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Emissions and NA performance mods

spock345

Well-known member
Joined
Nov 3, 2016
Location
Livermore, CA
I am currently feeling out options for upping the power in my 240. I am not looking for a 200hp+ car. Just to squeeze what I can out of this engine with stock parts and maybe a bit of machining and programming. I could strap my +T parts back on the car but being in California smog is a pain in the ass. I also have the means to build a nice NA car and chip the computers once I can find my chip programmer. I also probably wouldn't have to worry about destroying my M47. Ultimately though it all comes back to smog.

Currently I am running an A cam advanced 3 degrees, AC delete, Electric fan, 3.73 rear gearing, and an IPD sport exhaust. Soon it will be getting an EZK chip.

How would shaving the head 0.040", a bit of porting, and a more aggressive cam effect emissions? I have read some threads saying that they pass fine but others that express worry about more aggressive cams.
 
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You should be fine if the catalytic converter is up to snuff. Raising the idle speed also helps.

Kyle (klr142) has a decent cam in his dd and it passes the PDX sniffer test... though I think he run larger valve clearances to get it through smog (reducing the cams duration).
 
I ran an H cam with flat top pistons for years in a B23. 10.5 ish to 1 compression. Header, 2 1/2" exhaust. No cat (no smog checks in my area). 2 deg advanced. 40# injectors from a Ford 460 (blue tops). Idle was a little lumpy till warmed up. Would keep up with my intercooled 84 GLT.
 
Well I am due to replace the cat anyway. It barely squeaked by on NOX last time. I have narrowed it down to the 30 year old cat.

I am mostly worried about what shaving the head will do as that feels like a point of no return. The goal is the low 10.3-ish to 1.

At this point I am debating between a V, VX, or K cam. With the overlap I am guessing a K will probably hurt emissions the most.
 
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With shaving the head, and one of those cams.... you’ll be completely fine.
I run a shaved head with a B cam and passed Oregon DEQ with flying colors, even with a 30yo cat. That was without doing an oil change, spark plugs, or anything.
 
Upping compression ration will very likely bring up the level of NOx under load. Only very active/new cat can clean that up. Do they do dyno or just idle/2500 test where you are? Because mods will affect thing differently depending on type of test.
Overlap will likely bring up CO at idle and low RPM. Also HC at idle because of incomplete combustion.

Running K-cam on K-jet with Lambda I had a closed throttle switch wired into ECU to put it into open loop at idle. The CO would be still lower than running closed loop.

K-cam on K-jet with no Lambda: car passed emission part of test on the dyno just fine even without a working Catalytic converter and air injection pump. Probably because allowable levels for a '76 were pretty high. Ran CO around 1.5% IIRC.
 
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Upping compression ration will very likely bring up the level of NOx under load. Only very active/new cat can clean that up. Do they do dyno or just idle/2500 test where you are? Because mods will affect thing differently depending on type of test.
Overlap will likely bring up CO at idle and low RPM. Also HC at idle because of incomplete combustion.

Running K-cam on K-jet with Lambda I had a closed throttle switch wired into ECU to put it into open loop at idle. The CO would be still lower than running closed loop.

K-cam on K-jet with no Lambda: car passed emission part of test on the dyno just fine even without a working Catalytic converter and air injection pump. Probably because allowable levels for a '76 were pretty high. Ran CO around 1.5% IIRC.

Up here they do the dyno test if they don't fail you on the visual for having crimp connectors used to repair the wiring harness. It is rather easy to tell from the lumpy starting that LH2.4 has some difficulty with the A cam. The two I am mostly considering are the V and VX due to the lower overlap and higher lift. Hopefully those would play nicer with 2.4. The K would be nice but probably expensive and a bit more crazy than I am feeling right now, but it one popped up in front of me I would take it.
 
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The car used to be automatic so it has a 3.73 rear end. It gets moving pretty well.

How much would I have to advance the K or V to recover a bit of the lower end? I don't need a ton of torque down but some would be nice.
 
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The car used to be automatic so it has a 3.73 rear end. It gets moving pretty well.

How much would I have to advance the K or V to recover a bit of the lower end? I don't need a ton of torque down but some would be nice.

I had the K about 3 degrees advanced. M47 with 3.73 rear. Single muffler turbo style under axle exhaust.
 
Throw a new cat on there and use volcano wrap from the manifold all the way to the cat. Will help quite a bit at passing. Also drive it like you stole and it and don't turn it off before the test to keep the cat toasty. You can also take some of that wrap just for testing days and put it around the cat.
 
My slightly modified ford 300 failed the test here and I replaced the cat and it still failed...then I wrapped everything up and drove it hard and its passed every time since. I used to have a scan of the progression and the numbers before and after the exhaust wrap were significantly different.
 
About wrapping the Cat: part of visual inspection in CA is verifying correct EO# that is engraved on any replacement Cat. So if the tech sees the converter as not original he has to see that number and verify it against EO list.
 
I run a V15 n/a cam. Use a chipped ezk only and a simons sport exhaust. I pass emissions every time without issue. As my cat got older it started to get higher nox readings but still passed the last time it was checked. Then I got an exemption and no longer have to inspect or test the car as it's older than 1995.

Changes I would make for a bit more performance.
A lighter flywheel.
The 3.73 rear which you already have.
Shave the head a bit and some flow work.
While the head is off measure the piston height so you can make the engine tight squish.
Maybe go to slightly larger injectos like the 16v ones if I did the head work.

That's all I'd do and then leave it alone and enjoy. If you use the rear axle ratio of the manual cars you'r testing rpms will be lower so you'll have lower emissions. But the 3.73 is a better axle ratio for fun driving.
 
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I run a V15 n/a cam. Use a chipped ezk only and a simons sport exhaust. I pass emissions every time without issue. As my cat got older it started to get higher nox readings but still passed the last time it was checked. Then I got an exemption and no longer have to inspect or test the car as it's older than 1995.

Changes I would make for a bit more performance.
A lighter flywheel.
The 3.73 rear which you already have.
Shave the head a bit and some flow work.
While the head is off measure the piston height so you can make the engine tight squish.
Maybe go to slightly larger injectos like the 16v ones if I did the head work.

That's all I'd do and then leave it alone and enjoy. If you use the rear axle ratio of the manual cars you'r testing rpms will be lower so you'll have lower emissions. But the 3.73 is a better axle ratio for fun driving.

The V15 cam has been sounding pretty good to me. Is there any easy way to get one of those in the states? If I can't find one of those I am thinking a V or VX.
 
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