Outer Limits 4x4 Board

I have a timing problem that is driving me nuts.

Motor is 3.5l with holley carb. in 84 RR

Fireball electronic ignition.

Book says timing for Distributor is 5% after tdc (I forget the number of the distributor but that is what the book says.)

It seems to run better on anything up to 5% below tdc and coincidentally this is the setting for other distributor numbers. Does run a bit hot though.

Can anyone help with a sure fire way to time it properly using guestimation.

No wonder its driving you nuts, timing for 84 3.5 hi comp should be approx. 6 degrees BTDC ! What book are you referencing ?

a vacuum gauge might help you can time it off that and then read what the timing marks say

Tom

I am reading both a haynes manual and another range rover workshop manual. Both say the same thing.

It simply list several distributors with different numbers and gives a different % above or below tdc.

I am in Brisbane at the moment and off hand cant rememember the number of the dizzie. Off hand I think it end in something like 668A or something like that.

The book says a motor with this one should be 5 above, and the other types 5 below. Seems like a big difference to me. The simple an answer might be to get another distributor.

Got me stuffed. Stupid thing is that it idles perfect on either, just seems to run better, although hotter on the btdc setting.

Actually it is an 83 RR but motors should be the same either way - I think. Another one I acquired along the way. Actually the timing marks are highlighted at 5 atdc too.

Bugger it, better still I think I will piss it off and put a 4.4 that I have had sitting there for a while in it.

Still, I,m curious as to why they are so different if that is correct.

So where does it run the best?

Every 3.5 I have had has always been 5 or 6 before TDC.

my '76 3.5 carbie was always 6 degrees BTDC move it around to that and go for a drive.


Tom

G`day

The difference is in the advance of the dissy

The ones set at 5 deg ATDC will have between 0 degs and 4 degs advance at 1400 RPMs .

Others set at BTDC have betwwen 8 degs and 15 degs at the same RPMs

Timing marks are only a guide and only any good if TDC is known to be True .

There are other ways to check but the most acurate ( i think ) is with a dial gauge on top of the piston when the heads off .

Ours has TTDC and is set at 18 degs BTDC for lpg and 10 degs for petrol .

Set it where it`s happy if its a slug advance a bit if it pings back it off a bit , don`t worry too much about the actual figure , other than to use as reference .

Peter

Thanks for the feedback guys, it might be that I will need to buy another vacuum advance module.

I'll just have to start saving now ............ let me see, if I sell the kids, the wife and a set of dirty undies I might be able to afford one.

Oh well such is life.

Check the faqs

For Vacuum Advance replacments call

Carb N Gas
11 Mountjoy St Woolloongabba, Brisbane 4102 QLD, (07) 3891 5886

The do units on exchange for around $70


Tom

...do not buy the genuine unit, it's toooo expensive. Also seen vac advance units from Les Richmond

http://www.lrautomotive.com.au/