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1988 TBI Intake Manifold port questions...

This is a discussion on 1988 TBI Intake Manifold port questions... within the Technical / Maintenance forums, part of the General Discussion category; I'm replacing my intake manifold gaskets in my 1988 K1500 that has a 350 CI with throttle body injection. A ...

  1. #1
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    1988 TBI Intake Manifold port questions...


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    I'm replacing my intake manifold gaskets in my 1988 K1500 that has a 350 CI with throttle body injection. A few things look odd on my manifold ports. I looked everywhere for pictures, but couldn't find any.

    Questions:

    On my passenger side there are two smaller ports right below the EGR valve. Both of those ports are packed with what looks like burnt, hard ash. I looked at both my old and new gasket and those two openings aren't even in the gasket. Should I clean out the ash? I left my EGR valve on the manifold when I removed the manifold because the bolts that hold the EGR on look iffy. If I do clean out the ash will hot crap wear on the new manifold gasket? Why does that port have an opening on the manifold flange if it doesn't go through the gasket? No engine lights were showing to say I have a bad EGR.

    In the middle of each intake manifold gasket there's what looks like a smaller coolant opening cut into it. My drivers side center port on the intake manifold had some crud, but with a couple scrapes it revealed that post is closed off from the factory. Why do they cut out the port on the gasket???

    The two rear water ports are closed off on my gaskets which is the same as the one's I removed. There are weep holes to relieve air pockets. With the rear coolant ports blocked off and the middle on the drivers side closed off I only have three working coolant ports for the manifold. It really bothers me that the passenger rear coolant port on the passenger side is blocked off on the gasket when the heater hose connection is two inches from it. One would think coolant would only circulate back there when the heater is on. In the summer I wouldn't think that part of the manifold would cool correctly.

    Thanks for your insight!

  2. #2
    Supporting Member 1997chevydriver's Avatar
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    Re: 1988 TBI Intake Manifold port questions...

    The two little ones side by side I dont think are used the center port on pass side is actually your egr if i remember correctly.

    also with the back ports 98% blocked off with the tiny hole in them its normal. Coolant actually gets to the rear of the intake from the front by tstat housing under the throttle body
    <------Thanks to Mean Green
    1994 K1500 ECSB Z71 5.7L 350
    1997 K1500 ECSB Z71 5.7L 350 Vortec

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    Registered User Blue 04 Z71's Avatar
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    Re: 1988 TBI Intake Manifold port questions...

    Get that black crud out of the egr ports. Your egr cannot work if those ports are clogged.
    04 1500 Z71 6.0 LQ4 swap, BlackBear 06+ Grill/Hood, Vette servo, 3 BL,RC Keys, Truxedo, Bull Bar,KC, Cooper ST's Bilstein 5100's Tow's, Pypes M-80.


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    Re: 1988 TBI Intake Manifold port questions...

    Quote Originally Posted by Blue 04 Z71 View Post
    Get that black crud out of the egr ports. Your egr cannot work if those ports are clogged.
    The funny thing is that the two little ports that are clogged with ash is where the gasket isn't cut out. Why those ports rae cut into the manifold I don't know! I'm thinking it's a dead end where crud will accumulate over the years when the truck is turned off. If the crud id built up way past the EGR valve then it would restrict it's ability. I would think it would start throwing codes then. I'll did the crud out and see how deep it goes. I was a little worried it was done by GM to close off a passage that was originally cast, but not needed in my engine's case. Anyone else ever see the crud I'm referring to?

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    Registered User Snowboi's Avatar
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    Re: 1988 TBI Intake Manifold port questions...

    Are you sure the two holes are indeed "holes" and not where a bolt or bracket bolts to? Any pictures?
    Thanks,
    Richard.

    '95 Silverado Z71: 3"BL

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    Registered User t_alan_d2000's Avatar
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    Re: 1988 TBI Intake Manifold port questions...

    Mr.Gasket intake gaskets have the egr ports blocked Part #5821
    fed-pro gasket set part #93317 has open egr ports.
    Mr.G... back ports for coolent open
    F/P closed off but not all the way.
    most that have the egr blocked and the water port open are for more proformance based engines. where you dont want egr and want more collant flow. also they may be for a pre EGR engine they just keep staming the same thing.
    Remember: A government big enough to give you everything you want, is big enough to take away everything you have. Thomas Jefferson

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    Re: 1988 TBI Intake Manifold port questions...

    Quote Originally Posted by t_alan_d2000 View Post
    Mr.Gasket intake gaskets have the egr ports blocked Part #5821
    fed-pro gasket set part #93317 has open egr ports.
    Mr.G... back ports for coolent open
    F/P closed off but not all the way.
    most that have the egr blocked and the water port open are for more proformance based engines. where you dont want egr and want more coolant flow. also they may be for a pre EGR engine they just keep staming the same thing.
    You're correct that the Mr Gasket 5821 has the EGR blocked, but the water ports are open on that one. Look again at the Fel-Pro 93317. The EGR is blocked on that one because those are the gaskets I bought. The EGR ports are about have the size of a water port and sit beside that center water port on the gasket. The outline of the EGR port is pressed into the gasket. I assume that's if you want to cut it out or maybe to seal on the manifold so EGR gasses don't escape and foul; up other ports that the gasket seals.

    I looked at the heads on my motor and there aren't any ports for the EGR. So I'm sure the gasket is correct. I doubt my motor shouldn't have an EGR because all that ash is there so it's doing something. Does the EGR gas go into the manifold and mix with the air in the manifold. All I know is there's a vacuum line going to the EGR to open and close it? Does anyone know exactly what it does? I'm asking because I wrote above that the EGR on my manifold has a the two small ports on the manifold flange, but It stops there.

    Oh...I notice on the drivers side of the manifold flange there's a threaded bolt hole on the top of the manifold that goes all the way through ending up in front of the center water port . It's in front of that front stud for that center water port, BUT there isn't a hole in the gasket!!! I'll have to look at the pictures I took. I'm thinking maybe a bolt for the accelerator cable bracket goes there.
    Last edited by DearJimmy; 12-30-2011 at 10:36 PM. Reason: add info

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    Supporting Member 1997chevydriver's Avatar
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    Re: 1988 TBI Intake Manifold port questions...

    your egr valve port is actually the port in the center of the head not the two little rectangles together
    <------Thanks to Mean Green
    1994 K1500 ECSB Z71 5.7L 350
    1997 K1500 ECSB Z71 5.7L 350 Vortec

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    Supporting Member 1997chevydriver's Avatar
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    Re: 1988 TBI Intake Manifold port questions...

    edited because of bad pic
    Last edited by 1997chevydriver; 12-30-2011 at 11:37 PM.
    <------Thanks to Mean Green
    1994 K1500 ECSB Z71 5.7L 350
    1997 K1500 ECSB Z71 5.7L 350 Vortec

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    Supporting Member 1997chevydriver's Avatar
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    Re: 1988 TBI Intake Manifold port questions...

    <------Thanks to Mean Green
    1994 K1500 ECSB Z71 5.7L 350
    1997 K1500 ECSB Z71 5.7L 350 Vortec

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    Re: 1988 TBI Intake Manifold port questions...

    1997chevydriver are you doing your intake gaskets now or is your photo from a prior fix? Thanks so much for clarifying things for me! I thought that center port was for coolant. Do you remember if those two small ports were clogged with EGR crud on your manifold? Mine are clogged. Should I clean them out to see how deep the crud goes? Again, I didn't take off my EGR because the studs look iffy.

    Was your center port on the other side closed on your manifold? I forgot to look to see if there was even an opening in my head opposite that closed center on my manifold, but I know it's open on the gasket. Thanks again!

  12. #12
    Supporting Member 1997chevydriver's Avatar
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    Re: 1988 TBI Intake Manifold port questions...

    It was a prior fix i had to do head gaskets (nice color of oil in that pic huh?) IIRC those two small ports dont even make it very far into the intake, but I never scraped anything out of mine cause they never went trough the cyl head anyways, so I never even bothered with them. Yes there is a center opening on the drivers side cyl head but NOT on the intake (its because the cyl heads can be swapped side to side).
    <------Thanks to Mean Green
    1994 K1500 ECSB Z71 5.7L 350
    1997 K1500 ECSB Z71 5.7L 350 Vortec

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    Re: 1988 TBI Intake Manifold port questions...

    1997chevydriver Thanks again! Everything you said makes sense! I'm going to dig out the ash on my intake ports by the EGR. I'm worried since it's going on 24 years old that eventually the crud will close off the EGR passage. It can't hurt to do it now while it's all apart.

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    Supporting Member 1997chevydriver's Avatar
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    Re: 1988 TBI Intake Manifold port questions...

    No problem just let me or anybody else know if ya have anymore questions while doing your intake gaskets
    <------Thanks to Mean Green
    1994 K1500 ECSB Z71 5.7L 350
    1997 K1500 ECSB Z71 5.7L 350 Vortec

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    Re: 1988 TBI Intake Manifold port questions...

    I got motivated and used a screw driver to pick at the ash/crud. It came right out and was about a half inch thick. I'll need to vacuum and blow out the manifold tomorrow.

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    Re: 1988 TBI Intake Manifold port questions...

    I'll let you know how I make out in the repair later today. I have another question...my manifold/valley gaskets are toast. Wouldn't you know the fel-pro kit I bought didn't come with any. I read where some think applying a bead of sealant is as good or better. I have Permatex Ultra Black that I'll be using. Can I use that for the valleys, a dab extra where the valley meets the gasket, around the water ports on both sides of the gasket and to hold the gasket in place. Am I correct in thinking it's best to apply it on the gasket and let it set up for a bit then install the manifold. Then wait a day before adding coolant and running? Thanks again! I need sleep!!!

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    Re: 1988 TBI Intake Manifold port questions...

    UPDATE...The Permatex Ultra Black says not to use on head gaskets or areas in contact with gasoline. Oops! The intake has gas vapor and I bet when you turn off the truck liquid gasoline can get on the intake gasket. Should I buy something else?

  18. #18
    Supporting Member 1997chevydriver's Avatar
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    Re: 1988 TBI Intake Manifold port questions...

    Actually it is recommended NOT to use the rubber valley gaskets even if they are supplied. IIRC put a 1/4" bead between the cyl heads up to the intake gaskets overlapping the gasket by about 1/4". You only need about 4 SMALL dots of rtv on the intake gaskets to hold them in place on the cyl head, no need for rtv around the water ports. Also when I thought my intake gaskets were bad it actually turned out to be both intake and head gaskets, my intake gaskets were leaking outside the motor while a broken head bolt allowed coolant into combustion chamber and ALSO into the oil.
    <------Thanks to Mean Green
    1994 K1500 ECSB Z71 5.7L 350
    1997 K1500 ECSB Z71 5.7L 350 Vortec

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    Supporting Member 1997chevydriver's Avatar
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    Re: 1988 TBI Intake Manifold port questions...

    Also where I described putting the rtv it wont come into contact with gas
    <------Thanks to Mean Green
    1994 K1500 ECSB Z71 5.7L 350
    1997 K1500 ECSB Z71 5.7L 350 Vortec

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    Re: 1988 TBI Intake Manifold port questions...

    I did an internet search and a lot of message boards have people using the Ultra Black for their gaskets and valley ends. I'll use it unless someone in the next few hours tell me different. Here's one site where they mention using it:

    http://www.chevelles.com/forums/arch.../t-216099.html

 

 
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