Hello everyone!

Im having terrible issues to proper sealing my intake manifold.

long story, see my thread "oil burning 355".

Its an edelbrock performer aluminium intake manifold ob 7a heads.

I tried 3 times the fel pro turkey tray with problems like oil getting sucked into the intake runners and coolant in oil. In the past on my stock engine i NEVER had any issues with the turkey tray.

What i recignized is, that the 4 "locating bosses" are not fitting very well in the holes on the heads, so i always grind them a bit off to make sure, the gasket is laying flat on the heads, but they are still suspect to me not to allow the intake manifold laying proper to the heads. Maybe this is a quality issue of Fel-pro.

The 4th time, i tried the mr. gasket 305 composite gasket in combination with an old turkey tray, where i cut the "port section" off to keep the oil splash shield effect. I mounted it with the 4 locating bosses and put the composite gasket above the locating bosses. For sure i used RTV around the water ports. It havent worked, i was still getting coolant in the crankcase and my oil turned to mayonaise. Maybe the problem in this case was the combinstion of my splash shield and the 405 gaskets. I dont know.

Then i purchased another performer aluminium intake because i suspectet my intske no to fit snug between the heads and the new one is really sitting more snug. I dry tested it without any gaskets.

So, i installed the new intake with a new fel pro valley pan gasket an i really took care about the locating bosses, put RTV (maybe too much) around the water ports and used permatex aviation sealant around the intake ports. The torqued to spec in 71 CSM described sequence. The next day i pressure tested my cooling system, just to hear it hissing again in the valley .. damn, this stuff is really making me sick.


Here, you can see that the gasket was not properly crushed around the water ports, it looks nearly like never installed:




Can the be because of using too much RTV? So that the RTV, which was "captured" in the stamped crush section of the gasket prevents it "hydraulic" from being crushed by the manifold?

I alway put beads around the water ports, maybe this is a mistake. Here you can see that:



I have another mr. Gasket 405 gasket set lying in my garage and would give it another try with it AND less RTV. Maybe just putting a thin coat on both sides of the gasket. BUT, since that my exhaust crossover isnt blocked, i need a oil splash shield, and i have no idea how to make one out of an old turkey tray WITHOUT using the locating bosses to keep the shield in place.

I dont want to lay it just in there to prevent the pushrods from rubbing on the shield.

does anyone has pictures of some self made oil shield?

Maybe someone has a few tips for my problem.

I really HOPE that my water in oil problem is coming from the bad intake sealing. The pressure testing hissing is coming clearly out of the valley, im a bit afraid that maybe a head gasket is leaking from a water pocket to the valley.

Maybe on this spot:




Thanks for ANY help, this problem is really making me loosing my passion for this hobby 😑

 

Well, your problem is grinding off the locating bosses. If they are not fitting without modification, something is wrong. FelPro actually had a batch of BBO gaskets with those bossed located incorrectly a few years ago, but the last ones I've bought have not had any issues. Are you dry-fitting the gasket to the heads before doing anything else? That both checks the fitment of the locating bosses and also helps form the gasket to the correct shape. Are you sure the head and intake mounting surfaces are flat and co-planar?

 

Hi Joe, thanks for the answer!

i'm not grinding the off completely, just shortened them.

Yeah, i always tweak the gasket to the correct form on the engine before installing and make sure that the bosses are in theyre holes.

When i lay the intake between the heads without any gasket, i can push it a bit side to side. When i push it all the way to the driver side, i have a slightly gap of about 0.040 on the passenger side between head and intake manifold when i look from the front of the engine. This tells me that my intake manifold is not fitting really snug on the surfaces of the heads. I have my stock engine with the stock iron 2bbl intake lying in the garage, and there, the stock intake has absolutely NO play when trying to push it side to side.

my engine has the stock deck height an the heads have not been machined/milled. BUT it has aftermarket head gaskets, so the heads are a bit higher on the block, so i think the Performer manifold is "too small" for proper fitment. Can this be because of the thicker head gaskets?

What can i do in this case? Since i can not apply more material to the intake?

I was hoping that the thicker composite gaskets solve this problem..

heres a picture of the gap:



Even, i think that there is almost no gap between the end rails and the manifold. I am using RTV on the end rails instead of the rubber seals:



I have the same performer intake again and put it on my stock 350 for comparison. Here, the gap is MUCH wider:







Thanks a lot for the help.

 

I doubt that is the issue. My engine is the same, with un-milled heads and FelPro head gaskets, and I didn't have issues with either a Performer 350 or a Performer RPM fitting and sealing correctly. Over the years I used both turkey tray and composition gaskets with no issues.

 

Did you buy that Performer new, or was it used? I'm getting the sense that it's been milled.

 

Haha, this was what i suspected, thats why i bought the second performer intake (the gold painted one). The bare aluminium one i bought used, but never installed. This one i had for 4 years on my stock 350 without issues. Than i put it on my 355 and had all those troubles. So i purchased the second one (gold painted one) used but the previous owner said that it havent been milled.

weird would be if both of my intakes would have been milled 😮.

 

Yeah, im just curious what my problem is.

When i mounted the bare performer manifold on my stock 350 4 years ago it sealed perfectly with the fel pro turkey tray at the first try.

 

Check the intake manifold faces on the heads with a straight edge. These are not the same heads that were on your original engine ?

 

I only had it happen once on a 307 with a Performer manifold, resealed and all good. Send one or both to a machine shop. Don't just get them to mill the intake gasket surface, mill the end rails as well. I have found a motor with any amount of milling to the heads, only the turkey or other shim gaskets will fit. Are there .080" head gaskets, probably not. Good luck.

 

If you put the same intake on your stock 350 and you had more gap then I doubt the intake is the issue. More than likely either the heads have been milled a lot or the block decked or a combination of the two. Looks like you need to mill the front and back of the intake so it wont bottom out on the block. If its bottoming out it wont let the water passages seal and maybe even the intake runners . At the same time you really need to check alignment with the ports etc.

By the way, I used that intake on the 307 in my Wifes Riviera when I rebuilt it a couple of years ago and have had no problems with any oil or water leaks. I also used the Fel Pro turkey tray.

 

The intake (and exhaust) mating surfaces are at 90 deg to the deck on Olds heads. Milling the block or the deck surface of the heads doesn't change the end gap of the intake. The only thing that will change that is milling the intake mating surfaces of either the heads or the manifold.

 

i have to take a straight edge with me from my work to check this properly. I only checked it with my steel ruler, and the surfaces looked straight to me.

No, my Original engine has still its #7 heads on. The heads on my 355 are #7a's.

 

Yeah, i understand.

BUT, im comparing the fitment of my 2 performer manifolds on both engines, and on the 355, BOTH of my intakes are laying deeper. So the problem has to be on the engine. My opinion is still, that i dont have to mill anything off, because this would only make the problem bigger, since i have a loss of material between the heads.

What i will check today is laying my bone stock 2bbl iron intake on my 355 (i already feel my back breaking haha) to make sure if just my 2 performer intakes are the problem.

When i bought the engine, the pevious owner/builder had an edelbrock performer manifold on this engine too, but he sold it to me without the intake. I said no problem, i habe already one. Maybe i will contact him to sell or swap me that intake to check if this one fits better.

 

Today, i found some time to fabricate my Oil Splash Shield #2 out of one of failed turkey trays 😃.

This version is not held by the 4 locating bosses, so no more stacking gaskets when using a 4 piece style composite gasket set like Mr. Gasket 405.

I bent some lashes of the sheet metal 90 degrees down to give clearance to the pushrods but just that long that the shield is sitting under the intake sealing surfaces. The shield is now "spanned" between the heads and is sitting snug.

Here are some pictures:







Let me know what do you guys think about it. Maybe this helps some people with the same problem.

 

https://www.googleadservices.com/pag...BAgBECw&adurl=

you can use one of these. It does the same thing and bolts to the bottom of the lifter valley.

 

Yeah, i know them and im pretty sure that theyre doing the job, but the 350 block has no threads in the 2 holes of the lifter valley. I think theyre stock on 455?

+ my version is for free 😁

But thanks for the link!

 

Ok, as I am understanding this, you are having leakage problems with an intake manifold that was on your original engine....and didn't leak. Now you have a leakage problem with that intake manifold on this "new" (355) engine. You bought another manifold and it is also having the same problems on this "new" (355) engine.
The problem is NOT the intake manifold, there is a difference between the heads on the "new" (355) engine and your original engine. I am suspecting there has been some milling of the heads. The intake manifold side of the heads may have been milled a significant amount in error. (Yes, you can mill the intake side of the heads .005"to .010" for flatness.) Some "off breed" engines require the intake manifold or intake manifold side of the heads to be machined if significant material is milled from the head gasket side of the heads.
1. Get a large enough vernier or dial calipher and measure the WIDTH of the heads on your original engine and this "new" (355) engine.
2. You may also be able to insert a dowel pin in the appropriate locating holes on the head and measure to the intake manifold edge with caliphers (on both engines).
The items someone started call a "boss" that locates the head and gasket is using incorrect terminology. Those are pins sticking out from the deck surface. They can be call locating, alignment or dowel pins, but they are NOT bosses.
3. Talk to the previous owner of the "new" (355) engine to see if he had leakage problems.
4. Ask the previous owner of the "new" (355) engine what machining was done to the heads.

 

If the exhaust crossover on your intake is blocked off, putting the valley pan in is not necessary.

 

Thanks for the answer!

1: I already measured (just with a good measuring tape) directly on the front rail on both of my engine, and its true, the heads on the "new" 355 are about 0.040 wider to each other than on my stock engine.

I assume, that this is the small result of the thicker aftermarket head gaskets. This raises the heads up a bit and let the manifold go more down. As you can see on my pictures, the machined area of the end rails on the manifold was nearly (or was) touching the the front end rail of the block, while on my stock engine there is plenty of a gap.

So today i took a flat wooden block and sanded the manifold down for about 0.040 to make sure that there is space between manifold and end rails. Now, when i put the manifold on the 355 without any gasket, i have about 0.040 gap.

Then i took a few manifold bolts and wrenched them slighty snug in too check with a feeler gauge if the surfaces are laying straight together and now it looks better than before:






But, whats slightly visable on these pictures is, that the top of the sealing surface is touching the heads first, so there is a very slightly gap (just 2 intake bolts, slightly snugged) on the lower side.

I already checked the intake for 90 degrees, and with my 90 degree angle gauge, this looks pretty good.

i guess, since that i have that less gap between manifold and block end rail, even when i sanded some material away, the manifold maybe was laying slightly on the end rail before being able to crush the gaskets properly.

2/3: i talked to my previous owner and he said nothing has been machined. Not the deck or heads.

But i will call him again to talk about this problem.

Even, the manifold sealing surface of the heads look pretty "stock, unmachined" to me, since the small step above the ports on the heads is the same than on my stock engine.

thanks for the help!

 

yeah i know, but its not blocked and im using the hot air choke on my qjet

I was thinking about to block it off and switching to e-choke, but after some research, it seems that there is no really proper way to block it off than fillling the port in the heads with molten aluminium and dremel it in shape 🤔

 

My intake has aluminum plates welded into the crossover ports. Not the same flow characteristics as filling and shaping the head ports, but much easier than blocking the heads.

 

I thought about doing it this way, but isnt welding near the sealing surface a bit risky because of warping?

 

I don’t think the intake can warp in a localized spot at the center. I’m not a welder so I can’t comment on the process, but it seems a quick bead around the perimeter of the block off plug to hold it in place would be easy. Anyway, my intake seals up so no issues.

 

I have not seen a tape measure that was accurate.
Thicker aftermarket head gaskets will not change the distance between heads. I think you need to replace the cylinder head locating pins with ones that are the correct diameter and length. Worn, bent, or ____ will cause head alignment/intake manifold problems. Oldsmobile manufactured these engines for years and used only a .017" to .018" thick steel gasket for many years, and they sealed.
If the locating pins in the block are worn, undersized or bent, etc. the heads are not where they should be. If the locating pin holes are worn out of round, this will allow the heads to be to wide. Check the locating pin hole sizes in the heads.
If you have to grind locating pins to make gaskets and parts fit, something is wrong.

 

for sure, i know messuring tapes are not accurate, i measured just for comparison.

ok, i understand, for sure if the positioning pins for the heads are the wrong diameter or bent, the heads are not sitting where they shoulf be. I will talk about this with the previous owner too.

i haven't grinded the stamped locating pins of the valley pan gasket, it fitted wenn in the holes of the head, the pins just seemed a bit too long to me, since those holes are not really deep. In case of the location of them, i havent had a problem.

 

Not that this has anything to do with the manifold fitment and sealing issue, but decades ago, Car Craft had an article about a clever, reversible way to block the crossover. Wad up ***** of aluminum foil into about 3/4" - 1" ***** and fill the crossover in the intake with them. As they start to fill up, use a brass rod or punch and hammer to tamp then down, Continue until the crossover is filled. No welding, no grinding, no warping, and if you ever want to open it back up, you can laboriously pry the wads out.

This obviously does not give you the port flow improvement, but it does keep the intake cooler.

 

I am looking at the picture in your post #15. I dont think that is the factory surface finish on the cylinder head intake surface. I have two sets of Oldsmobile heads here and all four of them measure 1.625" from the head bolt hole to the intake surface and .405" from the locating pin hole to the intake surface. If you measure that it should give you an idea if the intake surface of the head has been machined.

 

Hello and thanks a lot for the pictures!

The engine you can see on post 15 isnt my 355, its the bone stock engine which came with the car. I doubt that something was machined on this engine, since it had the original 2bbl manifold on it and i never had sealing issues with the edelbrock performer intake on this engine.

today i gave it another try with my sanded down manifold, if it will not seal, im going to pull the heads and check for the correct locating pins and i will definitely check if my measurings on the heads will be the same than on yours.

 

Yesterday, i pressure tested again and the slight hissing in the valley was still hearable.

Damn. So i decided to pull the heads to check the measurings and head gaskets. What i found was this:





on the first picture, the lower head gasket is from the driver side head. It looks like maybe this could be the leaky spot that let the coolant go/air hissing into my valley. I heard the noise best when i listened into the valley with valve covers off.

I layed the other head gasket on the picture just for comparison.

BTW, i measured from the bolt hole to the surface and have nearly the same results.

The heads itself have no visable damages or cracks.






My position pins are looking quite good and not bent or misaligned or something else:






What do you guys think about the head gasket?

Isnt that a very untypically spot to leak?