Help with 1950cc MGB way down on power

[Billy_Whizzzz]

Posted this in the MG section but didn’t get a realise so am trying here! Got a ‘68 MGB that I bought with a 1950 Oselli engine that has been dry stored for a few years. I’m struggling to get it running well. It has been extensively recommissioned with a new stage 2 head, Weber, and 123 distributor. Sent it in to be set up on the rolling road and is way down on power - 65hp at flywheel and won’t rev beyond 4000. Compression is very good and I know engine is generally strong and in good condition. Carb has been rejetted. It was in the rolling road a few years back before it was put into storage and was showing 101hp at flywheel on twin SUs and standard head. We’ve been through most obvious things. Could for some reason the cam be a tooth out (can’t think how or why…). Anyone any other thoughts? No garage locally seems to be up for going through timing!

[gazza285]

There's no need to disturb the cam timing while fitting a new head, so I cannot see that being an issue.

You are opening the throttle on the Weber carb fully I hope?

[GreenV8S]

Billy_Whizzzz said:

We’ve been through most obvious things.

What does that mean?

Fuel mixture and ignition timing would be the first things to check. Are cylinder temperatures looking even? Checked the compression?

[phumy]

Check, plugs, points are good condition, gapped and have flat parallel faces, new condenser, check advance weights are working and not stuck, check springs for weights are in place, new set of leads, check distrbutor cap and central carbon contact is still sprung loaded, check the 4 contacts inside the cap are good condition and show no signs of arching, check rotor arm is good condion and clean on the rotationg face. Check timing. Thats should be good enough for the ignition.

On the fuel side, check fuel pump is delivering the flow it says it should, check carb floats are free to lift and drop, if SU carbs check in the jet hole that no restrctions, check needle is correctly centralised, check oil in dash pot and dash pot plunger lifts and drops using the lifter. Check carbs are in synch on the central throttle spindle and one is not operating before the other. Also check the synch of the air flow by listening down a peice of hose whilst the engine is running, you willl hear the difference if theyre out of synch.

Try to get it on an old school engine tuning testers.

[Billy_Whizzzz]

phumy said:

Check, plugs, points are good condition, gapped and have flat parallel faces, new condenser, check advance weights are working and not stuck, check springs for weights are in place, new set of leads, check distrbutor cap and central carbon contact is still sprung loaded, check the 4 contacts inside the cap are good condition and show no signs of arching, check rotor arm is good condion and clean on the rotationg face. Check timing. Thats should be good enough for the ignition.

On the fuel side, check fuel pump is delivering the flow it says it should, check carb floats are free to lift and drop, if SU carbs check in the jet hole that no restrctions, check needle is correctly centralised, check oil in dash pot and dash pot plunger lifts and drops using the lifter. Check carbs are in synch on the central throttle spindle and one is not operating before the other. Also check the synch of the air flow by listening down a peice of hose whilst the engine is running, you willl hear the difference if theyre out of synch.

Try to get it on an old school engine tuning testers.

Thanks for this - it has a electronic ignition (123 distributor) plus is running a Weber DCOE 45 so many of those things don’t need need doing. One of the symptoms is ‘sneezing’ a bit at about 1750 RPM - a symptom of running lean I think. Fuel pump pressure a good shout…

[phumy]

Billy_Whizzzz said:

phumy said:

Check, plugs, points are good condition, gapped and have flat parallel faces, new condenser, check advance weights are working and not stuck, check springs for weights are in place, new set of leads, check distrbutor cap and central carbon contact is still sprung loaded, check the 4 contacts inside the cap are good condition and show no signs of arching, check rotor arm is good condion and clean on the rotationg face. Check timing. Thats should be good enough for the ignition.

On the fuel side, check fuel pump is delivering the flow it says it should, check carb floats are free to lift and drop, if SU carbs check in the jet hole that no restrctions, check needle is correctly centralised, check oil in dash pot and dash pot plunger lifts and drops using the lifter. Check carbs are in synch on the central throttle spindle and one is not operating before the other. Also check the synch of the air flow by listening down a peice of hose whilst the engine is running, you willl hear the difference if theyre out of synch.

Try to get it on an old school engine tuning testers.

Thanks for this - it has a electronic ignition (123 distributor) plus is running a Weber DCOE 45 so many of those things don’t need need doing. One of the symptoms is ‘sneezing’ a bit at about 1750 RPM - a symptom of running lean I think. Fuel pump pressure a good shout…

Get all the jets blown through on the Weber, check fuel float. check for dirt inside. Check you have correct sized chokes, has head been flowed? A rolling road tune will find all the issues but if you look right through the ignition to illiminate those issues first then the fuel side im sure it will get sorted.



Sneezing? backfiring?