74 emmisions Removal

[JRGAPI]

I want to take the emmisions stuff off my 74 vette.
I have performed a search on this board and only
found information on 81's.
I know I will have to reroute the vacum advance to
another vacum source and remove the ERG valve and cover
with a plate. Where can I find this plate?
What else do I need to remove, do and plug.
All help will be greatly appreciated.

JR

 

[Vettehead Mikey]

You'll go to a lot of work and gain nothing. Why bother removing it?

 

[Mac]

You'll go to a lot of work and gain nothing. Why bother removing it?

I expect he's hoping to gain a bit more power on the cheap... a common enough fallacy.

JRGAPI, for the same amount of work and a bit of money, you'd be better off to upgrade the cam.

-Mac

 

[Vettehead Mikey]

I expect he's hoping to gain a bit more power on the cheap... a common enough fallacy.

Yup, another myth. The smog pump takes only 1-2HP at the most. None of the other smog devices absorb any power at all.

The '74 engines are low compression/mildy cammed to start with, not to mention a conservative ignition curve.

That's where you missing ponies are hiding.

 

[Vette79]

You can find the EGR Block-Off Plate at Summit.

 

[JRGAPI]

I know I will not gain any more power. My 74 does not have the
air pump. All I wanted to do was clean up the area where the
vacum lines are and find out where to locate a EGR block off plate.
Also see if I need to disconect anything else.

JR

 

[pbcanney]

I know I will not gain any more power. My 74 does not have the
air pump. All I wanted to do was clean up the area where the
vacum lines are and find out where to locate a EGR block off plate.
Also see if I need to disconect anything else.

JR

I got my egr block off plate off ebay. $14

 

[Vette79]

I know I will not gain any more power. My 74 does not have the
air pump. All I wanted to do was clean up the area where the
vacum lines are and find out where to locate a EGR block off plate.
Also see if I need to disconect anything else.

JR

I did the same project. I left the fuel vapor canister connected and plugged the rest of all the open ports. When I replace the intake manifold in the spring then the rest of the non-working emissions components will be gone.

 

[Hib Halverson]

I know I will not gain any more power. My 74 does not have the
air pump. All I wanted to do was clean up the area where the
vacum lines are and find out where to locate a EGR block off plate.
Also see if I need to disconect anything else.

JR

If you're going to remove EGR, know that some engines will require recurving the spark advance. This is because at part throttle with EGR, some engines run a lot more spark timing than they would without EGR. If you remove EGR then note the engine detonatiing at part throttle, you'll need to do that.

Some early-70s cars also used transmission controled spark (TCS) and you'll want to disable that, as well.

Lastly, typical of early-to-mid-70s cars, you may find the carb is calibrated quite lean as an emissions reduction measure. You may want to address that, as well.

 

[Bill75]

If you're going to remove EGR, know that some engines will require recurving the spark advance. This is because at part throttle with EGR, some engines run a lot more spark timing than they would without EGR. If you remove EGR then note the engine detonatiing at part throttle, you'll need to do that.

Some early-70s cars also used transmission controled spark (TCS) and you'll want to disable that, as well.

Lastly, typical of early-to-mid-70s cars, you may find the carb is calibrated quite lean as an emissions reduction measure. You may want to address that, as well.

Hib makes some good point here, especially about the carb being lean. I put a bunch of time and effort into retuning my carb (Q-Jet) to better match my engine requirements when I replaced the engine in my 75. You'd be suprised at the performance gains you can get. I had fun doing mine and learned allot about it, get Cliff Ruggles book about the Q-Jet http://www.cliffshighperformance.com/. He does a real good job with the details, it involves more than just changing jets to richen up the mixture.

Bill

 

[JRGAPI]

Thanks everyone for your replies.
"Some early-70s cars also used transmission controled spark (TCS) and you'll want to disable that, as well." What is involved in doing this?

I have already addressed this issue "recurving the spark advance."
Also have ordered Cliff Ruggles book and will maybe send carb. to
him for rebuild.

Any other issues I need to be aware of?

JR

 

[JohnZ]

Thanks everyone for your replies.
"Some early-70s cars also used transmission controled spark (TCS) and you'll want to disable that, as well." What is involved in doing this? JR

TCS used an electrically-operated vacuum solenoid between the carburetor vacuum source and the distributor vacuum advance unit, which denied vacuum to the advance can unless the car was in high gear or was not yet warmed up or was overheating. You'll want to bypass the solenoid so the distributor gets vacuum all the time. Details for your particular combination should be shown in the GM shop manual.

 

[pgtr]

with a plate. Where can I find this plate?
What else do I need to remove, do and plug.
All help will be greatly appreciated.

JR

Hi JR,

I've fabricated various blocking plates out of flat pieces of aluminum or steel say 1/8" thick or so.

While it might be nice to 'de-clutter' an engine, simplify things and perhaps remove a modest bit of weight, that alone may not make much of a difference. But it opens the door to more significantly addressing ho-hum mid 70s performance. Note the warnings re EGR mentioned above. In addition to recurving the distr and calibrating the carb, if you ever get this far into the engine some day - the dished pistons could be replaced for flat tops w/ reliefs and perhaps the heads could be shaved slightly if more compression is desired. The L82 cam of the era is 'OK' but a more modern cam profile from say Crane could be better yet.

 

[Crimson Thunder]

I am never one to badmouth anybodys car but,PBCANNEY's fuel line scares me to death.

 

[pbcanney]

I am never one to badmouth anybodys car but,PBCANNEY's fuel line scares me to death.

thats what came in the box from holley with the 670 hnoes
the egr had to be removed to fit the steel feeder pipes.
I hear ya. Trust the feed is no where near the exhaust, but coming from a holley regulator mounted on the inner fenderwell
there is no mechanical pump. the electrics in the rear

thanks for looking out for me :cool

 

[Crimson Thunder]

I have that same carb on mine.I forgot those were the hoses that came with it.The angle your picture was taken made the feed line look a little scary.Nice looking engine compartment.

 

[Mac]

Looks like I misunderstood your intent, JR. My apologizes if I offended. I'm glad to read the other interesting points brought up about this thread.

-Mac

 

[JRGAPI]

Mac

No apologizes are nessary. I am just thrilled to get replies and help
from everyone. This board has been so helpful to me and I really
appreciate it. Horsepower is not my main concern. All I want is
a good looking weekend driver and with the prices of gas being
mostly stock helps a lot.

I think I have everything I need now to begin this project.

In case anyone else needs a blockoff plate for the EGR valve,
I got mine at Auto Zone for $12.00.

Now can anyone think of anything else I need to know
before I do this project?

JR

 

[Vette79]

JR, very straight forward. Plug whatever you leave installed.

 

[C3alex]

:eyeroleAlso, go to the tech section and try to find a article by John Hinckley titled "timing And Vacuum Advance 101.:cool