1988 Mercruiser 454 Intake Gasket Restrictor Plates Question

I have a 1988 Mercruiser 454 with the stock intake and quadrajet cab and wondering if anyone knows for sure if you should install the exhaust gas restrictor plates in one or both sides of the intake manifold gaskets? The Mercruiser manual I have doesn't say anything more than it must use an intake gasket with an opening if it does have an automatic choke.

I also boat in Arizona so we don't have much cold weather but will have plenty of 100+ degree days of boating.

The old rebuilt block did not have them installed but they also put a Gen 5 head on a Mark IV block so I don't trust much of what they did.

It looks like Fel Pro says they should be installed in their instructions.
https://fme-cat.com/livedocs/982M(1-2).pdf

Typically if you have a carb and a mechanical choke with the "chimney by-metal spring", Then that side of the intake should be open to allow heat to reach the chimney. This is what heats it up for correct choke timing duration.


From the Mercruiser manual

Here is an old thread on the topic.
http://www.marineengine.com/boat-fo...-of-Spark-Plugs-Weber-4-Barrel-Carb&styleid=7


I would agree..... if your carburetor is equipped with what some refer to as a "divorced choke", then you will want to omit the block-off plates as to allow exhaust cross-over heat to operate the choke plate pull-off system.


If your carburetor is equipped with an electric bi-metal spring heating element, then by all means install the block-off plates as to prevent exhaust cross-over heat.


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RicardoMarine said:

Here is an old thread on the topic.
http://www.marineengine.com/boat-fo...-of-Spark-Plugs-Weber-4-Barrel-Carb&styleid=7


I would agree..... if your carburetor is equipped with what some refer to as a "divorced choke", then you will want to omit the block-off plates as to allow exhaust cross-over heat to operate the choke plate pull-off system.

View attachment 20368
If your carburetor is equipped with an electric bi-metal spring heating element, then by all means install the block-off plates as to prevent exhaust cross-over heat.


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Click to expand...

I would agree.........If your carburetor is equipped with a choke assembly (Mercruiser calls it "automatic choke") with an enclosed bi-metal spring with linkage, then dont use the block offs that came in package,

Hope the photo also helps, One might think your Mercruiser Rochester 4bbl doesn't look like or is different from EVERY other Mercruiser Rochester 44bl ever used including the automatic choke housing you already have and so does every other Mercruiser Rochester 4bbl....But I guess it should be posted just because....some person in Australia who happens to view this post 10 years from now may want to know what the automatic choke assembly looks like.....Too bad its not connected so we can see the correct connection point and also the appropriate adjustment procedure and a complete explanation on how to rebuild one and all adjustments including the differences between calibration parts with part numbers and such, Why stop so short of a complete post?............. Geez!


FYI.............

The choke "pull off" is a different sub system on the carb. It is vacuum actuated..............

No factory Mercruiser's came with an electric choke on Rochester 4bbl Carburetors that I am aware of.........so not sure about the reference to an electric choke on a Rochester 4bbl. Just Say'in.........

The choke is not the only thing to consider when it comes to the exhaust crossover.....Carbs do 'okay' when it comes to vaporizing the fuel....and this is typically completed by the heat passed thru the crossover port. If you have a 'stock' engine, keeping the crossover open is usually best....

Thanks. We did leave them open but I was wondering on the restrictor plates. The mechanics left them out because the instructions that were sent with the gasket set by the engine remanufacturer only had 1 set in them and sounded like they were not needed for newer engines on either side. But after installing the engine I noticed that although they say they use marine gaskets the set they sent is a Fel Pro Automotive set.

But then looking up the correct Fel Pro gasket they say the restrictors should be in there. And I finally found a picture of the correct Mercruiser gasket on Ebay and sure enough it has restrictor holes on both sides.


So now I have to decide if it's safe to run it as is with the full port open or if we have to tear the intake back off and install a gasket set with the restrictor plates in them or the Mercruiser gasket set. Screwed once again by the cheap engine remanufacturer it looks like.

Fyi,
Intake and exhaust manifold gaskets from marine or automotive can be used. Head gaskets are critical they are marine!!

I wouldn't pull the intake to put the restrictor plates in....

Thanks guys. I'm hoping they used marine head gaskets like they say they did but the documentation is weak to say the least that the company has provided. But luckily the automotive gasket set they sent with the engine does not include head gaskets so hopefully they pulled the correct ones.

If it is a felpro set, look up the part number.
I have used felpro marine sets many times!!
Great gaskets!!