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Blown head gasket? L18

Posted: Wed Jul 20, 2016 9:21 pm
by Bluebird_U

After fixing the problems with the SU's due to an air leak around one throttle shaft I have taken it out on the road and have found that it is using water - no, it doesnt have water injection (or at least a proper system) but about 2L disappeared from the radiator. Maybe it ran lean on 3 or 4 and overheated/ blew?

Ive checked the oil and theres no milkshake so Im thinking that the gasket has failed between a piston and a water gallery and that its just blowing through when it gets warm. There didnt seem to be much pressure in the radiator after it was run.

So unless its going somewhere else it looks like Im off to BNT or someone similar to get a full gasket set, timing chain? (and probably water pump too) and pull the head off. Is there any way to leave everything set up so that it can slot back together, or does it need to be reset to TDC and get the cam indexed? The other options would be to have the engine rebuilt to make sure that engine and head are good, does anyone have any recommendations for someone to rebuild the engine (from Auckland to Taupo - dont mind a drive for a couple of hours). Or does someone have an L18 out there that theyre not using? (I think an L20B just falls outside the increase in CC rating without getting a cert).

An ideas/ help greatly appreciated.


Re: Blown head gasket? L18

Posted: Wed Jul 20, 2016 9:48 pm
by 68p510sss
One area to check is the water galleries into the inlet manifold. If the lower bolts that bridge the inlet and exhaust manifolds come loose you can get a very primitive water injection. Since sidedaft manifolds don't have water galleries I get these welded up on race motor heads.

If taking the head off it is best to set it to TDC and then wedge the chain to hold the tensioner in place. If the tensioner comes out you will have to remove the front cover. Also make sure the head bolt threads are clean, it is very common for the bolts to bottom causing blown head gaskets.

Good luck

Re: Blown head gasket? L18

Posted: Sat Jul 23, 2016 9:49 pm
by Bluebird_U
Thanks for that. Cant see any water stains down the block and when I took the carbs off it was only down to the insulators.

When re-installing the head do the head bolts need to be oiled or dry? Have been looking on Youtube/ Ozdat/ Ratsun to just check everything out first and theres a bit of discussion as what to do. Might see if i can bet an old head bolt and cut a groove in it to clear out the threads.

Also, what is the best thing for cleaning the head/block to get rid of the gasket if any sticks? I will get a straight edge and feeler gauge to check the straightness of the head just in case it has overhead and bent it.

Re: Blown head gasket? L18

Posted: Sat Jul 23, 2016 10:53 pm
by Bartman
you can actually get a proper gasket scraper. If any sticks to the head be careful not to gouge the aluminuim.