How hot do valve stem seals get?

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I’m wondering how much heat valve stem seals can withstand. I’m asking because a machine shop screwed up my lower intake manifold and also gave me bad advice which resulted in me needing to use JB Weld on a $600 set of heads I had recently purchased. I’ve got the highheat epoxy which is rated for 800 degrees and the area in question is close to the water jacket. Before I take a chance of ruining my engine with a broken piece of JB Weld I want to place my heads in the oven at 550 degrees for a few hours and see how the epoxy holds up. I cleaned the area with denatured alcohol and carb cleaner and also filed it down before applying the putty, so I’m keeping my fingers crossed. Just wondering if I need to yank the seals off beforehand or not.
 
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I really don't have an answer, but I will say this. If you have any intentions of suing the shop that allegedly ruined your heads, JB Welding them will not help your case. I'd leave them alone until after you sue, if you are considering doing so. If not good luck....
 
Picture? On a head I would have it welded and machined at a good shop. JB weld as a long term fix on internal parts isn't holding up well long term. Is this both heads? Why did you feel the need to give performance machined heads to this clown?
I would probably get another head if its only one that's damaged and another manifold and leave them in peace.

I ship my stuff out because there is not one decent machine shop in this area anymore, there were lots of them when I was young that were run by real experienced engine machinist but those days are gone.

Edit: Viton seals can operate at 400f constant up to 700f short term, the valve stem in the region of the seal is probably around 250f. The face of the exhaust valve is many times hotter but the temp of the stem drops dramatically once it enter the guide and is being cooled with oil in the seal area.
 
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I agree with Trav, I'd ditch the head/heads and start with new, and find a competent shop. You could be out a lot more than you already are using those heads if your patch job lets go.
 
Without a stable plate to bolt it too I advise not taking a head to that temp. Warping a head is too easy to do.

Smoky
 
They’re stock reconditioned cylinder heads. It’s the inlet where the lower transitions to the head. Shop told me to open the port slighty wider than the gasket which I later found was bunk. It’s only 1/2 to 3/4 into the port itself and all I’m doing is port matching the opening aside from getting rid of any casting marks.
 
Former cylinder head development engineer here. I just sent you a PM with my email. Send me some pics and details and I'll do my best to help out.
 
Originally Posted By: 09_GXP
Former cylinder head development engineer here. I just sent you a PM with my email. Send me some pics and details and I'll do my best to help out.


How about posting tne pics here and keeping tne discussion public so we can all learn something?
 
DAA4_A506-6220-4646-_BF36-894414_DD2_ACF.jpg


The shaping is not perfect. I was told as long as the gasket seals it’s all ok. However the above picture is a gasket match, I’ve since learned cleaning up the port entrances and making it all uniform, then opening the lower to be slightly smaller than the head is best. The head is roughly 1.92 x 0.96 inches, many 3800 modders recommend 1.9x0.9 inches is the best for the lower. I’ve also read online that quite a few modders use JB Weld or equivalent putty to reshape intake ports.
 
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This is now. Intentionally used too much to give me more wiggle room.

It’s just this one port. Finishing it first then taking measurements to duplicate in other areas.
 
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OMG, please do not rig it up with any epoxy! Bad decision. Take them to a quality shop and they will weld then grind to shape. That is the only hope for permanent repair.
 
Only welding place in town is good with the guys who messed up my lower. After taking it back once and later finding tools marks under the paint, on top of not getting all services agreed upon I left a review simply stating ports weren’t uniform and Id be contacting my CC company. Got cussed out, threatened and harassed all in one paragraph. Let’s just say I’ve added additional reviews so that’s out of the question. Only other option is salvage yard but all those 3800s have been overheated so that’s a no go. Guess I could grab an EBay head. The JB weld chips when hit but I don’t see how the high heat will fall apart from heat and vibration. The main issue brought up was expansion and contraction but it’s an Iron head and if it withstands 800 degrees it souls be ok. I could be wrong tho.
 
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Porting is fine. It won’t net a large amount of power but given the L36 ported lower nets you 10 crank hp the heads can get you a little more. Add the rocker arms and upper intake into the equation and I’m hoping to see 20-30hp. On top of what I have. I’ve seen many a forum post where both the epoxy and putty were used to fixed cracked blocks, cylinder liners and and one guy even claims to have used it to repair a hole in the roof of the exhaust port that punched through to the water jacket. And no one except Aussie commodore owners have been using the aluminum heads.

EDIT: Looks like I’ll be using epoxy instead of putty. Stuff doesn’t chip like the putty.
 
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I was just trying to find him something better than old used up junk. I wish those Aussie heads were still around.
 
Originally Posted By: Hemispheres
Add the rocker arms and upper intake into the equation and I’m hoping to see 20-30hp. On top of what I have.


Pretty optimistic considering the difference between a L36 and L67 was 40 HP with a small blower and bigger injectors (19lb vs 30lb).
I hope it works out for you, you have a lot of money into it.
 
Supercharged uses the same heads and despite not having a tune I’ve noticed a substantial difference in upper rpm power. N/A stage 1 heads are good for 10-15 with complementary mods so the lower should net me another 5-10 at the very least.


https://grassrootsmotorsports.com/forum/grm/epoxy-for-intake-port-shaping/32877/page1/

https://mototuneusa.com/homework.htm

https://www.hotrodders.com/forum/cylinder-head-port-filling-203631.html#/topics/203631

After checking with folks online in regards to the gasket match I was told to do, I was advised to port the intake runners to match. 80 grit finish and removing casting marks. A cam would of course net me more power. As I’ve seen online with various 3800 cars many owners have gone with just rockers and heads that left them shy of 200whp. Some were much less that that but given I have other intake and exhaust mods I’m hoping to break the 200whp mark. I know 1 member did cam, DP and a dyno tune which gave him 220whp. Intense sponsered a vehicle that made 244whp with cam, heads and a tune. So 240-260 bhp seems doable if I take my time and do it right. This one port already had 10-12 hours into it.

4159258_E-9_D85-4254-_B714-851_D70_A61269.jpg


9_B43564_F-_E382-49_B0-8244-_B6_DBAEE40961.jpg
 
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