C4racing

I have an Accel big port intake manifold on a '90 block in my '89 C4. The original intake manifold (I/M) started leaking water near the distributor after 70k miles so I decided to put in a different engine combination. The new combination consists of (among other things) a '90 block with an Accel big port intake and ASM large tube runners.

The new engine started leaking oil after only a few thousand miles (pretty sure it's from the I/M near the distributor) and now at 30k miles I HAVE to do something about it. :cry I got some great feedback from one forum member on how to replace the I/M gasket but I'd like to ask if any other forum members have experience in replacing this gasket and if they could pass along any tricks or do's :) and don'ts. :nono:

Let me summarize by asking the following questions?
1) what brand of I/M gasket do you recommend?
2) what brand of sealer do you recommend and where do you apply it?
3) would you replace the runner gaskets?
4) if you would replace the runner gaskets, what brand and would you use sealer on these too?
5) do you have to completely disassemble the I/M (as per the GM manual) or can you leave the fuel rails and injectors on?

The plenum, runners, and I/M have been ported and the runner gaskets have been port matched. However, I don't think any sealant was used on the runner gaskets during assembly. It seems like a lot of work to re-port match a new set of runner gaskets if it's not necessary but I'll gladly do it if a new set needs to be installed.

Please, oh please, tell me that there is a I/M gasket installation method that will not leak oil or water in a short while. My current engine was assembled by a VERY well known engine builder and started leaking oil after only a few thousand miles. I don't mean to imply that I can do a better job than he did but with your advice, my patience, and the right materials I'm going to give it a try. How difficult could it be??? :eek:

85vet

I recently installed the SuperRam intake on my 85 and per one of the tech tips I used a fine punch to nick every 2 inches on the manifold and the block both in the front and rear. This gives the sealer something to grab onto.

I had a friend/mechanic come over to help and he recommended the black NAPA gasket sealer/maker. We cleaned the the old intake gaskets off and we used brake cleaner to clean everything up before installation.

Do not use the front and rear gaskets supplied with the gasket set you buy.

I did not have to take the injectors off of the rail.

While you have it torn down, why not add a fuel pressure regulator (check out Holley's version, it is awsome), do the TB bypass and relpace the temp switch on the front of the engine. :cheers:

You can port and polish your runners and plenum as well. :cheers:

This job is not that bad.

C4racing

85vet: thanks for the advice and the pep talk! :cheers:

85vet

You have mail - the copies of the Tech Tips I used. :chevy

Greg Johnson

85vet,
I am in the process of putting the Big Mouth manifold on my 85. I've got Fel-Pro 1204 gaskets. They supply short cork gasket pieces for the ends of the manifold. They have stickum on one side. They say to use black gasket sealer between the ends of these and the side gaskets since there is a slight gap.
When I removed the manifold, there were no gasket pieces on the ends. They had just used blue gasket sealer and as far as I know this is the first time the manifold has ever been off. So, I think the factory did not use the gasket end pieces either.

Question: Do these end pieces blow out or what?

Thanks, friends.

Greg :seeya

85vet

Greg,

The mechanics that I talked to say - DO NOT USE GASKETS - they will not hold!!!.

I will email you the tech tips I have.

:chevy


[Modified by 85vet, 11:53 PM 2/11/2002]

SpedRacr93

85vet, I dimpled my intake and block last time I put my intake on too. Seems to be working so far as I have no leaks as of yet.

Greg - 85vet is right about those gaskets. Just build a silicone bead along the front and back and be sure to go a little ways up onto the heads as well.

85vet

Forgot to mention that you MUST change your oil immediately after the intake change. You will have antifreeze drip into your oil and the antifreeze is very destructive to your bearings. :chevy

C4racing

Whoa!!!!! :eek:

In all the responses to this post and another one I had you're the first one to ever mention changing the oil after replacing the gasket. Seems to make sense to me so thanks for the heads up. :cheers:

The plenum calls, the gasket awaits......tomorrow..... :chevy

h rocks

Before you remove the intake manifold, drain off much of your coolant to avoid copious amounts of it dumping out of the water crossovers. Use the gaskets that have the rear water passage blocked off. Felpro makes one, but I don't think that Summit or Jeg's show it in their catalogs, but they will order it for you.

C4racing

Thanks for the advice. No one else has said anything about the block off plates at the rear of the gasket until you just mentioned it. I just bought a #5820 Ultra Seal gasket set (black with orange silicone around the intake ports) that I was going to use tomorrow but this gasket does NOT have the rear ports blocked off. Even a set of GM gaskets I have laying around has little metal plates in the rear ports. The Ultra Seal set looks like it might be a "universal" model but I bought it from the Mr. Gasket trailer this weekend at the NHRA Winternationals so hey, don't these guys know what they're doing??? :crazy:

More confusing yet is that the GM gaskets have a port in the center of the gasket and the Ultra Seal set does not. Maybe when I take the manifold off tomorrow "the light will come on"..... :confused:

The only FelPro number I have is 1204 but I don't know if that set has the block off plates or not.

What the heck do these plates block off anyway, water? If no water should be flowing here and if GM supplies a gasket set with the ports blocked off, why are the ports there to begin with? :cuss

pablocruise

I don't believe they do either. I was there too and asked some tech questions at the MSD trailer and it was like I was speaking swahili :lol:
The underside of the stock L98 TPI intake on the driver's side has that center port "filled in". The pass side is EGR passageway. Also, the rear port on the pass side is restricted except for a small hole for coolant to pass thru. I also dimpled the ends and used black RTV not the provided endrail gaskets. Chase/clean all your threads too!


[Modified by 89 Paul in cal, 12:13 AM 2/13/2002]

pablocruise

BTW, welcome to the forum and sounds like ya got a killer setup under the hood there! :cheers:

Greg Johnson

Friends,
My stock '85 TPI manifold has the FRONT ports blocked off. The Big Mouth manifold has all ports open except for the passenger side center port for the EGR. I am using Fel-Pro 1204 gaskets with both center ports for the EGR blocked off. I will remove the center port plate for the driver side because the driver side of the Big Mouth has a port opening there.

It sounds like we have a VARIETY of blocked off ports on these manifolds!

Greg :confused:

JAKE

This coolant port block off situation is as confusing as he**.

My friend's Mini-Ram from TPIS has both the rear ports blocked off, yet his heads (Brodix) have both of them open.

My heads (Edlebrock) have both open at the rear and I use the Mr. Gasket UltraSeals intake gaskets that are open on both ends; front and rear.

I've seen posts before about blocking off the rear ports but I don't know the reasoning for it in the L98.

Is this a mod strictly for the reverse coolant flow engines?

If anyone has a complete explanation for this "coolant port block off" issue, I'd love to read it.

Thanks,

Jake

bill mcdonald

I am confused as well.
I have my rear ports open currently on my 90 with the super ram. This is the intake gasket AFR said to use on the intake, so I used it.

Aggravated4life

I know that David Fulcher knows the reason for the block off plates,since Im pretty positive he knows everything Vettes anyway.
I think he posted once why GM chose to block the rear ports off but leave a little hole in the gasket to still allow coolant to flow.

A spare TPI intake I have doesnt have rear water passage and its off an 85.My current L98 '86 intake does have a rear water passage.
Maybe thats another reason some gaskets you buy have the block offs in the rear...some TPI didnt use them.

Hope Dave F chimes in soo.
:)

91Yellow1

I removed my intake last night and 5 of the 8 bolts with about 10 ft./lbs.(not tight) and someone else had been in there already(sloppy gasket sealer all over). that is not my point, once you remove your thermo housing if you can sneak past your wife/girlfriend get the turkey baster and use that to suck out as much anti-freeze as you can,hope this helps,Sean

C4racing

91Yellow1: thanks for the hint! The manifold is coming off in a few minutes and I'll make sure to baste it first......so to speak. :yesnod:

SunCr

Current production L98 heads are counterbored at the front and rear bolt holes for gaskets which have retainers (a nice feature) to hold the gaskets in place during installation. I believe all of the 91 L98's came with these heads as well as anything replaced after that. GM gaskets for these heads do not have the rear blockoff plates, but you can use the old style gaskets (without the retainers and with the blockoff plates) if you want to. I don't think anyone but GM makes the gaskets with the retainers and if the bolt holes aren't counterbored, you can't use them anyway. From previous posts, it doesn't seem to matter whether you use the blockoff plates or not. Some service manuals (the '89 in particular) have the installation instructions backwards in that it instructs you to install the blockoff plates at the front of the engine. GM issued a Bulletin correcting this. Correct installation is/was to install the blockoff plates at the rear.