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Hello from an indecisive Spit & 1300fwd owner


PeteStupps

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Hello all, please may I come in.

I only have enough energy to concentrate on one forum, and was using CT for a while. Recently got bored to death waiting for the pages to load so drifted away. I see a couple of familiar names here.

I've spent a lot of time reading this forum and am well impressed with the level of technical knowledge and discussion. I'm definitely more of a novice myself; did a bit of thermo / fluid dynamics as part of an electrical engineering degree so understand some of the words at least. 

In the garage I've got a mk3 Spitfire which is bog standard but due an engine rebuild, and a 1300fwd which has just had the dubious honour of being my first car engine rebuild. Still running-in, with a few snags to sort out.

I've got a few options with the Spit rebuild but am struggling to decide what to do. Will start a thread shortly to elaborate. 

Incidentally I'm based in London, close to Waterloo. Terrible place to drive but there are quite a few classics tucked away round here.

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Welcome, Pete!

Sideways has offered asylum to many refugees from other sites, I'm sure you'll like it here.

Aren't classics exempt from the new London ULEZ rules?    I've a feeling that they may become more sought after as a result!

John

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Welcome Peter!  Remember your 1300 FWD posts from the CT forum - glad to hear it is now running.  I had a 1300 FWD briefly may years ago and loved it's "baby limo" feel.  I fought with it's bizarre front pulley and starter ring gear at some length (it had the tapered version and was very reluctant to come off!) and also had some battles with the gear linkage.  Couldn't live with it's ridiculously short gearing in the end and sold it on.

Lots of possibilities with the Mk3 engine rebuild - but the Mk3 engine is a great starting point.  I have a small crank 1300 block, crank and rods here ex 13/60 Herald should you find any of yours too far gone - they'll need boring/grinding but are on std sizes at present.

Nick

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Thanks all, much obliged.

On 6/7/2019 at 8:54 AM, JohnD said:

Aren't classics exempt from the new London ULEZ rules?    I've a feeling that they may become more sought after as a result!

Yes John, not sure how the FBHVC pulled that out of the bag but I'm not complaining. In a way I don't really want more people to use classics to get around the charge, as then TFL would remove the exemption! 

On 6/7/2019 at 9:17 AM, Nick Jones said:

Welcome Peter!  Remember your 1300 FWD posts from the CT forum - glad to hear it is now running.  I had a 1300 FWD briefly may years ago and loved it's "baby limo" feel.  I fought with it's bizarre front pulley and starter ring gear at some length (it had the tapered version and was very reluctant to come off!) and also had some battles with the gear linkage.  Couldn't live with it's ridiculously short gearing in the end and sold it on.

Lots of possibilities with the Mk3 engine rebuild - but the Mk3 engine is a great starting point.  I have a small crank 1300 block, crank and rods here ex 13/60 Herald should you find any of yours too far gone - they'll need boring/grinding but are on std sizes at present.

Nick

Thanks Nick, yes I ended up getting my early straight crank re-cut with a taper, as the keyway was mullered. Hopefully won't need to remove the pulley any time soon! It's running but giving me headaches with chronic fuel vaporisation (I think). Lovely interior though so it's a nice place to sit while the bonnet's up, waiting for it to cool down.

Thanks very much for the spares offer; current block & crank are still standard sizes so shouldn't have any issues there, plus I've amassed a spare crank and rods. No doubt there will be plenty of surprises to come though.

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Re the fuel vapourisation I suggest binning the mechanical pump and fitting a Huco electric pump. Ideally a pusher pump in the boot by the tank, but if you don’t fancy the extra effort, a sucker type on the inner wing will come a close second. 

Rerouting the fuel pipe from pump to carb away from the engine block and thermostat housing (what were they thinking of!) will also help as Will a heat shield between carb and exhaust.

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On my 3a the fuelling route via the mechanical pump was very much as Nick described. 

The yellow track in the picture. Close to the block and above the front exhaust manifold.

i fitted the sucker huco pump and routed it around the back on the bulkhead the green track line. The pipe is a bit long as it will still fit the mechanical pump if needs be.

i have also taken out the fine filter after the pump. Leaving the mesh filter before the pump.

38D9CBFD-D213-4985-8328-F7AEB0B730B9.jpeg

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I was considering a Huco pump, but want to see how she behaves now I've fitted a heatshield and fixed the blowing exhaust downpipe flange, which was raising the engine bay temperature a bit! Just need some warm weather for a test drive...

I did look at re-routing the fuel line. Will go down that road as and when I ditch the mechanical pump.

Hamish I had a filter dangling close to the exhaust, and realised that probably was absorbing a lot of heat to removed it. Presume your mods had a noticeable effect? 

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Pete 

to be honest I don’t know the effect.

i have been chasing a high revs hi speed intermittent misfire on a few runs at sprints I do. It also happened on a rolling road with the mechanical pump. And the rr chap said it was fuel ?!

hence the changes. Not entirely convinced it’s not electrics as I have had the symptoms on a road test with the huco. So am trying a simple acuspark electronic ignition module and fitted a back up coil.

may even try a rr second opinion. ?

as you can see I’m not a stickler for originality so and the cost to change was very reasonable. 

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  • 5 months later...
Taking into account that SU carburettors require a supply pressure of between 1.5 and 3 psi I would advise anyone fitting a fuel pipe around the engine bay to 

ensure that there is a continual rise in the pipe to the carburettors.

This will help to avoid small vapour bubbles accumulating at high spots in the pipe and forming a large bubble (this acting as a shock absorber compressing 

and expanding with each stroke of the pump and not allowing any fuel to pass) therefore allowing the bubbles to rise to the carbs. where hopefully they will 

escape through the needle valve and into the float chamber/s.

I see that the majority of petrol pumps currently for sale have an outlet pressure of 5 psi which I have found to be slightly too much for SUs and cause 

intermittant flooding. 

Regards, Colin

 

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Thanks for that Colin, it's a good point about high spots in the fuel line. I had one of those large transparent inline filters just before the Stromberg carb, the upper half of filter body being slightly higher than the float bowl, and when problems started you could see the level of fuel in the filter had dropped very low. It took me a while to figure out what was going on! Petrol vapour was indeed collecting in the high spot and displacing the actual petrol. 

My vapour lock / fuel starvation issues are mostly solved now after moving the filter, replacing the fuel lines and fitting an electric pump. It was still getting a bit of starvation at high(ish) speed, which I eventually overcame by adjusting the carb float height to raise the fuel level as high as possible. However I don't really like this solution as I think it's causing a lumpy idle from being over-rich. Really ought to sort out the spare twin SU's and fit them but there are some plumbing and throttle linkage issues, and inertia is the most powerful force in my garage.

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Are you sure it's not an electrical problem?  I had something similar a while back.  Fitted an accuspark or something similar to my rebuilt S motor. It had a regular miss which I couldn't tune out. In  the end I swapped distributors with an identical one off my TC.

Problem solved, or just transferred to the TC. New Pertronix unit fixed it.

Tony.

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Thanks Tony, most of my carburettor problems end up being ignition(!) but I'm quite satisfied that this time it is fuelling. For once I've been quite methodical, and each change made an incremental improvement. Stuttering was occurring a short time after accelerating up to 70-ish, or trying to do it up hill. Once it starts it can be cleared by easing off and cruising at lower speed, but it gets worse if you try and keep the power on. If I build up speed gradually it will cruise at 70 or so without any problems. Everything about it makes me think the flow into the float bowl can't quite keep up with demand at top end when under load. Toying with idea of going for slightly larger diameter fuel line, to marginally reduce pressure loss.

Or do you mean the lumpy idle problem?! In which case ignore my waffling. I can solve that if I reset the carb float height as per the manual but then that seems to exacerbate the high-speed starvation, presumably on account of the float needle valve not being opened fully. Ho hum. 

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Thanks Phil, yes both of those avenues were explored when I had severe vapour lock on a hot summer's day. Tried driving with the filler cap removed but it was worse! I think due to stopping the car, which allowed more heat to collect in the engine bay fuel line.

Since mostly resolving the vaporisation, I don't feel like a restricted breather would give the consistent results with the top-end starvation that I'm getting now. But restriction in the fuel line wouldn't help, i'll have another look at that.

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