Just talking about VWs

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TFF

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High flow heads for the flow hurts at airplane propellor rpm. Look at ports on a Lycoming O-360 and a Chevy 350. They are close to the same size. But wait the lycoming is only 4 cylinders and the other is 8, Hummm. It's the RPM flow need. The potential for the Chevy to rev needs the ports to be big enough just in case. The Lycomings are capped at low RPMs. They would be huge if you needed to spin a 360 ci 4 cylinder engine 6000 rpm. The VW is the same. Never rev it over 3000 and you are probably loosing horsepower with big ports.

I do have to disagree about valve angles in a mild way. I have cut many mono angle valve seats knowing I'm doing it wrong. All Lycomings from the beginning of time have had 3 angle valve jobs. They just don't call them that. Cars too. When valve seat cutters came out that could do it in one swipe, they had to honk their horn about "new " technology. The other works ok but efficiency wise droplets of fuel stay in suspension better. Will the other work, of course. Most of this stuff is talking one to five percent differences in efficiency; only a dyno can tell. Your butt can't.
 

wanttobuild

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Well....
The 3 angle cuts in the valve seats in the case of the exhaust valve stops gas from flowing. It creates an airtight seal so the chamber can build compression.
It cools the exhaust valve when seated. It is not a waste of time.
Hydraulic lifters provide a "cushion" to allow a valve that is heated and stretched to still firmly seat.
I am pointing this out because I have read fifty posts on about high head temps.
Sodium filled valves are also available.
If I can get the plans for the a.c. I want to build, it has a pretty high Vne, so I will probably be turning 3000-3200.
The VW aircooled engine requires a compenate person to assemble, maintain and operate.
All of the info that I have read points to the fact that many are operating on the margins.
Ben
 

pictsidhe

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Wider seats give better cooling. Beryllium copper seats are used in some race engines as they have much better thermal conductivity than stellite, yet last well. Beryllium is toxic stuff, so finding a machinist is tricky. Probably not advisable to lap them, yourself, either. I've also seen Aluminium Bronze seats used, but I don't know how well they held up. Maybe someone could fit a single Al-bronze seat to a VW and see what happens.
I think some older bikes used Al-bronze heads. That was way back in the high lead days.
 

Hot Wings

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The hardest part of doing that on my 914 is getting the danged clips off the valve covers.
Wrap a shop rag around the center of the wire - and yank. A big screwdriver or pry bar helps with the return. A little contact cement on the gasket - if you don't have the valve covers with a dimple - keeps them from creeping out of place. Works on Tp 1s too.
 

rv6ejguy

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Well....
The 3 angle cuts in the valve seats in the case of the exhaust valve stops gas from flowing. It creates an airtight seal so the chamber can build compression.
It cools the exhaust valve when seated. It is not a waste of time.
Hydraulic lifters provide a "cushion" to allow a valve that is heated and stretched to still firmly seat.
I am pointing this out because I have read fifty posts on about high head temps.
Sodium filled valves are also available.
If I can get the plans for the a.c. I want to build, it has a pretty high Vne, so I will probably be turning 3000-3200.
The VW aircooled engine requires a compenate person to assemble, maintain and operate.
All of the info that I have read points to the fact that many are operating on the margins.
Ben
Only the one angle of the seat seals against the valve face. The other two angles are to narrow the seating face to the correct width and place it in the correct place on the face. I don't know why people proudly say "it has a 3 angle valve job", well pretty well every engine ever built does from the factory. So...

Oil is incompressible in a lifter. Hydraulic lifters take up clearance in the valvetrain caused by the expansion or contraction of parts with heat. Good idea on many engines not really needed on others. VWs are easy to check. Keep it simple and light.

High head temps in VWs are a result mainly of not enough cooling fin area for the sustained hp some folks want to develop but can be managed with attention to detail as outlined in the response from Peter last week.

Sodium cooled valves are less reliable than solid valves, not needed in this low hp application.
Some auto OEMs introduced sodium cooled exhaust valves on turbo models and later ditched them after failures, going to Nimonic or Inconel which are pretty bulletproof in this application. If you want to spend the money, you can have Inconel valves.
 

Pops

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Only the one angle of the seat seals against the valve face. The other two angles are to narrow the seating face to the correct width and place it in the correct place on the face. I don't know why people proudly say "it has a 3 angle valve job", well pretty well every engine ever built does from the factory. So...

Oil is incompressible in a lifter. Hydraulic lifters take up clearance in the valvetrain caused by the expansion or contraction of parts with heat. Good idea on many engines not really needed on others. VWs are easy to check. Keep it simple and light.

High head temps in VWs are a result mainly of not enough cooling fin area for the sustained hp some folks want to develop but can be managed with attention to detail as outlined in the response from Peter last week.

Sodium cooled valves are less reliable than solid valves, not needed in this low hp application.
Some auto OEMs introduced sodium cooled exhaust valves on turbo models and later ditched them after failures, going to Nimonic or Inconel which are pretty bulletproof in this application. If you want to spend the money, you can have Inconel valves.
Very well said.
 

revkev6

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does anyone put oil sprayers for the valves on aircraft vw's??? this helps pull the heat out of the valvetrain. We used them on our race motors.
 

Vigilant1

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I need to find the graph on the difference between single port VW heads and the dual port VW heads. Below 3000 rpm the single port produces more torque and above 3000 rpm's the dual port heads are better, But I cruise my VW below 3K so the single port heads are the winner.
I'm working from memory here, but I think we previously found some indications that the dual-port heads might be needed in the bigger VWs even at aircraft RPMs (e.g. 3400 max). Maybe we looked at what Sauer had done? I think the crossover point was 1900cc or so. Single ports definitely do a better job of fully filling the cylinders at the smaller engine sizes.
 

Topaz

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Wrap a shop rag around the center of the wire - and yank. A big screwdriver or pry bar helps with the return. A little contact cement on the gasket - if you don't have the valve covers with a dimple - keeps them from creeping out of place. Works on Tp 1s too.
Oh yes, I know. Still bang my knuckles every time. "It's not a project until you shed some blood." :gig:
 

revkev6

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I'm working from memory here, but I think we previously found some indications that the dual-port heads might be needed in the bigger VWs even at aircraft RPMs (e.g. 3400 max). Maybe we looked at what Sauer had done? I think the crossover point was 1900cc or so. Single ports definitely do a better job of fully filling the cylinders at the smaller engine sizes.
given cam specs, RPM range and cylinder volume the CFM requirement can be calculated easily. also runner length to tune the torque curve can be set.
 

Pops

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I'm working from memory here, but I think we previously found some indications that the dual-port heads might be needed in the bigger VWs even at aircraft RPMs (e.g. 3400 max). Maybe we looked at what Sauer had done? I think the crossover point was 1900cc or so. Single ports definitely do a better job of fully filling the cylinders at the smaller engine sizes.
Yes, you are right. But even running a 2180 cc engine, I would rather used the single port head so I wouldn't have the crack head problem with the dual port heads. Anything over that, I would use the dual port heads and deal with the cracks. Be sure you don't get a 1966 , 1300 single port head with the same small valves as a 1200 cc , 40 hp engine. Just made the 1300 in 1966 in the U.S.
I'm using single port heads on the 2180 cc, flywheel drive that I am building.
 

samyguy

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So, I'm just jumping in with dumb question.
I have a 2180 with a redrive on it. Take off rpm is 3600. Max 4000 in dive
Would single port heads work for this? If so, what size valves should I have installed???

thanks POPS Calvin
 

Pops

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So, I'm just jumping in with dumb question.
I have a 2180 with a redrive on it. Take off rpm is 3600. Max 4000 in dive
Would single port heads work for this? If so, what size valves should I have installed???

thanks POPS Calvin
No, stay with the dual port head running a 2180 cc at those RPM's

On my 2180 flywheel drive engine I will be cruising at 2700 rpm's using the single port heads swing a Culver 62"x 26" pitch prop on a light weight ( 450 lbs EW), draggy airframe.
 

samyguy

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I have two engines needing overhaul.
Same rpm's 1835cc would the single port work in that case?
Sorry, for not getting all my questions in one post.

thanks again calvin
 

Vigilant1

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I have two engines needing overhaul.
Same rpm's 1835cc would the single port work in that case?
Will the 1835cc engine also be on a redrive turning up to 4000 rpm, or is direct drive?

BTW, what are you flying with these VWs/redrives? From all I've read, this works okay for turning a large and efficient prop at, say, 3200 engine RPM, but folks have trouble when they try to use them to turn more engine RPM to get more HP.
 

Pops

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Correct-- The relatively soft magnesium case can't take the stresses of sustained high rpm. The center main bearing saddle will wear reducing oil to the rods because the saddle wears and the oil goes out into the oil sump between the saddle and the main bearing with reduced oil to the rod journals and a loss of a rod bearing. OR the case will crack in several different places. Far beyond the design of the engine.

There are aluminum cases, but they are 17 pounds heavier. Add that weight of the alum case to the weight of the belt redrive and the weight of an electrical system required to safely start a geared engine , the total weight is up to were you would be better to go to a Cont engine. My non-electric C-85 is 188 lbs.
 

N8053H

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When having my engine looked over by Hummel engine, I had the heads replaced. Scott asked if I wanted to change from single to dual port. I kept it single port. This is a 1770cc engine. The case was also replaced with a new case. Both heads and case are brand new and not used. This engine runs or turns around 3100 RPM. Single ignition and no electric system.

I had all sorts of issues with this engine when setting valves. I may have mentioned this last year when I noticed this. I pulled the engine almost one year ago and sent it off to Scott at Hummel. He found that the shop that built this engine bored the cam bearing journals to .20 over. He said the problem, they don't make a .20 over sized cam bearing. The stock bearing was then installed. The cam was moving all around, this is what Scott told me. I knew something was up with this engine.

She got new heads, case, main and cam bearings. The oil pump was the wrong one. I was informed the pump installed is the one Scott uses in a 1/2 vw. So a new oil pump. New breather, it had an auto style breather on it.


Sorry to hi-jack the thread, back to regular programming.


Tony

IMG_1488.jpg
 

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