Posted Saturday, November 22, 2008 @ 08:44 PM  

I have now had the cylinder heads off WGN three times, and ground in all the valves to improve its compression.
I have even fitted the copper rings between the cylinders and heads. Yes, I know they're only appropriate to the earlier engine, but they did actually make a significant improvement in its compression.

We have been using the very same propeller, the aeroplanes both weigh almost the same, with the same center of gravity, and they both have the same drag-reducing mods. Both ASIs have been calibrated. The are both 1400s, with the original carburetor and they both have the correct valve gaps and ignition timing. I have swapped carbs, but WGN is still down on performance. It does not appear to have a three-angle valve seat cut, but then I am not sure whether HDO has a three-angle cut, nor whether that would make so much difference.

After investigating everything I can think of, I can only assume that the difference (100 feet per minute in the climb) is caused by the camshaft. Red WGN's engine is not an original Rectimo, although blue HDO's is.

Unfortunately, I can't see the camshaft part numbers without dismantling both engines, which of course, I don't want to do.

We are going to build up a spare/replacement engine for WGN, so we want to be sure to fit the correct camshaft.

A British VW expert suggested that another expert, Barry Smith had discovered that a particular (early) 1200cc camshaft works much better in the low-revving engines than any other, but was not sure which one it was.

Another guy said 'use a van cam'.

Barry also said 'Many years ago we used to regrind standard cams to increase overlap and duration. The ACRO cam was 20-60-60-20 but comparison is almost impossible as cam manufactures all measure differently.'

Matthew has a spare camshaft, bought twenty years or more ago for a Rectimo. Embossed on it are: 113.109.111A VW H4. Lift is from low of 30mm to high of 37.2mm (7.2mm), although not measured too accurately.

A local expert here in Australia got me what he said was the best camshaft. That has three rivets holding the shaft to the gear wheel, and the numbers 113.109.111A VW1 on the inside face of the cam wheel.
On the shaft itself are: VW 37 113.109.101B 41. The lift is 7.5mm, but the lobes seem very 'pointy' to me.

Here is a photo of one of the lobes, but it seems too pointed to me. Not much overlap, so presumably not so good for a low-revving engine I would think. Somebody else has told me that this looks like a 1500 cam, and is not correct for our 1200s.

I wondered if anybody can tell me which is the best camshaft for us to use for a low-revving (3,000 to 3,500 rpm) high-torque 1400cc motor (either by part number, or by date & engine model)?

Posted Sunday, November 23, 2008 @ 08:17 AM  

Thank you very much for your quick reply.

I have not removed the heads from HDO recently, but it is a completely standard Rectimo except for the 1400cc (83mm) Cylinders & pistons, the same as WGN. I did not remove WGN's cylinders, because I did not want to replace the rings and break in the engine again, but there is no blow-by (no excessive breathing) so I guess the rings are probably correctly installed. Also the compression is now very similar on both aeroplanes.

I think the valves are also standard on both aeroplanes, certainly HDO, the better performer, has standard valves in its 40 year-old heads.

But HDO (the blue one) accelerates noticeably more quickly on take-off and climbs 100 feet per minute better. Also it flies quarter upward rolls at lower starting speeds. All I can think of, after eight months of investigation, is that they have different camshafts.

HDO has the original Rectimo camshaft, and I reckon that is probably the best, if it was a standard 1200cc Beetle camshaft, designed for good torque at low rpm. But, of course, I do not know the part number, nor whether I can still get one.

Posted Sunday, November 23, 2008 @ 09:26 PM  

That's just a clue.

Posted Tuesday, November 25, 2008 @ 04:29 AM  

Sorry, I of course forgot to look at this yesterday, but luckily we have plenty of time to spend

I totally had a wrong idea concerning the cam. The part number seems to be VW 113.109.021D. Or the first two parts seem to be the same.

My manual states that the cam has following values of valve openings and closings. It doesn't give any detail about lift or rocker arm ratio, though:

"Functioning of valves with 1 mm clearance (which seems a bit rough for Rectimo)

Intake valve opens 6º before top dead center
Intake valve closes 35º 30´ after bottom dead center
Exhaust valve opens 42º 30´before BDC
Exhaust valve closes 3º after TDC"

Engine types 1/1300, 1/1500, 2/1600, 3/1500 and 3/1600 seem all have similar cam with values:

Int open 7º 30´BTDC
Int close 37º ABDC
Exh open 44º 30´ BBDC
Exh close 4º ATDC

and 4/1700 has following values:

Int open 4ºBTDC
Int close 39º ABDC
Exh open 40º BBDC
Exh close 3º ATDC

My manual has lots of important information. It is a shop manual from 1969 and has been accepted by CAA Finland for Rectimo overhaul manual. Unluckily it's in Finnish, so I won't bother to scan it for you

-A-

Posted Tuesday, December 2, 2008 @ 09:13 PM  

Here is the lift of a std 1963 40hp cam. Part number 113 109 101 C

Intake cam lift 7.60mm (.299" )
Exhaust cam lift 7.10mm (.279" )

Intake valve lift w/1-1.13 rocker 8.69mm (.338" )
Exhaust valve lift w/1-1.13 rocker 8.02mm (.316" )

Posted Wednesday, December 3, 2008 @ 12:42 PM  

I am not sure if the std 40hp cam is best. I will compare it to a std Rectimo cam. I am currently running the std Rectimo cam with the 1-1.13 rockers in N2182. I have some 1-1.25 rockers to try.

Here is a cam card from a special cam grind for fuel economy. Designed by Jon Karcey in the '80s. He was getting good power at low rpm and 56 mpg.