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Valve Seat Repair/Replacement
Topic Started: Sep 11 2012, 06:08 PM (634 Views)
Felonious.Monk
Member
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Hello all,

I recently took my engine back from my local "machinist".

I dropped the engine off to have valve guides, valve seats, a light hone on the cylinders and the block deck machined.

I dropped the engine off January 11. We had agreed that it would be ready by memorial day. Labor day just passed. Last week I inquired as to how much longer it was going to take to be finished, an argument ensued, and I now have the block back in my possession.

The cylinders have been honed. The valve guides replaced. And new valve seats were put in and cut.

The block was not decked.

My questions pertain to the valve seats and decking the block.....

Posted Image


Posted Image

The block had previous seat work. The two replacement valve seats were cracked. So new seats were put in this last time.

It looks to me like the new seats are too far set into the block. I do understand that the block still need to be decked, but I can't imagine that it can be cut enough to make up the difference.

If it is possible to deck the block the neccesary amount, won't the original valve seats become too thin??? Also needing new seats cut into them??

Does anyone know the required valve head to combustion chamber clearance??

Help?? Thoughts?? Experience??


Thanks.

Pete
Pete

1953 CJ3B with Warn Overdrive
1988 Jeep Wrangler
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oldtime
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I don't see any valve seat inserts for cylinders #1 and #4.
The #1 and # 4 seats appear to be cut into the block and appear to be much too wide.
Those seats will need to be relieved.

# 2 and # 3 do appear to be deeply inset into the block but will likely be O.K.
The valve seat angle, the concentricity to the valve stem guide and the seat width are the critical concerns.

Just looking it does appear to need block decking.
This can only be known by using a straight edge.
The deck should be flat within .010".
The minimal amount should be removed or else the pistons might rise above the top off the deck.
.010" deck removal is usually sufficient.

Head / valve clearance will not likely become an issue.
Currently building my final F-134 powered 3B .
Rock Crawler using factory parts from the Willys Motors era (1953-1963)

http://s4.zetaboards.com/CJ3B_Bulletin_Board/topic/30228766/1/#new
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Felonious.Monk
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Oldtime,

You say the #1 and #4 seats appear too wide.

Are you talking about the width of the face on the angled cut.....where the valve contactsthe seat?

You say they'll need to be relieved. Do you mean made smaller/thinner?? Won't the machining of the decks surface thin out the width of that seat?? Or is the relief cut out of the bore?? ......am I making any sense?



About the block decking. I am assuming that the block has been decked once before. It isn't the first time the engines been apart. And the engines serial number is barely distinguishable.

If its been cut say .010 previously, will another .010 cause problems? How much room is there??

Again, Thanks.

Pete

1953 CJ3B with Warn Overdrive
1988 Jeep Wrangler
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oldtime
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Yes the #1 and #4 valve seat faces are too wide and they must be relieved.
"Relieved" means that the outside edge (sometimes inside edge) will be cut down deeper in order to narrow the seat width back to standard.

Yes the "decking" alone would narrow the seat width.
But that will not likely narrow them enough to make it right.

I suggest that you have stellite inserts placed into #1 and #4 also.
But that's not mandatory.
# 2 and #3 valve seats are much more critical due to there close proximity.
There close proximity to one another causes poor heat transfer in that area of the block which can readily manifest as cracks.

If the numbers are barely visable it was likely decked .005 or .010" sometime previously.
I fully expect its O.K. to shave another .010 off the top deck.


Currently building my final F-134 powered 3B .
Rock Crawler using factory parts from the Willys Motors era (1953-1963)

http://s4.zetaboards.com/CJ3B_Bulletin_Board/topic/30228766/1/#new
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Felonious.Monk
Member
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So if I'm understanding correctly, the relieving of the seats will leave them looking somewhat like #2 and #3..... Recessed??

I'm going to take the block to another semi local machine shop in a few days.

The block needs a good hot tanking, decking, and should get a new cam bearing while it's there.

I'll report back on what they say about the seat relieving.

Next comes a bunch of cleaning and hopefully I can have this engine running in a few weeks time!!!!! ......I did say hopefully didn't I?

Thanks again.
Pete

1953 CJ3B with Warn Overdrive
1988 Jeep Wrangler
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