Timming Help on 7.4L 330
 

'96 carb 7.4L 330hp how do I set/check timming & can it be advanced for performance gains?? what are the proper settings, want to check to make sure they are dialed in.

That engine will withstand a bit more timing due to it's low compression. Standard (If my memory is working) is 34BTDC. 36 would give the engine a bit more snap. 38 would be pushing it but you'd need premium fuel. Check the timing up to 3000RPM or so to make sure you are measuring it with all the advance in.

Increasing advance will not likely give you more speed but will increase torque slightly.

I want to check it out tonight - posibily water test - to take initial timming you connect the purple wire to a ground? than disconect to read advance???

DO NOT GROUND THE PURPLE WIRE!!!! That wire is from the ignition switch. It is a HOT wire. You will burn some wires or if you're lucky pop a breaker. There is no need to ground anything on a carb motor since the ignition is not computer controlled.

The correct way to set the advance on your motor is with an advance timing light set to the degree of advance you are looking for. 36* is a good safe number. First, with the engine at idle and the pickup on the timing light clamped over the #1 spark plug wire,(it is the front port side,) you aim the adjusted timing light at the pointer over the harmonic balancer on the port side of the motor. You should see the groove in the balancer when the light flashes if you are hooked up correctly. At this point the groove will be a couple of inches down from the largest V notch in the pointer. As you increase rpms that groove will get closer to the notch. That notch is 0*. Next, bring the rpms up slowly until the groove no longer moves. Rpms do not matter. You are looking for total advance. You may have to rev the engine to more than 3500 rpms to achieve total advance on a Thunderbolt IV system. When you have achieved total advance look at where the groove is in relationship to the notch. It should be lined up with the notch. If it is, your timing is OK. If it is not then you need to loosen the distributor hold down clamp bolt so you can turn the distributor. Turn it a little at a time to see how it affects the groove-notch relationship. When you get it where you want it, tighten the hold down clamp bolt and recheck the timing. It usually moves a little when you tighten the bolt so you will have to readjust the distributor until the timing is right with the bolt tight. When you are done make sure that the hold down clamp is tight against the distributor and has not moved away while loosening and tightening the bolt.

Sorry this explanation is so long but this is the correct way to get the job done right. It is not really very hard to do, it just takes the right tools and some trial and error to get it right on.

Good luck, Doug

Good description

Thanks Doug for your detailed instructions, I had one engine out of timming quite a bit, I set them @ 34 advance for now, but I will try 36 tonight, thanks again for the help OSO