Steps to scratch build a VW

Discussion in 'Hangar Flying' started by Little Scrapper, Aug 13, 2019.

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  1. Aug 21, 2019 #221

    Vigilant1

    Vigilant1

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    If you are going to build a 1600CC (or 1835cc engine and run it at 3600 RPM or less), I think most folks would recommend sngle port heads (because the intake velocity will be better and you'll get better cylinder "packing" of the charge for better torque at a given RPM). There are fewer choices in single-port heads. Maybe that makes selecting the best an easier one.

    For bigger engines:
    Sonex/Aerovee in the past used Mofoco heads, and reports have been mixed. I think some were recalled. I have a cracked one on my plane right now (cracked between the valve seats). Now, Sonex is reportedly sourcing their heads from EMPI, and at least one guy who bought them had to get a valve job done on a brand new head to get the valves to seat correctly.
    Revmaster has heds made to their spec in China. They are very good quality and have reportedly been engineered to cool well. A few quirks (e.g. to get to the lower plugs you need take off a panel, which introduces another spot for leaks) and not the cheapest heads, but they have a good reputation.
    I don't remember what GPAS and Scott Casler are using.

    These are the dual-port Panchito heads from CB Performance? How have they worked out for you? I can't recall what size engine you're running. I've heard the air passages are better than most, and they claim to have one more fin. Valves are 40mm intake, 35.5mm exhaust, which is the same (too big) size as is common in the street performance heads. But, I understand they've changed the valve geometry a bit and moved the valve guides so the valve seats are farther apart, which would be a very welcome change to help avoid cracks between the valves. So, if the valve stems come up to the rocker arms at a different angle than they do on my present heads, I guess I'd also need to make adjustments to the rocker arm locations and maybe cut new pushrods? And, for those of us running dual plugs, is there room for another hole in the Panchito?
     
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  2. Aug 21, 2019 #222

    Little Scrapper

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    Pops, Vigilant, dmar836,Hot Wings. If you were to source a head for a build what would you do today?

    Sorry to put you guys on the spot.
     
  3. Aug 21, 2019 #223

    Vigilant1

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    The VW can be a fine airplane engine, but, in high HP use, the heads are definitely a (the ?) weakest spot.
    Hot Wings started a good poll/thread on features desired in a custom-built head a while back.
    For smaller engines, I don't think we need anything exotic. A well-made single-port heads with fins free of flash would probably do the trick.
    For engines above 60 HP, I think we need smaller valves that are farther apart, we need larger fin capacity. I'd like steel inserts for the plugs already installed by the manufacturer. We might want to consider making minor changes to optimize the use of vastly increased oil flow to remove heat from the the heads (for the heads, maybe just some ridges for more exchange area and a convenient spot for in and out lines. Elsewhere, we'd probably need to add a high volume/low pressure stage to the mechanical oil pump. I've seen these somewhere).

    A "for aviation but not specifically labelled as such" VW head for 2180cc and above engines would be a big plus to homebuilt aviation.
     
  4. Aug 21, 2019 #224

    Vigilant1

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    I'm stumped, and I do need heads (I paid a few hundred $$ for a new Mofoco head to replace the cracked one on my 2180cc engine, and I don't know if I should even bother to put it on. I probably will).
    Starting from scratch, I'd probaly go with Revmaster or maybe this CB Performance Panchito (Dave? . . .). But others here have much more experience.

    I don't know about the single-port heads you're probably most interested in.
     
  5. Aug 21, 2019 #225

    Little Scrapper

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    Vigilant, one problem is nobody seems to know which head has left flash as an example. If you were a total newbie and started exploring the VW as a possible power plant they wouldn't even know where to start. That to me is a problem.

    Anyhow, I'm back to thinking of just a simple 1600 cc VW engine. The more I read the more I think that's a smart move.
     
  6. Aug 21, 2019 #226

    Turd Ferguson

    Turd Ferguson

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    Doesn't BBerson have a Limbach engine on his motorglider? How'd they solve the heat issues? Limbach built an engine that had 2400cc
     
  7. Aug 21, 2019 #227

    Vigilant1

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    They build a few models with 2424 displacement (97mm bore, 82mm stroke). Some use air cooling (they list these as 62kw max continuous=84 HP), the higher HP ones use water-cooled heads. But, if they are using 97mm bore cylinders, I'm assuming they are on the "Wasserboxer" and not the Type 1 engine cases, so they are really a different animal. Whatever heads they are using won't be usable on a Type 1-- I would think.
     
  8. Aug 21, 2019 #228

    blane.c

    blane.c

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    From What I have been reading on the VW, the heads if you take care of them and adjust the valves at regular intervals are good for between 250hrs and 300hrs, the rest of the engine is good for 800hrs to 1,000hrs if all the Hoover oil improvements and running a cooler and a filter/or change oil every 25hrs. So if you time out the cylinders and lower end you are going to go through 3 or 4 sets of heads to do it. Some have advised building two sets of heads from the get-go and then the second set is already matched to the engine (advised to be necessary) when you need them, then rebuild the first set for the next go around etc.
     
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  9. Aug 21, 2019 #229

    blane.c

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    I think Smart move is 1835cc. I doubt it costs anymore or certainly a negligible amount. There is no gain in weight. No additional machine work that you shouldn't do to the 1600cc anyway. You can get same hp as 1600cc at a little less rpm. What is the down side? Anyway I would trust Pops, Just ask him point blank which engine he would build.
     
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  10. Aug 21, 2019 #230

    Pops

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  11. Aug 21, 2019 #231

    Pops

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    I had two sets of heads and intend on swapping out at 500 hrs if I don't have any problems before that. A friend of mine put over a thousand hours on a 1/2 VW in a Mini-Max with no engine work. It was 32 Hp version. He worked many years as a motor cycle mechanic and knew what he was doing from the start.
     
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  12. Aug 21, 2019 #232

    dmar836

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    I might be a little weird as I would likely go with new castings based on the old replacement heads(I think that's what they were) with the 500 or 501 number. Get them cheap then go through them and dial them in - clean the flashing from the fins, check everything, etc. It's been some time since I've researched but the 040, 041, and 043 castings were more/less desireable. These aren't hogged out nor do they have huge valves but they are dual port. Get on the Samba and they are criticized primarily by how much material they have or don't have for porting the runners. I would either build them up myself or get them as-is, check them out(lap the valves, check spring pressures, etc.) and run them until a refreshing is needed. Then rebuild with stainless valves and a 3 angle job or get another set going in the meantime as mentioned above.

    https://aapistons.com/collections/c...vw-1600-stock-dual-port-cylinder-head-35-5x32

    Looks like another $50 will add stainless valves.
    Whether these would perform better or worse on a smaller engine over SP heads, I can't say. The Panchitos or about any "improved" street head might be too big for a 1600 especially run at low rpms.
    I got the Panchitos(the new ones - not the old 044s) even though they have one size larger valves as it was a compromise. Better cfm at less valve lift(.300-.400) vs the .450-.500 lift so many check and quote them at. At the time I was planning on the 2110 build I have going on(might still) and was (and still am) planning on cruise at higher rpms than the rest are. It's a race plane I'm building and it's a toy, an experimental toy with "war power" built in. I don't think the VW turning 4000 continuous will be my failure mode. Harmonics and other issues from the turned around engine with a 12" extension might just be! I'm confident there will be failure modes to overcome but not sure what will be the reason. I just hope it IS the power plant.
    Dave
     
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  13. Aug 21, 2019 #233

    Pops

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    Easy to answer. The 1835 cc engine.
    Some people has had problems with the bolt on 87 mm cylinders and pistons due to the thinner cylinder walls over the 1600cc 85.5 cylinder and pistons. For many years my OSH runner and other camping trips all over the U.S was in my 1966 split windshield VW camper bus with a 1700 cc engine that I built for it and pulling a small fold-out camper for sleeping room for my wife and I and 3 children. Put many, many miles on it and never had any problems except for a wheel bearing. Got 24 mph pulling a mountain or on the flat mid-western interstate. We had a lot of fun . My oldest 2 children took their drivers test in the Bus. My oldest daughter was 16 years old and just got her drivers license in the first of July and drove the bus and camper trailer around the Chicago loop at 5:00 PM and I was in the rear seat going to OSH. That was in 1977.
     
    Last edited: Aug 21, 2019
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  14. Aug 21, 2019 #234

    BBerson

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    My older G109 has a Limbach 2000 (90mm X 78mm)
    The previous owner replaced the heads with new auto heads. I don't know if Limbach heads are special or different. They look the same on Limbach overhaul manual.
    I put on a third set of heads in the total 1000 hrs. About every 5 years (flown or not) the valves need grinding or new heads if cracked.
     
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  15. Aug 21, 2019 #235

    Hot Wings

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    Good logical and proven combination.

    I'll offer an attractive alternative - but it does cost a little more.

    92mm thick wall pistons - 82mm stroke pin offset
    78mm stroker crank with VW length rods.
    Very little case grinding needed compared to a full stroker

    This gives you a 2L engine with an extra .080" deck clearance to help maintain the same compression ratio with the increased displacement.
     
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  16. Aug 21, 2019 #236

    Pops

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    Its a win , win.
     
  17. Aug 21, 2019 #237

    Little Scrapper

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    By now it's easily understood I'm not that knowledgeable in anything VW. That said, I find it hard to believe that going from a 1600 to a 1835 is done with no consequences. There's always a consequence, there's always a sacrifice. If not it would be the first time in my life that rule has been wrong.

    So if it's not cost what is it? Longevity? Heat? Cracks? Maintenance? There's gotta be something.

    30+ years ago I built a 283 with a 2 barrel carb using double hump 1.94" cast iron heads. The guy who taught me to lead steel panels told me we could build it and it would be fast as hell. I didn't believe him, I wanted a 327 with double hump 2.02" fuely heads and a GM aluminum bowtie highrise intake, yes the original rare one (still own it). Holly double pumper. You know the drill, everything cool in the magazines & movies.

    But I was broke so I had no choice. We built the 283 2 brl. The only thing we did besides a total rebuild was bump up the cam a little and put cast iron Corvette exhaust on it. Well, we did smooth out the cast iron runners on the heads and intake but just smoothed them, nothing else. We also.used the rare Corvette cast iron ram exhaust manifold, any car guy knows what those are. Anyhow, he tuned the schit out of the little 2 barrel engine and taught me to rebuild my first auto engine in the process. I was 16. That thing was a screamer!!!! I mean, it had a rock crusher 4 speed and it was an absolute stoplight monster. Past 55 or so forget it. In town it was a rocket. Some smoothing, a punched up exhaust and some tuning made it a screamer.

    Still wasn't satisfied because you know, I was smart now, I knew everything.

    I began building a 327. Keith Black pistons, 350 hp GM Corvette cam, BowTie intake, Holly carb, the 2.02"s, hooker headers, cherry bombs, the whole nine yards. Was it fast? Yup! Much faster than the 283? Debatable. Was it a better motor? No.

    30+ years later I have the Pistons, rods, cam, carb and intake nailed to a wall in my shop. Still own them. I ripped apart that 327 numerous times, swapped carbs, swapped cams, heads etc. It never ever ever came close to that almost factory but extremely tuned 283 with that embarrassing little 2 barrel. Lol.

    I have worked on a ton of motorcycles and it's really the same thing, it's always a compromise.

    So again, I'm not trying to be snarky, I'm really interested in great conversation and this thread really has been great conversation. I'm just tainted, i struggle with "free" horsepower at no cost. It just seems like there's gotta be something.
     
  18. Aug 21, 2019 #238

    Hot Wings

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    There was a cost to be paid. Way back in the early days of slip in 88s* we started paying those costs. We did this with the old 10mm stud cases, some of which had already been abused too much and old style cooling tin. There was a little mini evolution over the years that started with cut case 88s and has lead to thick wall 92s, 8mm deep stud cases with dual oil relief, 'dog house' oil coolers and Tp IV center main flanged cranks.**

    The Hp wasn't, and still isn't free. But it will cost you a lot less than it did the thousands of DB+HVWs readers that bought, used and real world tested the early parts.

    * total junk BTW. 87's weren't much better.
    **crank modifications not needed for aircraft use at the power/rpm levels we are likely to see.
     
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  19. Aug 21, 2019 #239

    Little Scrapper

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    Fair enough. So are you saying there's a zero percent Increase in less reliability, increased maintenance, heat, cracks etc.

    I'm game to do a 1835 if it's true, I have no choice but to trust others. Hardly anyone builds a straight up 1600 it seems. But the case was designed for the 1600. Heads too, which we know are less quality than the old ones. People are experiencing cracked head issues clearly, would they also experience the same head cracing issues on a 1600?

    Does a horsepower chart exist showing the HP curve difference between the 2 types? Curious how the 10 extra hp comes in to play over the RPM band.
     
  20. Aug 21, 2019 #240

    Hot Wings

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    Zero % less reliability? Probably not. So much less that you could quantify it? Again, probably not. Given the overlap between building an 1835 with good parts compared to building a 1600 with 'white box' parts the 1835 may last longer.

    The case was actually a clean sheet design for the 1300cc when they went to the 69mm stroke. It evolved from there with the first 1500cc being little more than a thicker casting.

    I can't point to any reliable hp charts. :(
     
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