Author Topic: Deck crack near head bolt hole (Read 5106 times)

thomcat · « **on:** March 06, 2009, 07:15:52 am »

I have a hairline crack running from the edge of one of the middle headbolt holes. Its aprox 5/8 inch long. My machine shop didnt think it was critical so I had them cold weld it (drill and plug). I am planning on running head studs to help with head gasket sealing and take some stress off the block . The head gasket was sealing fine when it came off . Does anyone have other measures or suggestions to help with reliability?.
Also is this a common problem? I will be picking the block up later today so If you want I will post pictures. Oh yea The engine is a 1.6 n/a from my 82 rabbit.

Thom

Rabbit on Roids · « **Reply #1 on:** March 06, 2009, 09:59:53 am »

DO NOT put any boost to this block. that will be the first thing to go. and then you will have more than one crack in your block. deck cracks are bad ones. but as long as your gonna stay with a stock 52 horses.. shouldnt matter too much.

TurboJ · « **Reply #2 on:** March 06, 2009, 10:22:45 am »

Post a picture, that way the experts here can tell you what's what :!:

thomcat · « **Reply #3 on:** March 06, 2009, 08:16:32 pm »

here is a pict of the crack . I Have given up on the idea of boosting this engine after finding the crack! I just hope it proves durable in NA configuration. If so I may boost my next project in a 2 door GTI .

[/img]http://i300.photobucket.com/albums/nn14/thomcat_2008/closeupcrack.jpg

thomcat · « **Reply #4 on:** March 06, 2009, 08:19:09 pm »

fatmobile · « **Reply #5 on:** March 06, 2009, 08:59:37 pm »

Did this block have 11mm headbolts?
The stock 11mm headbolts don't go deep enough into the block and put too much stress on a small area.
Haven't heard of this happening with 12mm headbolt blocks.

thomcat · « **Reply #6 on:** March 06, 2009, 09:13:58 pm »

yep they are 11 mm head bolts

bigblockchev · « **Reply #7 on:** March 06, 2009, 09:42:00 pm »

I would helicoil it if you are worried. This will increase the area that the threads have to bear on. Not perfect but better and not real expensive. cheers Dan

Rabbit TD · « **Reply #8 on:** March 06, 2009, 09:57:33 pm »

I think I would get a set of ARP headstuds and go from there as they go in the hole a lot deeper, I'll never put one of these back together without them. These 11's crack there all the time from the bolt not being long enough. that's the big reason they went to 12m/m to begin with and they go in deeper as well but they are the stretch type bolt and have their own problems and that's where the 12 m/m ARP's come in

maxfax · « **Reply #9 on:** March 06, 2009, 10:12:59 pm »

THe block I'm running now has more cracks than a plumbers convention.. I used head studs and some hylomar sealant on the threads into the block.. Fingers crossed it's been holding for 50,000+ miles..

Now if there's a crack between the coolant passage and the bolt hole next to the oil passage (Front of the car second bolt in from the trans) consider it toast... The oil pressure is just too much and pushes oil in the coolant.. I've debated using a thread insert for a situation like this since the inner threads are completley closed off from the outer on those, but I'm afraid it'll require removing too much metal from the block to hold properly..
Still may give it a shot one day... I'd only be out a headgasket and the thread insert if it goes sour...

Rabbit TD · « **Reply #10 on:** March 06, 2009, 10:59:11 pm »

This is just a thought but if it is a question of trying something or junking the engine I wonder how filling that coolant hole with JB weld and doing the insert trick. Do you think that one whole will make it run hotter or not if it's blocked off, just a thought and depending on what the motor actualy has to withstand.

maxfax · « **Reply #11 on:** March 07, 2009, 12:08:31 am »

Hmm Now that is a thought.. Not sure what would happen having that one hole blocked.. Even if it were to be partially blocked..

The hardest part woudl be getting the hole cleaned out well enough for the jb weld to stick, short of pulling the engine and having it cooked.. If it were to come to that point I'd probably just replace the darn thing..

Back in the olden days when compression was low and there wasn;t so much stress, brass was a popular block repair.. I've seen alot of old tractors and Willys Jeeps with cracks in the deck drilled and filled with brass.. I would imagine it would have about as much of a chance of holding as JB weld wil less cleaning.... Plus it would give for expansion and contraction...

thomcat · « **Reply #12 on:** March 07, 2009, 05:44:19 am »

Its settled then, I will go with the head studs and good old red loctight. Whats the part # for an ARP head stud set?

With this crack I dont want to over stress anything so what is the best head gasket to use? ( I hear some require alot more force to compress. the block might not like that)

My jetta has a fatal oil pressure problem so I have had to start using my full time 4wd truck with 32 inch tires to commute :evil: . lol good incentive to get this rabbit done!.
thanks for everyones help
Thom

burn_your_money · « **Reply #13 on:** March 07, 2009, 06:19:59 am »

Quote from: "maxfax"

Hmm Now that is a thought.. Not sure what would happen having that one hole blocked.. Even if it were to be partially blocked..

I bet you'll warp the head. I've had 2 engines where people used too much silicon sealing up the waterpump or flanges or whatever and a nice chunk of silicon got stuck in the headgasket. Both heads were severely warped in that area.

I'd use loctite thread sealer instead of red loctite.

maxfax · « **Reply #14 on:** March 07, 2009, 07:14:01 am »

[quote="burn_your_money]I bet you'll warp the head. [/quote]

That was sort of my guess...

x2 on the sealer.. PLain ole loctite doesn;t do such a great job at sealing..
Not to mention if you do have to pull the head on it at a later date you'll find that the head won;t come up off the studs without removing the studs, or the manifolds, and the red loctite isn;t gonna make removing the studs fun...

Author Topic: Deck crack near head bolt hole (Read 5106 times)

Rabbit on Roids