I am going to install a 4bbl carb and performance intake on my truck. the current set up has EGR with the carbon canister and the lines going all over. I want to pull all the EGR out including the carbon canister to simplify the engine and to gain more vacuum pressure. Should I pull it off and can I just block holes in the intake, carb, and gas tank? or should I leave it on and match it to my performance intake?
I think you will need to stay with the EGR. I have seen spacer plates in the Summit catalog. Taking it out, I believe, will increase pinging and negatively affect performance. I have a 351M in a 1977 F-250 and the spacer will get partially blocked with carbon periodically. When this happens, it will ping no matter the octane grade of gasoline. Someone with more familiarity with this engine design may have a different but, if everything is currently intact as far as the system, I would leave it in.
If you go with an afermarket non-emission carb, you can do away with the egr. firstonraceday is correct about pinging IF you keep the original emission carb. Do not plug the line from the gas tank. This is a vent line and needs to be open. You may get a gas smell from this, but there's nothing else to do since the gas cap is sealed and the fuel tank needs to get air from somewhere to replace the fuel when the engine uses it. One recommendation I have is to keep the original air cleaner and tube going to the exhaust manifold. This will help driveability when it is cold.
>I am going to install a
>4bbl carb and performance intake
>on my truck. the
>current set up has EGR
>with the carbon canister and
>the lines going all over.
The carbon canister is not related to the EGR; it is part of the evaporative (EVAP) emissions control system. It's purpose is to capture fuel vapors from the fuel tank(s) and the carb bowl in the carbon canister when the engine is not running, then burn them off each time the engine reaches operating temperature. The EVAP system has no affect on performance.
> I want to pull
>all the EGR out including
>the carbon canister to simplify
>the engine and to gain
>more vacuum pressure.
Unless you have leaky vacuum switches or hoses, the EGR and EVAP systems should have no affect on manifold vacuum.
>I pull it off and
>can I just block holes
>in the intake, carb, and
The EGR system on M-block engines (351M/400) consists of exhaust passages in the intake manifold, an adapter plate under the carb, and vacuum operated the EGR valve itself. The carb has no EGR ports or fittings.
You can disable the EGR by simply plugging off the vacuum hose that operates the EGR valve. If you disable the EGR, you must tune the carburetor to operate correctly without EGR (i.e., enrich the mixture). EGR allows excessively lean mixtures to be run without pinging.
>or should I
>leave it on and match
>it to my performance intake?
For future emissions compatibility (even if you decide to disable the EGR), I suggest an EGR-type manifold, like the ones provided by Edelbrock and Weiand. If you choose the Edelbrock manifold, their EGR manifold's carb mounting pad is much better than the one on the non-EGR manifold.
I have my EGR disabled (EGR valve vacume hose disconnected with EGR block plate in) on my 400 and don't have any pinging problems with 85 oct gas. I bought Edelbrock non-EGR intake manifold as it'll get rid of the whole EGR system for cleaner look. I'd test to see if your engine will ping with EGR disabled, and if it doesn't, go for it!
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