changes drove some of the engine changes, and not for better power output, either.

 

[yellowdartdave]

2 darts is correct.
They switched the way they reported HP output from Gross HP ( engine sitting on the dyno with a huge fresh air tube stuck on the carbs, no accessories, etc. to NET HP as is sits in the car....water pump, exhaust manifolds with full exhaust, air cleaner, etc.
And they also killed the compression ratio and retarded everything they could for emissions.
All they did was kill the performance and also the fuel mileage.

At least it led up to FI and electronis ignition.

 

[69B-Cuda]

Big thing to remember is to plug the smog ports on the heads. (tap them for a pipe plug and put a plug in them, it is a lot easier to do before the engine is installed in the vehicle! )
The smog port is a small hole below the ex port. IF you use headers or stock pre-smog manifolds, you will have exhaust leaks if they are not plugged.