intake manifold

[wlas]

I bought an edelbrock 2104 manifold that awhile back someone here said they used on there 350 mercruiser. It has two holes that go into the exhaust crossover. I think one is for the automotive choke and I am not sure what the other is. My Question is what do you do with them ? I am thinking of putting a alum. plate over both of them. Seeing how the marine engine doesn't need them. Also in the mercruiser manual it says to use RTV between the heads on the block to install the intake. The gasket kit I got has the two short rubber type gaskets in it. From what I read in the manual I dont use these, is that correct.

 

[Don S]

Re: intake manifold

Mercruiser has used "350's" for about a million years. A year, model, or serial number would sure help answer your question.......... All 350's are NOT the Same.

 

[wlas]

Re: intake manifold

Its a 1994 5.7 mercruiser s/n OF 275001 with roller cam. non vortex heads, four barrel carb.

 

[Fishermark]

Re: intake manifold

Throw away the rubber end pieces. Make sure everything is clean and then apply a ribbon of RTV sealer on the block between the heads. After bolting and torqueing down the manifold, (remembering to use some sealer on the bolts), then you can use a paper towel to clean up any excess RTV and have a nice clean, leak free seal.

For the other question... not sure. Others will chime in.

 

[John_S]

Re: intake manifold

I think you are talking about the exhaust crossover passage. That is used to heat up stove type chokes and to provide drivability improvement with heating the intake manifold. Aluminum manifolds transfer heat much quicker than cast iron. As long as you have elec choke, you could block that pasage off or use one of the restricter plates to reduce the heat. The restrictor plates have a hole about the size of your pinky. Given vortec head engines have this passage blocked by design, you should be fine as long as you have elec choke.

 

[wlas]

Re: intake manifold

Thanks, thats what I figured for the sealing of the intake. The intake gasket has a restricter plate build in at the crossover, but the intake manifold has two boss areas one for the choke and the other, I am not sure what its for, maybe something to do with the choke. I am thinking I'll make alum. covers with gaskets to block them off. I sure don't need them. I was hoping that someone had dealt with this before.

 

[John_S]

Re: intake manifold

I'll look at my 2104 this evening. I believe there is a small plate and gasket that covers the stove choke area, for use with elec chokes. If that plate is not there, I don't think it has direct access to the exhaust crossover. It is just a chamber that gets heated by the crossover. I'll post back tomarrow.

 

[wlas]

Re: intake manifold

I just figured out that the forward one is for a EGR and the other is for the choke. So John let me know what you find out. Thanks

 

[Silvertip]

Re: intake manifold

Perhaps the second exhaust port is for an automotive EGR (exhaust gas recirculation) valve. You can't just put a plate over it because it would still be dumping exhaust gas back into the intake. You could however, tap the small round hole and insert a plug and then put a plate over the out cavity where the EGR valve would sit. That plate needs to be sealed well as it is subject to manifold vacuum. The other option would be to put an EGR valve on it and just not attach a vacuum line to it. EGR valves will be closed in the static condition.

 

[Silvertip]

Re: intake manifold

Guess we were typing at the same time.

 

[Silvertip]

Re: intake manifold

Forgot that this is a newer, electronic style EGR valve. You would indeed be able to just block it off with gasket and plate.

 

[wlas]

Re: intake manifold

Well it turns out that the manifold I have is not a 2104 its a 3701 that I bought on ebay, it came in a 2104 box which is a non EGR manifold and this one is a EGR type. Silvertip ,You are right, the manifold has holes in the bottom of both intake ports, which I can not understand why they put those holes into the exhaust crossover, you would think the manifold pressure would be affected. I don't get it. But I would not only have to plate the top bosses, but tap and put pipe plugs in the holes. I got taken to the cleaners on ebay.

 

[Reel Poor]

Re: intake manifold

If it's a 3701 it won't fit your 94 model engine. The two center bolt holes on each side are different.

 

[John_S]

Re: intake manifold

2104: Non-EGR
3706: EGR

Not that it matters now, but mine just has the provision for stove choke. A small alluminum casting, held in place by two bolts. It does have direct access to the exhaust passage. It is not a seperate chamber, as I surmised above.

wlas, my 2104 is new and has been painted with alum primer and black ceramic paint to match Mercruiser. Let me know if interested. I decided to go vortec heads and will be purchasing a 2116.

 

[Silvertip]

Re: intake manifold

Exhaust gas has been introduced back into the intake on cars since about 1971. At various throttle settings the egr valve admits a small amount of exhaust gas to help control detonation and to deal with emissions. It is still used today and is responsible for a fair amount of idle related issues since these valves get gummed up with carbon-like, gummy deposits. Just for the record, unless an engine is turbo- or super-charged there is no manifold pressure. There is manifold vacuum however on a naturally aspirated engine.

 

[wlas]

Re: intake manifold

John, how do I get in touch with you, I am interested in your manifold ? I am not going to use this one I've got. I think i'll send it back to the guy or sell it back on ebay. silvertip, pressure can be neg. or pos.

 

[Silvertip]

Re: intake manifold

WLAS -- Agreed! In engine-speak however, a vacuum line is generally not referred to as a negative pressure line. d

 

[FreeBeeTony]

Re: intake manifold

I have a GM cast iron highrise with a matching weber carb if your interested, send me a pm or give me your email. I can send pics if you want.

Carb was recently rebuilt........I replaced with new Edelbrock during a troubleshooting frenzy, then went to Vortec heads........that's why I have the manifold available also.

They came off a '92 vintage 350 Mag.

 

[John_S]

Re: intake manifold

Wlas, post an email address. My home email is down while I futz with a Windows XP problem. I'll email from a work account, which I can't post. Thanks.

 

[wlas]

Re: intake manifold

John I sent you a PM, with the info you need to contact me.thanks