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cam question (overlap)

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as Andre stated in a video, we typically have some overlap (in a DOHC engine) bewteen intake and exhaust periods in the S.S.B.B. cycle.

as far as my understanding goes, the "choppy" sounding engines get their sound from "big" cams, and from my understanding "big" is relative to the amount of overlap between intake and exhaust valves being open

my question is, is it possible to create a smoother sounding engine if we had no overlap? and if so, would it be harmful to the engine or other internals?

in an rb26 lets say the cams are 264* (both IN. & EX. and have the same specs [such as lift etc]), from my understanding of cam spec knowledge, there is no overlap on this cam setup and should then theoretically sound 'smoother' (smoother meaning less or no "chop" or, as Andre put it in the ghost cam tutorial video, "lopey").

am i correct in my theory? what have i gotten wrong if anything? also can someone link me a good video on cam specs if possible please?

You seem to have it "wrong".

"Big" camshafts refer to the lift and/or duration of the lobes, which are what open the valves. There are physical limitations to camshaft design that means as the lobe is made 'bigger', the opening point and closing points are spread out further from the centre line of the lobe. In turn this normally means an increase in 'overlap', as the exhaust closes later and the inlet opens earlier.

You're correct in that this 'overlap' affects the engine's ability to expel burned exhaust gases, as the valve is open longer on the intake stroke and can draw those gases back into the cylinder, and as the intake opens earlier on the exhaust stoke, some of the exhaust gases can be pushed into the intake port. Both these mean that when the spark plug fires the mixture may burn poorly or even fail to ignite at times.

If you're looking for increased airflow with a smoother idle and better low rpm driveability, you should be looking for high lift camshafts with a minimum of increased duration. Another option may be to retard the intake and/or advance the exhaust to reduce the overlap - the first 'may' give a little more low rpm torque, and the latter a little more top end.

Oh, regarding the "264" camshafts - that designation is usually the opening duration in crankshaft degrees, and as each stroke is 180 degrees, that means there are 84 degrees excess that will be partly before, and partly after, the nominal stroke for that part of the operating cycle. if you look at some of these illustrations, it may be made clearer - https://www.google.com/search?client=firefox-b-d&sca_esv=569124370&q=camshaft+opening+chart&tbm=isch&source=univ&fir=dhvPTut6gqnRhM%252CZ11flmf348298M%252C_%253B_BsyVLY8-a-A3M%252COfBwxxxwep4u2M%252C_%253BRwULQpd6RrmchM%252CxPhAZnKP_woIGM%252C_%253Bdw-O7PI8u-2xMM%252CEoRC9DKPHNF_LM%252C_%253BaxcCuwvdzSGuUM%252CoERv9e9kMWgQvM%252C_%253BiS3n9sZj-m9T1M%252C_rAIU58TrpvGaM%252C_%253BdGB7DmvKkJ31OM%252CrcTtWTQtnr3rDM%252C_%253BxdiDgMNi3fxZxM%252C7NTlieZkn9px4M%252C_%253BJlK83aOUG9sjwM%252CeJvmNWB5JyfY8M%252C_%253BSK1y74cI7HRQPM%252C3Y1Xk22poddHYM%252C_&usg=AI4_-kQchZ3jiqI4FEYmu5zY93Taj6eCug&sa=X&ved=2ahUKEwix4d25l82BAxWdslYBHXirBLQQ7Al6BAgyEFc&biw=2400&bih=1321&dpr=0.8

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