Another Timing Question

[Emyers]

I have been going thru the archives for the last couple of days looking for a specific answer....no joy.

I am well aware of the Carb motor 1400 rpm, Tii 2400 rpm timing requirement. Here is my question: 9.5 compression, stock cam, Crane XR 700 w/PS 91 coil, dual Mikuni PHH44, and 002 non vacuum mech advance distributor. I need to confirm the directions that Uncle CD stands by, that ALL carbed motors, regardless of compression, are timed at 1400 rpm. Would not the higher compression require the use of the approximate timing spec, 2400 rpm, of the Tii since it runs a similiar compression?

Thanks

Earl

74 02Lux

02 M Roadster

72 Volvo 1800ES

[02for2]

Have you re-curved the dizzy? When substituting the mech dizzy for the vac one, you need to recurve it so the advance kicks in sooner and also that it has an add'l 5° - 10° advance.

This difference likely explains the different RPMs used to set the timing.

Cheers!

[eurotrash]

I have been wondering if, since I have a 008 mechanical distributor on a carb'd motor, if the 2400 rpm needs used not so much because of the compression or MFI, but due to the nature of the mechanical distributor..

I have it set to the ball at 1400 now, and it runs well, but could it be better at 2400?? Or should I use the adjustable light to time it 5-10* more advanced??

Guess I needs to essperamint..

[williamdholmes]

best to use a timing light that can determine the total degrees of advance. for non turbo engines 30 degrees is sufficient. normally this will give you 5 or so degrees of advance at idle speed. the advance curve does not influence amount of total advance, just piston speed.

[M3M3]

I have been going thru the archives for the last couple of days looking for a specific answer....no joy.

I am well aware of the Carb motor 1400 rpm, Tii 2400 rpm timing requirement. Here is my question: 9.5 compression, stock cam, Crane XR 700 w/PS 91 coil, dual Mikuni PHH44, and 002 non vacuum mech advance distributor. I need to confirm the directions that Uncle CD stands by, that ALL carbed motors, regardless of compression, are timed at 1400 rpm. Would not the higher compression require the use of the approximate timing spec, 2400 rpm, of the Tii since it runs a similiar compression?

Thanks

Earl

74 02Lux

02 M Roadster

72 Volvo 1800ES

once you go "off the reservation" by having a non-stock motor build, the 1400/2400 timing numbers no longer apply. those are for stock engines. you can use them for base reference, but then you have to play with the timing to get to the spot your particular combo of mods needs. carb or tii is not relevant. the factors are compression, cam, type of fuel used, how much mixture the induction system can get to the chambers, etc.

[Harv]

Years ago I messed around with a recurved vac dizzy when I was running dual 40's. No matter what, there was too much initial advance and not enough later on. Due to what I feel was a not properly recurve distributer. I swapped in a new (then) full mech tii distributer and what a difference. Gone was the knock and ping at lower rpm and throttle tip in and good power in the top end.

John

[TobyB]

the advance curve does not influence amount of total advance, just piston speed.

?

You mean, rate that the advance kicks in.

Here's another way to go about it, but you'll need a degreed

front pulley and a shot at it.

Start with 36 degrees total advance WITH THE MECHANICAL ADVANCE ALL IN

and the vac advance out.

Ususally this means shooting it at over 4500 rpm.

Then attach the vac advance and watch to see what it does as you idle it

up to 4500- sitting, you'll see the MOST vac advance you'd ever see.

If it goes much over 45, drive it carefully at first to see if it's going to

predetonate. It probably won't.

a different way.

t

[schwarz75]

Harv, are you using the distributor in your car that's depicted by the brown line in the graph? I like the lower limit of advance that's shown. I was not able to use a #002 mechanical distributor without suffering detonation at high revs, so that distributor depicted in the graph would probably solve the pinging while providing a nice smooth idle.

[jp02ti]

set it the same as a ti, which i think is also 2400 rpm.

your motor is essentially a ti motor.