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Opinion on exhaust advance or retard

How to Degree a Cam

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queria pedirte tu opinion.

Busco la maxima potencia en un motor de construccion antigua, es un 3.0cc de 6 cilindros en linea, con 2 valvulas por cilindro y un solo arbol de levas.

Ya conocemos el problema de tener un solo árbol de levas, que al buscar un objetivo de escape o admisión, perdemos por el otro lado.

Poniendo datos, con el tiro con las levas centradas es 50º-88º/77º-40º, esto me da la apertura máxima de la válvula de admisión y escape a 109º.

Tengo la opción de adelantar admisión quedándome en 58-78/84-33 o lo contrario sería 43-96/70-47

¿Qué ajuste crees que me puede beneficiar buscando la máxima potencia?

muchas gracias



I wanted to ask your opinion.

I am looking for the maximum power in an engine of old construction, it is a 3.0cc 6-cylinder in line, with 2 valves per cylinder and a single camshaft.

We already know the problem of having a single camshaft, which when looking for an exhaust or intake target, we lose on the other side.

Putting data, with the shot with the cams centered is 50º-88º/77º-40º, this gives me the maximum opening of the intake and exhaust valve at 109º.

I have the option to advance admission by staying at 58-78/84-33 or the opposite would be 43-96/70-47

What setting do you think can benefit me looking for maximum power?

thank you so much"

Advancing a little usually helps low rpm torque, retarding a little usually helps high rpm torque - 4 degrees can make a difference.

You need to be SURE there is enough valve to piston clearance before adjusting it.

The only way to be sure is to try it.

Avanzar un poco generalmente ayuda a un par de rpm bajo, retrasar un poco generalmente ayuda a un par de rpm alto: 4 grados pueden marcar la diferencia.

Debe estar SEGURO de que haya suficiente espacio entre la válvula y el pistón antes de ajustarlo.

La única manera de estar seguro es probarlo.

I would add just a few words to it. When planning to make any adjustments one needs to realize what his goal is. Maximum peak power isn't always the best solution, very often it's better off to gain some mid range RPM torque at the cost of peak power at high RPM and yet get better results on the track... Just a peak power number on the dyno isn't going to do any good on it's own- it has to be in line with car's targets (drag, dtrift, circle etc)..

Thank you very much for the answers. Yes, I agree that most times the maximum power obtained on the dyno is not what we need the most to make a good engine. but you already know that this is difficult for the client to understand... when they are looking for the highest power figure.

So I have no other way than to try and see what gives the best result and sensations.


Forgot to ask, what engine is it?

8 degrees might be a bit too much either way - perhaps suggest actual tuning to the client? Old engines can often be significantly improved reasonably cheaply because they weren't that good in the first place.

You may need to go "old school" with offset woodruff keys, offset pin/peg drives, etc.

I'm not quite sure what the setup is but it sounds like there are two possible fixed cam positions, so I'd try both on the dyno and see what the dyno results favor. In the future, with a single adjustable cam gear, you could try more settings to optimize further.


Sorry I didn't explain myself well. It's not like I only have these 2 positions. what I indicate is the maximum and minimum position that the pulley allows me to regulate.


Got it, thank you.

This course may at first glance appear for continuously variable timing engines only, but it actually covers your situation with a mechanically adjustable gear as well. I think you'll find solid explanation of the impact of the adjustment, as well as tuning workflow in the course.


Ultimately you'll want a dyno to test various cam positions and see what works best for your application.

Thank you so much,

I will look at it!


I see I wasn't clear before, by "tuning", I mean going back to improving intake, exhaust, cylinder head's ports, valvetrain with valves and aftermarket/reground camshaft, etc.

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