valve/ piston contact ?
Seasoned HDF Member
Joined: Mar 2010
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From: Honah Lee
Broke a cam shaft at the gear end and the bolt kept it together but let it index around over a few miles. Sounded a little odd and it quit shortly when the bent valves stuck and stayed open.
Club Member
Joined: Jun 2007
Posts: 45,429
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From: Bedford UK
Under normal circumstances it is not possible for valves and pistons to come into contact, or so I am told! If, for example, the engine is over-revved, the engine management will cut in before damage can be done. So for there to be contact something serious has to happen, such as Ripsaw describes.
Why do you ask? Tell us more!
Why do you ask? Tell us more!
Seasoned HDF Member
Joined: Nov 2010
Posts: 17,548
Likes: 7,197
From: Oxford, Nc
Under normal circumstances it is not possible for valves and pistons to come into contact, or so I am told! If, for example, the engine is over-revved, the engine management will cut in before damage can be done. So for there to be contact something serious has to happen, such as Ripsaw describes.
Why do you ask? Tell us more!
Why do you ask? Tell us more!
( Well , at least I do like my new heads
)
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Tourer
Joined: Dec 2009
Posts: 440
Likes: 7
From: wisconsin
Under normal circumstances it is not possible for valves and pistons to come into contact, or so I am told! If, for example, the engine is over-revved, the engine management will cut in before damage can be done. So for there to be contact something serious has to happen, such as Ripsaw describes.
Why do you ask? Tell us more!
Why do you ask? Tell us more!
HDF Community Team
Joined: Jun 2006
Posts: 12,776
Likes: 2,607
From: san antonio
1.9 intake valves se flat top pistons heads decked have .510 cams I have 1200 miles on build with know problems but I know valae may be choose to valve relief edge from what I see with bore scope.Hard to tell because scope magnafies top of piston so much . This is why i ask. Valve might be coming close and not letting carbon to build on valve releif edge and thats what Iam seeing.Its running fine,
The intake valve reliefs need to be opened up. This can be done by a machinist as shown in the above image but the pistons have to come out. Or, the reliefs can be opened up by pulling the heads, bringing the piston to TDC and using duct tape to seal off the gap between the piston and cylinder wall; cover everything but the relief. The reliefs can be opened up with a Dremel tool. Won't be a pretty but just as effective. Which either way, be sure and smooth off any rough spots that could become a "glo plug" and cause the engine to detonate.
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Tourer
Joined: Dec 2009
Posts: 440
Likes: 7
From: wisconsin
anytime oem intake valves are replaced with 1.9 intake valves, the valve reliefs shoud be opened up to the outside. The reliefs are deep enough but not positioned far enough to the outside edge of the piston to avoid contact.
the intake valve reliefs need to be opened up. This can be done by a machinist as shown in the above image but the pistons have to come out. Or, the reliefs can be opened up by pulling the heads, bringing the piston to tdc and using duct tape to seal off the gap between the piston and cylinder wall; cover everything but the relief. The reliefs can be opened up with a dremel tool. Won't be a pretty but just as effective. Which either way, be sure and smooth off any rough spots that could become a "glo plug" and cause the engine to detonate.
the intake valve reliefs need to be opened up. This can be done by a machinist as shown in the above image but the pistons have to come out. Or, the reliefs can be opened up by pulling the heads, bringing the piston to tdc and using duct tape to seal off the gap between the piston and cylinder wall; cover everything but the relief. The reliefs can be opened up with a dremel tool. Won't be a pretty but just as effective. Which either way, be sure and smooth off any rough spots that could become a "glo plug" and cause the engine to detonate.
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Cruiser
Joined: Jun 2012
Posts: 108
Likes: 0
From: East Tx
you got real lucky..i mocked mine up and checked with clay when putting together, and only had .012 between piston and valve. Had to open reliefs up .050 to get it right
Last edited by jrgreene1968; Apr 21, 2013 at 01:36 PM.
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Joined: Sep 2009
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From: deland,florida
check to see what you TDC lift is,most smaller cams dont have enough TDC lift where the valve will come anywhere near the piston.I dont like useing clay,as ive seen alot of guys actully bend valves using this method.what i do is ,with the springs off (seal still on),with the valve on the seat,mark the TDC lift +.060 on the valve stem with dykem (or even a majic marker will work)up from the seal,put head on the motor with 2 head bolts snug,bring motor to TDC and push the valve down,if you have contact before the TDC mark gets to the seal,you`ll have to machine pockets,if it opens past the mark your good to go