New 1296 engine, build and development.
Amphicar needs more power - but it also need to be reliable. So I need to find the best information I can (historic and current) and then very carefully and precisely put something together. Base block I chose from the few I have here is a nicely run in 1296cc GE small crank, that had been rebored +40 a few years ago. The endfloat only needed a single 0.5 thrust. It has a normal Herald spec late 1296 cam (don't want a peaky Spitfire power curve, torque is critical). I used the original chain and tensioner (new one I had bought was rubbish). It was balanced as carefully as I could in a home workshop and has a heavy flywheel as I want a really low idle (about 800) for water crawling. I also don't want any oil leaks so need to get it running up to temp on my test rig as even with the best Payen stuff you never know..
March 2011. All running and looking good except for distributor advance curve, can't quite get that right, eventually rebuilt a couple of other distributors and tried different weights to alter the advance curve, also fitted Magnatronic electronic ignition and a red rotor arm (that's really important).
The Pierce manifold I brought back from California where they are popular with Spitfire racers and on top of that a Weber 28/36 from FastRoadCars in the UK that was jetted for a Spitfire 1300.
Head came from Newark Engineering, rebuilt with large valves and unleaded seats.
Pictures below show significant steps in build.
New big valve head for extra breathing, flowed, new seats, balanced
Block cleaned, bored 40 thou then 1000 miles, run-in. Honed and tested,
Thermostat and temp sender testing.
Debugging misfire with more distributor testing, Sun diag box is showing something wrong with spark on number 1.
An Update - March 2014 - it's done.
A continuing distributor problem and then an issue with the float level in the Weber (all 3 that I tried) had me scratching my head. In the end I fitted an original Herald side draft Stromberg which is a very simple carb and that allowed me to narrow things down.
Another rebuild of the Weber and switching to electronic points and we were getting somewhere.
So, out with the old:
And in with the new 1300
The result a few hundred miles down the road is fabulous !
The 1147 engine that had been in my Amphicar for the last 10 years is an 1147 Herald spec from a 12/50 so a better cam than Amphicar. The HP figure below is at wheels and assumes 20% driveline loss so 32hp is about 41hp at flywheel . That is about right, it would have been 48hp when new and although not super worn I could feel it had lost its edge and it certainly needed a tuneup. The original Amphicar had a very flat cam and so never produced more than 43hp.
Readings taken with the Dynolicious iPhone App which I’ve used on many cars and found to be amazingly accurate.
0-10 MPH: 1.86 sec
0-20 MPH: 4.96 sec
0-30 MPH: 10.17 sec
0-40 MPH: 18.97 sec
60': 3.91 sec @ 16.9 MPH
330': 11.15 sec @ 30.6 MPH
1/8 mi: 17.41 sec @ 38.7 MPH
1000': 23.14 sec @ 41.3 MPH
1/4 mi: 28.37 sec @ 42.2 MPH
Max Speed: 42.3 MPH
Max Acceleration: 0.95 G's
Peak Horsepower: 32 HP
And this is the 1300, officially a 1296cc but has been bored +40 so likely about 1350cc and has been carefully built with a Newark big valve head and Weber 28/36 fed via a custom air box I made of aluminium and a Rover 2000SC air filter. On the exhaust side the manifold is standard 13/60 with a custom stainless exhaust to original pattern so a bit restricted.
Only other change is I’ve gone to electronic ignition as I could see it loosing spark power above 4000rpm with traditional points, there was not enough dwell. This engine revs very well, have taken it to 6500 and it was still going. In fact it revs a bit too well for its own health so I’m going to fit a rev limiter.
It is giving about 65hp at the flywheel, makes a huge difference to the way it drives. There is of course a lot more torque but that is not quantified.
Only downside it is not quite as smooth but I did fit Gordons “heavy duty” engine mounts so that may have contributed and it idles around 800rpm which is higher than I’d like. Some Weber rejetting should get that down. Emission figures are pretty good.
0-10 MPH: 1.64 sec
0-20 MPH: 3.94 sec
0-30 MPH: 6.80 sec
0-40 MPH: 10.11 sec
0-50 MPH: 16.39 sec
60': 3.33 sec @ 19.0 MPH
330': 9.39 sec @ 37.7 MPH
1/8 mi: 14.43 sec @ 48.0 MPH
1000': 18.99 sec @ 52.8 MPH
1/4 mi: 22.94 sec @ 56.4 MPH
Max Speed: 56.9 MPH
Max Acceleration: 0.51 G's
Peak Horsepower: 52 HP
The CO and HC figures look good for something without injection or a cat.
And finally, making a custom airbox to keep the original look, this uses the Rover P6 2000 air filter.
More Spitfire engine tuning info in this excellent article written by Paul Geithner in the States