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Almost new to A7s - frequentflyer - 09-02-2022
We are newish to the world of A7s but having built a trials special over lock down and undertaken a few trials in recent months including the excellent Dave Wilcox event over christmas we have become quite keen. We are a husband and wife team and share the garage duties mostly on our regular Thursday evening date nights. Our special seems to be a good strong build with plenty of ground clearance but our almost standard engine is leaving us a bit short in the power dept. I would be interested as we have just started to build a new engine what the best mods are for trials? So far we have procured a pheonix crank and the main castings crankcase and block. We also have the pheonix crank and the rods soon to arrive. So far we have bored the block out in our little workshop using the milling machine to about 57mm and reshaped/ported the inlets to the 1"sq. I have plans to regrind the valve seats and reprofile the valves a bit 45deg and 30deg as per standard practice. Now thinking and interested in cam, carb, flywheel,clutch and head choice. Engine is a 34 Mk1 ruby engine.
RE: Almost new to A7s - flywheel1935 - 11-02-2022
Welcome aboard., are you in the Cambridge club, joined last year, but my Ruby was out of commision. Should be back on the road very soon, so I can get to local events.
Are you a 'flyer' , I've a very very lapsed PPL, and a kitplane in bits !!!!
RE: Almost new to A7s - Howard Wright - 11-02-2022
Hi Frequentflyer
I’m no expert in engine tuning nor on trials but as no one has responded here are my suggestions
Head….Dave Dye sells alloy Ricardo heads which seem to have a good reputation. I have one on my Special and it goes well.
Carb…..SU is the route to go IMHO. You probably don’t need more than an 1 1/8” although on my Special a 1 1/4” H2 seems to work well.
Flywheel…There is a good section in the A7 companion on flywheel lightening. I’ve gone half way on the suggestions.
Clutch…Stiffer springs may help but I’ve got standard ones on my Special.
Cam……I’m using a standard cam but Paul Bonewell is the man to talk to if you want good advice.
Hope that helps?
Cheers
Howard
RE: Almost new to A7s - Austin in the Shed - 11-02-2022
Some use a reprofiled cam,I had good results using a std cam and re radiused followers.Aim for good bottom end torque,no good revving to 6-7k if it does'nt pull till 2k+.
Four speed box preferable,3speed too high in 1st unless a low back axle.Or a lot of power.
Preparation is better than breaking down and trying to fix at the side of the road.Many often used to drag their cars out the night before and expect no problems.
RE: Almost new to A7s - Steve Jones - 11-02-2022
(11-02-2022, 01:48 PM)Austin in the Shed Wrote: Preparation is better than breaking down and trying to fix at the side of the road.Many often used to drag their cars out the night before and expect no problems.
Dave's last sentence is absolutly correct. I'm now retired from trialling after more years than I can remember including 20 years doing VSCC trials but I think I only retired twice in that 20 years because of mechanical problems. Never used double clutch springs, if you decide to lighten the flywheel, don't do it too much, 3 speed gearbox fine if you use a low axle ratio and a low first gear (and essential if you want to do the VSCC Welsh Trial), 1 1/8" SU works well for trials and one of Dave's Ricardo heads every time.
I've a Pigsty trials cam that must be used with standard radiused followers here that I'd sell on. PM me if you're interested.
Steve
RE: Almost new to A7s - austin - 11-02-2022
Welcome. Trialling is fantastic fun, the last one we did was a full family affair, two cars and lots of swapping passengers around.
Both from 750MC trials near Tunbridge Wells. (ish)
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The best thing you can do for trials is get the tyres and pressures right. I'm sure others will make suggestions but we use Cheng Shin, (now hard to get sadly) and at the lowest pressure you can get away with.
Engines pretty much standard, sometimes run out of torque rather than outright power.
RE: Almost new to A7s - frequentflyer - 16-02-2022
Yes to the Cambridge club you possibly came to the car of the year show at our place and have seen my wifes A7 special. Its the Garter Blue thing. No PPL just spend my time flying about for work or in one of our old toys.
Thanks all very useful. Have had a spair flywheel in the lathe tonight to work out what comes off and how to hold/set things up. I did one on my 1930 morris but only went some of the way as you suggest. It seemed to work well so will do the same again. Possibly a bit out of the clutch parts as it seems to be rather heavy.
We visited the very trial at Surrey/Kent boarder wihout car in the autum and had a look round and gathered much useful information. Hopeful of taking the car to the event in that area in April.
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Not sure I am great at driving the forum tool but a few pictures of the car. Mostly Amys work, some of the machining, welding and painting was me all the mechanic skills are down to Amy.