605 replies to this topic

[timmy850]

The brass wingnuts look really cool!

I discovered that having gloss paint on the crank pulley can make it harder to set the timing with a strobe light as it reflects a lot of the flash back in your eyes!

[johnR]

The brass wingnuts look really cool!

I discovered that having gloss paint on the crank pulley can make it harder to set the timing with a strobe light as it reflects a lot of the flash back in your eyes!

Good point, I've now taken the gloss off with a scotchpad - I'll also strip the paint from the boss that goes through the seal.

[johnR]

Engine starting to come together - I've spaced the fan to clear the timing cover breather - I know ideally the fan should be only halfway into the cowl but with a more efficient radiator I don't think it will make much difference - we'll see!

now need to torque the head, add dizzy cap and leads, fill with oil, replace carbs and exhaust and we should be ready for a start-up - hopefully a bit more successful than when I first built this engine!   

[Cheeser]

Good to see your progress. Just to refresh my memory(without trawling through the thread!), what was the cause of the previous failure? Good luck, hope to see you on the road soon.

[johnR]

Good to see your progress. Just to refresh my memory(without trawling through the thread!), what was the cause of the previous failure? Good luck, hope to see you on the road soon.

I wish I knew! I'm hoping is was only the engine getting very hot while we tried to find the reason it was running lean which turned out to be a redundant bolt hole through the wall of the inlet manifold hidden behind the heat shield. The big ends went after @ 100miles. 

[johnR]

A bit more work on the engine, exhaust fitted after opening out one of the header flange holes which was binding on it's stud, carbs on. Rocker gaps set and HT leads fitted. I've primed the oil pump, just need to top the oil up before she starts.

These HS4's have their vacuum ports on the outside of the carb bodies as opposed to the inside on the HS2's so I'll need to re-jig the breather pipes to suit.

[johnR]

I'm getting closer to the big start-up, filled it with oil, mopped up all the oil that came out of the diff outputs because I'd forgotten that the driveshaft sockets need to be in, re-filled it with oil.

I loaded the app for the distributor onto my phone, then spent several hours trying to find where I'd written down the PIN for it. 

Then I connected the wires and switches that make up my off the car starting rig to the battery and engine, then put the battery on charge because it's only showing 8volts

So more charging (or a new battery) tomorrow and we should be ready to go. 

[timmy850]

I went back and reread the thread a few weeks ago and was trying to work out what went wrong with the 1275 the first time.

How have you got the distributor wired up now? Is it getting the full 12V? What coil were you using on the 1275?

[johnR]

To initially set it up the positive to the coil and earth to ground only are connected which gives you an LED indicator of orientation, then the neg to coil is added. The coil is a lucas sport gold one, although I also have a Bosch alternative. I'm hoping the problem was the overheating caused by running lean due to the hidden air leak into the manifold, but to be safe, once I get it started i'll leave it, carry on replacing the wiring loom , then take it to Tipton St John for set up.

[timmy850]

Was the coil fed by the pink ballast wire or was it a constant 12v? And was the distributor fed by 12v or the pink wire? I believe most electronic modules need the full 12v to work properly

If it was running the ballast & 3 ohm coil it would have had very poor spark under load, and even more so if the distributor had a variable dwell (according to the 123 website it is variable dwell).

Ballast + 3ohm + variable dwell = very poor spark
Ballast + 1.5ohm + variable dwell = decent spark
No ballast + 3ohm + variable dwell = decent spark
1.5ohm + variable dwell = best spark (if the distributor is rated for it)

Are you able to measure the coils you have now to check the resistance?

[johnR]

Both coils seem to be 3ohms - I'm fairly sure the Bosch one was recommended by 123 as suitable for their distributor. I was using a direct feed. It seemed to run allright up to @ 50/60mph when it bogged down then ran OK again after a short stop, which I guess was probably the big ends binding as they failed at 100 miles. I had plastigauged them onto the crank during the build so the tolerances were good.

[johnR]

New battery arrived the next day, which was good service! I now have oil pressure and fuel delivery to the carb float bowls. What I can't work out though is the distributor fitting - the slot in the drive doesn't quite line up with the two clamp bolts as per the Haynes diagram no matter how many ways I try it and at TDC the rotor points between two posts when the distributor is set up as the instructions. I'm 99% sure the crank & cam sprockets were aligned correctly dot-to-dot but I suppose I'll have to start by re-checking that. Annoying, as otherwise it's ready to start.

[sonscar]

The slot is off center so care is needed as it is only just obvious.Set the rotor position by rotating the body till it lines up one of the posts.Steve..

[johnR]

The slot is off center so care is needed as it is only just obvious.Set the rotor position by rotating the body till it lines up one of the posts.Steve..

With a standard dizzy that would be the procedure, but with this 123 you are supposed to rotate the body counter the rotor's normal direction until a green LED is just visible and that should be the position. But it isn't. 

[sonscar]

All this twist this light that etc is smoke n mirrors.Stick a strobe on it,crank it and turn till the timing is set to your number of choice.Works every time.The dissy is not magic.it is a switch which you set to turn on and off at the right time.Just my old timer mentality here.Steve..