Sounds like its starving for fuel at tip in. Im not a carb person just know from tuning FI. There should be a plunger on the carb that injects fuel at tip in called a accelerator pump. I dont know if there is a adj. or a jet you can change but you need more fuel.
As I have been thinking about it, that thought crossed my mind as well. But, being a new Holley I didn't think that that would be the most probable cause. I could be wrong though.
Anyone else have any more suggestions? The more the marrier. Anyone know if there is an adjustment for the accelerator pump?
I think I just found the answer to one of my questions and hopefully my problem. This is what I found on the Holly website:
QUESTION How do I adjust the pump shot on my carburetor?
ANSWER Look down in the carb without it running move the throttle and see if the two sprays of fuel shoot as soon as the throttle moves if it is not instant back off the nut on the pump arm 1 full turn counter clockwise then check it again do this until it is instant.
I'll check into it, hopefully tomorrow morning, and let you know.
If you look at the linkage that actuates the pump arm, there is a plastic cam. It's held on by a screw that usually has two different holes it can go into, which changes pump timing. These cams come in a few different colors which are also different timing and volume. The squirters also come in different sizes to increase or decrease volume.
Holleys are very tunable, but it takes a bit of experience and good info to refer to in order to get them dialed in just right. There are some good Holley books available and of course there's a wealth of info on the 'Net, as well as right here on FTE. If you continue to have trouble you might ask in the carb/EFI forum.
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Thanks tigerdan. I think I'll have to check into the carb/efi forum.
Last night I went out and checked the pump shot. If I moved the throttle linkage real slow it would travel about 1/8" to 3/16" before the fuel would spray. If I moved it fast it seemed pretty much instant. Just for kicks, I adjusted the throw on the cam by increasing the length of the push screw. It seemed like it got a little better. Looked like I got a fuller shot from the start. But the problem was still there. I tried going the other way (Decreasing the throw) 1 turn at a time for a total of about 4 turns. Still no help. Tried adjusting the timing again. No help. I have not yet pulled the spark plugs to see if they could tell me what is going on. I think that I will pull a couple of them tonight. Being a 750 CFM I can't help but wonder if I'm getting too much fuel at tip in.
Once this carb is tuned in I think the truck will be a real running machine.
I just noticed last night that the pickup coil in my distributor has a cracked housing. It's about 1/16" wide. How bad is that? What kind of problems would it cause me?
Political Correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
I read through this thread and it is helping me figure out how I'm going to build up a 351. How is everything going now, have you had time to perfect everything? What kind of mileage are you getting?
TIME? Do you have any for sale? LOL Time here is the major factor. I've got about a million and one things going on at the same time and haven't had the time that I would like to have to get it done.
Anyway, the only time that I checked the mileage was right after installing the fresh build and only checked it on one tank. I got 12.5 MPG on that tank running 93 octane. I haven't really taken the time to just get in it and drive without checking something out that didn't seem right. Basically all of my troubles right now are with tuning the new carb. I'm a beginner at this stuff so it takes me twice as long to figure some of this stuff out. Needless to say, I have learned ALOT. But so far it's all good. That's why I took on a project like this.
As far as the performance, it's very good even with the tuning issues. I haven't tied into any heavy (10Klbs) loads yet though. I know that hauling a load of wood and a little over a half ton of coal didn't make it "sweat" at all. As a matter of fact with about 1200lbs of coal on the bed, bringing the total weight of the truck to 7000lbs, I was able to pass cars going up a mountain very easily at 1/4 throttle and truck never down shifted from drive. No, I was not driving like an idiot either.
My truck is an 87 F-250 Ext. cab long bed with D50/D70 drivetrain with 4.10 gears and C-6 tranny. From a dead stop, not powerbreaking it, it'll smoke the tires or should I say tire for about 50 feet. I got out of it at that point.
The powerband with my setup seems to be around 3300 to 3500 RPM's. The true 2.5" duals coming off the hooker long tubes and 18" magnaflow's are LOUD. Much louder than I like. It really barks at about 3000 RPM if I'm in the throttle. I just can't justify spending the extra cash to quiet it down right now.
I am very close to having it tuned in. Hopefully it'll be good to go here in about a week or two, TIME permitting. Gonna possibly try a different power valve as soon as I check my vacuum again. Maybe go to straight mechanical advance also???. Not sure on that yet.
Overall I am pretty pleased with the build. I don't believe that ya can ever have too much torque and HP but I'm content, and broke, at this point.LOL
If you have anymore questions feel free to ask. I'll help the best I can.
Anybody ever have any trouble with comp lifters? I have hydraulic flat tappet in my engine and can't for the life of me get all of the "tap" out of it. It's not a super loud tap but it is enough to really irritate me. I've tried setting them with it running. Basically backing them off until I heard a distinct tap, tightening them until they just quit and then going another half turn. I don't know, I thought that that was the best way to do it. Is there a good way to find out exactly which valves are noisy? Screwdriver to the ear test or some form thereof? Any suggestions?
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