View Full Version : Head swap question. Is decking necessary?

06-14-2010, 07:36 AM
I have a good head from a working motor and will be putting it on a motor that had timing belt break. Should the good head be decked at a machine shop before mating it to the block?

06-14-2010, 12:42 PM
i have been told if neither motor had a heat related failure then it should be fine.

i have done 1 and im doing another this week and have not had a problem...i always replace gasket and always use the copper gasket spray stuff..and make sure to TQ correctly and do not reuse head bolts.

06-14-2010, 01:08 PM
I did it on my A4 and S4 when I rebuilt them. Plus if you shave the head you get a little more compression :)

ECS Tuning-Audi
06-14-2010, 01:09 PM
If you are building a serious motor, deck your head. If you ABSOLUTELY know the head was well cared for and not over heated then you might get away with it. I'd strongly recommend you deck the head, replace gaskets and use new head bolts. The new head bolts are not terribly pricey at all, nor are the gaskets. Cylinder Head Bolts (http://www.ecstuning.com/Audi-B5_A4-Quattro-1.8T/Engine/Mechanical/Cylinder_Head/?salesrep=CArmbruster&utm_source=audizine&utm_medium=forum&utm_content=CArmbruster&utm_campaign=postreply) and a whole cylinder head gasket kit is only 90 bucks (http://www.ecstuning.com/Audi-B5_A4-Quattro-1.8T/Engine/Gasket/ES1751/?salesrep=CArmbruster&utm_source=audizine&utm_medium=forum&utm_content=CArmbruster&utm_campaign=postreply).

ECS Tuning-Audi
06-14-2010, 01:11 PM
I did it on my A4 and S4 when I rebuilt them. Plus if you shave the head you get a little more compression :)

Ah yes, a little bit more indeed, good call!

06-15-2010, 05:05 PM
check all mating surfaces with a straight-edge and feeler gauges. cams may have to be removed so you can check the head for warpage diagonally (with all valves closed). refer to bentley or look online for tolerances but i would say anything greater than .005" is a no-go and would require machining to be milled flat again. if it were my car i would say .002" would be excessive.

if you are already having work done to the block and head (p&p, extrude hone, bore & hone, blueprinting, etc) you might as well mill it anyway, especially if increased compression is a goal, however on forced induction motors, lower compression can make for a safer running motor and thus happier motor. more compression will net you a negligible amount of power under the curve and have an minute amount less spool.

if you are just trying to get the engine running again and know the head wasnt overheated, smooth out the dings on the pistons, slap a headgasket on it and bolt it down in the PROPER torque sequence. replace the t-belt, hydraulic tensioner dampener, and water pump. hope this helps. peace.

06-15-2010, 05:07 PM
if you do...get an adjustable cam gear, it is NECESSARY, i chased my ass for a long time, only to find out the cam was off a hair from the machining.