Engine top shroud/cover

[StuartR]

Can some one please enlighten me as to the different versions and what models/when they were applied to?.

As far as I can see there several versions, one without air intake

One with

The Invacar version

I assume that the version without is the earlier version, and maybe a military one as well, and the version with is the later version that has an air intake pipe that is routed to the gap in the rear engine flap?

[pathfinder700ap]

Stuart,

it's not an air intake, but an exhaust. The engine version with the exhaust has the large oil cooler and more shrouding inside to guide the air which is going through the oil cooler to this exhaust.
The versions in your top and bottom pictures don't have this hot air exhaust. The air that is going through the oil cooler just moves on to the LHS cylinder and is then exhausted. Top and bottom pictures show engines with small and large oil cooler, hence the difference in the covers.

Regards,
C.

[StuartR]

Constantin,

Thanks for the clarification, I was sure you would know.

So the next question is what are the differences in size on the oil coolers? I have the Shroud with the Exhaust tube on the engine it came with which I believe is the DHSS based on the mounting hoop and the exhaust. I assume this was fitted when the engines were swapped.

The other two engines have no shrouds one is Haflinger the other another DHSS, the oil coolers and my spare, are the same size:-

246x53x70mm is this the small or large?

All are marked LR and one with a date code of 03/67 clearly stamped in the outer plate.

I assume that the shroud with the Exhaust tube would be the better option?

[pathfinder700ap]

Stuart,

Prokschi has some cutaway oil cooler models on his website, see:
http://www.puch500.at/?action=schnittbilder

The taller one with round ends is the "large" oil cooler, while the one with the "roof" on top is the older and smaller version. For your Haflinger, the large one and the shroud with exhaust should be original.

There are different opinions about the oil cooler systems. Some claim that with the oil cooler exhaust system, the LHS cylinder gets less cooling air due to the smaller channels along the sides of the oil cooler and that the cylinder is hence getting hotter. On the other hand, I am not sure if SDP would have introduced that system without thinking properly about it and without intensively testing it. Also, in my opinion, it might be, that the cooling fins of the cylinders/heads produce a flow resistance that grants a good equal distribution of the air anyway. It's really hard to tell without having measured or simulated anything.


Kind regards,
Constantin

[StuartR]

Constantin,

Thanks for clearing this up for me, now its back to the drilling, cutting and welding!