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non emissions/non stock timing

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XJRpilot

Jedi Hopeful
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my 74 mgb no longer has the air pump or any of the emissions connected(shame on me!). the original carbs that were on it were HIF's. the previous owner changed them to HS4's. so i have HS4's and no emission components to deal with. i have the stock 25D distributor on the 18V engine. which timing application should i use in the bentley manual?
i was wondering since the timing for my "B"
is listed as 11 deg btdc at 1500rpm vacuum disconnected, but that applies to the engine with hif's and emissions( 18V 73-74). the hs'4 engines (18V 71-72)timing is listed as either 15,16 or 20 deg btdc at 1500 rpm. it also lists in addition to the 18v engine, 18gk,18gf,and 18gh engines. or does it matter? did the air pump and emissions
play a part in the timing setting?
also, how would one adjust/set the retard/advance for the vacuum advance? cant seem to find that info in the bentley. if you can, let me know what page its on. thanks

[ 04-29-2003: Message edited by: XJRpilot ]</p>
 
There is a simple way!! Advance it what you think it should be, take it for a drive and continue to advance it a couple of degrees at a time!! When it pings under load, back it off a couple of degrees and you will be fine!! The main thing is to make sure that you don't get pre-igniton!!
 
A decent way (from a performance point of view), is to time the car at about 32 to 34 degrees BTDC at high RPM (around 5000). This will insure that you are getting proper advance in the power range...if you don't have to deal with emissions, then it doesn't matter what your idle timing is (unless you have starting problems).
 
nial,
i like the performance viewpoint idea.
the notch's on the timing scale only go up to 20deg btdc. should 32-34 deg btdc be a guesstimate distance on the scale and pully?
 
Yes...I forgot to mention that the timing marks don't go up that high.....I have a 34 degree notch filed in my pully, but you could make a pretty good mark with paint or finger-nail polish. Use the distances on the existing pully marks to figure out about where 34 degrees is.

Alternate idea:some timing lights have an adjustment so that you can change the timing stobe.....with these, just set the adjustment at "34" and be sure that the "zero" mark on the pully lines up at around 5000 RPM (either way, leave the vacuum advance on, if the ditributor is fitted with one).

Note: Be careful! It's no fun to have the wires of the timing light get tangled on an engine spinning at high RPM!
 
I usually time all B's by driving them. Have the engine warm, take it for a drive. Fourth gear 30mph, nail it, should hear a slight ping that goes away at 40. Not scientific, but it seems the easiest with modern fuels and the variety of mods on some of these cars.
 
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