Hi Mike,
At first I thought it was weird to do so as well, but on consultation
with several engine builders, engineers, and general muscle car types, I
found that this is a very common practice. I am told that every 426
race hemi came from the factory this way. Keep in mind I say Race hemi,
not Street hemi, though this was often a hemi racers first mod when
racing in street class drags in the 60's. There are several
manufacturers out there that manufacture paints specifically for this
purpose. I personally use Rustoleum (not hardware store variety, but
the specific stuff you get at a good auto parts store.) So here is why I
do it. By painting the inside of the block you allow the oil that is
being flung around inside the engine to return to the pan much more
quickly. This is because the oil no longer has to flow over the porous
surface of the cast iron, it is moving over the slick surface of the
paint. Now I know you are asking what benefits this has. By returning
the oil to the pan more quickly you decrease the amount of time that is
required for oil to cycle though your engine and therefore the amount of
time for it to reach the rotating assembly, and you decrease power loss
though windage (oil sloshing around inside the engine and interfering
with the rotating assembly). This is important when running a high
volume, high pressure pump. An added benefit is that the oil does not
collect as much heat when it returns quickly, less heat equals more oil
pressure and a cooler engine equals more power. I know I don't have to
tell all of you why heat is bad. All the engines I build now are
painted on the inside and run a good 5-10 degrees cooler than without
this simple modification. If you do this, obviously don't paint the
machined surfaces of the block, just the cast areas and keep in mind
that you should also remove any casting flash in the block before
painting to further smooth the oils return to the pan. I know someone
who goes as far as to polish the inside of his blocks before he paints
them, but he runs a Blown Alcohol-injected Hemi. Removing the flash and
painting the inside of the block are a simple modification that yields
good benefits without a lot of cost.
Mike Sealey wrote:
> --- cpollock@xxxxxxxx wrote:
>
> > Yes, I have tried it on the block and tranny. I
> > specifically tried it on the inside of a fresh
> > clean block and on the inside of a fresh clean
> > tranny case. Apparently there was some
> > contamination, because none of it stuck on
> > either pieces.
>
> I have to be missing something here. Why did you paint
> the inside of the block and tranny case?
>
> Seems like whatever contamination may have existed
> before painting would be nothing compared to the
> contamination level after painting...
>
> =====
> Mike Sealey, San Francisco CA
> '57 Plymouth Sport Suburban
>
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