If you can't get a good visual of the timing marks, I have used a white paint pen to brighten up a mark close to your targeted timing. It also might help to verify that the timing marks are valid if the motor is rebuilt because different harmonic balancers and timing pointers have been used on small blocks. Make sure that zero on the balancer is TDC. I have had a couple of instances where a car seemed to run fairly strong, and then get the timing truly right and the difference was startling. Electric fan ... there is a great tech article on adapting a factory Taurus fan. The radiator you are running seems thicker than a stocker, so you may want to double check measurements. Everything listed in this post bears looking at. You well may have more than one thing contributing to this problem. More to consider ... is the fuel tank clean? Good fuel that hasn't set for months? Fuel filter changed lately?
I plan on checking all these out for sure! What is a good timing to aim for, I know that timing changes with vacuum. So what should I aim for on the harmonic balancer. The motor is a 1974 302, with 351 heads, slightly better than stock cam. I am running an edelbrock dual intake with a 600 cfm carb. Also using pertronix one ignition.
It's actually the other way around. Vacuum changes with timing. You want the absolute HIGHEST vacuum that your motor will produce since that denotes burn efficiency. That doesn't necessarily mean that you need to pump more fuel into the chamber.. only that you want to try and maximize the amount of fuel that gets burned on every power stroke. Timing lead requirements go up as the cam and combustion chamber gets larger. There are many other factors here as well but those two are fairly dominant. Some quick pointers. You can paint the numbers you have but they are usually limited in resolution and range. I myself would measure/find out the balancer diameter and get a timing tape to glue in place while paying special attention to true TDC or the power stroke. Also best to clearcoat the cheaper tapes too because they wear out rather quickly if you drive the car a lot in the weather. Just be sure to prep and solvent clean the balancer well beforehand. Once it's dry you simply spray the clearcoat at the tape while the engine is running(usually easier if the car is up on stands NOT just the jack itself). Assuming you have the piston down in the hole slightly as it would be in stock form(this is one of the ways Ford reduced compression with shorter pin heights and taller decks), the cylinder heads haven't been purposely milled to reduce volume, you're probably struggling to hit 9:1 compression with this motor. That hurts the overall result but you can still greatly maximize cylinder pressures with improved timing lead. Timing lead should be in the neighborhood or about low 30's at idle with the vac advance hooked to full manifold vacuum. Total timing lead(without the vac advance hooked up) should be somewhere in the high 30's to keep it on the safe side. The problem you will quickly run into here is that the timing advance mechanism is extremely long in factory form and you cannot/willnot be able to give the motor the heavier initial lead that it prefers because you will end up with WAYYYY too much total lead once the mechanical comes all the way into the picture. This can often partially be remedied by rotating the advance limiting arms to the shorter stroke. This is just one link of dozens of good ones but see here. http://www.reincarnation-automotive.com/Duraspark_distributor_recurve_instructions_index.html You'll also need to check to see if your distributors vac advance pot has an allen wrench(5/32 IIRC?) adjustment feature built into it. If not, then you will end up with way too fat advance supplementation being added to the initial numbers that you should be seeking, especially at higher rpm/low throttle angles such as highway cruising would give. Which then requires you to pull some initial away to avoid lean-outs.. lean pops and surging at lighter throttle angles. That is the WRONG thing to do because you want the initial number to stay higher so when you abrubtly drop the hammer from idle/low engine speeds.. and the vac advance suddenly falls away due to loss of manifold vacuum.. the motor doesn't labor while trying to rpm and come up on the mechanical advance. Although most Fords come with them, it's always best to order an adjustable advance pot if yours is not equipped with one. This allows you to run heavier initial lead, while limiting the vac advance pot to around 8-10°, and also limiting the total mechanical sweep. It would look something like this. 20-24° initial lead(advance pot unhooked) 10° vacuum pot supplementation(adjustment mechanism tightened almost all the way up and running off full manifold vacuum source) 13-16° mechanical advance sweep(after you've flopped the advance arms to the tighter sweep mentioned in the link) This gives you a ballpark sweep of 30-34° at idle.. upwards of 40° at higher engine speed/light throttle cruise(this is NOT too high because the engine isn't heavily loaded and mixture density/combustion speeds require more spark lead and it will fall away as the pedal is pushed/manifold vacuum falls away.. and anywhere from 20° at minimum to about 38° maximum at full throttle/higher rev's. To do all this effectively will require some learning and carb adjustments along the way. Most will never go to the extreme of the available gains because the carb tuning will typically become too daunting(IFR and air bleed resizing). Not a big deal as most is gained earlier on in the adjustment curves here anyways. You will need a vacuum gauge and timing light to help dial it all in. Sorry I'm limited on time to go into more detail here. Hope that helps steer you in the right direction. PS. make sure you have the correct amount of front transition slot exposure on the carb too or you'll be chasing your tail here. Too much and the engine won't respond to mixture screw adjustements.. too little and it will require too much mixture screw to smooth things out or even hesitate and stumble like something's wrong with the accelerator pump shot. Get the front close to right and then adjust idle speed with the secondary opening. Patience is key but the reward can be very substantial if you stay the course in getting it all dialed in. Another easy trick to see what power you are missing out on here is to LOCK the advance mechanism completely to about 36-38° and run the car hard from idle on up. You may have to twist the distributor to retard timing just to get the car started due to starter kickback, then readvance it back to the 36-38° for testing. Just be sure to readjust idle mixture screws and take note of the manifold vacuum when running that much advance. If it detonates?.. just pull back some timing till it calms down. The amount of manifold vacuum that WILL be gained here and more importantly.. the additional power at throttle tip in will amaze you. The motor will suddenly seem MUCH bigger down low in the rev range. And that's when you'll fully realize that all I said above is completely worth the added effort and learning curves involved.
