Race Engine Forum UK

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Good to hear T.

Nice work. Feels good when you hit the sweet spot.

I'm sure I would benefit from vernier pulleys on my Alfa boxer if I had the time, resources and money. Plus of course a bit more education in this area of engine tuning.

The left pulley is about 1/4 tooth out with my stock pulleys and cams.
Would be interesting to play around with that.

You don't measure cam timing in the amount of teeth on the pulley, but in degrees. Have you measured timing of the cam lobes, related to the crank position? It could very well be that your timing is spot on, or off in the other direction. The markings on the pulleys are merely there to make sure the workshop mechanic doesn't need to learn the skill and spend the time on laborious timing, when merely changing a belt as part of regular maintenance.

It could also be that with a warm engine, when the metal has expanded, your timing is different than with a cold engine. The belt doesn't stretch so timing is generally a bit more advanced on an engine that's up to temperature. Make sure you record the temperature your engine has when you measure/change cam timing, so your experiments are repeatable. With a chain driven cam, your engine will probably be less effected, but it could still be significant. If at all possible, make sure to measure differences warm and cold for your specific engine, to see if it's anything you should take into account in the future.

The markings on the pulleys are merely there to make sure the workshop mechanic doesn't need to learn the skill and spend the time on laborious timing, when merely changing a belt as part of regular maintenance.

wink

That's me.

I haven't learnt the skill of the fine art of precise cam timing yet. Once I've fixed the tappet issue and it's all running sweet, and then after I find the time to do this I will return to read up about the subject and probably have many noob questions.

In the meantime I place the 2 belts on the stock cams and pulleys while lined up at TDC, rotate a couple of times by hand to make sure it's all smooth, re-check the alignment and then start her up to check the distributor timing is 8 degrees +- 1 at 850 rpm when hot.

Not even sure how I would time this engine precisely at TDC. You can't measure the lift of the valves at TDC with the timing belt on I believe due to the design. Maybe I'm wrong.

Thanks

Chris

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I like the brutality of dual carbs. And the sound. Who has heard an engine which sounds bad with dual carbs? I personally never encountered one...

Have to agree with you there. Especially when you release the induction sound either with foam filters or a more 'open' airbox.

My flat four boxer with 2 double DRLA's has an addictive sound and mid-range torque which just asks you to push harder on the throttle!

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Torque is the amount of force the engine can give per rotation. In my opinion, the flat line tells you that your engine is making the most of the air it can pump through, so it is essentially healthy and well balanced through a wide rev range. Because the line is so wide, I'd expect the limitation to be in the amount of flow and not in your cam profile, ignition curve or mixture. If you want more torque, I think you'll have to find a way to get more air through the whole setup. Inlet, carburetor, plenum, inlet port,inlet valve, exhaust valve, exhaust port, exhaust manifold, exhaust.

That being said, I think you have a very, very nice result for a 1.6 8V streetable engine. I myself would think twice about doing big modifications to it. Before you know it, you're overdoing it and you'll have a dyno queen that won't give you the easy of use and "fun" driving, for 20 more BHP you'll almost never use on the road. Looking at these graphs, I can imagine this car belting off at the traffic light, leaving lots of "modern" cars behind, and if you accidentally forget to shift back, you'll still have plenty of power to drive on. If you modify it to be a high rev screamer, you'll be burning clutch plates at the traffic light if you try to outrun someone, and driving in the snow will either be a crime, or you'll be sideways most of the times.

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Try and make a double shield with something heat resistant in between. Stainless is the best single layer insulator if you compare aluminum at the same thickness to it. Most heat shields on cars these days are double layered aluminum, with either air or some padding between the layers. With a little luck, some shield from a car in the wreck yard can be trimmed to fit your exhaust. It will be a lot of work to make a decent fitting double layered one by yourself, so I'd look into that option.

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