I have replaced the fatory holley 4 barrel on my 460 with a 750 edelbrock. I originally kept the factory intake, but it is getting replaed with an edelbrock performer later this week. Looking for low end pulling power. I did have a lack of off idle power with the factory intake, turns out a 600 would have been better for that intake, but the 750 is better when added to an aftermarket intake (according to edelbrock and a local shop). Question is, any one with a similiar set up had to change the jets or anything more complicated than setting the air and idles screws? I have a 3.55 rear, so I need as much off the line as possible. I want to go to FI down the road, but want to get the most out of this truck now without spending $100 per hour to set it up on a chassis dyno. Have spent to much on this truck already, and still trying to save for headers. Finally got rid of the glasspacks Sunday and installed two flowmaster 50 series ( it's amazing what you can do with a saws-all!), along with another istrument cluster that has a tach. A piece at a time...

 

You may want to play a bit with the timing, too, to get the response you want for the new carb/intake addition.

 

Melisa,

Yes, the smaller carb would have given a bit more velocity and probably a better transition between idle and acceleration. Ford spec’ed a 600 CFM and the calculators call for about that amount too.

Anyway, the Edelbrock will likely have to be tuned to your motor. Carbs are not a very efficient way of delivering air and fuel and when you factor all the variables of each motor – normal operating elevation, wear, age related vacuum leaks, and such, a carb is going to have to be dialed in for each motor. If you swapped an Edelbrock from a motor in which it runs very well and tried it on yours it would probably run lousy. When the motors come out of the factory they all ran about the same, but with age and such they can get pretty far off the mark. That is one of the benefits of a good FI system – it can adjust to the conditions.

I have spent a fair amount of time getting my Edelbrock dialed in and it has made a world of difference in the performance. Follow the instructions in the owner’s manual to get it set up. Changing metering rods and jets is a piece of cake so don’t let that concern you. Just make sure you note the changes you make so that you can go back a step when you have gone too far or know which next step to take if you have not gone far enough. I normally make a change and then live with it for a week or so before I finalize my decision as to whether I need to make another change. Ultimately, I stepped up two levels on power enrichment with a little less on cruise enrichment.

The first thing is make sure you have fixed all vacuum leaks and then get the idle mixture set up as detailed in the owner’s manual using a vacuum gauge and tach. Setting the timing as advanced as you can get it without pre-ignition is important too.

Good luck and ask if you have any more questions.

Mark

 

I have to agree. Tripple check that there are no vacum leaks. They make a world of difference to a carbed system. As for timing, I agree also. I just adjusted the timing on my truck this week, and found some of the power that I was missing. Get everything else set up perfect, and then go to town on the carb.

 

Thanks for the info. You listed all the reasons I would love to go FI, just can't afford it right now. The sticker under the hood says to set the timing at 8BTDC, but I have seen allot of posts on this forum where they recommend going to 10BTDC. The engine in my truck is a Jasper with only about 6,000 miles on it, and the distributor is a new rebuild, which runs straight off teh front of the carb. I think we have found all the vacuum leaks, and after the 15 years of neglect that this truck went through before they would finally sell it, we have been through just about everything! Should I leave the timing where it is, or move it a little before I try the carb or vice versa. I know when you change one it affects the other. I am hoping to have time this weekend to put the new intake on, no point in trying to work with it now, have to start all over once the new one is on. Any advise on a safe timing mark to start with this new, otherwise stock motor would be appreciated. Thanks

 

I have a 750 on my 390, but its a built motor also. It runs great. I did not have to change a thing, 2 turns out on both screws, and go. A rv cam might help off the line thing, and timing also. Check the vacum advance setup, might have bad spring in there. If they are bad, it will advance all the way and possibly have a flat spot. As for off the line, i assume we are talking low end grunt here. My 390 has more grunt than a constipated dog. throw a x pipe on your exhaust, that will probably help. your 460 should torque the heck out of that truck.

 

This coming from mchild:

The initial should be checked with the vacuum nose removed and blocked (vacuum should be sourced from ported vacuum). You would be wise to check how much the full mechanical advance is and at what RPM it is achieved. My guess is it should be around 35 – 36 degrees with it being fully in around 3,200+/- RPM. If you find that to be the case and the initial is around 17 then so be it. The initial needs to enough to allow it to idle and reach the total under power. Recurving the mechanical advance to give you sufficient initial and total is commonplace.

Good luck,

Mark

this was a search as you have more displacement; also some
general info at one place:
https://www.ford-trucks.com/forums/a.../forum/53.html

 

My timing is set around 12, and has a slight ping at full acceleration in top gear. When I am towing, I just add a bottle of octane booster, and with her fully loaded, there isn't even one ping.

 

melisa,

It is quite possible to set the initial timing at more than the spec, especially on a new motor that shouldn’t have much carbon build up in the combustion chambers. Manufactures always are conservative on the spec since the motors have to run on all kinds of pump gas and at many different elevations.

The way I set timing is to start at the spec and see if there is any pre-ignition under load with a fully warmed up motor. If not, then advance it another two degrees and again see if there is any pre-ignition under load. Keep doing that until you get pre-ignition. Once you find where it has pre-ignition, then back it off two degrees (back to the last setting that did not have pre-ignition).

The final test is to make sure that you do not have trouble starting the motor when it is hot and set at that timing. If you do, then you will need to back if off a bit more until the hot start is not a problem. A hot motor with a lot of initial advance is harder to start than when cold.

I would not be surprised if you end up with an initial setting of around 12 – 14 degrees. If the vacuum advance is working properly and you can dial in that much advance you will really find it helps with low end torque.

Good luck,

Mark