cracked head ?

[richard]

hello there ive go a aircooled 126 with a apparent cracked head ??
(as was told to me by a garage ?? )

on removeral could / should i be able to see the crack?

and if there isnt one , should i just assure its the head gasket thats gone and not the head itself ??

or should i replace it anyway at more cost?

please help reguards

richard

[Pete126]

Hi richard, its difficult to check the head for cracks especially air cooled, in water cooled you can usually see some discolouration round the crack. but heres something you might try, take the valves out, turn the head upsidedown, level the head so its flat, seal the valve inlets (i think wine bottle corks might work) fill the chambers up to the top with parrafin then leave it for 24 hour, if there is a crack the parrafin should drain out as its very searching, the only allternative is to take it to an engine rebuilders as they have the equipment to check and pressurize the head, usually the cracks are between 1-2 cyl, valve seats, or from the chamber to the head bolt holes

[richard]

I HAVE PICTURES OF IT..  CHRIS MAY POST THEM FOR ME ??

hello there , ive got a fiat  126 650 engine AIRCOOLED ..

ive taken the head off and found its cracked , can it be skimmed? or if its cracked can it be fixed ?

or will it need to be replaced ??  as i have a replacment but like a idiot i have managed to snap a bolt off one of the exhaust flanges inside the head .... is there anyway this can be removed??  possible drill it out ?


ALSO WHEN I GET THE HEAD DONE OR AM READY FOR REPLACING BACK ONTO CAR , DO I NEED SOME KIND OF  GASKET PASTE? LIKE FROM HALFORDS OR SOMETHING ? OR CAN I JUST USE OIL?  


anyhelp would be great

anyone in leicestershire that could skim a head for me for free that would be excellent

all the best

richard

[Pete126]

Hi richard, in my opinion if you can see the heads cracked its not worth repairing, you don't just get cracks on the surface it will be cracked through to the other side of the casting, there are engineers that will weld heads but won't give a guarantee for the work, as i have found to my cost, i'd go for drilling and retapping the exhaust stud on the other head

[Chris Lakin]

[ChrisRLewis]

Richard
I cannot make out the crack on the pictures, where is it? beteen the valves? or where the gasket blew?

[richard]

crack is right on the thread where the gasket blew .. near the very lightly coloured valve

[slater]

By the time you have welded it up, skimmed it and machined the groove back in you may aswell have just got a differant head.

I have a spare head, needs a full recon tho

[PaulB]

Use petroleum jelly to fit the gasket, but follow haynes to the letter to avoid future problems.

I agree that you should fit the good head. There is just an airway behind the broken stud so drilling it is quite safe. However, despite your best efforts, the thread may get ruined - its common for the thread to come out with the bolts or studs for the exhaust manifolds. If this happens there is a good work around.
Firstly though, get the broken stud out...
If any of the stud is sticking out, you can use locking pliers or weld another nut or bolt to it  and turn that. The heat may also help to free the stud from the thread. be careful re/ heat though - it can help loosen the stud but can also warp the head.
If welding isn't an option, use a centre punch to make a dead centre guide for a 1/8 drill bit (or it will wander off and wreck the thread). you may have a centre guide if you have an extraction tool - either way getting the drill dead centre is going to mke removing the stud much easier. really soak stud with wd40 and leave for a while. use a left handed drill bits.  they may bring the stud out as they drill. Start at 1/8 and work up. Try an extractor when the hole is large enough, but if it dosn't work you are going to have to keep drilling wider until you can collapse the stud with a small screwdiver or similar and wiggle the bits out.  You may have to repair the thread - you can get thread repair tools cheaply. If the thread is totally shot its should still be okay as there is a work around - just do everything you can to preserve the thread behind the stud.

the thread should be 8mm x 1.25 pitch

there's a good article at

http://www.asashop.org/autoinc/may2003/techtotech.cfm

use copper grease when replacing stud as it resists the high temps.

[richard]

hello people , ive decided to use the spare head ive got.

ive took it work today and the nice engineer has drilled the broken stud out and kindly retapped the head for me

all i gotta do is wait on the decoke gasket set, and i will be replacing it ...

i will follow haynes as has been suggested. as i dont want to risk further or unessary damage .
thank you for all your help so far

[PaulB]

Nice one - saved you a tedious job. Be sure to use a torque wrench (borrow one if you don't have one) when replacing head.