When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I am trying to diagnose a valve failure on a 1996 varioram engine with roughly 60k miles. About 3k of them were track miles
Currently in the process of pulling the engine apart but what I am finding makes no sense.
The engine gave no signs of any issues period. No valve train noise. No smoke, tapping or anything else. Suddenly it just puffed some blue smoke and a fireball out the back end while it was at low rpms
Pulled the plugs and covers and found that cylinder #5 had a broken valve spring retainer and worse yet a broken valve guide and valve. The valve smashed against the cylinder and lodged itself into the head so a complete teardown and new parts is in the works. I am just curious if anyone has had or has heard of a valve drop for no apparent reason. I understand that broken spring retainers can result from over revving although the last few hours of driving it the engine was never revved above 6000 rpm.
I don't see anything in the archives that lean towards this as being a common problem. I would suspect over rev but I know that isn't the case so what am I left with that could have caused this?
Other points: the valve stem broke in 2 places leaving a piece about 1"+ long and it is nearly a perfect clean strait break on one side, the end of the valve guide broke off and the material appears to be brittle as I was able to snap the remaining piece in half with little effort and no signs of a crack.
I am waiting on a yoke to mount the engine and will remove the heads in a few days.
No doubt I will be needing a top end at minimum most likely new P&C's and a new head. Any concerns with using used P&C if I can find some in the same weight as the others? Wasn't planning on a rebuild but I figure this will cost me about $10k min by the time I am through. Ti spring retainers and heavier duty springs along with ARP studs will be going in.
PS: the broken valve is an intake not exhaust which makes it more confusing.
If I had to bet I would say it looks as though it was a manufacturing defect that took 60k miles to fail.
Now the question: How far to go now that I am in there.
Might be.
Engine overrevs (piston-to-valve contact) leave many tell-tale signs and thats the first place I look when this happens. You are VERY VERY lucky that the valve embedded itself since they normally fly back into the intake system and wreak utter havoc in other cylinders.
Can't help with the other stuff without seeing everything for myself.
Originally Posted by Steve Weiner-Rennsport Systems
Might be.
Engine overrevs (piston-to-valve contact) leave many tell-tale signs and thats the first place I look when this happens. You are VERY VERY lucky that the valve embedded itself since they normally fly back into the intake system and wreak utter havoc in other cylinders.
Can't help with the other stuff without seeing everything for myself.
Believe you me I know how lucky I am. Especially since I found a couple of the pieces sitting just next to #4 cylinder intake. The borescope shows a couple of impacts to the piston of cylinder 5 but nothing that looks as though it was the cause of the damage. i will know more when I open it up. I was lucky this didn't happen at WOT. I will let you know what I find but no doubt this will be a lengthy expensive build either way. Question is do I break down the entire engine or just do a top end. Can''t make that decision until I learn more.
Wow, that's a bummer. Sounds like it will be very hard to determine what caused the failure. In case you are looking for pistons, I have a set of new Porsche pistons and rings sitting in a box. I purchased them before I rebuilt my motor. Decided to have my old pistons cleaned up and purchased new rings.
Wow, that's a bummer. Sounds like it will be very hard to determine what caused the failure. In case you are looking for pistons, I have a set of new Porsche pistons and rings sitting in a box. I purchased them before I rebuilt my motor. Decided to have my old pistons cleaned up and purchased new rings.
I won't have the engine apart until next week so not sure what I will be up against although if you want to PM me a price I might be in the market. LOL
Since I am now in the rebuild stage I have a myriad of options all depends how deep I want to reach into my pockets. I was contemplating a 3.8 & ITB's but that slope can get very slippery.
Anyone have an idea what a Vario ram intake is worth?
If I think about how many moving parts are part of the valvetrain, I’d wonder why things like this don’t happen more often.
Under normal street use, this is VERY rare. Track use is another thing altogether.
The retainers, springs and seats seem to fail more often than valves themselves, although those failures are often rare as well.
This is precisely why we upgrade the springs & retainers to prevent such occurrences. Factory valve seats never fail unless someone didn't install a replacement one properly.
.
Would it be more economical to find a good used engine and just swap the engine out?
I was looking at another engine and waiting on a price but honestly I will be back where i started and I am leaning towards just building this correctly with Carrillo rods, new valve springs, Ti retainers, shuffle pin the case and line bore etc.
I begin the engine tear down today and will see how bad it is. It didn't seam all that bad when it let go but no doubt we will discover more as we go.
So I opened up the engine which is in remarkably excellent condition overall. Clearly a low mile well cared for unit with no signs of carbon buildup or any obvious wear on 5 of the 6 P&C's. Honing marks still present on the cylinders. The only cylinder that looked bad was 5 and it was heavily oil laden and clear damage from the valve head which chewed everything up including a gauge in the cylinder wall. I have to assume that either the valve spring retainer snapped for no apparent reason or the valve head broke off.
In either case I am SOL.
So I have the opportunity to pick up 964 3.6L Mahle cylinders and JE pistons for reasonable money. 102m with an 11.5 compression ratio. I can't find out what the differences are and if it will impact my build but at this time the price works all I need is a head. Anyone with experience using the JE pistons. I read someplace Geoffrey Ring was not a fan and they made noise which I'm not concerned about for a track build.
Post some close-up shots of both ends of the valve stem. Look for typical beach marks vs. clean fracture to identify the source, my hunch is you'll see some fretting @ the base of the keeper grooves but will be interesting to see if the valve head went first.
Post some close-up shots of both ends of the valve stem. Look for typical beach marks vs. clean fracture to identify the source, my hunch is you'll see some fretting @ the base of the keeper grooves but will be interesting to see if the valve head went first.
Keepers were the first thing we looked at. I will try to get some pics tomorrow but no signs of there being an issue there as far as we can tell.
08-01-2018, 07:59 PM
Can valves just break?
LOL
