Thread: V8 with Carby-Timing

My 101 (standard 3.5) is set at 10BTDC (static) and I run it on 91RON petrol or LPG - runs fine on both - no pinging etc.

I think the book says about 3 or 4 BTDC and I guess LR had reasons for that but 10 is a good compromise for me.

The 6 you are set up on would be OK but I think 10 will be better .

Garry

Is the vac advance working?

Is it getting vac from the manifold or the normal port on one or both of the carbs?

The 350 in my POS ran fine on gas using manifold vac source, but I couldn't tune it after switching to electronic ign. Is fine now after going back to normal (pre-butterfly?) vac source.

10 deg with the vac can line(s) plugged would be ballpark IME.

DL

Originally Posted by 350RRC

Is the vac advance working?

Is it getting vac from the manifold or the normal port on one or both of the carbs?

The 350 in my POS ran fine on gas using manifold vac source, but I couldn't tune it after switching to electronic ign. Is fine now after going back to normal (pre-butterfly?) vac source.

10 deg with the vac can line(s) plugged would be ballpark IME.

DL

The vac is off one carby only..maybe I need both? I will up the advance to 10 BTDC

Cheers

You shouldn't need both but if you have no luck then anything is worth a try. But suck on the vac advance on the dissy to see if you have movement - what are the weights and springs like in the dizzy? Something to check as you rev the engine up.

Yep, 10 degrees to start with is the go - my 101 was set at 14 when I got it and ran great - apart from when heavily worked on really hot days. I've dialled it bac k to 10 or 11 now and it is fine. The dissy could have the advance springs fallen off or the shaft seized where it's supposed to move. Just pulling the rotor arm off can dislodge the springs if it was stuck on tight. A drop of oil down the middle of the shaft is part of regular maintenance but rarely gets done.

I have just put a rebuilt 3.9 8.13:1 compression in my Range Rover. Its running LPG through a BLOS mixer and over the last few weeks I have been playing with the timing. I started at 6 degrees, then 12 degrees then 20 degrees. Even at 20 degrees the motor ran without pinging but it seems to run best on about 12-14 degrees. The vacuum and mechanical advance in my 35DLM8 distributor both work correctly.

I have a hotwire 3.9 .... It loves about 10degrees timing (I also have an ignition advance module that cranks in extra timing when running on gas ..... I think I have it set to add another 6degrees from memory).... Throttle response and power is excellent on gas. Generally the only way you could pick which fuel its running on is the pop and crackle from the exhaust on the overrun (when running on petrol the injection will shut of fuel on the overrun).

Originally Posted by DoubleChevron

I have a hotwire 3.9 .... It loves about 10degrees timing (I also have an ignition advance module that cranks in extra timing when running on gas ..... I think I have it set to add another 6degrees from memory).... Throttle response and power is excellent on gas. Generally the only way you could pick which fuel its running on is the pop and crackle from the exhaust on the overrun (when running on petrol the injection will shut of fuel on the overrun).

Not sure if I've asked before, but can you provide the name and ballpark price of this module?

Does only allow extra advance or can you alter the curve as well?

Gas really needs all the advance (static, mech and vac) just off idle then tapering off up the rev range apparently. People put lighter springs in the dizzy to help with this.

Petrol is somewhat different.

cheers, DL