Tuning Acceleration and top speed

[Phild76]

Hi, I've got a 500 engine with the 70mm cylinder head and piston upgrade.. the carb is a webber imb28 and the drive feels very slow and takes an age to get up to speed.. has anyone got any tips on getting better performance from the carb. The top speed is maxing out at 44mph, is this normal or should it be capable of a bit more.. going up hill today were usually holds it speed it was slowly losing acceleration.. it is hot today so not sure if this hurting the performance as the coil was red hot thanks

 

[Ant Knox]

Sounds like potentially a timing issue.

 

[Phild76]

Sounds like potentially a timing issue.

How would I check the timing, when I checked the top dead centre, timing mark and distributor arm they look correct.. would the engine sound different if the timing is out?

 

[giardini]

How would I check the timing

Check that the points gap is correct, stick a piece of ciggie paper between the closed points, rotate the engine until the paper is released, should be at the 10° advance mark. Adjust by rotating the distributor. All made easier by removing the sparkplugs first.

 

[the hobbler]

Check that the points gap is correct, stick a piece of ciggie paper between the closed points, rotate the engine until the paper is released, should be at the 10° advance mark. Adjust by rotating the distributor. All made easier by removing the sparkplugs first.

Make yourself a little 12 volt test lamp---a couple of small 'croc clips' and a 12 volt bulb in a small holder (any small 12 volt lamp would suffice--it doesn't have to be white). Clip one wire to the NEGATIVE side of the coil (the wire that goes to the distributor) and the other clip to a good earth. With the ignition turned OFF, turn the engine (clock-wise)until the timing mark on the pulley is just before the mark on the timing-chain cover. Pull the ignition lead out of the coil---you do NOT want the engine to start when you are checking the timing---it can be detrimental to one's fingers! Now turn the ignition ON. Slowly turn the engine until the timing mark on the pulley is either aligned with the 1st of the timing marks OR 14mm before the timing mark (which will be TDC) if you have only 1 timing mark. As the marks align, the test lamp should illuminate. If the test-lamp illuminates BEFORE the marks align, your timing is too advanced. If the test lamp has not illuminated, the timing is too retarded. Leave the engine with the timing marks aligned----if the timing is advanced, loosen the distributor clamp and turn the distributor CLOCK-WISE until the light goes out---then turn the distributor ANTI-clockwise until the light comes back on. If the light didnotilluminate when the timing-marks were aligned, turn the distributor ANTI-clockwise until the light comes on. Re-tighten the distributor clamp. With the ignition still on and the test lamp still connected, turn the engine over 1 full revolution (a spanner of socket on the dynamo/alternator nut is the easiest way) until the timing =-marks are about to align---when they DO align, the test lamp should illuminate---if it does,your "static-timing" has been set to 10 degress BTDC.Turn the ignition off and reconnect the ignition lead to your coil. When you stat the engine, you will almost certainly have to re adjust your idle and mixture screws.
With the 70mm barrels and pistons, your car should easily be able to attain 60mph---what jets have you got in the carburettor? I wouldn't be a bit surprised to find that it has been jetted for a 652cc '126' engine. There are a number of differences in the jetting between the '594' and '652' variants of the 126 engine when using the same carburettor.

 

[Phild76]

Make yourself a little 12 volt test lamp---a couple of small 'croc clips' and a 12 volt bulb in a small holder (any small 12 volt lamp would suffice--it doesn't have to be white). Clip one wire to the NEGATIVE side of the coil (the wire that goes to the distributor) and the other clip to a good earth. With the ignition turned OFF, turn the engine (clock-wise)until the timing mark on the pulley is just before the mark on the timing-chain cover. Pull the ignition lead out of the coil---you do NOT want the engine to start when you are checking the timing---it can be detrimental to one's fingers! Now turn the ignition ON. Slowly turn the engine until the timing mark on the pulley is either aligned with the 1st of the timing marks OR 14mm before the timing mark (which will be TDC) if you have only 1 timing mark. As the marks align, the test lamp should illuminate. If the test-lamp illuminates BEFORE the marks align, your timing is too advanced. If the test lamp has not illuminated, the timing is too retarded. Leave the engine with the timing marks aligned----if the timing is advanced, loosen the distributor clamp and turn the distributor CLOCK-WISE until the light goes out---then turn the distributor ANTI-clockwise until the light comes back on. If the light didnotilluminate when the timing-marks were aligned, turn the distributor ANTI-clockwise until the light comes on. Re-tighten the distributor clamp. With the ignition still on and the test lamp still connected, turn the engine over 1 full revolution (a spanner of socket on the dynamo/alternator nut is the easiest way) until the timing =-marks are about to align---when they DO align, the test lamp should illuminate---if it does,your "static-timing" has been set to 10 degress BTDC.Turn the ignition off and reconnect the ignition lead to your coil. When you stat the engine, you will almost certainly have to re adjust your idle and mixture screws.
With the 70mm barrels and pistons, your car should easily be able to attain 60mph---what jets have you got in the carburettor? I wouldn't be a bit surprised to find that it has been jetted for a 652cc '126' engine. There are a number of differences in the jetting between the '594' and '652' variants of the 126 engine when using the same carburettor.

I have order one so will try this on Friday, many thanks for the advice this forum is amazing for advice saves hours fault finding.. I've also released that the idle jet I've never adjusted and that the one in was set up for the 650 engine so will be running the engine lean.. so ordered a new one recommended for Weber 28 500cc combination.. thanks for the help

 

[Pete O]

Make yourself a little 12 volt test lamp---a couple of small 'croc clips' and a 12 volt bulb in a small holder (any small 12 volt lamp would suffice--it doesn't have to be white). Clip one wire to the NEGATIVE side of the coil (the wire that goes to the distributor) and the other clip to a good earth. With the ignition turned OFF, turn the engine (clock-wise)until the timing mark on the pulley is just before the mark on the timing-chain cover. Pull the ignition lead out of the coil---you do NOT want the engine to start when you are checking the timing---it can be detrimental to one's fingers! Now turn the ignition ON. Slowly turn the engine until the timing mark on the pulley is either aligned with the 1st of the timing marks OR 14mm before the timing mark (which will be TDC) if you have only 1 timing mark. As the marks align, the test lamp should illuminate. If the test-lamp illuminates BEFORE the marks align, your timing is too advanced. If the test lamp has not illuminated, the timing is too retarded. Leave the engine with the timing marks aligned----if the timing is advanced, loosen the distributor clamp and turn the distributor CLOCK-WISE until the light goes out---then turn the distributor ANTI-clockwise until the light comes back on. If the light didnotilluminate when the timing-marks were aligned, turn the distributor ANTI-clockwise until the light comes on. Re-tighten the distributor clamp. With the ignition still on and the test lamp still connected, turn the engine over 1 full revolution (a spanner of socket on the dynamo/alternator nut is the easiest way) until the timing =-marks are about to align---when they DO align, the test lamp should illuminate---if it does,your "static-timing" has been set to 10 degress BTDC.Turn the ignition off and reconnect the ignition lead to your coil. When you stat the engine, you will almost certainly have to re adjust your idle and mixture screws.

What an excellent description of static timing with a test lamp. It can also be done without a test lamp, if you disconnect the ignition condenser and with the distributor cap removed, observe the points as you slowly rotate the crankshaft towards TDC, there will be a small spark across the points as contact is broken (it's the opening of the points that makes the ignition coil produce the ignition impulse). You may not even need to disconnect the condenser, but as it's there to suppress the arcing when the points open, you'll get a more visible spark without it.