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Hey guys,
When I smash the gas on gear, the motor feels like it wants to die. In neutral it revs a lot better, under load not so much. It's a 351w, .030 over, I'll have to get the cam specs, but pro comp aluminum heads, weiand intake manifold, edelbrock 750cfm. My plugs were black so I went up in jet size just one size. Haven't checked plugs. I took the air cleaner off, and the motor runs 10x better. But still under WOT, not 100%. Is there anything that jumps out that could be an issue??
Fuel filter is clean, manual fuel pump. 6psi. Maybe timing? Accelerator pump on carb?
Black plugs are rich so going up is backwards. If you have no pinging go more advanced on timing and go the other way with jetting. See what happens
Report back
Hey guys,
When I smash the gas on gear, the motor feels like it wants to die. In neutral it revs a lot better, under load not so much. It's a 351w, .030 over, I'll have to get the cam specs, but pro comp aluminum heads, weiand intake manifold, edelbrock 750cfm. My plugs were black so I went up in jet size just one size. Haven't checked plugs. I took the air cleaner off, and the motor runs 10x better. But still under WOT, not 100%. Is there anything that jumps out that could be an issue??
Fuel filter is clean, manual fuel pump. 6psi. Maybe timing? Accelerator pump on carb?
Since you pulled the air cleaner and the engine runs better your engine is telling you it wants a leaner mixture. A 750 cfm carb might be too big for a 351. A 600 cfm carb would be about right if not still be a little on the large size. But I am betting your engine is going to like the 600 better. Did you check you carbs float level, then set the idle mixture volume screws? I don't know a lot about Edelbrocks, but if this was a Holley the next things I would look very closely at is maybe a leaking power valve or accelerator pump. No matter which carb you use, start with the stock settings the carb came from the factory with, then tune from there
This is especially important if you bought the carb 2nd hand.
I thought the idle mixture screw only affected the engine at idle? I'm gonna adjust the accelerator pump setting first, then see what happens...
[
QUOTE=hooler1;16553933]Since you pulled the air cleaner and the engine runs better your engine is telling you it wants a leaner mixture. A 750 cfm carb might be too big for a 351. A 600 cfm carb would be about right if not still be a little on the large size. But I am betting your engine is going to like the 600 better. Did you check you carbs float level, then set the idle mixture volume screws? I don't know a lot about Edelbrocks, but if this was a Holley the next things I would look very closely at is maybe a leaking power valve or accelerator pump. No matter which carb you use, start with the stock settings the carb came from the factory with, then tune from there
This is especially important if you bought the carb 2nd hand.[/QUOTE]
Definitly too rich that's a lot of carb , you should be able to make it work jet down , set the accelerator pump down , set your timing up and probably most important with an edelbrock you can set when the secondarys open so you want to set them to come on much later when the engine is reving and needs more fuel
Edelbrocks use metering rods, no power valves. They sell a tuning kit that includes charts showing how metering rod changes affect Air/Fuel ratio, and include an assortment of jets and rods.
Believe it or not a 500cfm would probably be enough carb..... but a 600 would be fine. You can jet down the 750 carb, probably cheaper than getting a replacement carb.
You are definitely getting too much fuel, hence the running better with no air cleaner... as there is less air restriction..... and the black plugs.... way too much fuel.
You are a little rich based on that plug. You can always go smaller jets but the other thing on those carbs is the metering rod springs. With any kind of cam you usually need a lighter spring to delay going rich when the spring and low vacuum pushes the m. rod up.
I don't agree that the carb is to large. It just needs to be tuned to the combo he has. Using the link provided they recommend either a 670 or 750 cfm carb. No 600 and definitely not a 500. Like everything, when it is modified, items out of the box need tweaking. That carb is based on the old Carter AFB, which is a great carb. It has mechanical linkage secondaries and engine vacuum activated butterfly for air flow through the secondaries. It will only pull what it can use, that is one of the reasons why it is great carb. Spend the time learning how to adjust it correctly and you will not be disappointed. I run them on several engines and installed lots of them at the speed shop. Never an issue when adjusted correctly. You can always pm me for tips and tricks on tuning.
Hmmm . . . well maybe we are looking at a different page. Here is what I entered:
Carb sizes are 570-650 cfm with 22 choices.
Per the Holley book over-carburetion is the most common error made. It robs bottom end torque and raises the RPM where max HP & Torque occur. If this is out of the normal driving range your drive-ability will suffer. It is a common error made by off-roaders where bottom end torque is a necessity for control particularly in severe off-road conditions at altitude like the Rubicon Trail.
