Rover Sports Register Forum

Any one come across this problem I am sure many have, I remember reading in Freewheel about core plugs leaking and discovered in April/June 2004 issues the same problem although with six cylinder cars which have 3 of these in the top of the head at the rockers. My car is the four cylinder 12 and I have looked but don't see any core plugs. OK so I am pretty sure where the problem is, it is seeping from the head gasket at the push rod area,behind the access plates and leaking into the sump, (car is running fine). So I checked the head bolts after removing the rockers and found that the torqueing down I did last year which was was 40 lbs ft the bolts seemed to be only around 20 lb ft not the 40 I originally did it too. I torqued it down to 40 lbs ft thinking that the torgue spanner I used was not accurate (I also checked know with a neighbours wrench to double check that it was indeed 40 lbs this time). I filled up the rad to check for leaks and the area at both pushrod joints seeped ( not much ) I tightened down to around 45lbs ft but it did not stop seeping so I then removed the head, everything seems fine, the gasket ( a new one last year from Mike Couldry) looks undamaged although it is around .190 thick, against the one that came of last year is .220 thick and a spare good one I have is also .220 thick. I would have thought at 40-50 lbsthe bolts would not stretch but maybe the material in the 30’s was not so good? Mike Couldry did suggest before I started the job either core plugs or stretched bolts any one got any other ideas?

Bolts will stretch especailly at that age and if you have the ally core plugs in the 4 they could well leak - only a pressure test will confirm this. Your bolts seem to have stretched though if tightened suffiiently in the first place and will do so gain and shear

I have about 3 full sets of original head bolts (also for a 12). Every single one is badly stretched. I don't think there is a lot of thread to spare at the bottom of the threaded holes in the block and it is possible for the bolts to bottom out, particularly if the head has been skimmed, as most probably have.

Also, if the head is off, check for any distortion (a steel 12" rule should be good enough) and check whether the stretched bolts might have raised the metal around the holes in the block by pulling the upper few threads.

When I last fitted my cylinder head I used cap-head (i.e. allen key) bolts. These have longer threads than standard hexagon-headed bolts (as do the Rover originals), and are MUCH higher tensile. I milled hexagons on the bolts which were to go under the rockers, so I didn't have to take off the rocker-shaft to tighten them, and I made push-on hexagon caps to go on the visible ones above the manifolds so that they don't look too anachronistic!

Thanks for the replies, I measured the bolts this morning and three look like they are stretched they are around 35 thou (roughy) longer than the rest, the head appears flat but may get a skim to double check. Like the idea of cap head screws. Plus I intend to get it pressure tested, it is a nuisance as the car is going really well. Oh the joys!

The length of the bolts might not be a reliable guide to whether they are stretched or not. The best test is to use a thread gauge, but you can often detect a stretched bolt by running your finger and thumb lightly along the top of the thread near the plain shank. If the bolt is stretched you may be able to feel the stretched area as a slightly 'waisted' section.

One problem I remember with the cap-head bolts is that they were not all completely straight. I think the threads must be rolled before heat-treatment and the bolts distort slightly. This would not be a problem, of course, if you were using them with a nut; but when you are fitting them through a close-fitting hole in a few inches of cylinder-head, if the thread is not accurately aligned to the shank, it can be difficult, or even impossible, to get the thread started. If you put a saw-cut in the side of a 3/8" BSF nut, put this in the vice, screw in the bolt and tighten the vice to close the nut until you can only just turn the bolt, you can use this as a test jig to find which way the bolt is distorted. This should enable you to straighten it well enough to fit easily.

Further to the last post I have bought new bolts from MC and skimmed the head although it looked fine, I also intend putting a flat plate with marking blue (engineers blue) across the head, it means removing the three studs (easy they have only been in there for 75 years). I appreciate that it is not as good as skiming the block but if the "high" spots show a less than perfect face it well may mean engine out....anyone for Lucky White Heather!!

It doesn't really need to be absolutely perfect! Engineer's blue and a surface-plate may be rather an over-sensitive test for an engine block. It will show up errors of half a thou or less, which are really of no consequence when the head gasket is as thick as it is on the Rover. If you try it you will probably find the block looks pretty desperate! Most likely the test will show high points round all the bolt and stud holes. It would be worth taking these down with a scraper, but make sure you don't get swarf into the bores, and as little as possible into the bolt holes themselves. Obviously you'll be looking for low points around the water passages. Again, a steel rule might be the easiest way of seeing how much of a problem there is, if any, but you need to be sure you hold it absolutely square to the surface of the block.

Hi the suggestion of a plate to test the top of the block was partly to see what the forum thought, mostly if this was a good idea for testing the flatness or not of the block. I have already removed the "crowning" of the stud holes with a countersinking tool. I also checked for flatness the block and the head and although both appeared flat, it was easy to skim the head. That has made impriovements to the areas around the waterways where 75 years of use have caused some erosion, as well as removing some scrathes that Ithought might be hiairline craks. Ideally the block could probably do with the same, but it is a big jod to remove the block (may come to that!!!) I have been delayed in completeing the repair but hopefully this week will see the replcement of the head and testing. Please feel free to offer advice or comments as I say there are no dumb questions only daft answers!

Well head is on and tested, the block was pretty flat although idealy would probably benefitted from a light skim (another day) if only to improve the sealing around the waterways, where as in the head light erosion has taken place over the 75 years. The one thing that this has taught me is use new bolts (advice from Stewart Devlin and MC) when doing the head and a "light" skim also of the head, my local machine shop uses a grinding machine so a few thou is possible. The problem is I have no idea how much is available to remove, I remember 60 thou coming of mini heads but then there are thousands of them around, not so Rover 12's, would be interested if anyone does know what is available safely to remove. Also what I have done is to connect the water pipes and test the head for leaks before finally fitting the rockers and boxing up the side covers, not assuming that with the head torqued down it will be sealed. Ideally putting a few pounds of presure over a couple of hours to test the integrity, would also be a wise move, although I assume that the main problem was the bolts. Thanks for all the advice and comments the only down side was I was unable to make the Lakes but next year.