As MNTony points out, whatever carb you run you have to tune it to YOUR engine combination. It's very seldom you can take a carb out of the box, bolt it on, and it runs perfectly. It's not a self adjusting computerized gizmo like EFI. I remember a story about some magazine writer asking Vic Edelbrock why he runs a Holley carb instead of one of his own carbs on his road race car. His reply was, "The Holley makes more power".
As has been pointed out, the smaller size of the 500cfm carb is not your problem. The 302 with the 500 will perform as well as one with a 600. The engine doesn't know what carb it has. It's simply an air pump. At some rpm the 500 will not be able to supply enough air. Until that point the 500 will supply a stronger signal and probably make more torque. My "guess" is that the 500 will perform well (tuned properly, of course) up to about 5500 rpm. Remember, the Nextel cup cars are running 355 CID at 8000+ rpm and only a 390 cfm carb. I recommend you tune the engine/carb right before you spend money on replacing the carb with a bigger one.
Mcknight, this is what I was HOPING to hear. So does it sound like I need to jet the carb down. When idling, you step on the gas it stumbles before it revs. However, if you are already reving it and step on it, it's fine. Does this make any sense. I really need to add a tach to see where this thing is failing me driving wise, but still other than driving, what about the idling issues.
timing/carb My opinion- you need to get the timning correct and set properly before you assume you have a carb problem, was the carb working properly before? Have you checked the jets for sizing? I would think that 12* initial and 36* total would be fine and easy to check. Then start looking at carb issues. Try one thing at a time so you don't confuse the issues involved.
Slk70, If you determine the carb needs tweaking, the Edelbrock website has a pdf of the owners manual (in case you don't have one) for that carb, which gives instructions for adjusting it. Summit sells a calibration kit for about $50.00 that has an assortment of metering rods, jets and springs that will allow you to tune the carb to your engine's liking.
This is the transition from the idle circuit to primary circuit. If the timing is correct. and it stumbles before it revs, you can adjust the acelarator pump to give it more gas or less. I would adjust it to the hole closest to the carb body. This will give the motor more gas when you rev it from an idle.
richard if you bought my radiator your wouldn't have had this problem... j/k funny thing is no here one has asked what the plugs look like. how do we know it is rich? with your set up and if it was a holley i'd say put some 66 jets in the primaries and put two steps bigger squirter on the primaries from stock and there goes your bogging / stumbling issue but its not so... what the hell is a metering rod? lol! i'll shut up now. but someone did meantion the vac line from the dist... make sure that is hooked up in the right place. either way i hope you find out whats wrong.
The wrong power valve can have that effect also. And I might add that the secondaries on an Edelbrock will effect this if they aren't adjusted correctly. But you guys are all correct...fix the timing, then move on to working on the carb. And the plugs are a great indicator of what is going on inside the motor. It should have been mentioned earlier to check them, but I personally thought that it had already been done if it was determined that it was rich. Good luck SLK! Read everything you can to figure this out and let us know what you discover!
Ok, I let her get good and hot this time because the last time we adjusted timining the motor was not quit warm. My mechanic wanted a full advance of 38-40 degrees. I told him to set it at 17* at idle per someone reccomendation here or on another forum. I was told my total timing would be right at about 37* Well he set it at 18* initially and his timing gun showed him a total of over 60* total timing. He mentioned the distributor is wayyy too loose and needed to be re-curved. Not sure what he means by this. I insisted he put it at 17* he did and we were still in the 60 range. I had him put it at 10* where my initial guy put it and he said that it would still be in the 50* range. He mentioned that even if I recurve the distributor properly, it still will not fix the bogg issue. Is this true. We also adjusted the accelerator pump linkage and this seemed to help a lot. We put the link in the bottom hole. Before we did this, it was in the top hole and you could just smell and physically see the black smoke coming from the pipes. Also, Derrick, we did not need to pull a plug because the smoke was obvious. More help please. What to do next. He mentioned something about going into the carb to change metering rods and or jets. I wanted to know though before we do this will re-curving the distributor solve my problems and or what will re-curving actully do or fix other than making sure the "mathmatical" number reads what it should i.e. 37* total timing. Thanks
Just my way of doing it. Plug your vacuum line and recheck your timing. Initial an total. Try your total at 34-36 and leave the line off. Test drive an see what you think now. If you like,,,bump your timing 2 degrees at a time and see what's best. Best to stick with one side of problem an get as best as you can, then tackle next. When you get all in ball park, then you can fine tune all together. Good luck
Are you setting the timeing with the vacume hose conected? This is what I would do: 1. Disconect the vacume line. (dont forget to plug the port on the carb) 2. Set base timeing to 10* BTC. 3. Slowly increas engine rpm till you get full mechanical advance. Take this number, -10* (base timeing) this is your total mechanical advance, should be around 22-28* 4. If the number is higher than this you will have to adjust the distributer to limit the maximum mechanical advance. Re-curving a distributer has more to do with how slow or how fast the distributer advances the timeing (mechanical advance), and at what rpm it gets to the maximum mechanical advance. If you have a total of 60* of timeing your engine is working against it self
Yers I did with the hoses connected. I will follow your instructions above today and see what I get. Also, You are saying I shoudl be around 22-28, so the 37-40 is way too much total timing correct.
How do we get to 37-40 from 22-28. Where is the additional 10 * coming from? the mechanical advance. Thanks guys.
I've never seen it the way he stated it, but if the total is 38 and the initial is 10, then it's advancing another 28* as you increase RPM. Also you have to set/check your timing with the vac advance disconnected.
