edlebrock 600 on 390

[Barry_R]

A 600 cfm carb will run fine on a really mild 390.  Not my personal favorite but it will work.  Ford ran 600 cfm carbs - and smaller (2 bbl) all the time.

It's a tuning - or maintenance - or fuel pressure issue
 

[390owner]

According to everything I have read the 600 is not too big. This engine has around 300 horse or a little less. the fuel pressure is around 6 pounds. The float is correct. It runs perfect with plenty of pulling power also. The funny thing is that my plugs did not look like this until I started using 89 or higher octane gas. When I used the cheap stuff it was hard to start when hot but the plugs were always clean.  It has a little over 10000 miles on a complete rebuild.

[390owner]

Ok on a dura spark What do I need and where do I get what I need. The hei unit in the 390 was less than 100 dollars but I have had 0 trouble from it. I do have a stock dist but I was having trouble with coils, brains, and pick ups. Every time I bought one of these pieces they did not last long so I got sick of buying these parts and went with the one wire unit. I take the bronco everywhere including out of state so I dont want to get stranded because of some china junk.

[ToddK]

I have dual AFB’s on my 426 Mopar, they are very sensitive to fuel pressure. My was running rich and leaking with the fuel pressure at 6psi. I dropped the pressure down to just under 5psi, runs good now with no leaks.

[GerryP]

There's nothing wrong with the HEI.  If you don't cheap out with a module made of Chineseium, the HEI module is better than the Ford Duraspark since it can vary dwell and offer better performance.  In fact, it's pretty easy to wire up an HEI module in place of any other module, Duraspark, MSD or whatever.

Some folks get very provincial when you start crossbreeding your parts, like using an HEI on a Ford.  But you have to go with what works.  There's nothing wrong with AFBs.  They don't have the nearly infinite tunability that some Holleys do, but most folks screw those things up once you get past jet and power valve changes.  In many ways, an AFB is easier to work on than a Holley since you can affect your tune up just in the rod and spring selection and never spill a drop of fuel.

[cjshaker]

I take the bronco everywhere including out of state so I dont want to get stranded because of some china junk.

A Bronco? That sounds interesting. Can't say I've ever seen that combo before.

I understand the negativity towards the HEI GM design, but if you have something that is trouble free, unless looks are super important, keep it that way. You don't fix something that ain't broke 

[390owner]

The reason I went with hei is the easy one wire and I can get a new pick up coil at any parts store. Like I said I have had zero problems. I will check the fuel pressure to double check it is okIMG_2906 by Daniel Crymes, on Flickr

[frnkeore]

The fuel pressure that counts, is under WOT. If it doesn't go  under 3 lb @ WOT, your fine. No matter what the line pressure is. Fuel pressure, should only fill the bowl. To much pressure can push the seat open and flood.

You want to increase the needle and seat size, to increase volume, rather than increase pressure.

[Falcon67]

Edelbrock carbs ( and their sisters) only like around 5 PSI fuel pressure.  Not the 6~7 you'd most likely use with a Holley.  IMHO for most street applications, the Ed/Carter design carbs are superior to Holley.  Better choke operation, better low speed/light throttle operation and response and once set they work.  As for "too small" - I used by go-to 650 DP on my 393 CID / 575 HP dragster engine as a test, it was only off about .2 in the 1/8 and maybe a couple MPH from running a billet "750".  A 600 is good from a 302 to a 400 IMHO. 

[RustyCrankshaft]

According to everything I have read the 600 is not too big. This engine has around 300 horse or a little less. the fuel pressure is around 6 pounds. The float is correct. It runs perfect with plenty of pulling power also. The funny thing is that my plugs did not look like this until I started using 89 or higher octane gas. When I used the cheap stuff it was hard to start when hot but the plugs were always clean.  It has a little over 10000 miles on a complete rebuild.

Not sure about the gas wherever you are but if the hi test you're running now is non-ethanol and the carb was jetted for typical ethanol blend you may have to rejet. I've found when going through carbs that have been sitting for a long time (like "field find" cars) I've had to jet up a couple sizes if running regular pump gas. There are a few stations around here that have non-ethanol gas and if I put a full tank in anything I normally run normal pump gas it's a little fat.

This will depend on the blend of gas, but something on street stuff I've found gets overlooked a lot around here. 

[blykins]

Edelbrock carbs ( and their sisters) only like around 5 PSI fuel pressure.  Not the 6~7 you'd most likely use with a Holley.  IMHO for most street applications, the Ed/Carter design carbs are superior to Holley.  Better choke operation, better low speed/light throttle operation and response and once set they work.  As for "too small" - I used by go-to 650 DP on my 393 CID / 575 HP dragster engine as a test, it was only off about .2 in the 1/8 and maybe a couple MPH from running a billet "750".  A 600 is good from a 302 to a 400 IMHO.

A .2 loss is actually quite a bit in regards to horsepower.  That's a good 30-40 hp. 

[427John]

There's nothing wrong with the HEI.  If you don't cheap out with a module made of Chineseium, the HEI module is better than the Ford Duraspark since it can vary dwell and offer better performance.  In fact, it's pretty easy to wire up an HEI module in place of any other module, Duraspark, MSD or whatever.

Some folks get very provincial when you start crossbreeding your parts, like using an HEI on a Ford.  But you have to go with what works.  There's nothing wrong with AFBs.  They don't have the nearly infinite tunability that some Holleys do, but most folks screw those things up once you get past jet and power valve changes.  In many ways, an AFB is easier to work on than a Holley since you can affect your tune up just in the rod and spring selection and never spill a drop of fuel.

Not all HEI modules have the dwell stretch circuitry,the only ones that I'm certain have it are specific part numbered GM modules,the 990 numbered module seemingly being  the preferred one.The Ford Duraspark I red grommet box has equally sophisticated features but it is pretty hard to find anymore,the Duraspark II blue grommet box is the more common and basic version with some wiring differences.HEI module failures may be a result of a lack of the correct heat sink compound HEI modules require a specific  heat sink compound that has a white chalky appearance,I've commonly seen dielectic grease substituted of the correct  heat sink compound  sometimes leading to failure due to overheating of the module.That may be a cause of the failure of the offshore stuff,maybe something was lost in the translation to chinese.Also the OEM modules are the only ones that will have the features attributed to them, aftermarket modules may or may not have them.

[Barry_R]

There's nothing wrong with the HEI.  If you don't cheap out with a module made of Chineseium, the HEI module is better than the Ford Duraspark since it can vary dwell and offer better performance.  In fact, it's pretty easy to wire up an HEI module in place of any other module, Duraspark, MSD or whatever.

Some folks get very provincial when you start crossbreeding your parts, like using an HEI on a Ford.  But you have to go with what works.  There's nothing wrong with AFBs.  They don't have the nearly infinite tunability that some Holleys do, but most folks screw those things up once you get past jet and power valve changes.  In many ways, an AFB is easier to work on than a Holley since you can affect your tune up just in the rod and spring selection and never spill a drop of fuel.

Not all HEI modules have the dwell stretch circuitry,the only ones that I'm certain have it are specific part numbered GM modules,the 990 numbered module seemingly being  the preferred one.The Ford Duraspark I red grommet box has equally sophisticated features but it is pretty hard to find anymore,the Duraspark II blue grommet box is the more common and basic version with some wiring differences.HEI module failures may be a result of a lack of the correct heat sink compound HEI modules require a specific  heat sink compound that has a white chalky appearance,I've commonly seen dielectic grease substituted of the correct  heat sink compound  sometimes leading to failure due to overheating of the module.That may be a cause of the failure of the offshore stuff,maybe something was lost in the translation to chinese.Also the OEM modules are the only ones that will have the features attributed to them, aftermarket modules may or may not have them.

I have a pretty savvy electronics friend (some of his workmanship is likely in orbit over your head as we speak...).  He is quite fond of some of the OEM HEI modules.  He had us using one as part of his own design ignition system which was tested and run in a couple EMC competitions on my entry.

[Falcon67]

>A .2 loss is actually quite a bit in regards to horsepower.  That's a good 30-40 hp.

Agree - but here, bracket racing, we can lose that much between Saturday and Sunday depending on the weather.  Easy from Friday night testing to Saturday afternoon.  2500 DA on Friday to 5500+ DA on Saturday is not an odd thing LOL.  One reason I want to run methanol out here.  I like using the 650 for a test carb because that one just works on everything. No jet changes, just bolt it on whatever and go test.  Only sorting is the pump shooters, if that.  It's on the 351C right now.  It's my carb version of a Timex watch. 

Most of the Ed 600s - model 1406 - that I've used for regular pump gas driving ended up +1 calibration change on both ends.  But that all depends on the engine, climate, fuel, etc.  The tuning book and kit make it easy.  I've run two of those 600s on my 302 and had them work well. 

[fryedaddy]

back in the early 80s i bought a new 650 dp holley.i loved that little carb on my mild 390,cam,headers,etc.it got good mileage if i stayed out of it,but when you kicked it in it ran great.good 390 carb.i later bought a new 850dp,put it on and it ran even better but didn't get the mileage of the 650.my buddy tried my 850dp on his 350 chevy and it boiled smoke out the back.way too big and rich for the mild sb.