Forgive me for this, but I am learning this timing thing now that my car is going. How much timing is advancing 10 degrees. That's what my mechanic mentioned he set my timing at. It seems to be a doggg though and stumbles before she goes. She does go, but there is a stumble as if it's getting too much gas. My dad wanted me to get a 600cfm carb, but she is too rich with the little 500 I have. I thought it was the distrubutor at first ( and still may be), but want to get to the bottom of this. Here are some particulars that may help solve this puzzle 302 - .40 over Custom cam 217-227 @.50 480/505 Heads 190X160 valves, no port work to my knowledddge 500 cfm Edelbrock Carb PROCOMP Distributor I took the car to another mechanic and he said it could be one of two things, but wanted to address the main one first and it may solve the second problems. These are TIMING and Carb Jetting. He believes the distributor needs to be curved for my cam and that may solve to running rich issue. If not, what size comes standard in the Edel 500cfm carb. What would you recommend to smooth acceleration out a bit. Also, we did bump up the timing, but now I noticed when you go to start it, it does not fire right up like it used to at 10 degrees. Before I could stand outside the car and start without patting gas. Now, I have to PATTT!!! ? What's going one here guys. Is the PROCOMP HEI unit junk and the root of this, or does it sound like it's other tuning issues
Is the PROCOMP Distributor a vacume advance type? If it is what vacume port do you have it connected to?
Yes it is a vacum advance one and I am not sure about the port. Please describe what it will do if not connected properly.
10* usually isn't too much initial timing, many SBFs actually like closer to 14*. The cfm rating of your carb does not affect the A/F ratio unlesss you're way off base. A 600 cfm would work better on your 302. Sounds like you just have some tuning issues. You need to get the ignition figured out first, then the carb.
With your mild cam you'd probably do best by connecting the distributor vacuum to the timed port on the carb. Don't know where that is on an Edelbrock.
On an edelbrock there are two ports in the front. the lower one (just a bit lower, not much, maybe 1/4" or 1/2") will have full time vacuum. The higher one will have vacuum only on acceleration. Hook the higher one to your distributor.
Hey SLK, do you know what your total timing is? Basically if you put a timing light on it and rev it up above 3000 rpm what the timing mark says? You may have to mark the damper or use a timing tape to get this number. But usually you would want it somewhere around 32 to 36 degrees total. There are other ways to calculate it using the amount of advance in the distributor and the initial advance...but this is the most accurate way. I would also think that 10* of initial shouldn't be a problem. I set most of my motors there to make sure that I don't have starting problems. Certainly if it is running rich I would work on that issue too. But it sounds like your problems didn't start until the timing was changed. What was it set at originally?
The timing was changed to help solve some sluggish issues. It did seem to pick up and run better, but now like I mentioned, I have to gas it before it starts. Also, why would a 600 be better if I am already running too rich with the 500 cfm. That does not make sense unless something else is different about the 600.
I think you are confused. I'm not really sure how to word this, but I'll try: The CFM dosen't have a whole lot to do with how much gas the motor is getting, for the most part. The jets and stuff in the carb are what controls how much fuel the engine is going. Think of it this way, if you are running rich now, then put a 600 CFM carb on that is giving the motor the exact same amount of gas as the 500, it probably won't be acting rich anymore because you now have more air to go along with that extra gas. And that should give you more power. The 302 in my car (Fiat Spider) seems to like about 13 degrees initial timing, and about 32 degrees total.
the bigger carb does not = more gas 500 / 600 these numbers are how many cubic feet per minute of air can flow through the carb. Jetting determines how much fuel is put into the air, your carb can be lean or rich regardless of how big it is. I hope this helps to clear things up. Dave
CFM stands for Cubic Feet / Minute, it's a measure of how much AIR the carb can flow, not how much gas is ingested by your engine. A larger carb (600 cfm vs. 500 cfm) can actually provid a leaner A/F mixture when using the same size jets (more air, same fuel quantity). To pick the correct size carb the whole car has to be considered; intake, cam, heads, exhaust, trans, rear gears, car weight, etc. Always work on getting the ignition timing correct before messing with the carb.
Lightbulb on now. I get it... so when my dad was so adamant about me running a 600, I should have listened is what it sounds like. DAMMIT. I had the opportunity to return it to Summit because it was not used. The 600 is the same price. Someone also told me the Holleys were better for Fords than the Edelbrock. So it sounds like I may not be getting enough air. When I built this motor, everyone told me to be careful not to over carberate. They honestly said a 500 would be sufficient. Now it makes sense that I need more air...
You can overcarburate an engine very easily, but a 600 on a small block Ford with the mods you've mentioned will be a better fit than the 500. But having said that, with either carb you are going to have to jet it to get the maximum performance out of it. In my eyes the Holley is easier to tune due to it's modular design, but either carb will work great if tuned properly.
