checking for bent valves
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checking for bent valves
Okay, I goofed. It happens. I don't want to get into it but I had the heads on an engine and got my vavle train misaligned so when I was barring the engine over with a socket wrench, I think I contacted some valves with a piston. Okay, I know I did. The engine is a dual over head cam V-8 Jag engine (see this is ford related because I can't get back to my truck until this jag engine is fixed). How do I check to see if the vavles are bent or okay? Shoudl I do a compression test (engine is outta the car)? Pull the heads and have a shop do a leak test? Pull the valves and check them with a square to see if they are bent? Suggestions?
Eric
PS Thanks and looking forward to getting back to a real Ford
Eric
PS Thanks and looking forward to getting back to a real Ford
Postmaster
Joined: Jun 2004
Posts: 4,190
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From: Riverside, So Cal
If you have the valves out of the engine, rolling them on a flat surface is an easy way to see if they are badly bent. Short of that, certainly a compression test will tell you if there is a problem that needs a tear down.
Hotshot
Joined: Oct 2004
Posts: 15,882
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From: Durham NC
A leakdown test would be easiest IMHO. Put the piston at BDC with both (all?) valves closed, add compressed air thru the sparkplug hole, listen for air escaping out intake manifold and/or exhaust.
I find it highly unlikely you bent a valve turning the engine over with a wrench unless you jumped up and down on it when the engine locked up. Then again it is a British manufactured engine so they might have used coathanger wire for valve stems...
I find it highly unlikely you bent a valve turning the engine over with a wrench unless you jumped up and down on it when the engine locked up. Then again it is a British manufactured engine so they might have used coathanger wire for valve stems...
Post Fiend
Joined: Mar 2007
Posts: 5,776
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From: springfield il
oooh jag engine this sounds expensive !!!! notjing to add as ax and randy jack said what i wouldve .
doesn't ford own jag now ? if so it is defineteley ford related , just a different flavor .
doesn't ford own jag now ? if so it is defineteley ford related , just a different flavor .
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I rigged up an air hose last night and didn't have a ton of time
but my first check is that all the vavles seat*. The manifolds are
off so it is easy to see them.
But now for the asterisk (there always is one, isn’t there?)
Some seem to seat better than others. I was putting in about 110psi. SOme of the intake valves ''gurgled'' in that there was some hissing (like a frying pan) and could see
some bubbles from the oil that was on the seat. I am guessing that
they shouldn't do that. I hand lapped the valves during the
rebuild and made sure to reinstall them in the spot they came out
off. Maybe I did a crappy job lapping the valves. I'll check
better this weekend.
And 55 f350, the way this is going, when I finally get the engine running right and into the jag, $1 says the car gets totaled this winter. When that happens, look for the “How to install a Jag engine into a ford pick up” article that I will be writing.
As always, thanks. I think this site sometimes counts as therepy
where we get to share our car problems and say ''Ooooooo, Been
there. Sorry it happened to you too.''
Eric
but my first check is that all the vavles seat*. The manifolds are
off so it is easy to see them.
But now for the asterisk (there always is one, isn’t there?)
Some seem to seat better than others. I was putting in about 110psi. SOme of the intake valves ''gurgled'' in that there was some hissing (like a frying pan) and could see
some bubbles from the oil that was on the seat. I am guessing that
they shouldn't do that. I hand lapped the valves during the
rebuild and made sure to reinstall them in the spot they came out
off. Maybe I did a crappy job lapping the valves. I'll check
better this weekend.
And 55 f350, the way this is going, when I finally get the engine running right and into the jag, $1 says the car gets totaled this winter. When that happens, look for the “How to install a Jag engine into a ford pick up” article that I will be writing.
As always, thanks. I think this site sometimes counts as therepy
where we get to share our car problems and say ''Ooooooo, Been
there. Sorry it happened to you too.''
Eric
Fleet Owner
Joined: Jul 2004
Posts: 27,283
Likes: 1,046
From: NM
When you say you hand-lapped the valves, is that the extent of your valve job? Or were the seats cut with a professional stone? I don't think hand-lapping is adequate on an engine like this, if that is all that was done. In other words, the bubbling you see may not be from valves touching the pistons but because they weren't seating anyway.
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If I may, a brief history for history of jag V-8s: THey are aluminum blocks that were lined with Nikasil on the cylinder walls. Long story short, the Nikasil went ka-put (well documented problem) so I had the block sleeved with iron sleeves.
So the problem wasn't the valves (or so I thought). I just lapped them by hand since I just wanted to refresh them since I had to get down to a bare block for the resleeving. Maybe a recutting of the seats is in order. Only $$, right? Ugh.
How long should a cylinder hold its pressure? Obvisouly no seal is perfect.
Part of me is wondering what happens at high temp. Valves get hot hot hot so maybe at operating temp the gurgle will lessed.
Hmmmmmm
Thanks for your help and allowing me to ask a question 'ford' related project.
Eric
So the problem wasn't the valves (or so I thought). I just lapped them by hand since I just wanted to refresh them since I had to get down to a bare block for the resleeving. Maybe a recutting of the seats is in order. Only $$, right? Ugh.
How long should a cylinder hold its pressure? Obvisouly no seal is perfect.
Part of me is wondering what happens at high temp. Valves get hot hot hot so maybe at operating temp the gurgle will lessed.
Hmmmmmm
Thanks for your help and allowing me to ask a question 'ford' related project.
Eric
Last edited by Minger; Oct 18, 2007 at 09:45 AM.
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