There's little point in sticking to the standard settings on a rebuilt &
modified engine. The only way to set it up properly is on a rolling road (it
really is worth it).
To get the car running properly in the short term, forget using a timing light
simply twist the distributor until it runs ok, take it on a run and check for
pinking. (15 to 20 degrees is not an unusal setting) Pull the plugs out and
check whether the mixture looks rich/lean and adjust the carbs to suit (or use
one of those colourtune things)
Do check the valve timing, but once again the standard settings will be wrong
for a modified cam. Most performance cams require bigger clearances + will
have
different settings for inlet and exhaust
Hope this is of some help
Regards
Alan Tong
In your message dated Wednesday 16, August 1995 you wrote :
> Hello All!
>
> I've got a 72 MGB/GT. I've recently put in an electronic ignition,
> replaced the vaccuume advance, put on a tuned exhaust header, a new
> muffler and pipes, and rebuild the carbs. With all of these mods, one
> would expect a nice running MG, no? (p.s. Dual SU carbs.)
>
> Now to the fun part - tuning it all up! Here's what I've done:
>
> 1. Removed vaccuume hose from vaccuume advance. Set static timing to 10 BTDC.
> Hooked the vaccuume hose back up.
>
> 2. Adjusted the mixture jets so they were even with the bottom of the carbs,
> then backed them off two turns each.
>
> 3. Set the idle adjust screws so that it's idling at approx 800 RPM.
>
> 4. Tried to do the adjustment on the mixture so that it is at the knee of
> the curve. (Fastest lean speed.) This is a hard one to do.
>
> Voila, should have a tuned MG, no? Well, it doesn't run very well. It's
> week in acceleration, when cruising at most speeds, it kinda stutters.
>
> Something which I observed however: Before I did the tuning, I drove it
around
> after I got it all back together. Really Peppy! However, it was idling
around
> 1500 RPM. When I put the timing light on, it appeared to be ruuning about
> 20 BTDC. When I changed the timing to 10 BTDC, it dropped down to a nice slow
> idle.
>
> The PPO has put a High-performance cam in. Would this affect the
> timing?
>
>
> So, here's what I'm going to try:
>
> Slowly keep advancing untill idle speed starts coming up. Stop when it gets
> to 1000 RPM. Try it there. (See if pep comes back, smooth running, etc.)
>
> Buy a carb balancer so I can for sure get the carbs in synch.
>
> Any other suggestions? Am I missing something? (Valves? - I haven't touched
> them yet.)
>
> Thanks for any help! :)
>
> David Hall
> dhall@vcd.hp.com
>
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