Street Hemi. Oil in the tubes ,,,,,HOW ?

New tubes. New plugs with the sealing rings removed. A small dab of thread sealant on the spark plug threads.
Yet on a couple im still getting oil inside the tube. .

I just replaced everything a few days ago because i had oil halfway up the tube...a few plugs were completely submerged in oil


Im about to smear a small amount of anerobic sealer on the bottom of the tubes and see if that does anything

Pretty common issue, the oil is coming from the bottom of the tube where it meets the block. I just ran in a HEMI for a customer build and used the Milodon seal tubes.

https://www.summitracing.com/parts/...gz1KWYn7CsZ3DxSL9sIGHYrdCYBoClnAQAvD_BwE

Mike, dont these inserts require mods to the head to use or a shorter spark plug tube maybe ??????

I had the same problem with my 426 Hemi. I got the seals, put them in the freezer, tapped them in with a wood block. Buttoned it all up and no more oil. No mods straight forward install.

I didn't use the seals on this engine because they make getting the valve covers off a real pain. I have a FTS cam, so they need to come off regularly. I do get a bit of oil at the bottom of some of the plugs. But I just sop it out with paper towels once in a while. Half a tube of oil is a problem that paper towels won't stay on top of, but the root cause should be large enough to identify.

A couple of other choices for your application. The 574 specifically lists oil resistance.

www.henkel-adhesives.com/us/en/product/gasketing-sealants/loctite_510.html

In the 33 years I had my Street Hemi, I never had that much oil in the tubes.
Pulling the plugs, I'd see maybe 1/4" of oil up the threads, as the tube's fit to the head was of course opened up without the plug holding it tight.
Stock heads (though ported) & covers, NOS tubes & o-rings, nothing special.
(Even ran the plug sealing rings early on until I figured that out & replaced the galled tubes.)
I'd make sure the fresh plugs were tight, but nothing herculean.
Half full of oil sounds like the tubes are cracked/split...

My tubes pull out easy from the Milodon inserts, no oil ever on plug (tubes pulled before the cover)
Inserts get tapped in with rubber mallet

thanks all.
I will look into the Milodon seals . but for now I want / feel like I have to do something. Its enough its causing the plug wire boots to swell in a couple cylinders. NOT enough that its getting a spark scatter problem but I feel if I don't do something it will get to that sooner or later.


Plugs and tubes BOTH are brand new


Ive had hemi cars in the past and I don't remember ever having this issue with either one of them back then

Are the valve cover aftermarket, they are pretty flimsy.

I "THINK" they were Mopar Perform covers when engine was built ( 20 years ago ) But Im not 100% sure

tops of the tubes near the O ring is bone dry


At this point , Im thinking My plan at the moment is pull valve covers again when car goes down for summer break late June thru late Aug / early Sept time frame ( black car with no air in 110-115 degrees ambient temps doesn't sound like much fun )

I'll do these tube inserts and valve seals same time . But I'm taking it on a 4-1/5 hour trip the 1st weekend in June and I want to stop oil getting inside the tube if at all possible .

I hate to come late to the party but do you have a picture of the worst leaking tube? Especially the bottom. The seal between the tube and the head has to be compromised somehow (here we go with the Captain Obvious jokes) and it has to be at the bottom. Is the bottom of the tube convex? Like it is a bit short and is being distorted when the plug is installed?

I cant get to it till this weekend to pull all the tubes back out . will report findings then. But when I put the tubes in I did ck them over and didnt notice anything unusual . I want to ck the seat in the head and make sure they are ok as well. Probably be Sunday before I can get to it to take it apart.

When I put them in I did compare to the ones I took out and they were same length. Going in the plug bottoms out right about same time it pulls the tube O ring into the valve cover and I didn't notice anything unusual like it was pulling the valve cover down anything weird like that

Try installing the tubes - especially the leaky ones - and plugs, without the top o-ring, and see if the plug isn't pulling the tube tightly to the head.
The o-ring could be masking a problem there.

Since the plugs are supposed to seat the tubes into the heads, it seems to me the issue is at the bottom of the tubes.
Take a careful look at the sealing area at the bottom: heads & tube face, plug threads.
Either the tubes, or the seating surface, or loose plugs/threads would be the culprit, I think.

I was going to say he might have the wrong o-rings and they’re holding the tubes to high. FHO guy has the correct ones

Please excusa my ignorance, I find lots of oil in the spark plug tube (70 Hemicuda) and I have read about this problem and how to fix it. Shall I remove the valve covers to insert the Milodon
seals? Or they are installed on the spark plug tubes? Thank you

Pressed into the head, put some sealer on them.

I honestly dont think the O rings are to big.

I put the spark plug in the tube, slide said tube into the valve cover, and screw the plug in by hand till it starts pulling the O ring into the valve cover.
It never really deforms the cover that I can tell, it just pulls/slides the tube / O ring down into the valve cover down so to speak,
spark plugs I feel are quite tight ( I did not put a torque wrench on them though. )

Im going to pull the tubes and spark plugs back out this weekend and double ck the seat area in the head with a flashlight . If all appears ok. I plan to put some kind of sealer around the hole in the tube and re-install .
This summer will pull the valve covers off and do the Milodon seals and planning to do valve stem seals same time

I do get some oil in a few of my tubes. Nothing like you are getting. And I have thought about using some Hylomar under the tubes. I have used it elsewhere and like it a lot. But I kinda figured that if it would have worked, someone else would have already been there/done that.

If you decide to try some non-hardening sealant under the tubes, Hylomar would be at the top of my list to try. Permatex used to make version of it, but they discontinued it. The original stuff is expensive and a bit of a pain to get a hold of.

www.amazon.com/Hylomar-Universal-Non-Setting-Silicone-Jointing/dp/B07NJHZJQQ