Engine Block Replacement

[cwchrisp]

Hi All,

I had contemplated building a replacement 2-bearing engine for my RM.

I am now thinking of setting my sights a little lower and maybe replace the block, pistons and top end of the engine to reduce oiling plugs etc. I already have a replacement block rebored and honed to +40 thou. with standard new pistons to suit.

Is it practical to remove engine from the car and seperate block from crankcase and keep all the "tricky to get tolerances right" parts like crank, cam, white metal bearings etc. and replace the pistons, block, valves etc? (assuming no untoward damage is found down there)!

Sorry if this is a stupid question and I have overlooked some fundamental reason why this can't be done !

Chris

[bob46320]

Fitting new pistons will hopefully increase power output, putting extra load on the bottom end. How sure are you (without inspection) that the bottom end will cope ?

[Greig Smith]

Yes it's entirely feasible, but be warned that it's a bit like working through a toilet seat with the engine still in the car

I honed the block on a friend's Ulster rep by doing just that, except I pulled the pistons & rods out to inspect the bearings as the car was a brand new unknown quantity in his life. Successive previous owners had tried all sorts to fix oiling plugs & all threw in the towel. In this case it was highly glazed bores due to wrong firing order & a hopelessly over rich SU. Bottom end was excellent, so I put the rods & pistons back in their original positions. We did a bunch of other stuff to the car from brakes to steering arms & track rod as well as re-shaping the clutch & brake pedals to suit the lowered seating position. Had to re-weld the exhaust manifold as well

Diagnosis was spot on, he went from oiling up new plugs within half a mile to a full day of belting it up the hill at Simola 3 weeks later & he's done several hundred miles since.

Probably worth it to give the bores a light hone while the block is off & you will likely want to discard the tin oil cups as they are not really necessary and a swine to position when dropping a block onto an engine in a car. Good time to go with a silicone block gasket from one of the cherished suppliers.

Plus he's my main opposition at the hill climb.... 

Aye
Greig

[Chris KC]

I would try to establish what is causing your specific problem then fix that.

Bores can readily be inspected / measured (at least you'll get a good idea) with the head removed (which is easy); as can valve guides.

If worn / poor condition you know what to do; if good your attention might turn to pistons and rings which on many cars can be removed without taking the block off. Rings are sometimes fitted upside down which might well cause oiling issues.

Are you sure you have the right plugs? Have you tried a compression test?

Not saying 'don't do it' but be sure of the reason to do so or you may find yourself back to square one again.

[Martin Prior]

I remove engines routinely and as a matter of course, even for quite minor work. It's much easier in the long run.

[cwchrisp]

Thank you all for your contributions to my question.

I was intending to remove the engine, after reading a previous post regarding the pros and cons of insitu versus engine removal.
Thanks for the pictures and the thoughts on loading the bottom end with more powerful top end.

I have inspected the pistons previously and the block is at +60. I have used hotter plugs (D21). Compression good.

This will be a winter job (or lockdown) and I wanted to know if leaving the bottom end as is, but replacing the block, pistons etc was a) possible and b) advisable.

I guess its a case of 'if it aint broke' for the bottom end but happy to swop over my refurbished block and new pistons. I have limited facilities for getting alignment and tolerancing right with when it comes to bearings etc.

[John Mason]

I removed the block, pistons and rods on my Ruby leaving the crankcase in the car. The main reason I had not long had it re spayed and did not want to remove the cowl, valance or radiator. From under the car remove the sump and big end caps noting there place for re assembly. The block can then be removed after all other stuff has been removed. The pistons come out with the block and can then be removed. Assembly is a reverse procedure.

John Mason

[Reckless Rat]

Whilst it is possible to do this with the crankcase still in the car, it is SO MUCH EASIER to take the engine (and/or gearbox) out of the car and do this on the bench. I can get the engine and gearbox out of my RP in less than an hour. Having recently rebuilt the top half I can testify to the fact that doing it on the bench is far less difficult ( for me at least) than crawling about under the car. In particular, when fitting the block to the crankcase with a new silicone gasket cleanliness is very important in order to avoid leaks. The joint must be clean and dry. You will find that retightening the block holding down studs and resetting the tappets is also a lot easier.

If using a silicone gasket, tighten it down and leave it overnight and then check again before removing any excess material with a stanley knife.

As Jack Reacher says. Do it right, do it once.

[Colin Wilks]

As you are taking the engine out I think it would make sense to remove the conrods and then remove the pistons using the plugs detailed in Woodrow. I am on with this job on my RP at the moment and I am not convinced I could remove the little end clamp bolts with the rods in situ without the possibility of bending a rod. Removing the rods also allows you to check for cracks and to check the state of the white metal and the big end journals. As a matter of course I would replace the big end bolts along with new nyloc nuts. While they're out it would be good to weigh each rod to make sure they are all the same weight. One of mine was about 20 grammes more than the others, another rod was tight on the big end and I was lucky not to have run the bearing, and yet another was scrap due to a two inch crack, so they do merit close inspection!

[Alan]

I agree. If you don’t do it properly why bother? Interestingly, I reckon about one in every three rods I look at is cracked at the pinch bolt slot.