Need advice on valve sticking in 426 hemi alum head

Posted By: DLP4

Need advice on valve sticking in 426 hemi alum head - 12/30/08 04:22 AM

I have an exhaust valve that sticks open. I've got less than 200 miles on this hemi I had built and I was running it hard dialing in the carb when it starting huffing and running like crap. I limped home and discovered one of the exhaust valves was hanging open about 1/8" when it should be closed. I looked inside the cylinder and there is no sign of the valve hitting the piston.

What's also strange is about 50 miles earlier I decided to do a compression check and none of the cylinders would hold pressure. But since I just had the engine built I dismissed it as a faulty compression gauge.

I'm in the precoess of pulling the heads but I was wondering if any of you guys that know engines can tell me what to look for? Maybe the wrong kind of oil seals causing the stems to run dry? Is there something I sould be looking for or be careful of?

Thanks

Posted By: Neil

Re: Need advice on valve sticking in 426 hemi alum head - 12/30/08 04:35 AM

Rebuilt engine with new guides?

Years ago my brother rebuilt a 455 Buick and the machinist installed new guides, but didn't bother to measure/ream them to the proper size. The result was two stuck valves (one on each head) several months apart. Finally when he realized what was going on he took both heads to another shop and had them reamed out for the proper clearance and it never happened again.

Posted By: CrAzYMoPaRGuY

Re: Need advice on valve sticking in 426 hemi alum head - 12/30/08 04:52 AM

Are you sure it's the valve hanging open or could it be the seat in the head moving around? Is it aluminum or iron heads?
I would pull the head and look before guessing to be honest..? Could be guide clearance, or a number of things.

Posted By: DLP4

Re: Need advice on valve sticking in 426 hemi alum head - 12/30/08 06:15 AM

That's interesting about the Buick. I hope that's all it is...still a pain but could be worse

These are all new parts. Using MP aluminum heads but the engine builder replaced the guides because he said the guides the heads come with are a sloppy fit. That's what kinda makes we wonder if he fit them too tight.

I can't say for sure about the seat. I pulled the hedders and used a dental mirror and a scope and from what I could see I think the seat is ok.

Posted By: torkrules

Re: Need advice on valve sticking in 426 hemi alum head - 12/30/08 07:44 AM

Are these the new Mopar heads or the older ones that look like the old A990 heads? If they are the older ones, they are notorious for having problems.

After suffering through a year of using an excessive amount of oil, it turns out that all 16 guides had excessive clearance. Also, they have been known to drop seats. This usually shows up either when they are first run on the dyno or after a few miles. I spoke to Tim at FHO about this and he confirmed the problems with these heads.

I'd get them off and go through them pretty thoroughly.

Posted By: MO_PA

Re: Need advice on valve sticking in 426 hemi alum head - 12/30/08 02:06 PM

Quote:

I'm in the precoess of pulling the heads but I was wondering if any of you guys that know engines can tell me what to look for?

If those were my cylinder heads I'd locate a competent engine builder!! The guy that built your heads may correct things for you by reaming the guides TOO much which create a new problem.

Valve guide clearance is VERY important!!

Posted By: DLP4

Re: Need advice on valve sticking in 426 hemi alum head - 12/30/08 04:12 PM

Quote:

Are these the new Mopar heads or the older ones that look like the old A990 heads? If they are the older ones, they are notorious for having problems.

After suffering through a year of using an excessive amount of oil, it turns out that all 16 guides had excessive clearance. Also, they have been known to drop seats. This usually shows up either when they are first run on the dyno or after a few miles. I spoke to Tim at FHO about this and he confirmed the problems with these heads.

I'd get them off and go through them pretty thoroughly.

How do I know which heads I have? Is there a casting series or something to look for?

It survived the dyno and I'm at about 200 miles.

Funny you mentioned oil consumption. I'm blowing through a lot of oil. But that would contradict the tight clearance theory.

When I get 'er opened up I'm take some pictures and post. thanks everyone

Posted By: DLP4

Re: Need advice on valve sticking in 426 hemi alum head - 12/30/08 04:22 PM

Quote:

If those were my cylinder heads I'd locate a competent engine builder!! The guy that built your heads may correct things for you by reaming the guides TOO much which create a new problem.

Valve guide clearance is VERY important!!

That kind of leads to my thoughts about valve stem lubrication. Of course, I won't know 'till I get it apart but I'm wondering if maybe the clearance is ok but the lubrication is not. He seemed pretty concerned about getting the clearances correct...of course that doesn't mean they are so we'll find out.

Posted By: 4BBodies

Re: Need advice on valve sticking in 426 hemi alum head - 12/30/08 05:41 PM

It sounds like the guide got dry (of oil) and the valve siezed to me. Could the machinist have made the clearance too tight for the valves? My books say .001 to .003 thousandths clearance, I use the pilots from my valve seat grinder to measure them, they have been pretty accurate to date. Good luck, I hope you figure it out.

Posted By: DLP4

Re: Need advice on valve sticking in 426 hemi alum head - 12/30/08 06:01 PM

Quote:

It sounds like the guide got dry (of oil) and the valve siezed to me. Could the machinist have made the clearance too tight for the valves? My books say .001 to .003 thousandths clearance, I use the pilots from my valve seat grinder to measure them, they have been pretty accurate to date. Good luck, I hope you figure it out.

I've never done a valve job but I have experience machining non-automotive stuff. Should each stem be measured and each guide reamed to fit? Seems the stems should be consistant but I don't know. I want to figure out what the problem is before I send it off to someone to have it fixed.

Posted By: Neil

Re: Need advice on valve sticking in 426 hemi alum head - 12/30/08 06:21 PM

You can buy the tools to measure inside the valve guide holes if you want to, Powerhouse tools sells them as a kit. Then all you would have to do is take a set of calipers and measure the valve stems. Subtract the two numbers and you have your clearance.

If you don't have the tools you can just take the head to the shop and have them measure one or two valve guides while your standing there.

Posted By: 4BBodies

Re: Need advice on valve sticking in 426 hemi alum head - 12/30/08 07:33 PM

I didn't catch above if you were going to be taking the heads off, (I am assuming you are,) so I think you will get a good picture after the springs are off the valves. The valves will either slide in the guides good or they won't, and a simple "wiggle" test will at least give you an idea on how loose/tight they are.........then you can actually measure them with some sort of measuring tool.........maybe when they get hot they expand, and tighten up.

Posted By: DLP4

Re: Need advice on valve sticking in 426 hemi alum head - 12/30/08 08:18 PM

Quote:

I didn't catch above if you were going to be taking the heads off, (I am assuming you are,)

Yes, I'm pulling the heads. Started last night but there is a lot of stuff in the way. Hopefully I'll the one head off tonight that has the offending valve and we'll see what's there.

Posted By: torkrules

Re: Need advice on valve sticking in 426 hemi alum head - 12/30/08 10:48 PM

Under the valve cover there should be a part number 2531100-M (the A990 heads are the same part number without the -M). The newer heads should have a fancy "E" cast somewhere on the head denoting EDELBROCK.

When I spoke to Tim at FHO with regards to my particular problem, he mentioned that there was a real problems with sizing on the guides from the folks who were machining the heads for MP (I think it was Dart). Ditto on the valve seats.

I would still have a look at the seats. I had a friend of mine that was working on an engine with a set of factory '65 A990 heads. The lash kept opening up on one valve. They pulled the head and found that the seat was starting to drop out. They caught it before it became a disaster.

I wish I could post pictures, but they are too big.

Posted By: jbc426

Re: Need advice on valve sticking in 426 hemi alum head - 12/31/08 12:02 AM

Do a search on the microsoft site about Microsoft Toys and then look for the resizing tool. It works great and is as easy as a right click from your mouse.

Posted By: SSAAHemiFan

Re: Need advice on valve sticking in 426 hemi alum head - 12/31/08 02:49 AM

Tight guides and seat issues are very common with MP heads.

I noticed you said you were running it hard AND fiddling with the tune. Both of those items COULD have contributed (over-rev or mixture problems). Not pointing fingers just thinking out loud.

Pulling the heads will tell the story. Keep us updated please. Hopefully it's a simple fix for ya'.

Posted By: DLP4

Re: Need advice on valve sticking in 426 hemi alum head - 01/01/09 04:47 AM

Quote:

Tight guides and seat issues are very common with MP heads.

I noticed you said you were running it hard AND fiddling with the tune. Both of those items COULD have contributed (over-rev or mixture problems). Not pointing fingers just thinking out loud.

Pulling the heads will tell the story. Keep us updated please. Hopefully it's a simple fix for ya'.

I'm sick with the flu so it's going to be couple days before I finish getting the heads off.

Posted By: DLP4

Re: Need advice on valve sticking in 426 hemi alum head - 09/12/09 05:00 AM

Well, after getting over the flu I just felt sick of working on the car and let it sit for about 10 months.

Got the heads off today. 2 lobes gone on opposite banks. The wear marks on the lifters look like they never spun like they should have (mechanical flat tappet). The lobes apparently mushroomed the bottom of the lifters jamming them and the 2 valves hit the pistons bending the valves. not a good day.

My first thought is the cam was not broke in properly or possibly a bad cam. It was a CompCams 557/540 solid flat tappet. Any thoughts?

Posted By: 1_WILD_RT

Re: Need advice on valve sticking in 426 hemi alum head - 09/12/09 06:30 AM

First thought what oil was used/is being used.. Are you familiar with ZDDP, what it does & the fact it's been removed from most oil... http://www.zddpforum.com/forum/viewtopic.php?f=2&t=7
Second thought were lighter springs used during cam break-in?? There are plenty of other questions but those two are biggest...

Unfortunately flat cams are all to common these days & unfortunately when the lobes go they send metal particles throughout the whole engine... Often damaging pistons, bearings cylinder bores & sometimes cylinder heads...

Your whole engine really needs to come apart for a thorough inspection

Also I would strongly suggest a roller cam to eliminate the potential of this happening again

Posted By: DLP4

Re: Need advice on valve sticking in 426 hemi alum head - 09/12/09 06:59 AM

Quote:

First thought what oil was used/is being used.. Are you familiar with ZDDP, what it does & the fact it's been removed from most oil... http://www.zddpforum.com/forum/viewtopic.php?f=2&t=7
Second thought were lighter springs used during cam break-in?? There are plenty of other questions but those two are biggest...

Unfortunately flat cams are all to common these days & unfortunately when the lobes go they send metal particles throughout the whole engine... Often damaging pistons, bearings cylinder bores & sometimes cylinder heads...

Your whole engine really needs to come apart for a thorough inspection

Also I would strongly suggest a roller cam to eliminate the potential of this happening again

I'm not sure what the engine builder did or didn't do. I suppose it's water under the bridge at this point.

I was considering a roller because of not requiring break-in and also because the roller tolerates low speeds and idling better but most of the roller cams I've seen are pretty tall and I want to keep the car driveable. I need to figure out what direction to go pretty quick though so I can get it back together. Should do a complete tear-down like you said.