Which carburetor gasket..

foilled

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Lou C

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Normally you would use the open gasket with an adapter plate. Do you have an adapter plate on the intake manifold for the Holley?
The '87 OMC if you are using a stock intake would have a spread bore intake manifold therefore it would use an adaptor plate for the square bore Holley 4160. The Quadrajet 4bbl was the carb used up until '89 then in '90 they switched to the Holley 4bbl. The V6s used the 4160 with the adapter plate and the V8s used the 4175 spread bore Holley. Those did not need an adapter plate. The later models with the 4175 spread bore Holley show the gasket with the 4 holes in the OMC catalogs I've seen.

Post a pic of what you have.....
here is a pic of the adapter plate used on the V6 models with the Holley 4160, these definitely took the open gasket.....
 

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foilled

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Normally you would use the open gasket with an adapter plate. Do you have an adapter plate on the intake manifold for the Holley?
The '87 OMC if you are using a stock intake would have a spread bore intake manifold therefore it would use an adaptor plate for the square bore Holley 4160. The Quadrajet 4bbl was the carb used up until '89 then in '90 they switched to the Holley 4bbl. The V6s used the 4160 with the adapter plate and the V8s used the 4175 spread bore Holley. Those did not need an adapter plate. The later models with the 4175 spread bore Holley show the gasket with the 4 holes in the OMC catalogs I've seen.

Post a pic of what you have.....
here is a pic of the adapter plate used on the V6 models with the Holley 4160, these definitely took the open gasket.....

I will take a photo tomorrow and post it. I noticed you said v6s used the 4160 while v8s used another model. My 5.7 is a v8 and i have a 4160. Is this normal?
 

Lou C

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Well someone probably changed it from the Quadrajet which was standard then to the Holley 4160, so no its not 'normal'. The V8s used the 4175 spread bore Holley which was intended as a replacement for the Quadrajet.
 

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Lou C

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In case you are wondering; the 4160 (square bore) was used on the V6 models because the 4175 spread bore is too long to fit on the V6 manifold. The front float bowl has the fuel line coming in the front rather than on the side like the 4160 so it would interfere with the thermostat housing on the shorter V6 intake manifold. The Quadrajet was actually more compact than either of the Holley carbs because it has a much smaller float chamber unlike the large float bowls of the Holleys front and rear.
 

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kenny nunez

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I would try to keep the primary/ secondary sides of the carburetor seperated with a dual plane manifold. An open adapter or gasket causes a “reversion” with the intake air charge and sends confusing signals to the carburetor. It affects the low-midrange rpm. Wide open is usually not an issue however.
 

foilled

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Well someone probably changed it from the Quadrajet which was standard then to the Holley 4160, so no its not 'normal'. The V8s used the 4175 spread bore Holley which was intended as a replacement for the Quadrajet.

Is my engine still running efficiently with the 4160 or is there any reason i should not be running the 4160 and get a 4175?
 

foilled

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Normally you would use the open gasket with an adapter plate. Do you have an adapter plate on the intake manifold for the Holley?
The '87 OMC if you are using a stock intake would have a spread bore intake manifold therefore it would use an adaptor plate for the square bore Holley 4160. The Quadrajet 4bbl was the carb used up until '89 then in '90 they switched to the Holley 4bbl. The V6s used the 4160 with the adapter plate and the V8s used the 4175 spread bore Holley. Those did not need an adapter plate. The later models with the 4175 spread bore Holley show the gasket with the 4 holes in the OMC catalogs I've seen.

Post a pic of what you have.....
here is a pic of the adapter plate used on the V6 models with the Holley 4160, these definitely took the open gasket.....

This photo shows where my 4160 is directly ontop of. Looks like directly to the intake manifold. I had a fully open gasket with a 4160 no adapter plate on the v8. Is this a effective setup or is something wrong here
 

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Lou C

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Actually what you have is a square bore intake so it is fine with the 4160. No adapter plate needed. The odd thing is I don't recall that OMC ever used a square bore intake on these engines esp that far back since they were using Quadrajets which require a spread bore intake. Is that intake cast iron or aluminum? If aluminum it could be aftermarket (ie Edelbrock, etc). So if the Holley works well on it, leave it be. A bit of a mystery to me though....

Back to your question though, I'd use the open gasket on that.

Since you got my curiosity up, I went back and looked at the BRP catalogs for OMC sterndrives, from 1987-1980 for the 5.7 engines with 4bbl carbs. They ALL used the Quadrajet, with the spreadbore cast iron manifold. So at some point, someone changed the intake on that engine to a square bore to use the Holley 4160. If it works, then no worries. It is very easy to get Holley parts and many marine mechanics are familiar with them. More so than the Quadrajet which has not been made for a long time (since 1990) even though I feel the Quadrajet is a superior carb.

http://shop2.evinrude.com/Index.aspx..._id=0&siteid=1

this is the official OMC catalog, you select sterndrive from the drop down (where it says 'Evinrude') and then find your year, model number etc.
 
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foilled

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Actually what you have is a square bore intake so it is fine with the 4160. No adapter plate needed. The odd thing is I don't recall that OMC ever used a square bore intake on these engines esp that far back since they were using Quadrajets which require a spread bore intake. Is that intake cast iron or aluminum? If aluminum it could be aftermarket (ie Edelbrock, etc). So if the Holley works well on it, leave it be. A bit of a mystery to me though....

Back to your question though, I'd use the open gasket on that.

Since you got my curiosity up, I went back and looked at the BRP catalogs for OMC sterndrives, from 1987-1980 for the 5.7 engines with 4bbl carbs. They ALL used the Quadrajet, with the spreadbore cast iron manifold. So at some point, someone changed the intake on that engine to a square bore to use the Holley 4160. If it works, then no worries. It is very easy to get Holley parts and many marine mechanics are familiar with them. More so than the Quadrajet which has not been made for a long time (since 1990) even though I feel the Quadrajet is a superior carb.

http://shop2.evinrude.com/Index.aspx?s1=csidahqrj56r020jhmkc4tg0s7&catalog_id=0&siteid=1

this is the official OMC catalog, you select sterndrive from the drop down and then find your year, model number etc.
Good information thanks. I originally took the carb off to drain gas over winter from fuel bowls. I thought i had an extra gaskets left over from a rebuild kit but i dont. the old owner gave me the original 4160 box and it has a 1/8 in thick gasket that almost feels wooden. Its an open gasket but should i use this really thick gasket or find a different one. THe ones i remember from rebuild kit were real thin and definitely didn't nfeel wood and stiff.
 

Lou C

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The wooden one is not a gasket per se but a heat insulator, that keeps the carb from getting too hot from the exhaust cross over in the intake manifold (if it has one). If there is no exhaust cross over you do not need the insulator, just the gasket. If there is an exhaust cross over, then you can use the insulator but put the open gasket on each side of the insulator. On the GM cast iron intakes, used on the pre-vortec engines, the exhaust cross over was used to provide heat for the thermostatic spring mounted on the intake, used with the original Rochester carbs. Since the Holley uses an electric choke, this is not needed and many aftermarket intakes do not have the exhaust cross over.
 

foilled

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The wooden one is not a gasket per se but a heat insulator, that keeps the carb from getting too hot from the exhaust cross over in the intake manifold (if it has one). If there is no exhaust cross over you do not need the insulator, just the gasket. If there is an exhaust cross over, then you can use the insulator but put the open gasket on each side of the insulator. On the GM cast iron intakes, used on the pre-vortec engines, the exhaust cross over was used to provide heat for the thermostatic spring mounted on the intake, used with the original Rochester carbs. Since the Holley uses an electric choke, this is not needed and many aftermarket intakes do not have the exhaust cross over.

Sounds good. do you know were i can get the correct open gasket without having to buy the rebuild kit?
 

Lou C

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jegs or summit racing. Its a standard Holley open gasket. Got any hot rod shops around you? We have this one....

https://www.skspeed.com/

and Holley sells just about everything off of their website....
 
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