318 - intake vacuum leaking

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Syleng1

Syleng1

Karma is real and Life is short...
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Has anyone had an intake vacuum leak (oil being sucked thru ports from poor sealing) due to shaved heads?
74’ basically stock 318
Heads shaved .100”
Edelbrock LD340

will that much throw the angle of the intake to head angles off and open up lower side to oil in lifter galley?

“why did I shave .100” off the heads?”
Replaced steel shim head gaskets 0.017”with the fel-pro blue 0.040” gaskets and tried to raise compression in the process up from the crappy factory 1974 specs 8.1

with all that said- what intake gaskets will fill the gaps to seal ports (intake to heads) because all signs point to that is my oil issue. Fel-pro makes a std gasket 0.060” or a special gasket 0.120”- I’m just not familiar with using thicker gaskets for this situation.
Syleng1
 
Take the intake off. Clean everything up, and set the manifold on the motor with no gaskets. Test fitting. It's possible just the end gaskets are leaking.
 
RustyRatRod said:
Hell yeah it'll leak. You need to have the intake milled to match.
Click to expand...
Okay- how do you know what to mill it? Or does the machine shop know that calculation? When my heads were done the owner a guy who has done a lot of machine work for me over the years said it was minimum amount “don’t worry about it.”
Honestly back when these engines were “modern” .100” was nothing to save a warped head and they machined the intake side as well. These were not machined on the intake side.

anyone have that calculation?
 
V8 Intake Port Surface Mill

okay- not as tired and frustrated as I was before I went to bed. I found some interesting materials on this subject.
This is a good read. Fudge! Now I need to remove the intake and get it machined OR take the heads off for some intake side machining.... or new heads and rebuild engine with better pistons. hmmmm!
Tough decision after just getting the car together after all these years.
I just want to drive!
 
Make sure the china wall gasket is not jacking the intake up. see post #3
 
.100 on a small block mopar head? Wow.... .060 is the max I've know folks to go. Slant six head? yeah, done .120 on them..
 
Syleng1 said:
Has anyone had an intake vacuum leak (oil being sucked thru ports from poor sealing) due to shaved heads?
74’ basically stock 318
Heads shaved .100”
Edelbrock LD340

will that much throw the angle of the intake to head angles off and open up lower side to oil in lifter galley?

“why did I shave .100” off the heads?”
Replaced steel shim head gaskets 0.017”with the fel-pro blue 0.040” gaskets and tried to raise compression in the process up from the crappy factory 1974 specs 8.1

with all that said- what intake gaskets will fill the gaps to seal ports (intake to heads) because all signs point to that is my oil issue. Fel-pro makes a std gasket 0.060” or a special gasket 0.120”- I’m just not familiar with using thicker gaskets for this situation.
Syleng1
Click to expand...

To my knowledge the factory steel shim is .019-.021. Call it .020..lol splitting hairs right...

So you milled .100 and added .026 by means of a .046 crushed pt8553 gasket.
So the head is sitting roughly .074 lower than it was...if trusting the .100 milled part.
One way you could have a vac or oil leak is if the The Machinist didn't set the head up right on The Jig when Milling it. A lot of guys don't do the old scratch test. You mount your head up on the jig... you get your levels out n you check it make sure it's level catty-corner across and long ways...then crank it down TIGHT and check it again...then you dial the cutter head up to clear the deck by a visual amount and move it over the end of the deck surface of the head...then you then spin the cutter by hand and slowly dial the cutter down till it just scratches the head...now with it hand spinning still... you move the cutter across the deck while watching the scratch width..it wants to be even...wrong will look like 'narrow to wide' as it goes across... and as the same end to end...it needs to be even ...this makes damn sure you are making a level cut and not deviating from the factory angle. I always do that, checking your level accuracy and beyond any margin of error.
Not all machines are the same, some do it digitally. I started with the machinist 1st because you stated you had him mill .100

With that said, it could only leak if A.. he deviated on the cut..so the angles are off. B... The intake is tapered or ootb incorrect angle-Common on those.
Or C... you used the metal gaskets on the aluminum ld340 and that's a leaker every time. Been there done that and bought the t shirt. It's almost a prerequisite. Lol


Like mentioned, look close with light under it or behind it to see if the angles are off.
Also keep in mind many use thick gaskets..and the gasket can eat .025 worth of gap on the bottom..so they never know.

Pics?
 
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318willrun said:
.100 on a small block mopar head? Wow.... .060 is the max I've know folks to go. Slant six head? yeah, done .120 on them..
Click to expand...
I called my machine shop and he questioned that amount too. States he never cuts that much with out machining intake side also.
Maybe my number is off. The heads were done 2 years ago. Sucks to get old.

Make sure the china wall gasket is not jacking the intake up. see post #3 [/QUOTE said:
Do you mean the crossover snap in steel plate? Sorry never heard it call the "china plate" before.
I do not not have those because the LD340 is solid- no cross over openings


Johnny Dart said:
Take the intake off. Clean everything up, and set the manifold on the motor with no gaskets. Test fitting. It's possible just the end gaskets are leaking.
Click to expand...
"End Gaskets leaking?" I'm sucking oil out of the galley directly into the intake port. Not leaking oil.
I think the intake is sitting too high now with the machining of the cylinder head block surface being cut.

Basically I just wanted to use a thicker gasket but realizing now a thinner gasket or more machining needs to be done.
I hate to cut intake but easier than pulling heads. Okay - i will stop crying. I sound like a newbee when I've been doing this for over 35 years. Just getting old.
.
Click to expand...
 
Syleng1 said:
I called my machine shop and he questioned that amount too. States he never cuts that much with out machining intake side also.
Maybe my number is off. The heads were done 2 years ago. Sucks to get old.
Click to expand...
I think it's more about how much "can" be taken off before the head is no longer useable, aside from sealing the intake.
 
MOPAROFFICIAL said:
To my knowledge the factory steel shim is .019-.021. Call it .020..lol splitting hairs right...

So you milled .100 and added .046

So the head is sitting roughly .054 lower than it was.
One way you could have a vac or oil leak is if the The Machinist didn't set the head up right on The Jig when Milling it. A lot of guys don't do the old scratch test. You mount your head up on the jig... you get your levels out n you check it make sure it's level catty-corner across and long ways...then crank it down TIGHT and check it again...then you dial the cutter head up to clear the deck by a visual amount and move it over the end of the deck surface of the head...then uou then spin the cutter by hand and slowly dial the cutter down till it just scratches the head...now with it hand spinning still... you move the cutter across the deck while watching the scratch width..it wants to be even...wrong look a like narrow to wide as it goes across... this makes damn sure you are making a level cut and not deviating from the factory angle. I always do that, checking your level accuracy and beyond any margin of error.
Not all machines are the same, some do it digitally. I started with the machinist 1st because you stated you had him mill .100

With that said, it could only leak if A.. he deviated on the cut..so the angles are off. B... The intake is tapered or ootb incorrect angle-Common on those.
Or C... you used the metal gaskets on the aluminum ld340 and that's a leaker every time. Been there done that and bought the t shirt. It's almost a prerequisite. Lol


Like mentioned, look close with light under it or behind it to see if the angles are off.
Also keep in mind many use thick gaskets..and the gasket can eat .025 worth of gap on the bottom..so they never know.

Pics?
Click to expand...
I'm pulling the intake tonight and will have pics then. I used the STD Fel-Pro blue intake set for the aluminum intake to steel heads because I too have tried steel gaskets with plently of leaks.
This guy has been machining for about 40 years. Good and smart guy. He has done quite a few engines for me with excellent results.
IF the heads have to come out then the engine is too and a replacement engine will go back in. I dont want to waste the summer waiting for a machine shop assembly and testing. Hoping when I measure the thickness of the intake gaskets I find an opening or leaking point. From there I can make a decision and move forward. I'm really hoping it is oil in the runners south of the gasket.
Good compression ( 151-158 psi range) plugs show burning oil but not as much as you would think at 1 quart per 100 miles.
Maybe a crack in the crossover ports or leaking /split gasket. But all 8 plugs show oil consumption.
Check back later tonight after surgery.
 
.0095 off the intake side of the head for every .0100 off the block side. Measure twice, cut once. Use the printoseal intake gaskets. I hate steel shim gaskets.

FABO 001.JPG


FABO 002.JPG
 
418BCC36-DD14-4CE9-B92C-278E7483877A.jpeg
UPDATE: pulled the intake- found 5 loose bolts- finger tight. Pulled intake off and almost all intake valves have a glossy oil coat but runners in head AND intake are clean.
The end gaskets were crushed paper thin -cork and started out almost 1/4” thick.
The fel-pro gaskets were thinner in the middle of the ports than they were at the ends. But solid seals.
I pulled the plugs and there were 3 heavily crusted in burnt oil 5 were like what you would find in a new car... slight tan. No build up. 100
Miles today on them.

I found my compression gauge was wrong- used my back up and 5 good cylinders are like 175-177psi.
The 3 burnt oil spark plug cylinders were 150-155psi. I think I am going to reinstall the intake with new gaskets. Tighten all down and install new spark plugs and change the oil and run it and see if it improves. If it does not- sadly I will go from there.
FF5B076D-3A46-4065-B6F9-09C5AFF7A4BA.jpeg
80B82625-5BBB-4CF0-AF2B-CCF1DE3F35CB.jpeg
14EE2FEF-563B-4528-9CFA-E5247B7FE7D0.jpeg
 
Quick question- when I went thru the engine the gasket kit- Fel-pro came with 340/360 ports. Think I should use those again or 273/318 port sized gaskets. Kit was for a 1974 318 complete set.
 
Syleng1 said:
Quick question- when I went thru the engine the gasket kit- Fel-pro came with 340/360 ports. Think I should use those again or 273/318 port sized gaskets. Kit was for a 1974 318 complete set.
Click to expand...
360/340 gaskets work fine on 318 heads. Been doing it for years and did it again 2 days ago - never an issue
 
Syleng1 said:
View attachment 1715535753 UPDATE: pulled the intake- found 5 loose bolts- finger tight. Pulled intake off and almost all intake valves have a glossy oil coat but runners in head AND intake are clean.
The end gaskets were crushed paper thin -cork and started out almost 1/4” thick.
The fel-pro gaskets were thinner in the middle of the ports than they were at the ends. But solid seals.
I pulled the plugs and there were 3 heavily crusted in burnt oil 5 were like what you would find in a new car... slight tan. No build up. 100
Miles today on them.

I found my compression gauge was wrong- used my back up and 5 good cylinders are like 175-177psi.
The 3 burnt oil spark plug cylinders were 150-155psi. I think I am going to reinstall the intake with new gaskets. Tighten all down and install new spark plugs and change the oil and run it and see if it improves. If it does not- sadly I will go from there.
View attachment 1715535750 View attachment 1715535751 View attachment 1715535752
Click to expand...
When you put it back together dont bother with those cork china wall gaskets. Just lay a good bead of Right Stuff down and call it good.
 
Syleng1 said:
Quick question- when I went thru the engine the gasket kit- Fel-pro came with 340/360 ports. Think I should use those again or 273/318 port sized gaskets. Kit was for a 1974 318 complete set.
Click to expand...
You should use this gasket set.
Fel-Pro Performance Intake Manifold Gasket Sets 1243

I like the ones you have, they technically work, though I'd use them on the large port.. if all is perfect.
 
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I'm wondering if the LD340 has holes for these dowel pins that are in your block ?
Usually with an aftermarket alum intake, these pins are removed.

14EE2FEF-563B-4528-9CFA-E5247B7FE7D0.jpeg
 
I think you have multiple issues
#1, I doubt yur gonna get away with that much cylinder pressure for long.
#2, I have seen those big-port gaskets not seal on the lower edge, on the backside. I would not use them, unless I was sure there was meat enough on the head.
#3, if you really took off .100, then the bolt holes should not line up in the intake attaching windows. When you pull the intake down, there is no way of telling when your tightness is because the gasket is crunching or if the bolt is jamming in the holes.
#4, if oil is sitting on the intake valves, you got a problem! Don't just bolt this back together until you fix it. 100 miles per quart is a ridiculous amount of oil to be losing.
#5, you said
Syleng1 said:
Has anyone had an intake vacuum leak (oil being sucked thru ports from poor sealing) due to shaved heads?
Click to expand...
The assumption is that this is happening to you. Did you actually put a vacuum gauge on the CC and see it, or were you assuming things? If you measured it, then you gotta fix it, not bolt it together and hope for the best.
#6, with 175psi cylinder pressure, and no Quench because the pistons are .057 down in the holes (or more); How are you planning to deal with the inevitable detonation? Are you running a big cam with a very late closing intake valve?
#7
Syleng1 said:
and 5 good cylinders are like 175-177psi.
The 3 burnt oil spark plug cylinders were 150-155psi.
Click to expand...
This is a problem; you may already have detonation damage in those low-pressure holes; I would do a LeakDown test before going any further.
#8, IMO, before this is over, it wouldda been better to install the proper pistons.And I think yur gonna end up there, sooner or later. But I'm still gonna wish you luck.
Happy HotRodding
 
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Maybe he said .010? .100 would not line up well as AJ said, and I can attest to that pin holding up the works. I cracked a 273-4 intake in half trying to torque it down onto a 318 block that had those stupid pins....and the intake didnt! The LD340 may have those pin guides already: one online had them, one didnt. I also witnessed a 340-360 intake not seal on a 318 port. along the very bottom. What do the bolt holes look like with the intake laying on only the intake gaskets, no china walls? The head bolt holes will be moved toward the camshaft under the intake, worse untorqued. That cork is doing you no favors, use a silicone sealant once you determine if the heads will even line up. 318 heads are not rare, you may be ready for some different ones....
 
When I spoke to the machinist he said he definitely did not take 0.100” off the heads - he remembers working on the heads for me but seems to think 0.040” is more like it.

as for cylinder quench area. With felpro blue .040” thick gaskets and factory low compression (1974 318) pistons I’m not worried about anything destroyed.
The LD 340 was drilled for the line up pins.
The engine ran fine it just was loosing oil and obviously burning it looking at the plugs. I’ve decided to install a set of 273/318 port sized gaskets, new plugs and reassemble. I will leak down the cylinders before assembly. I can pull the heads but not sure what that will bring me other than more questions. Even if I spend $40 on new gaskets and rtv the ends and run it over the summer and in the fall pop a new engine in the fall. If I send a used engine out to be rebuilt- it will take weeks if not more. Damn Subaru and Honda motors now occupy machine shops time. No money for them in old iron rebuilding. Anyhow. Thanks for the input. Syleng1
 
Syleng1 said:
When I spoke to the machinist he said he definitely did not take 0.100” off the heads - he remembers working on the heads for me but seems to think 0.040” is more like it.

as for cylinder quench area. With felpro blue .040” thick gaskets and factory low compression (1974 318) pistons I’m not worried about anything destroyed.
The LD 340 was drilled for the line up pins.
The engine ran fine it just was loosing oil and obviously burning it looking at the plugs. I’ve decided to install a set of 273/318 port sized gaskets, new plugs and reassemble. I will leak down the cylinders before assembly. I can pull the heads but not sure what that will bring me other than more questions. Even if I spend $40 on new gaskets and rtv the ends and run it over the summer and in the fall pop a new engine in the fall. If I send a used engine out to be rebuilt- it will take weeks if not more. Damn Subaru and Honda motors now occupy machine shops time. No money for them in old iron rebuilding. Anyhow. Thanks for the input. Syleng1
Click to expand...
You may think of using a thinner Cometic head gasket. They are great gaskets and you would gain some compression.
 
Uh he either milled 18+ cc out of them to 50cc, or he milled 8cc out. Sounds like 8cc.
About .005 per cc for small 318 head, hair more for closed small chamber 273/318
Felpro "blue" ? Assuming a PT8553, measured crush is about .046.
He milled .100, or .040...
The stock shim was about .019-021

He's either .074 lower or .020 lower... the later points to just nothing but a bad gasket seal sucking oil. He may need nothing but the right gasket.

Gotta have the correct info.
 
measure depth of that spark plug relief from the deck as described. Thats pretty cool to know where you can check a milled head. Use sliding probe end of dial caliper from a straightedge across deck.
 
MOPAROFFICIAL said:
Uh he either milled 18+ cc out of them to 50cc, or he milled 8cc out. Sounds like 8cc.
About .005 per cc for small 318 head, hair more for closed small chamber 273/318
Felpro "blue" ? Assuming a PT8553, measured crush is about .046.
He milled .100, or .040...
The stock shim was about .019-021

He's either .074 lower or .020 lower... the later points to just nothing but a bad gasket seal sucking oil. He may need nothing but the right gasket.

Gotta have the correct info.
Click to expand...

yes my mistake- called machinist- he remembered the job as he does a lot of work for my shop. He said it was probably 0.40” as .100” was for a similar head on a diesel we did for a farm tractor. Anyhow when I removed the gasket and dropped the intake on the heads bolt holes lines up with a tad more hole above the threads. A quick leak down test showed piston ring leakage only on the cylinders that had crusty plugs. All valves are sealing tight. A new compression test after sitting 24hrs and my readings were between 150psi and 154psi. I’m getting a proper set of 318 intake gaskets and putting it back together with new plugs and driving it and retesting results. If it clears or slows oil consumption I’ll leave it alone. It if continues I will pull this engine back out and take apart lower end. Thanks for the help.
 
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