Could it be likely that if your car (any car) was running the wrong dizzy timing (too far advanced) and you then took to retarding it, would it be likely that the power curve would be much smoother/longer/better?

Also just another question ive always wondered but never asked, in regards to tappet gaps, if say your ccam was supposed to be set @ 19thou and you had it at 15 thou or visa versa, what would be the tell tale signs if any?

I just ask because as i understand it the 'meaner' cams out there often require
larger gapping, but wouldnt smaller gaps open the valves more = more fuel and air in??

just wondering just wondering..

thanks very much :)

Could it be likely that if your car (any car) was running the wrong dizzy timing (too far advanced) and you then took to retarding it, would it be likely that the power curve would be much smoother/longer/better?

if your timing was too advances then hypothetically yes you would be loosing power as the combustion would be happening before the piston has stated decending, and this is harmfull on a motor as it puts a massive force on a piston that is still rising. This is not a good thing to happen as it will destroy a motor quicker than usual.


Also just another question ive always wondered but never asked, in regards to tappet gaps, if say your ccam was supposed to be set @ 19thou and you had it at 15 thou or visa versa, what would be the tell tale signs if any?

I just ask because as i understand it the 'meaner' cams out there often require
larger gapping, but wouldnt smaller gaps open the valves more = more fuel and air in??

This is relative, and needs to be adjusted carefully (you don't want the valves hitting the pistons) but as a rule the closer the gap on your tappets then the longer the lift and duration of the opening (letting more air in and out) This should be done in reference to the cam that you are running. a stock cam is best at stock settings.

If you are wondering about this I would urge you to read a workshop manual and set everything to stock if you have a stock motor. If your not confident take it to someone who has experience in tuning.

Hypothetically I would check the "free play" in your dizzy if it's hard to tune, a worn dizzy will give you the illusion of set correctly at idle then get worse as you go through the revs

_________________
-doing a Degree in Mechanical Engineering,
and a few conversions:
13B Extend in a 1600
4EFTE in a mini ute (all slowly)

Hotter cams run a larger tappet clearance due to the lift on the camshaft lobes being larger. This means the thermal expansion has more affect (difference in expansion between the high and low sides of the cam lobe is greater), so it is necessary to have a larger tappet clearance. Once everything is up to normal running temp the gap should be very similar to that of an engine with stock setup etc. If the tappet clearance is too small the valves will not seat properly and the dynamic compression goes down.. , so while it might lift the valves higher, the valves may not seal when 'closed' when the engine is up to temperature.

All stock cams have opening and closing ramps on them, many performance cams do too, but they are more agressive in their opening and closing profile.
Use the clearances the cam grinder or engine maker suggests, otherwise you may burn valves.

Note that if you go from 1.25 rockers to 1.5 rockers the clearances need to be opened up in proportion. If not, you have reduced the cam follower to cam lobe clearance when valves are closed.
General rule of thumb is go up .003" approx with 1.5 rockers.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Most if not all cams have what is referred to as a quietening ramp. The idea of this is to take up the valve clearance gently before the actual valve opening ramp comes into play. If you didn't have this you would probably get shock loading on the cam and followers which would cause excessive wear as well as a lot of noise.
This is why valves get noisy if the clearances are too large.
If you plot the follower lift vs cam rotation using a degree wheel you will get 2 different lift rates, the first of which is the quietening ramp rate.
The thermal expansion is taken care of by the difference in hot and cold clearances when adjusting the valves.

Hope this helps.
RonR