head gasket again (2000 miles +/-!!!!)
Posted:
Mon Mar 16, 2020 3:04 pmby el-saturn
had the head skimmed (0,1mm) to make sure it wouldn´t leak ---- it started AGAIN - i haven´t opened it yet, BUT its water in cylinder 4 and i´m pretty sure it´s the end of the gasket/block where the 2 water chanels meet. i´m sure cyl. 4 is sucking the water thru the (brocken????) gasket into the chamber. i want to keep the motor where it is! sandy --- any good ideas and i think its the block?
Re: head gasket again (2000 miles +/-!!!!)
Posted:
Mon Mar 16, 2020 6:03 pmby nigelrbfurness
I would suggest you look closely at the head surface, particularly where the coolant openings are in relation to the fire ring. On older heads these corrode to the point where there is insufficient material to support the gasket in this area and the coolant will be sucked into the cylinder. No.4 seems especially susceptible, I've certainly encountered this a good few times. I consider it unlikely that the block surface is damaged but you could examine it for cracks under a strong light and with a magnifying glass. A precision straight edge will tell you if the block is warped, which I will lay money it won't be. The cure, if it is corroded waterways, is to have the holes welded up then redrilled using the gasket as a pattern - you will note the holes in the gasket are much smaller than those in the head, usually. The head will have to be planed again but if you use a goid engineer it shouldn't affect the head depth too much. The problem occurs more frequently on large overbores, 85mm onwards, you don't say what bores you are running. Don't use a Cometic head gasket, use an Ajusa fibre one. Common sense and a thorough examination will reveal the problem - twin cams are not notorious for head gasket failures so you are definitely looking for a fault.
Re: head gasket again (2000 miles +/-!!!!)
Posted:
Mon Mar 16, 2020 8:50 pmby The Veg
nigelrbfurness wrote:you will note the holes in the gasket are much smaller than those in the head, usually
Mine is apart right now and I noticed this. Why are the holes so small? I figure there's a good reason, but I'm curious.
Re: head gasket again (2000 miles +/-!!!!)
Posted:
Mon Mar 16, 2020 9:46 pmby rgh0
The Veg wrote:nigelrbfurness wrote:you will note the holes in the gasket are much smaller than those in the head, usually
Mine is apart right now and I noticed this. Why are the holes so small? I figure there's a good reason, but I'm curious.
It was around getting the right flow distribution through the head and block of cooling water
cheers
Rohan
Re: head gasket again (2000 miles +/-!!!!)
Posted:
Mon Mar 16, 2020 9:47 pmby rgh0
el-saturn wrote:had the head skimmed (0,1mm) to make sure it wouldn´t leak ---- it started AGAIN - i haven´t opened it yet, BUT its water in cylinder 4 and i´m pretty sure it´s the end of the gasket/block where the 2 water chanels meet. i´m sure cyl. 4 is sucking the water thru the (brocken????) gasket into the chamber. i want to keep the motor where it is! sandy --- any good ideas and i think its the block?
Hi Sandy there are many potential causes - post some photos of block, head faces and of failed gasket and take lots of measurements of surface flatness. How many times did you re-tighten the head bolts ?
cheers
Rohan