Engine rebuild Full strip down or partial?

Right after finally getting round to lifting out the engine. I’m now pondering on whether to strip right down to block replacing bing end bearings, piston rings etc. 

The car is restoration project so has been sitting for 2 years, 1 year was prior to me owning! I have no service history either.

My only area of concern/ caution is it‘s 1989 eunos with short nose crank, it has 97000 on the clock. 

So my question is with how much work i’ve had to do so far with getting the engine out, do i continue and strip right down and replace these parts or leave so don’t have to mess with crank bolt! 

prior to engine being removed i did a compression test, readings were fine when checked in Haynes manual with varying between 11-12bar over the 4 cylinders.



A full strip down and say rebore but you should get away with new rings and have the bores honed with all new bearings and Mazda genuine gaskets could cost well north of £500 to say £1,000.Your compression is say 50% between worn and new at 90k miles.

The problem is you want the cylinder head off and the sump off, then check the bores and crank and you may as well just replace everyting by that time.

How much oil does the engine use per 1,000 miles?

Is there an oil pressure issue, what is the pressure when hot after a hard drive?

No correct answer here but unless it is broken, why fix it?

As long as you replace, not re use the short crank, crank bolt and tighten to the lesser torque for the short crank engine and the crank pully does not have any wobble, then not an issue.

I would be tempted to put it back in after doing the cambelt and any other easy to get at bits replaced while it is out the car.

Just more questions than answers.

You will replace the clutch pressure and driven plate and the release bearing and the spiggot bearing when it is out the car I assume!!!

Had already planned on getting head off to replace the head gasket, though wasn’t sure about a skim and bore, will check the condition first to see. 

Unfortunately, since owning, I’ve never driven the car more than in and out of the garage! Due to no MOT when brought. 

oil has surprisingly remained consistent.

When idling pressure has been around 2-3 on the gauge. 

Had planned to replace both crank bolt and woodruff key if do go down the route of stripping all out. 

With the clutch, yes am replacing the lot and am currently seeking to get flywheel resurfaced too. 

Just don’t want to get back on the road in say 6 months then have 2month later problems that result in engine requiring to be removed again.

Might be worth swapping the Eunos flywheel for a UK spec 1.6/Mk2 1.6. The Eunos flywheel is significantly heavier than Euro 1.6/Mk2 1.6, which both used a flywheel used by Mazdaspeed/M2-Inc. Used flywheels are peanuts from Autolinkuk. Allows the engine to rev more freely.


You have got things a bit the wrong way round.

What are the issues with the engine.

You have not used it in anger and do not know if it uses oil or does not hold it’s oil pressure when hot.

I guess you have no real idea if it overheats or uses water as you have only driven in and out the garage, or if it has a blocked radiator.

Yes a 30 year old cylinderhead gasket can fail but if you go that far you need to get the head checked for flatness and while the head is off you want to get the bores inspected by a trusted machine shop to advise you on possible bore wear that may or may not be an issue.

The oil pump pressure relief valve can stick open and wreck the engine.

I can only advise that the only real way to sort the engine that may have a fault or may not, is a full strip, check and replace worn parts or not.

We have no idea what is worn, therefore either go the full way at say £1,000 or just do the head and clutch and assume everything is OK.

It can get to a point when you are spending too much on an old car or you are investing in the long term use of a nice car for the next 5 or 10 years.

Only you can decide on that as I said “no correct answer”.

I would change all the clutch bits and say get one of those lighter flywheels. A new cam angle sensor seal and change the cam belt that can be done with the crank nut in place.

The rest is up to you but it can get expensive and you will never get the money back you spend on those parts and services.

Good Luck with the refurb!!!

Hi Wolfeman

The general advice with this engine would be to leave the internals well alone.

No expert on full engine rebuild but guess we are talking big end shells, piston rings, bores, gaskets, valve seals, etc, as well as valve regrind, cambelt/waterpump change, etc

It’s a lot of money and time so the risk of an issue with the short nose crank bolt is too much I would say.

At the moment you have a £200? engine but with rebuild could easily be a £1500 engine - too much money to place on that under engineered crank bolt solution that has caused too many previous issues. 

Having removed the engine I would be seriously tempted to replace it with a good long nose crank, 115bhp engine. If you are going to rebuild that is the engine that you are better advised to spend the money on. Important to assess these engines on use to identify adequate power in use, oil burn, etc.

Here is an interesting engine spec sheet from the Mellens website. It’s a 2005 car but you get the idea of what is termed worn and difference allowable between cylinders. Was your compression checked cold or hot? - this does make quite a difference. 

I would not touch the main crank bolt on a short nose engine. It is possible to do the cambelt as the pulley can be split without undoing the main bolt.            

Had planned originally planned, seals gaskets and pumps etc to repair, but was curious as to whether do rest while at it!  know is always the risk with a short nose crank bolt. 

I have done quite a bit of research into short nose crank and am aware sweet spot seems to be 87 ft lb torque and should continue to run fine. so would like to hold on to the engine, but I am aware the risk will always remain. 

The Engine spec you attached was interesting to look through, thanks for that  

The compression I ran was on what felt like a hot engine! probably warmed up quicker due to thermostat sensor being rusted in the closed position