Updates and SU Spring Info

I have moved the reservoir to the firewall until the new header tank arrives from Merlin Motorsport. Conversion looks much cleaner now and with the new tank should look even more at home. Thermostat cover has been drilled and tapped 1/4NPT with 1/4 barbed fitting to purge air from the high point in the system.

Megajolt components permanently mounted and wires wrapped. Now just to remove the induction unit for the tach and get the tach out feed on the Megajolt working.

Tank Mount Position and Megajolt vacuum line

Reservoir Plumbing, tee'd into manifold heater and take off from
 the thermostat cover which is the highest point on the motor.

Megajolt takeoff using a .030" MIG Tip

EDIS module mounted properly to firewall,
nearly out of site from above

Crank Sensor Adjusted

Rad Plumbing

Dirt Road Life

STD 4.5oz HS2 Springs shortened to 3.625" for 2oz preload
(I have added this to my previous mod post)

Picture Update

The CRX and Spitfire make a run to Port Perry for some Pizza. The first official cruise for the two cars.

The CRX looks massive next to the Spitfire.

The head on the workbench with the perfect bur for porting. 

The shop where I work.

Verdict on HS2 Modifications

Worthwhile! Cost was almost nill (could have been if I modified the needles myself)If you plan on running HS2's with any type of head that flows better that standard strongly consider these simple mods. Loads of difference above 4500rpm. Pickup is FAR better as the pistons aren't restricting the flow as badly now and on the top end they aren't hanging around in the threw flow. The 1.8oz springs are working nicely, no flutter or hesitation at low rpm and those piston dampers are useless. That racer who complained about flutter without the dampers is crazy. The only way I can get flutter is to remove the springs completely, pistons start jumping up and down like crazy at idle then. Video to come

Summary: 

Started with lean BO needles in standard carbs with dampers on the standard mk3 cam.

• Removed dampers - somewhat better 
• Modified Spring to 2.5 oz - top end went lean
• Fitted ABT needles - mixture went a touch rich on the top end, noticeable, positive change, hesitation at 3500rpm
• Modified Spring to 1.8oz - mixture perfect, noticeable quicker
• Modified Spring to 1oz - mixture went lean and hesitated at 2000rpm (Could be solved by a richer needle I think)
• Pistons and Dashpots shaved .100" - Improvement at 4700rpm to red line (now 7K)

On another note; I am going to have to return to an early slave cylinder however as the pedal has far to much through to work the clutch now. It's be perfect for daily driving but for quick shifts I hate having to drive the pedal all the way to the floor now. Will have to order a rebuild kit for the other.

First video is a takeoff, second is just cruising to show the engine runs perfectly fine and normal under normal driving circumstances.

Head v2.0 and more HS2 modifications

The head is hopefully going to be one which I can run for a long time. It began it's life as a low compression emission head on a European triumph 1500. It has no air injection ports which is rare for North America. The head has the larger but not largest valves as standard but it does have hardened valve seats installed. Once the majority of the porting and I decide which valves I am going to the use, the head is going to get a massive .165" skim which should bring me up around 10:1 compression. I will them work on removing some of the shrouding from the inlet valve. Minimal modifications though. Just enough to help it a bit as it will almost be toughing the wall of the combustion chamber. 

To start of this head I needed a better depth gauge. Here is v2.0 which has a much nicer point, adjustment and grip.  Depth is set to 2.0mm for the first pass on the short side radius.

Depth Tool v2.0

End is profiled to sit flat against port walls

As far as actual port work. Today I concentrated on smoothing the manifold side of the intake ports. For this I just take one of my 1.250" (1147cc inlet) valves which is coincidently the exact same diameter as the entrance to the port and the inside diameter of the valve seat AND more importantly is perfectly within the 81-83% of the intake valve diameter as outlined by A. Graham Bell in Four-stroke performance tuning (Chapter 2, Page 16). I work this down the port until the beginning of the short side radius. It would fit clean through the port although there is a bit of a pinch about 1/2" in similar to the other manifold, once I worked through this section it was clear sailing to the ssr. This should give a much smoother path keeping the port velocity very similar to what it is in the manifold.

60 Grit Flapper Wheel Finish on the long side of the port
(least important but easiest to photograph)

No More Pinch Area

Core Shift. I chose not to remove the material needed to
smooth this surface in order to keep the port volume and
diameter consistent. Goal wasn't to remove material

Core Shift wasn't as noticeable on these two ports

But they did have some on both side unlike the others

LARGE step right below the valve seat.
I'm deciding how to go about it.

Another shot of this step which is present in all intake ports.

I also got the second dash-pot back today which had been shortened .100" the same as the other which brings the piston perfectly flush with the carb body at the REAR of the piston. I will install these in the morning. I am also running springs which are shortened to give 2.5oz force at 2.625" which is very close to 2oz of pre-load when installed. (~1.25" shorter than standard 4.5oz @ 1.625 springs). Modification was done using a nice digital scale which has come in very handy. Pistons are also within a gram of each other.

Unaltered on Left, Altered on Right

I don't run dampers. Incredible change in pickup.
No negative effects so far, no flutter or lean.

 The only modification I have made to the actual casting bodies was to clean up the casting in this area. The piston bore is straight down and clear but the through bore has a bit of a casting ridge where it meats the piston bore. I smoother this ridge out both before and after the piston bore. What a bore, and it probably don't make much of a difference but it looks much cleaner and shouldn't rub again the piston.

Casting Cleanup Area

My philosophy is that if I do 10 things which only gain 1hp each that's 10 hp. On their own each is insignificant but in the whole picture they each contribute. Make all the small gains as well as the easy one. The small gains are usually much cheaper and DIY too.

HS2 Modifications Applied

I picked up a copy of Des Hammill's "The SU Carburettor High-Performance Manual" to see what extra information I could get on how to get more flow though the pair of HS2's on the Spit. The way I see it this is a point of restriction in the system, each intake port is nearly 1.25" in diameter all the way through the manifold up to the point where they merge at the carb outlet. Up until this point there is little restriction. To help this out I want to increase the flow capacity of the carbs to allow the pressure at the valve to be as close to atmospheric as possible. Then the only limitation on the engine is what the valve can flow. Anyways, here is a comparison between my prototype modified carb and a stock one.
I also found the book extremely helpful in initial needle choices and how to modify them reliably. There is a lot of information on this on the net but I found it a struggle to sort through. I might scan in some pages and put them in the manuals section. Ssssssshh!

Stock Butterfly, Shaft and Piston travel.

Showing the stock piston travel better, all stock components

I modified the spindle in two ways, I thinned the tapped side removing ~.050" and cut off the other side leaving ~.060 on either side to help retain the butterfly. I also cut a pair of tappers in the butterfly's holes to allow the screws to sit more flush with the face of the butterfly. When permanently installed I plan to flash solder the screws and butterflies in place for extra security. The increase in effective area at the butterfly is visually amazing. Flow simulations are showing a 20.6% increase in flow from 108cfm to 130.24cfm. With these two simple modifications. The springs were also shortened(1.25") to give a spring rate of 1oz preload as per Hammill's book.

Modified Spindle and Piston Travel (increased .100" as per Hammill)

Better Showing the increased piston travel with modified spindle

You can really see the piston is now completely flush with the through flow section of the carburettor and the the spindle takes up far less cross sectional volume than the stock version. Not bad for an hour of work and zero cost. The final version will be done on a pair of new spindles.

Piston Travel a bit more in focus, modified spindle

Springs were shortened to 3.625"

New Wheels!

Four Allycat Supa Slots, just need to save up for tires now

DIY Guides Update: Nippon Denso Spacer Drawing

I added a drawing to the DIY guides section of the spacer I used between the front plate and the alternator. Very simple part but it's better than using washers as spacers.

Spacer

Triggers Wheels, Belts and Brackets

The smaller trigger wheel and megajolt brackets arrived from triggerwheels.com today. I ordered a usb adapter from Autosport Labs the same day and it still hasn't left Washington state. Props to Royal Mail, you destroyed USPS.

I also capped off the dizzy today, simply brazed a circle over the whole.

Parts from Triggerwheels.com 4.5"OD Trigger Wheel

Megajolt mounted on proper mounts, soon to be moved inside the cockpit

New Trigger wheel installed, much better fit

Alternator Spacer for 6061 Aluminum Alloy 1"OD

An alternator size comparison, dizzy is capped too

Shorter Belt and New Trigger Wheel

New Trigger Wheel

Proper Alternator

40 Amp Nippon Denso Unit Arrives to replace the dead Lucas model. That's a whole lot of box for such a small alternator!

That's a whole lot of box for such a small part

Just for Size

Header Designs

I'm trying to work out a design for my neighbor and I's custom headers. I am using standard bends available from Burns Stainless and straight sections of tubing. With these models I can constrain the lengths to be equal and move around the bends until I get the same head losses through each tube. This way each cylinder theoretically flows as well as the others. I tried to keep the pipes as straight as possible coming off the engine and still leave enough clearance around the float bowls and carbs. The Secondaries still have to be sorted but here is some eye candy on the progress. (Also car is LHD so steering column isn't a problem)