172 gas engine two questions

jlewis457

Member
First are these engines prone to blowing head gaskets between cylinders # 2 & 3
Second question is what is the difference between the 1/2 and 7/16 head gasket other than the 1/16 of an
inch also is there any advantage or disadvantage to a non metallic head gasket
Thank you for your help John
 

No, they are not prone to blowing head gaskets at all. I had one on which I replaced the head gasket, and it blew the gasket the next year, but it turned out to have other issues. This one was between 3 and 4. I think that the gaskets will interchange but there are likely to be problems. On the earlier 172 if it doesn't line up just right it may not hold the sleeves down. You should go to the Felpro website.
 
I found out from a New Holland dealer today the 7/16 studs are used after 1958 so that tell me the newer
172 use the smaller head bolts
 
I had one that would blow the head gasket between 3-4, the block needed decked, there was a low spot between the cylinders - I don't think it's any kind of general problem, but if the gasket does let go, take a straightedge to the block and head and see if something is warped -

use a tap and clean out the threads in the block, wire brush your bolts, follow the correct pattern when torquing the head
 
I ve just rebuilt a 172 gas engine that chronically blew the gasket between 2&3. Because of this the engine was removed and replaced about 20 years ago, basically given up on. The last time it was "fixed," Dad used a lot of copper paint, cleaned the head bolts, and torqued the head to a diesel spec. It didn t last long.

Recently, a straight edge showed the low spot on the block and so I had it decked. The head was in good shape. We ll soon see how it does.
 
(quoted from post at 17:27:17 05/03/19) I ve just rebuilt a 172 gas engine that chronically blew the gasket between 2&3. Because of this the engine was removed and replaced about 20 years ago, basically given up on. The last time it was "fixed," Dad used a lot of copper paint, cleaned the head bolts, and torqued the head to a diesel spec. It didn t last long.

Recently, a straight edge showed the low spot on the block and so I had it decked. The head was in good shape. We ll soon see how it does.

Anytime that a head gasket fails between cylinders the block really should be decked. BUT, that makes the job four times bigger so it doesn't usually get done. I recently had a block get rejected due to rust just under the deck. I took a back-up block to the machine shop, so they decked it as standard procedure. There was a suspicious looking area between 2 and 3 and it took a few passes on the miller to clean it up.
 

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