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I have a kind of a peculiar motor installed on my beetle. It's a stock looking engine, including single port heads, that I had made tuned to be a 2100cc with about 80hp at 4100 RPMs and 165 Nm at 2600 RPMs, but the engine revs up to 5500 RPM.
I had a whish to have a very drivable daily driver with much more performance than stock still retaining stock look (which in Italy is important)

It drives great, but it has a tendency to run hotter than it should on highway although I refrain from going more than 110 kmh (Gene Berg deep stick goes on). When driven on streets where RPMs go down and up it keeps good operating temperature even if I do like to push on the gas pedal!
(It has 69 (my 69) gearbox from a 1200, modified with a 8x31 ring and pinion on '74 car).

What would you suggest to check or do to fix its cooling trouble on highway?
I have two possible causes in mind: 1) too much oil pressure and 2) it is not getting adequate air/fuel mixture with a single carb. For both have already done some testing and hereafter are the details.

Here we go with engine details:
Type 1, 2100cc (94x76 stroke), 7.7:1 CR
built on a modified '73 "D" engine case, bearings are standard crankshaft, +0.50 case bore and 22mm stock thrust, Silverline
Dog house shroud, 26mm CSP OIL pump with full flow and pressure valve, standard aluminum oil radiator (more on oil pressure hereafter)
modified original heads (form 1600), single port, 32x35.5 stock valve size
Web Cam Split Duration Camshaft 218/119 with 1.1Rockers
1 Solex 34 pic3, main jet at the moment is 140
123Ignition with vacuum advance mapped as a Bosch 0 231 170 034
38mm J tubes and Vintage Speed exhaust

As far as carburation is concerned short tests on CO have suggested that the car is not lean ... it smells a bit of HC on cold days and also has a tendency to back fire when gas is lifted during hard driving (running second gear up to 5000 rpms, full gas) countryside roads.

As far as oil pressure is concerned, I am mentioning it since I spent some time considering it part of the overheating problem.
I run 5w40 oil and live in northern Italy, and run a few tests on warm days (about 20°C outer temperature). At cold start pressure is at 65/70 PSI (4.8/5 bar on 0 to 5 gauge). On countryside road oil stays at 70\80°C, while pressure is fairly high between 50 to 60 PSI (3.4 and 4.1 bar). On highway at 120 km/h, after about 10 minutes oil reaches 107°, while pressure is still 4 bar (at approximately 3500 RPM) which drops to 1.4 bar at idle as I stop. The engine doesn't burn oil at all and I have already replaced a 32mm oil pump with a 26mm CSP oil pump to reduce pressure to the recommended 10PSI each 1000RPM. Unfortunately oil pressure has not dropped as I whished after changing the oil pump and I ma considering thinner oil, perhaps 5w20...
Finally I have also checked forcing the bypass so oil goes into the radiator all the time, but this hasn't helped.

Many, many thanks for your advice and help on this!
Steve

Hi in my experience I would guess you need more cooling air for the bigger engine. How many vents does your decklid have? I think up to early 70s they had 2 vents and layer models had 4 vents to allow more air to enter.

With my engine I found that the decklid with 4 vents couldn't keep the engine cool and using stand-offs at the top solved the heat issue by allowing more cooling air.

Your oil pressure does sound a bit high but maybe someone with more insight on that will comment.

Thank you Wentzel,
indeed I do have 2 vents, but also have applied CAGERO Pro Hinge decklid lifter, which does open the lid at the top quite a bit... Made a noticeable improvement but did not solved the issue. As a reference, prior to that I was overheating at about 100 KMh after 15 minutes constant speed driving (engine warmed up previously). Now it does the same but at 110/120 kmh (again after about 15 min).

Would be interesting to see the temps of the oil cooler at highway speed via a thermocouple, to see if the cooler is getting colder (if the oil is bypassing).

Guess the other possibility is the carb is going lean at the top end under load.

There is a modification you can do to remove the stock 34pict carb Venturi to increase flow with a larger engine. Not sure that would solve your problem but it would probably increase your HP.

Thank you for the feed-back Bruce.m.
Do you know of any test I can do to confirm the problem is on the carb?
Carb going lean from mid range to the top end under load sounds like what is happening and at least part of the problem.
https://www.ahnendorp.com/ sells a modified Solex for large displacement type 1 that retain a single carb. I am incline to buy it but is fairly expensive and would be pointless if I do not get the root cause of the overheating. They call it PICT3 39 Tuning BAS, number 32422 at their shop.
Maybe someone here has given it a try (not confident, but you never know...)
Cheers!

Ideally you want a wideband o2 sensor & gauge to see the mixture under load. Or increase the jetting until you overshoot a touch & see what happens to the temps. Or you could “read the spark plugs” to see if they are showing signs of overheating/lean.

If you can find/buy a 2nd solex pict34, you could modify that to remove the Venturi. You have to add a hose to the top of the carb so it compensates for the missing venturi. Then experiment with jetting.

what's your timing set at?

Gentlemen,

A 34PICT with stock venturi on that size engine is going to run lean at high RPM. Even with a slightly larger venturi, it will go lean because the Solex emulsion tube can't keep up the richness as airflow increases.

There best solution is the Solex 40-44 EIS as a single carb (not a pair) with a 28mm venturi and 130 0r 135 main jet. There is an adapter made to fit a single port head manifold. I wrote the book on these Solex's and we race them relentlessly.



I recommend this vendor: http://www.kaddieshack.com/

Thanks FJCamper for the feed-back,
I already own your book and liked it quite a lot!
I am in the process to check more accurately at the dyno how severe is the getting lean of the carb as RPMs go up and will come back with some more information.
In the process I have found a few other things I need to do as fine toning. 1) bring some hot air to the carb, 2) add a venturi on the fan shroud.
The point 1 is interesting, have been told by a reputable motorist that when the temperature of air at the intake goes lower than 25*C the engine tend both to get hot and to get too much fuel.
If I get confirmation that main cause is the 34PICT not able to cope will need to move to the 40-44, but parts are not easily available, especially the adapter here in Europe.
Cheers!

Some info on solex 34 with lots of CCs

https://youtu.be/Ni3ikEDmPEU

Hi everyone!
I am still trying to achieve optimal cooling on this engine, but hasn't been successful yet.
Have changed oil pump and have now have a 21mm that provide for the right oil pressure. It helped but didn't solve the problem.
Haven't decided yet to spend the money for a different carbs set-up....
In a recent conversation a friend (quite expert actually) suggested it might be too low CR. Indeed the cam is a Web Cam Split Duration Camshaft 218/119 with 1.1Rockers and CR is 7.7
He suggested dynamic compression might be too little and the combustion too slow resulting in overheating engine.
How possible do you see it from your experience?
Thanks

FJCamper wrote: ↑Mon Jan 17, 2022 3:00 pm Gentlemen,

A 34PICT with stock venturi on that size engine is going to run lean at high RPM. Even with a slightly larger venturi, it will go lean because the Solex emulsion tube can't keep up the richness as airflow increases.

There best solution is the Solex 40-44 EIS as a single carb (not a pair) with a 28mm venturi and 130 0r 135 main jet. There is an adapter made to fit a single port head manifold. I wrote the book on these Solex's and we race them relentlessly.



I recommend this vendor: http://www.kaddieshack.com/

Does any vendor stock and sell single kadron kits or intakes? I haven't seen one available for years.

I think Empi was the last to market one, but they look to have been out of production for the last 5 years or so at least. I wouldn't mind grabbing one to play with at some point myself.

Have you checked your gauge and oil temp sensor calibration in boiling water. I have checked a few VDOs in the past and they can be off 40 degrees.