intake manifold

[dunhamfield]

Hey guys, I have a intake manifold #3844465 that does not have the tin plate attached to the bottom.
My question is, is it necessary? If so, what is its purpose?:scratch

[johnnyrod]

I think its a heat shield. Oil is splashed up and with a heat cross over for the carb. Sounds logical. John

[fatride]

Yes it is needed. It serves as an oil separator/baffle for the PVC oil draft tube. And yes it does double duty as a heat shield.

[models916]

Do you think it's really needed? Just kidding.

[Ronnie Russell]

models, You are a bad, bad boy.:rofl

[dunhamfield]

I will be using the road draft tube but no PCV.
I'm guessing that I could make this shield if I had a pattern.
I havent seen this item for sale in any of the catalogs I have.
Any suggestions?

[raymar58454]

:nono1: It wasn't going there till you mentioned it Models:nono1:


I have seen them on ebay in the past.
Ray

[models916]

trace it out on the bottom of the manifold in cardboard and transfer it to sheetmetal. Nothing real technical here. Keeps the oil from migrating where it shouldn't. Oil splashing on an iron manifold will probably have no effect on temp. That iron manifold is going to get real hot from the heads and block anyhow. Get rid of the crossover port under the carb while its off.

[dunhamfield]

Anybody got an old rusted out one that is intact enough to use as a pattern?

[SS425HP]

I'm pretty sure that all the heat shields are the same. If you can find one on any 409 intake, it should work, truck included. Sometimes you can find the old cast iron intakes for next to nothing. All you want is the heat shield. They were done in a press by the factory. I don't know if you could make one with a bender or not. Not my line of work, so I don't know. I do know it is pretty important to have them on there, though. There are a lot of swap meets coming up in the next few months. Might be a good place to look. Might just have to buy an old cast intake to get the shield, and throw the intake away.

Fred

[JimKwiatkowski]

My M/T Crossram does not have a shield,I've run this intake for 15 years and have not had any problems.Do we really need one :dunno

[SS425HP]

Jim, that's another animal. Maybe it was made so as to not need one. Never saw the bottom of one of those, so can't answer that question. The only thing I can say for sure, is the General put them on there in the beginning. He sure wouldn't have done it if they thought it wasn't needed. Extra cost and all. It does something, for sure. I'm sure it helps keep hot oil off the intake bottom, or helps to do that. The way the back is made would tell me it keeps oil from going out the draft tube, or into the PCV tube. Only my opinion. Maybe the cross ram is made different on the bottom, and doesn't need this. I don't know on that.

[Ronnie Russell]

Jim, Obviously you are wrong or mis-guided. As you know, EVERYONE (except me) claims the shield MUST be installed. Better take your intake off and install the shield.

[JimKwiatkowski]

Ronnie your funny :rofl ,do you know how long it takes to install a crossram,if you have big fingers forget installing one,you need thin fingers for the center bolts.

[MK IISS]

I believe one of the purposes of the heat shield is to help prevent oil from carbonizing on the underside of the intake where the oil comes in contact with the heat crossover area. If the intake has a blocked crossover passage the shield may not be as important, unless it has another function as Fred indicated about the draft tube/pcv.

[models916]

Offenhauser calls the tin on the bottom an oil heat shield that is not required on a manifold that has the heat passage under the carb blocked or is not there because of design. NEXT?

[SS425HP]

Then that pretty much confirms what Richard said. Without the shield, the oil will bake onto the bottom of the intake at the crossover for the exhaust. A blocked crossover would then negate the need for the shield. Maybe it won't do anything about oil going out the draft tube hole. I said I'm not sure about that. I'm not going to take mine off, though!

[models916]

Can't do any harm beinig there.

[fatride]

If Ya'll want that hot oil splashing on the bottom of your intake reducing your intake charge, by all means, remove the shield. I'll be waiting for you at the finish line :rolleyes: The shield is needed! Why do you think there is such an animal as the "AIR GAP INTAKE" ? Really, I think Offy is missing the boat here by their need for profit. It costs $ to add this shield to the bottom of the intake. The GM engineers added this sheet metal shield for more than one job "I'll bet". I will not be removing the shield from any of my intakes, as a matter of fact I have a three two manifold now that does not have the shield, but it will. Please send me all the shields you remove. I'll pay postage! Seems awfull big just to protect the crossover from baking the oil. This is only my thoughts, I may be full of ****.

12555320 Manifold Oil Shield
An oil splash shield improves engine performance by isolating the intake manifold from the hot engine oil in the lifter valley. This lowers the temperature of the fuel/air charge and increases its density.

[dunhamfield]

My M/T Crossram does not have a shield,I've run this intake for 15 years and have not had any problems.Do we really need one :dunno

Jim, are you using a road draft tube?

[JimKwiatkowski]

Terry,I run a PCV on my crossram.It sounds like you should run a sheild,my crossram must have been designed not to use a sheild.

[models916]

Milodon makes a lifter valley baffle if you really think you need one. An aluminum intake will not get any hotter than the water running through it. On the other hand Smokey recommends Cold outside air through an insulated carb. and a hot engine and intake runner to keep the gas suspended. That's why all the wood and plastic spacers today. Intake will stabilize at water temp. Olds had the right idea years ago. All of the mfgs. are using cold air intake on a hot engine today. Want to go fast use a cool can for the fuel line, outside ram air to the carb and insulator between the carb and manifold.

[Ronnie Russell]

Ray, Nobody is suggesting that anyone take off a shield. If its on there, leave it there. If it aint broke--dont fix it. But why blame Offy? Ive never seen a shield on any brand of aftermarket intake. It aint about profit, its just not needed, at least in my opinion.

[dq409]

If Ya'll want that hot oil splashing on the bottom of your intake reducing your intake charge, by all means, remove the shield. I'll be waiting for you at the finish line :rolleyes: only my thoughts, I may be full of ****.

.

geezzz man,,, You should watch all this I`m the bada** racer dude that wins all the time stuff !!
Aren`t you just finishings that first real racey engine and car ???
Confusious say :Fancy pants and fresh car can cause very full belly of crow !!!:rofl :rofl :D

[fatride]

geezzz man,,, You should watch all this I`m the bada** racer dude that wins all the time stuff !!
Aren`t you just finishings that first real racey engine and car ???
Confusious say :Fancy pants and fresh car can cause very full belly of crow !!!:rofl :rofl :D


:takethat Ouch,:takethat Ouch,:takethat ouch. I'll have to watch my bench race ravings from now on. :nono1: I was a little grumpy last night :evil .

[models916]

Aftermarket performance manifolds don't have the crossover for the exhaust so no shield. Thats the only reason its there and why its called a shield not a baffle. Still, does not harm being there or using one. Maybe on an engine with a lot of blow-by it serves a purpose by accident.

[Firepower354]

How 'bout pouring the head passage full of aluminum then there's an "air-gap" where the crossover in the manifold was...

Thermal barrier coating on the bottom? We coat the bottoms of about everything. Really does help. DIY kitand a cheap electric oven in the garage or at your buddy's house:brow

All the "racey" guys use a vac pump anyway, right? Then you can seal it right up. No road drip tube, no mushroom headed breather..

[fatride]

12555320 Manifold Oil Shield
An oil splash shield improves engine performance by isolating the intake manifold from the hot engine oil in the lifter valley. This lowers the temperature of the fuel/air charge and increases its density.[/QUOTE]


Not my words, but I still belive this to be true. Only my opinion though. :dunno

[models916]

When was that written and by whom? Anybody run an oil temp gauge? I would think oil in the lifter galley is around 180-200 at its hottest. Manifold would be that temp or hotter with water passages and connection to the heads. How much hotter can it get. If you don't completely block the exhaust crossover in the head, you have 1200 degree air touching the intake. I don't think it has anything to do with a modern built engine.

[models916]

I sent an email to my pal Roger at Custom Metal Design (Wilson Mnifolds) with the question. I'll see if he cares to get involved. I will post when he does.

[models916]

Early simple answer from friends at Wilson Manifold. Engines that use the exhaust crossover (GM) attach a sheet metal shield riveted to the bottom of the intake to prevent the oil splash from 'coking' or burning to the bottom of the intake in this hot area. More details to follow as time permits.

[fatride]

GM Performance parts thinks this is needed!http://www.crateenginedepot.com/store/Oil-Shield-12555320-P1185C60.aspx

Only one of many sites/ threads that I have read supporting the splash shield lowering intake manifold temps for better performance. This is my last post on this "HOT" topic. :p

[MK IISS]

Some of the "Z11" style valley pans, maybe it was the '62 version, had a heat shield. Not sure why because the heat passageway was in the upper intake.

[Ronnie Russell]

Sorry Richard, I am unclear on this. I have never seen a Z11 intake in person. Are you saying that a Z11 intake had a exhaust crossover provision in the intake manifold? Why would a race only engine have an exhaust crossover? If so, maybe there is more to this heat deal than we know. The engineers who designed the intake must have wanted the heat going through the intake, even for race only. I dont know, as I said, Ive never seen one.

[fatride]

Someone did research showing that a "limited" amount of heat in the intake made for better fuel atomization. Can't remember where I read this. Article addressed the heat passage block off issue.

[MK IISS]

Ronnie: Maybe someone can post a picture of a Z11 intake. It has a heat passage way just like the regular 409/409-425 intake. Of course the heads do also. In my opinion Chevrolet originally planned to use the "Z11" style heads/intake, which first appeared in 1962 as over the counter parts, on the regular production 1963 2X4bbl 409 but changed their mind and only used them on the '63 RPO Z11. I have this opinion because of the heat passage. I've seen the '62 and '63 version but not at the same time. Fred has seen a side by side comparison of the 62 & 63 versions....they are different castings. There was also an "experimental" Z11 intake that had open plenums and a single 4 bbl. NASCAR version.

[models916]

According to that web site/dealer, chrome wire looms make the engine faster. That number is a sku not a part number. Even so if GM thought it was important they should have installed it in the crate engine. I'm done, I see there are many sides and possible answers to this one.

[dunhamfield]

OK guys, I have decided to replace the missing shield. I have located one at a place called Chevy 409 performance Parts in Ca.
As far as plugging the crossover, I,m thinking that I will leave it stock as well.
I am not building a race engine, I am building an engine with lots of low end torque to put in my 56 Chevy pick-up. It will be driven daily.
Thanks again for all your inputs as I'm sure that I will have many more questions during this build.:D

[bignbad60]

Good choice, Jacks a knowledgable guy and a member here, I'm sure you will get a quality part and as always on a street engine " better safe than sorry"
Tim

[damnitdave]

Wondering if anyone had a pic of the stock 348 / 409 shield? I think I'm going to have to make one. Do any GM parts interchange with this shield?

[W Head]

Dave, All intake shields are the same (348 or 409) I have several off truck intakes. I will buy a truck intake at swap meets (CHEAP) just for the shield. So many of the old intakes have been setting around and the shields are full of rust holes or beat up and I have replaced several on intakes . I will be in Austin over Thanksgiving, let me know if you are interested.

W Head

59 El Camino 348-3,2s
59 Impala 409-2,4s