1776 single port, single carb?

[StefansBus]

Hi All

Anyone here who has had success with a 1776 single port single Solex carb setup? I want to mildy upgrade my stock 1600SP to 1776 primarily for more torque. I want to go from the current 30 PICT 2 carb to either a rejetted 34 PICT 3 or an enlarged 34 (37 or 39). I'm planning to use this Ahnendorp equal lengths stock style exhaust. https://www.ahnendorp.com/VW-Kaefer-Typ-1-Motorenteile-und-Bearbeitungen/Auspuffanlagen-51/Ahnendorp-Bus-T2a-a-b-Auspuff-mit-gleichen-Rohrlaengen-ohne-Vorwaermung-1828.html?language=de

Will this work good? Would going dual port be significantly better? I guess dual port would mean slightly higher RPMs and slightly higher peak power. But what about low down and mid range?

I'm planning to keep a stock cam but am open to a mild performance cam. Planning to run stock valve sizes. Either on the SP heads I have or on new DP ones. Flywheel and clutch will be upgraded from 180mm to 200mm and will be dynamically balanced with the stock crank when the case is apart.

Any thoughts on this concept.

I will not consider twin or dual carb on this project. Has to be a single Solex.

Cheers

Stefan

 

[Bluesnailman]

Expensive exhaust!! I might be tempted to try standard exhaust if you're sticking with standard carb. And keep a stock cam, as flow at higher revs will be limited

 

[StefansBus]

Yes, expensive exhaust. But seems to be one the best out out of al the stockish looking ones I like that it has equal length tubing. It won a comparison test in a German VW mag:

https://www.ahnendorp.com/info/Pressemitteilungen.html The results are quite stunning. They used an 1835 with dual Weber 40 IDF, a 308 degree Schleicher cam, 9:1 CR and heads with 39/35 valves. Not as mild as my project but not a wild screamer either.

With the stock Leistritz exhaust the engine produced 77hp at 4400 rpm and 132NM torque at 3100 rpm.

With the Ahnendorp exhaust it made 98hp at 5000 rpm and 163NM at 3000.

I am sure with a milder engine the difference will be less pronounced but I would very much expect it to still be significant.

I am afraid that the stock exhaust will not only choke it but also result in higher head temps.

I have done a bit of reading on cams and the CB 2280 "cheater" cam seems to get very good reviews. People say it runs like a stock engine just a lot stronger in low and mid range, especially with a single carb. I'm tempted to give that a try. Not very expensive and not much extra work as the case will be open anyway. Torben Alstrup (Danish engine builder) recommend using it with 1.25 rockers on the inlet side only.

Any thoughts very welcome.

Stefan

 

[atafonso]

The main question is how it will be driven?
Mostly below 3k rpm's?
How heavy is your Bus?
Mostly city or motorway?
What gearbox do you have?
Tyre size?

The cam is one of the most important parts in any combo for it will dictate the behavior of your engine. If not chosen correctly, you can end up hating it. Most people don't realize that the stock cam is all they need. There is no cam that will give you more torque at low rpm's no matter what. If that's what you looking for, keep the stock.
With cams there will always be a compromise, you either sacrifice low end torque for high end power or vice versa. Now what you need is to have a good balanced compromise depending on YOUR APLICATION.
Your engine builder should ask the above questions and based on your answers he will suggest the right cam for you.

The SP 1776 can be a nice engine, it will have loads of torque off idle but will struggle after 4k. In fact, the power curve will drop so rapidly that there is no point in revving higher as the power will disappear. I would recommend it only if you very ocasionally rev past 4k. Also using a 34 or an enlarged 34 carb on the SP is a no no due to the bottle neck effect of the intake small diameter tubes. The 30 or a 31 will be enough to feed the 1776 as there is too much restriction anyway on the manifold and cam profile.

Abel

 

[StefansBus]

Thanks Abel. Some great Info.

You mention the restrictions of the SP intake manifold. What if one changed that to the aftermarket high flowing centerpiece plus the aftermarket aluminum end pieces for single port heads? That would leave the actual ports in the head as the most restrictive parts. Given that SP engines are frequently run with twin 34s I would have thought that a single 34 would not be too large for a 1776SP. Am I wrong? At the same time a bit more cam should help, right?

I think you are basically saying that for low end torque one cannot do better than the stock cam. But is it not true that the stock cam has been chosen to be very tame, to ensure long life of the valve train etc, accepting the fact that it will strangle the engine somewhat? Surely a bit more lift for example must be a good thing even at low RPM.?

Cheers

Stefan

I'm currently in touch with a builder and it looks like I will end up having him build me a stroker instead. It will still be single carb but dual port. Still interested in the above, though as I always like to learn.

 

[atafonso]

Hi Stefan

You mentioned using the 34 only, not changing the entire manifold. I said it would not be a good idea IF using the stock SP manifold.

SP engines are are not frequently run with a 34 for it does not fit the manifold. A flange or mods are needed.

Why are you talking about high flowing if your initial question was about having an engine with more torque?
Torque and power are two different variables. For low end torque, you need air speed, which means smaller diameter ports, and low duration cam. That is what a stock cam provides. It's not a tame cam designed to be reliable on the valve train only, it was designed to have high torque at low revs. For that reason the engine max out at 4.5k but 90% of the torque is available at around 2k.

Ask on the Samba if there is any cam known that will provide MORE torque than the stock AT THE SAME RPM RANGE. You will be surprised.
What Torben Alstrup has recommended you was a combo that will make decent torque but more power at the top and extend the rpm range a bit. Ask him if the cheater cam will provide more torque than stock at low revs; he will say def no.

More lift at low rpm kills air speed, therefore killing low end torque. Same with larger valves.

There is no miracle cam that will give more torque and more power in the same engine without changing the rpm range. In a Beetle or a light car, it can be fine. But in a Bus, having an engine with no low end can be very very frustrating.

The only way to have more low end torque and more power at the top is increasing capacity. That will increase airspeed therefore you can run a performance cam witnout losing loads of low end.

Funny, the engine i build the most is the 1776 with stock cam and dual 34 ICT's. When i ask my customers all the questions, then i suggest the above combo, some say: "On the forum they said the Engle 110 is the best cam for the aircooled engine, so i want one" . I ask them to drive a Bus with one of my engines first. Afther the drive, they come back very happy saying "this engine has a lot of power". Actually it's the torque and instant response of the stock cam, it makes the Bus much more driveable and really enjoyable. Most of them won't rev high, so no need for a performance cam and loads of power up top.



Abel

 

[StefansBus]

Hi Abel,

Many thanks for the expanded explanations. I apologize if I have been mixing different approaches into my question, such as changing the intake manifolds. Much of what you say makes a lot of sense to me and in fact I knew much of it already (such as torque is not the same as power and is actually more important in how a heavy vehicle like a bus works as a daily driver etc). It makes sense that high flow and low end torque don't mix well. I also understand one can't have it all when it comes to cams. I would have thought that there might be a cam making more torque available down low than a stock cam does without sacrificing max power or torque. I might be wrong.

Will let you all know what I end up doing and how it has worked out.

Cheers

Stefan

 

[atafonso]

Hi Stefan

No need to apologize, we all learning everyday
Please keep us informed, and just reminding, we love pics

Regards

Abel

 

[ozziedog]

Hi Stefan

No need to apologize, we all learning everyday
Please keep us informed, and just reminding, we love pics

Regards

Abel

That’s spot on, you tell em Abel, we most definitely positively and absolutely love pics.

Ozziedog,,,,,,,,,,and lots of them too :mrgreen:

 

[atafonso]

Hi Stefan

No need to apologize, we all learning everyday
Please keep us informed, and just reminding, we love pics

Regards

Abel

That’s spot on, you tell em Abel, we most definitely positively and absolutely love pics.

Ozziedog,,,,,,,,,,and lots of them too :mrgreen:

Well said sir :mrgreen:

 

[K@rlos]

In my opinion the limiting factors with cam selection are gonna be the single port head, single carb selection. You can only get so much from them. An engine is essentially an air pump, the more air/fuel goes in the power and torque it will make and obviously a twin port head will flow more, even more so with twin carbs.

If your set on using a single port head with a single carb then stick with a stock cam as they compliment each other perfectly. If you had tp heads and twin carbs then I’d say an Engle w100 or W110, I fitted a 1776 with ported stock heads, a 110, stock ratio rockers and twin 36’s to Stu C’s bus. It is a superb thing to drive, pulls from idle like a train. Any decent engine builder will agree with me when it’s about components that compliment each other not whats the biggest etc.

 

[StefansBus]

My new 1776 dual port, single 34 PICT-3, 28mm venturi, CB2239 cam, 1.25 rockers on intakes, CB center section, AA500 heads by Torben Alstrup, Ahnendorp exhaust.

79 bhp at 4500 RPM, 143NM at 2500 RPM. Nice flat curves. Still a bit rich.

Red curve is without the stock oil bath air cleaner. Much better air/fuel ratio.

 

[atafonso]

My new 1776 dual port, single 34 PICT-3, 28mm venturi, CB2239 cam, 1.25 rockers on intakes, CB center section, AA500 heads by Torben Alstrup, Ahnendorp exhaust.

79 bhp at 4500 RPM, 143NM at 2500 RPM. Nice flat curves. Still a bit rich.

Red curve is without the stock oil bath air cleaner. Much better air/fuel ratio.

Congrats Stefan, your engine turned out great

I am a big fan of AA500 heads, the modern chamber is big enough to allow a tight deck resulting in great efficiency.

Your combo shows what can be achieved when care is taken and proper parts selection is made, like the 1.25 rockers on intake,28mm venturi on the 34, etc. A very well built engine

Abel

 

[StefansBus]

Thanks Abel. Yes, I'm very pleased with the result. Torben says there is potential for a few more horses and torquies (I just mad that animal up) with better ignition wires for a stronger spark and better (leaner) jetting. Will keep you updated.

Stefan

 

[Jan Toft]

How much is an engine like that in Dkk built by Torben.
Jan.

 

[StefansBus]

I don't know. He didn't build it. He is a very busy man as he also has an unrelated day job. He wrote the parts and specs list, made the heads and end castings and provided advise along he way. Everything else was done by a local builder.