Restart after rebuild

[pharriso]

My First assignment out of Uni was in Quality at the Ford Dagenham Engine Plant working with Dover & Kent engines. Had to do things like dis-assemble, measure ,then rebuild & dyno test a Kent Engine. Plenty of Oil splashed about during assembly, then straight to the dyno & fire her up.

After 3 months at Avely I had 4 years in Engine Test at Dunton (Ford of Europe UK HQ.) again, no spin over with no spark before firing them up...

A significant difference might be that sometimes people wait weeks / months / years between rebuilding & firing up their engines?

[Emma-Knight]

I made a simple device - after undoing the oilfilter thread adaptor (it came out by accident with the filter) I fitted a standard hydraulic insert thread / tube adaptor, made a little oil tank that could be pressurised ( I used a spare clean eezibleed brake fluid pressure bottle which now is just for oil of course). Then a little air pressure (as the bottle allows) and turning the engine by hand, then by starter, the oil will fill the engine on the intended way, showing oil pressure on the gauge. In my case, I had to check this way as I had no oil pressure reading on a running engine. I found
the needle of the rebuilt dual gauge came loose on postal transport, just enought to slip on the shaft. A second pressure gauge revealed the
erratic readings.
But - a good point - start without pre-cranking oil.
Anna

[davidj]

Clever.

[Andy8421]

I'm not a mech eng myself (electronics in my case), but it has always seemed a good idea to get oil pressure before starting a rebuilt engine. Comments above about manufacturers may well be correct, but a production line may have hours or days before an engine is started after building, not the months (or years in my case) for a home rebuild.

There are firms who make a feature of pre-oiling after rebuild:

https://www.ms-motorservice.com/en/technipedia/post/pressure-oil-filling-on-reconditioned-engines/

and firms who sell products to establish oil pressure before each start:

https://www.merlinmotorsport.co.uk/knowledge_base_articles/view/accusump-oil-accumulators-how-do-they-work-281

and formula one teams who establish oil pressure before starting:

https://www.auto123.com/en/racing-news/f1-technique-starting-a-formula-1-engine-part-1?artid=157706

Overall, for the time taken, it seems like a good investment to get oil pressure before firing the engine for the first time.

[RichardHawkins]

When I dismantled my engine, It had been 35 years since it last ran, but there was still oil in all the crank bearing, cam bearings and followers. Whilst I expect that having pressure before starting does no harm I expect that none of the manufacturers of our everyday cars pressurises the system before start. None of my everyday cars has had a pressure gauge, ignorance being bliss I just start the engine, the oil light goes out and I drive, the very presence of an oil and temperature gauge provides something to worry about. If I remember correctly from my student days, it is the hydrodynamic pressure generated within the bearing that keeps the metal bits apart, the main purpose of the oil pump is to provide sufficient oil within the bearing for the hydrodynamic process to occur.

Hope this helps,

Richard Hawkins

[2cams70]

Overall, for the time taken, it seems like a good investment to get oil pressure before firing the engine for the first time.

It's actually quite a bad investment if you are spinning an engine over on the starter for a long period of time where the oil pump is not designed to provide pressure under these low speed speed conditions.

A simple Ford Kent based bears no relationship to an F1 engine. I'll bet they turn it over a lot faster than 100RPM to start it and the oil pump has completely different design parameters. It probably has lengthy internal oil channels, lengthy external oil pipes and coolers, maybe engine oil controlled hydraulic actuators all of which need to be filled before oil pressure can be achieved for the first time.

Yes it makes some sense to externally pressurise with oil prior to first start if you've got high volume internal parts that need to be filled with oil for the first time before oil pressure can be achieved - eg. 16 hydraulic valve lifters in a V8. That's not the case with a simple Kent engine.

Personally I've pulled apart quite few engines that have been sitting for years and there's still quite a good film of oil trapped between bearing surfaces so I don't agree there is a significant risk there.

I agree with a previous poster though - great idea to pre-fill the oil filter and good precaution to pour some oil over the cams because unlike plain bearings they aren't enclosed surfaces and therefore oil can run off.

[Hawksfield]

Well done 2cams

I have never had the Ba**s to post that, I only make sure all is lubricated and oil in the pump and fire up.
Always a bit nervous but always pressured up.
I am sure someone will post and say they had a disaster but that would be down to some other problem


Glad I am not alone

[Donels]

I have rebuilt several Kent engines and never managed to get any significant oil pressure by cranking prior to start. However, no pressure does not mean no oil. I always assemble the engines with Graphogen, prime the pump and fill the oil filter. Then give a couple of dead cranks and go for a live start. The pressure then usually comes up pretty fast. It just seems good practice to me.

If you've fitted a new cam and used cam lubricant I don't think you want lots of cranking before a start.