i judt got back from a classic car gathering at the local sonic and a few of the older gentlemen informed me that a Holley 600 cfm carb is way to much carb for my 302, they recomended a 450cfm of somthing. is this true and i would love to hear your opinions and comments. my car has a alluminum weiand stealth intake and dual exhaust,everything else is stock.
Does your car run okay with it? If so stay with it. I hear the same a lot. My motor has been bored +.040, and has a bigger solid lifter cam, and aluminum heads, etc. but I run a 750 at the track.
A 600 cfm carb is large for a 302 if you go by VE formulas,it comes out about 40 cfm too large.Realistically 600cfm workes well for a stock 302.
eeh it stutters around 30 mph and it seems to bog down on hot days and in the morning. but i slapped the carb on right after i bought it and holleys cant sit or they mess up i hear so it may need to be rebuilt. also it seems to run rich at times but that may be just because its a holley i hear you have to adjust them perodically according to weather and humidity.
most carbs. can't sit or they mess up. running rich at times is something sticking not an adjustment... i have a 600 CFM Holley on my car and it's sweet... all my Hollys (600 VS-650 DP-750 VS), once set have stayed set. my understanding is the Edelbrock is the one that needs messing with all the time.JMO ...LMH600...:Handshake
If it has vaccuum secondaries, you ought to be fine if it is tuned and jetted right. The motor will only pull them open as needed. A 600 really woke up the stock 302 in my Comet. Made it even more apparent how awful 4 wheel drum brakes are ... the car was a LOT quicker. When I swapped the 351W into the car, I used the same carb on it. I have had to rejet it a couple of times to get it right, but it does fine. Milled the choke off of it, so in theory, it is now about a 630 cfm. My motor has a decent cam and headers. If it was any wilder, it would be time to move up to a 750, but it still has stock heads.
600 cfm is good for a 302 that revs up to 6000 rpm. if the people recomending that the carb being to big is the cause of your problems, they are wrong. start with a rebuild. also does your car still have points in the distributor? if so the dewell could be off or the points could be going bad. keep the carb.
A 600cfm should be fine on most small blocks with room for a little cam, intake, and some exhaust work,
Dont forget that 600 cfm is the rating at full flow. Doesnt mean you will use 600cfm. Thats what makes the vacuum secondaries nice for the street. 600 is not too big and will work fine when tuned. Holleys do require some adjusting but the flexibility they give goes hand in hand with the adjusting now and then. Sounds like yours may be due for a rebuild. Make sure to use a Holley kit. If you want simplicity I suggest an Edelbrock carb. They dont seem to be as fussy. Great street carbs. Just because they are older doesnt mean they know what they are talking about. An awful lot of car guys would be Mensa members if the knew half as much as they profess. Not any of our members of course.
With a VE of 75% the 302 pumps around 470 cfm at 5500 rpm. The minimum recommended carb size would be 500 cfm and the maximum is around 720 cfm. It depends more on the actual VE of your engine and the use. A car on the drag strip uses a bigger carb so the fuel distribution stays in the middle of the carbs airflow region. This gives more even air/fuel ratios and keeps peak power coming from the engine. On the street a carb can be smaller to provide better throttle response and better economy. It makes the car easier to drive when cold, hot, in stop and go traffic, and on the hiway cruising. For a fairly stock street car the 600 with vacuum secondaries is just abot right. A new Holley Street Dominator carb at 570 cfm works just as well and give a better low end response without losing too much at 5500 rpm. Your problems are probably not with your carb.
