DIZZY CURVE

[CHESTNUTXE 7,300]

I always here that in any sort of performance build ,the dizzy has the curve changed to suit the new cam,i imagine thats the advance springs that are changed ? can people add what they had done as i am about to get my factory xe electronic done,as with the more expensive units like ICE  and MSD some models have over 60 settings to suit your engine.

[gerg 10,871]

A bigger cam needs more initial timing but total ends up about the same or less. Example: say stock timing is 6 deg, total timing is 35, that means mech advance is 29. A moderate cam (say 214/224 @ 0.050") might like 15 initial but 30 total, meaning the mechanical advance is 15. As the torque curve will peak later, the advance will need to come in later also (heavier springs). This is why the dizzy needs a re-curve.

[CHESTNUTXE 7,300]

hmmmm ok so my mild cam will need just a little bit heavier spring,im gunna get old mate mr dizzy to do it.

[judgetread 757]

springs only control the rate advance comes in at. He'll modify the stops to adjust total advance, maybe lighter springs to get it in all earlier

[gerg 10,871]

My MSD curve is actually a double curve, it kicks up at about 1500, dips back down at around 3000, then ramps up again to 4500 to a soft limit at 5500. I say that just because your engine will want whatever curve it wants.

[CHESTNUTXE 7,300]

to get all in earleir sounds right in my app,atm my home tune with a std xe dizzy i feel there is to much initial to get it to run ok,the powerbond street balancer is painted black by the factory and is bloody so hard to read so i put a white marker at 13 deg ,and also one at 35 deg total,anything under 13 it fuels up and coughs but seems to come near perfect around 2000rpm and above.

[CHESTNUTXE 7,300]

Maybe a energy polarizer will fix it.

[gerg 10,871]

Been watching the mini-series on Brocky?

[CHESTNUTXE 7,300]

The way it was portrayed ,he sought of went a bit hippi or alternate in the end,i hope DJ doesnt grow his hair long lol.

[FORD_MAN 1,026]

He did go hippy/alternate at one stage when he hooked up with a guru,

heard some old blokes who used to pit crew for a local car at bathurst saying about it the other week.

most blokes having a beer, brockies drinking chamomile tea

[brianj 48]

Every cam is different, but I've done a little rule of thumb that most performance set ups want all the mechanical advance in by 2500 to 3000 rpm. If your distributors are set up the same, there should be a pair slotted cams in the bottom under the pickup or points plate. They are reversible, and should have a number stamped on them, that equals half of the avance the cam will allow. A "10" stamped plate allows 20 degrees of mechanical, a 15 gives you 30 degrees, etc. There are several internet sites that can give you an exact measurement for the slot size to equal what you want for advance, and you can weld up the slots and file them to get exactly what you want. For example, i wanted 10 degrees of mechanical advance on my car, so i welded my slot closed, and filed it to .410 (or around there- I'm not sure what it was) and my distributor is now restricted to 10 degrees, which let me run way more initial advance, without going over 30 degrees total. For how fast it comes in, you can play with different weight springs (light springs bring the timing in faster) until you get what you want. If you don't have a selection of springs, you can also bend the spring attachment tabs to increase or decrease spring tension. It is actually pretty simple to do yourself. The only other thing I would advise, is while you are playing with getting your advance curve how you like it, unhook the vacuum advance. Once you have your mechanical advance how you like it, THEN you can hook the vacuum advance back up and tinker with that. Trying to do both at the same time can get confusing.

[CHESTNUTXE 7,300]

I understand about the weights and springs,but im going to leave it to the dizzy guy to do,how big is your cam ?

[brianj 48]

It's a Comp Cams XE270HR. I'd have to look for the cam card to remember the numbers, but it's around .512 lift with 1.6 rockers. It's a dual grind, so it favors the exhaust a bit. My timing curve is pretty odd, because it is a blower car.

 

 

EDIT found the cam card. All of those lift numbers are for 1.7 rockers. I'm running 1.6, so lift is .512, not .544

[CHESTNUTXE 7,300]

ok i assume thats a 5.0L your running with 1.6 ratio.

[brianj 48]

I didn't even realize i was in the Cleveland section until after i posted. F'n new guys.

[CHESTNUTXE 7,300]

seems everytime i watch something ford on you tube in america its one of those 80's mustangs,and the 5.0L is very popular,over here we were still using the cleveland until late 1982 in new cars,and 1985 in f trucks and others,tell me did the 351w ever come out in those 80's mustangs.

[brianj 48]

A very few 1995 Cobra mustangs had the 351W. I believe it was something around 250 cars total. They were pretty much a dealership sold race car. I actually have a 1973 351C sitting in my garage, with less than 40k miles on it. It almost went into my car, but the cost of anything 351C related here is quite high. I could build a 600HP 408 stroker Windsor from a 351W cheaper, by far, than i could get 500HP from a Cleveland. They just have very little support here. Ironically, all of the good stuff comes from Australia, and I'm sure you are familiar with the shipping cost.

[CHESTNUTXE 7,300]

Can you send me the 73cj 4v and we will send 351w 69 model lol

[cpe351 3]

I bent the posts ever so slightly to tighten the tension a tad in the springs and put a stop in the plate to restrict the total advance,, used to run 16-18 @ idle advancing to total 32 degrees,, it absolutely screamed. When hot it would crank a little slower for about one second and then fire like an angry beast.