Low compression

[heinkeljb]

Hi Jim,

Just had a look at the rocker box covers in the link you posted. They look very different from the one on my engine! The oil drain is different and would require alteration of the existing oil drain pipe to work. I am not saying that is impossible, just another thing to have to do.

I understand that the cover is only held on by one nut, but my point is that there is a huge amount of dismantling and cleaning to have to do in order to do what should be a very quick regular maintenance job!

I don't think there will be much more in the way of oil leakage than you get already from an engine that keeps being taken apart... As for the plugs, the ones i have posted are just to give an idea of what I am proposing to do. The thickness of the rocker box cover need not be a big problem as you can use some thing like chemical metal or even aluminium welding to make a suitable boss. The holes would be at right angle to the cover where ever they are made in the cover so boss would not have to be very think.

As for rotational forces being placed on the cover whilst undoing or doing up the plugs, I don't think that will be excessive. The plugs will have seals on them so will be oil tight. It is not as if the interior of the cover is under any oil pressure!
The oil return pipe would be more than enough to stop the cover from rotating unless you were very heavy handed.

I understand not everyone will want to alter things on their vehicles, but then not vehicle would change once the plans for it were drawn up if nothing was altered to make an object / task easier, better.

Still we will see what happens, I will see if i can get some better pictures of those rocker box covers.

John

[jhon]

John - I'm assuming that you have the access doors in the sides of your engine bay.

I set my tappets the other week through the side doors - two bolts to remove the cover and one to remove the rocker cover - literally less than 5 minutes; checking and setting the tappets took maybe 10 minutes each side. No need to remove any tinware; as my engine was relatively clean a quick blow over with compressed air prior to disassembly reduced the risk of dirt or dust inside the top-end. You have good access to clean around the rocker cover prior to removal.

Reassembly was easy too, with reasonable vision/access to feed the oil return tube back in to its hole without contamination.

I think that it is a good design - you should try it.

[heinkeljb]

I think it is a bad design just because of the oil return tube being bolted to the cylinder head!. That requires you to open two entrances to the engine, when it would have been so easy to design it with covers over the tappets.
I have worked on plenty of engines from the era of these engines. admittedly this is the first horizontal twin I have worked on - VW's are a flat four and the rocker box is held in place by a wire spring clip, but just the cover comes off - no other pipes...

Having a "relatively" clean engine to start with will obviously make cleaning the joint between the oil return pipe and crank case easier, but the left hand one is more hidden and more difficult to get to to make sure it is clean.

Sorry, I don't like the idea of just doing a "quick clean", pulling the rocker cover off, adjusting the tappets. Then spending time trying not touch the edges of the rubber seals on the crank case in case I dislodge even a small amount of dirt into the oil system. I spend enough on this vehicle with out having to do a major engine rebuild because the big ends are scored or the oil pump no longer pumps oil with enough pressure.

I don't dispute that undoing one nut allows you take the rocker box cover off and adjust the tappets - nice and quick like it should be, but it is the points raised above I am not so keen on.

On a connected point, what gap should I use? The repair manual states 0.15mm, the operators handbook states 0.20mm and in the fold out maintenance schedule, 0.15 and 0.20mm!

John

[jhon]

In my manual it states 0.15mm, and 0.20mm for 'tropical' conditions. That figures - in a hotter climate you would want a wider gap. So I set mine at 0.15mm and it seems fine.

John

[walderse]

John,
I think what may be throwing you off about the valve covers on the Puch500 website is that those covers have had a barbed vent threaded into the flat boss at the top of the cover. One cannot see the actual mating surface for the valve cover oil return tube. The seller is focused in on then vent.

If there is some question about other valve covers not fitting your engine, just use the pair you have. You know they fit already. Please keep us informed as to your progress and the end result. The final cost with all the machining is going to be interesting.

Best wishes.
Taek care.

Jim Molloy
Waldersee Farm
http://www.northwestmogfest.com

[heinkeljb]

Hi Jim,

I take it from your comments that the pictures on the Puch500 site are of the side opposite the oil return flange? That the barbed little pipe that is shown is an extra breather that has been added / there for the TR650 type car application?

I did not think the joint to the cylinder head was different, I just thought the barbed pipe adapter was INSTEAD of the oil return flange / pipe.

If that is the only difference in the rocker box covers, then I shall see about getting a pair in the new year to see if my idea for modifications is feasible on them without too much effort.

John

[Westernair]

Where in the manual does it say what the proper compresion should be?
I built mine with VW cylinders and pistons (Mahle, and chose a 8:1 compression ration which is giving me close to 140 PSI in each cylinder.
since the motor is new (couple hundred miles) I am just wondering if I should be worried about anything. She purrs like a kitten and cruises great. the dyno shows it at 29.4 hp at 4200 rpm. I did have to open the fuel jets up a bit with a jet needle file to get it is tuned just write.
Do any of you run a cylinder head temp gauge on your truck? I have a under the spark plug type VDO system I have thought about installing.

[heinkeljb]

I don't know for sure, but i seem to remember reading that compression for a standard motor was around 7.5:1 although 8:1 was mentioned. Maybe that was for later engine? Anyway, on a new engine I would expect the compression in terms of PSI to be higher than in an engine which has more than a few thousand miles / hours running time.
140PSI is very good, but to be honest, I don't think it will stay that high as you continue to run the engine.

In a normally aspirated engine, compression in terms of PSi is also affected by the ambient air temperature, which affects the air pressure. That's one of the reasons why turbo charged engine are needed when you run a piston engine at altitude. So it can be quite variable to quote PSI in a cylinder of a piston engine.

My engine currently shows about 115PSI in one cylinder and about 105PSI in the other - Yes, I would like those figures to be higher, but with a engine that as far as I know has not be taken apart since it was installed in 1983 as a new factory engine, I think those figures are quite acceptable.

I gather from your post that you put your Haflinger on a rolling road dyno? Have you got a print out of the power? If so, why not post it up? It would be nice to see how the engine manages to deliver it's power.

I plan on fitting a oil pressure and an oil temperature gauge as being relevant to running of engine. The only problem I see with a cylinder head temperature reading is that you have nothing to compare it against - how will you know when it is too high? Trial and error I suppose.
Oil temperature will show if you are near maximum that the oil can handle before boiling / burning / carbonising. Oil pressure also has known values which you hope your engine can produce all the time.

Any form of engine monitoring has got to be good thing if you can work out where the normal readings are - then when the readings start to move away from those "normal" readings, you know something is not right!

I think it would be an interesting bit of information about the running of the engine to know, so go ahead and fit it.

John

[Westernair]

Leo out of LA did my dyno pulls on his bench. I did not get the printouts but thought he sent me an e-file with them.
I will look and post if I find them

[Westernair]

No luck finding the dyno curves for the motor, though I will ask if he still has them.
He did quite a bit of tweeking on the motor, the 83mm pistons had to be shaved down to get them correct. That and some head work to open the chambers up and run a modified set of BMW valves.
The truck is in Riverside CA currently waiting for me to drive down and tow her home. With any luck I will make the pilgramage on the 17th of January if I don't find a reasonable shipper to tow it in the trailer home before then

[AustHaflinger]

I built mine with VW cylinders and pistons (Mahle, and chose a 8:1 compression ration which is giving me close to 140 PSI in each cylinder.
since the motor is new (couple hundred miles) I am just wondering if I should be worried about anything. She purrs like a kitten and cruises great. the dyno shows it at 29.4 hp at 4200 rpm. I did have to open the fuel jets up a bit with a jet needle file to get it is tuned just write.

My engine also Mahle cylinders - 87mm bores giving 762cc but I am not sure of the compression ratio but my numbers are close to Johns rather than your 140psi-.

I have had carby problems as the previous removed the Zenith 32NDIX and put on a Solex 34mm carby and it has not run right. I am about to put on a refurbished Zenith and it has standard jets with a 115 main jet but I am not sure these will be large enough for the enlarged engine.

You said that you had to open the fuel jets up a bit with a jet needle file to get it is tuned just write - do you have any idea of what the jet sizes now are?

Cheers

Garry

[heinkeljb]

This is the reason I don't like attacking jets with a file "just to make it work".

I know it is not always possible to have / use the correct replacement part(s) just when you need them so with the best will in the world there are times when you have to attack something and alter it.

It would be nice if it had been done with rejetting with known sizes so it could be repeated on another engine without having to "re-invent the wheel" again.

Gary, maybe it would be worth sending an Email to this "Leo" guy and ask first hand for info on Jet sizes.

John

[AustHaflinger]

Gary, maybe it would be worth sending an Email to this "Leo" guy and ask first hand for info on Jet sizes.

John

hi John - I was emailing Leo back in July and he seemed to think that standard jets in a the Zenith would be fine but comments on taking them out a bit more intrigued me.

The zenith is a big carb for such as small engine and indeed when the a Unimog 2.3litre 6 cylinder engine the same carb does not have all that larger jets (i have these jets) than are in the haffie version.

Re your compression readings - I have a good screw in compression tester and on my right cylinder I get 115psi and on the left I get 90psi dry and 110psi wet so I have about the same as you so your readings would indicate your compression is good - better than mine.

[heinkeljb]

Gary,

My compression figures are on the opposite cylinders to yours. I keep coming across references to High compression Haflinger engine which suggests there were at least some low compression or at least lower compression engines made.

Most mass market petrol engines seem to have compression ratios around 7.0 ~ 7.5 ~ 8.0 : 1. Those labeled as high compression seem to start at about 9.0 and go to about 13 as maximum when running specialist fuel for racing.

It's a shame they didn't go for a "multi-fuel" engine like those fitted to some Army vehicles! That would have made running a Haflinger a doddle!

I am really intrigued by the accounts of the expedition to the Andes which had Haflingers with superchargers fitted. I would like to find a suitable supercharger to fit to mine!

John