hello, i was wondering, im in the middle of rebuilding my engine and fancyd painting my engine,

firstly should i?
2 should i paint it asembled or the short block split
3 what colour should i chose, the cars the dark green.

 

i'd paint it split personally

as for colour, i'd say something contasting, red/silver........

 

Surely anything that stops the heat dissapating from the block would be a bad thing IMHO

 

Personally id only paint an iron block and that would only be for the purpose of rust prevention.

Its all so get it washed and leave it if i were you

 

Painted mine running 452bhp, no problems. I used Hammerite Smooth Aerosol.

 

hmm, mixed thoughts ai, i think ill leav the block and just do the inlet manifold.

 

LOL, I've done 30K miles on mine 452bhp at 1.5 bar.
Paint your engine, you'll be fine. This isn't specualtion. its fact!!

 

if you want to paint it get it painted wont effect heat at all only ceramic will

 

see P20SPD for some sexy engine painting, Steven did a project on 22b about it.
I think Cord also did a Noddy paint job on a rather quick Datsun

 

The alloy block on a Subaru engine is a heat sink and should not be painted.

Anyone that has painted their block is distinctly ' Getting away with it '

Not the best idea in my opinion.

David APi

Midlands agents for Simtek; the most exciting new Ecu for years

 

I find the main problem is trying to keep it scratch free on the install

 

i have seen plenty companys that rebuild these engines paint them silver before they sell them on

was planning painting my cdb but dunno what to do now, i have painted many of my engines without problems.

 

I have to disagree with you there David, As I've painted two engines now. One was a forged 2.0L running around 400bhp which did 20,000 miles before I sold it on in favour of a 2.5 (452bhp) which I also painted and did around 30,000 miles before that too was sold on. Both are still going strong and are still the colour I painted them.

You'll also find that there are plenty of high revving alloy bike engines that have been painted and run alot hotter than the subaru lump. Again these seem to be problem free.
I'd love to hear of examples of failures that have been attributed to painting

I cannot for the life of me see how a couple of light coats of hammerite smooth from an aerosol can be deemed harmful.

Cheers

Daz

 

You missed my point:

Anyone that has painted their block is distinctly ' Getting away with it '

Maybe I should have added Subaru and alloy to keep it in context, but nothing changes.

David

 

by reiterating a previous point in red David you are hardly backing up the statement, I'm also intrigued about any potential issues

 

I've not missed your point David, you've not quantified the point you're trying to make.
Also both the blocks I've mentioned were Subaru alloy ones. Myself and countless others have painted these Subaru Alloy blocks running subastantially over standard power (thus generating far greater heat) without issue.

Please give examples where an engine has failed due to it being painted.

 

Well I've just painted my CDB silver and it looks wicked. The bare alloy can get grimey beyond what cleaning up can achieve and it only needs one coat of engine enamel to come up tasty. TBH I did wonder about whether it would affect the heat retention but then figured it's a water cooled engine with a radiator - it can handle a thin coat of paint.

 

The manufacturers go to great lengths to determine optimum cooling under the bonnet. That includes water capacity, rad capacity, incidental cooling [ Heat seepage through rubber hoses, alloy manifolds, cylinder blocks and so on ] that determines the size of radiator required to cool the engine and also the diameter of the hoses moving the water around the engine bay.

So, if they can gain cooling capacity without paying for it they will. If the block is left unpainted it will dissipate heat quicker than if the heat is partially sealed in by paint.

If they can reduce the radiator size by one row it will save X pence per car. That mounts up.

If the water/inhibitor quantity can be reduced by a pint that saves on production costs too.

It isn't just chance that a car with an alloy block has no paint on the block, it is a cost / efficiency equation that the manufacturers explore fiercely.

By painting a non painted block you are reducing the efficiency of the heat soak, thus reducing the safety margin of cooling versus overheating.

Nobody bothers much with changing rads on a 2.5 conversion; sure the block is about the same size as on a 2.0, but the heat generated by an engine 25% bigger in cylinder capacity is greater. Therefore the safety margin is reduced, Paint the block and the safety margin reduces yet again.

Take off the plastic undertray and ruin the carefully calculated under bonnet aerodynamics, which have an effect upon cooling. Not just of the water but the oil and the gearbox and so -on. The transmission tunnel needs to be there to have somewhere to put the gearbox, BUT, it is a venturi to funnel cooling air down to cool the gear box.

Take off the undertray and the air spills all over the road surface and is no longer going where Subaru want it to go. That will effect the oil temperature in the engine which has a knock on effect of transferring more heat into the block, making the water temp rise.

All of these little things add up to a loss of cooling efficiency, making it more likely that when an engine overheats, due to the reduced safety margin it happens much more quickly than it was designed/calculated to do.

Simple really, it just needs thinking about.

David

 

have you had any cars engines or know any that have failed then down to painting them?

 

David, all that looks great written down.

The reality is most people running big power with painted engines dont have a problem, now you've thrown in Rad size and undertray into the equation.
Once again most of these guys are doing exactly what you've said not to do are running 2.5s with 2.0L rads, six speeds and no undertrays and painted engines without any issue whatsover.
Is there really a need to over complicate things for people wanting to go down this route?

You've also still not given your statement about getting away with it any substance.

 

Nuff said, I have been around motor racing and competition all my business life. There is a well known saying in motor racing

" It is either right or wrong "

In the case of a Subaru cylinder block - painting it is wrong.

I'm gone now, won't be back.

 

so can't say if you know of any failers down to painting the block then?

and saying you wont be back sounds like a bit of a cop out to me

 

It's not really worth falling out about guys is it?

Both camps have perfectly reasonaable and correct arguments. David is completely correct when he says it's wrong. It does not take Einstein to work out that from a purely theoretical standpoint it won't help, so if you want to get everything absolutely efficient as you can do (for example a competion engine) then don't paint it. Indeed i have stripped crankcases and heads of powder / wet paint when the rules allow it on competion bike engines. can't say it makes an appreciable or measurable difference, but it HAS to make a small change in the correct direction.

Safety margins have also been talked about, and it's plainly clear that the tiny diffference a coated engine will make to oil or water temps is not going to push an engine over the edge, if you are that close you should be looking at things other than a bit of paint on your engine.

Of course no-one can say a painted engine caused a failure swifty so i don't know why you are pushing it. You could say "i had a big end failure due to high oil temps" (although thats almost impossible to say without some data that won't be avaliable anywhere other than the most well equipped test cells) and point out some things that could have been contributing factors but thats about your lot.

If you have a race car and want everything optimal (wieght included as paint ain't light), don't paint your engine. If you have a road car (or even a race car) and want everything to look pukka then paint it, it's not going to do any harm as proven by countless cars of all types.

The 'paint it' school could also argue that painting it could actually help combustion temperatures by not allowing as much heat conduction into the underbonnett area where you may well have an induction kit, but thats probably as stupid and inconsequential as the argument that painting your engine could cause a failure.

 

I don't think anyone's falling out. This seems a fairly sensible debate for SN.

What I cant accept is David's very bold yet unsupported statement that people with painted engines are narrowly "getting away with it" meaning that they could self destruct at anytime.

I do agree that its probably not thermally efficient to paint them but that's not the discussion here.
I cannot and will not accept that A subaru engine will self destruct simply because its painted. To say so is complete and utter rubbish!

 

p1mark

the point i was making about asking if he'd had any engine failers down to it been painted are because of his statment saying

"Anyone that has painted their block is distinctly ' Getting away with it ' "

now that statment to me means paint it and your asking for it to fail which is pure rubish!

we all know if you paint the engine the temps might be affected slightly if at all and you'd soon see if this was the case if you have oil and water temp gauges i'm sure daz can answer that.

but the main thing that got me was david saying your "distinctly Getting away with it" as if a layer of paint would course an engine failer by upping the temp massively now if that was the case dazs engines would of both failed which they haven't.

also if paint was that good to add that much extra heat everyone would paint there headers and exhaust

 

I believe a thin layer of Black paint will aid better dissipation of heat. Its to do with emissivity in Thermodynamics. It will however be very small in comparison with what the cooling system's water and radiator already do.
Thick paint in lighter colours wont help.

 

ooo ek, i didnt mean to start a argument, sory, iv decided to stick to painting the inlet manifold and the water cross over.found some heat resistant paint the same colour as the car.

 

" hey is this your coat "

 

im bit of a novice to this but was that hard to take off the inlet manifold?do need any thing else other then some tools?

 

new gaskets