Cruising speed of P1800
 

I’m about to buy a P1800 and will have a long motorway journey home. The tachometer seems eratic, think because retrofit electronic ignition. So, what’s a comfortable cruising speed and what mpg can I expect?

I have owned my 1800S for 9 years. It is a 1964 built car, built in the early part of that year, hence with cow-horn bumpers.
I have driven almost exactly 20,000 miles in the time of ownership.
I have taken it to to Scotland twice including the North Coast 500 trip. I have taken it touring in France. Also driven a 2,500 miles trip through Holland, Germany ,Denmark, Sweden, & Norway, and return.
In the UK the car is happy to cruise at 70 mph all day.
On the continent it can cruise at 80 mph as long as you want to keep it at that speed.
For regular touring /driving mixed routes it will average 26mpg.
On constant throttle at 70mph around 30mpg can be achieved.
I hope that can give you a guide.

I have 123 Tune electronic ignition on my cars....

https://i.postimg.cc/6QtmtMG0/IMG-2115.jpg

On the beach on the west coast of Denmark!

Groundes-Peace; exactly what I needed to know, thank you.
Stunning looking car by the way.
Cheers
Simon

Simon; Good info from GP, and general dittos to comments...if you engage OD, the resulting drop in RPMs will bring the cacophony at those cruise speeds down, which is always nice...(so will a carpet kit and sealing all the holes between engine and passenger compartments...even small ones!).

Regarding Tach...I was under the impression that if they work with the Elec Ign fitted, they work (and not intermittently), but you could try reversing sensing polarity at the back of Instrument. They can develop age related issues...see: https://www.sw-em.com/Smith's%20Tachometer.htm

GP; Was that on the mile wiiiide beach at Rømø? I enjoyed my visit there a few years ago.

Cheers

Cheers Ron, good to get further confirmation.
The Tach was fluctuating all over the place on the test drive. I read a thread that it was likely the retrofit Elec ign. Useful hint, thanks. Probably a bit beyond my tech skills. I’ll get the garage to try it.

Thanks
Simon

Very nice car, have you had to do much renovation yourself?

Thanks for comments on my car photo on the beach in Denmark. We parked on the beach to see the Rubjerg Nnude lighthouse, in North Jutland, that was slowly sinking into a sand dune due to coastal erosion. Since our visit this lighthouse has been jacked up and slid on skates 70 metres inland to a more secure position.
My original speedometer still works, despite having electronic ignition fitted to my car. However the needle does wander up and down and the odometer was out by 5%, and I had this recalibrated a few years ago. I use a Tom Tom satnav in my car which gives a more accurate speed indication.
I have done a lot of 'rolling' restoration of my car over my time of ownership, so that I could use the car over summer months throughout the last nine years. The car is no 'show princess' but a tidy enjoyable classic that has proved to be very reliable. It has proved a joy to own!

Groundes-Peace is correct with his assessment that 70 to 80 mph is a good highway cruising speed. I've had similar experiences with this '67 1800S and have put over 25K miles on it in the last four years plus 1500 miles of on track vintage racing and hill-climbing with the VSCCA https://www.vscca.org/

The car has its unmodified original matching number 115 hp 10:1 compression B18B engine with SU's and only a .030" overbore. The tach accuracy has been checked and it is happy to travel all day at 4,000 rpm which equals 80 mph. Top speed on the track so far has been 118 mph at 6500 + rpm.