6-71 blower trouble

I am in the process of ordering upgraded parts for the carbs you suggested and that are listed on page 17 of the manual but have run into a glitch. The manual says I need: (Step-up Piston Springs - 5" (orange, stock); Needle & Seat assemblies - .110"
(#1466).
More than anything how many of each of these items do I need. I know nothing about these carbs. i.e. how many metering rods are in one carb??? Stuff like that!!!!

search for the edelbrock tuning/service parts on Summitracing.com

For the blower application without boost referenced eddy carbs you want to install the stiffest power piston springs available.

If/when you change to the .110" high flow needle seat assemblys you ahve to mess with the float height spec a bit to get it just right.
The key is to get he fuel pressure regulated properly to 5psi to 6psi at idle.
Edelbrock carbs do not like high fuel pressure but need plenty of fuel system flow capacity (volume).
if the fuel system cannot keep up with the engines WOT fuel flow demand the engine will go lean and burn up.

Start your tuning with the stock out of the box default carb jetting/rods for the 1407 model and work from there.

The model 1407 carb is the one to use for blower aplications.

I'm currently running twin holley 750dp blower carbs with 8.5 p.v.'s on my 6-71 sbc, and have no complaints. In fact... they work great! no start-up issues or any other probs to speak of. I don't have to wait for it to warm up to hit the gas, even when I fire it up in the high 30s (been cold here the last couple days!) No backfire or popping at all. I do have the 'blower surge' some people speak badly about though, after it runs for a few minutes. So do most of the other blown cars I've heard around here, and on u-tube. Plugs look good, no fouling problems... yet! Not to mention the fact that I like that surging sound!! So far... so good! Knock on woooood!

I have almost the same setup on my SBC and it works the same. Cold start at 32 deg and it just sat there purring away. We took off and drove up to the gas station and filled up and came back. We let it run for over 1/2 hour while we went over the timing and carb adjustments. It never over heated or got the headers red hot. It runs at 1000 rpm in Park and 700 rpm in gear. We let it idle for 10 minuted to simulate getting caught in traffic and it didn't go rich or lean. The AFR stayed right at 12.5 the whole time. We then took it out for the daily cruise for 3-4 hours. Runs great. Gotta love those 750 dp's.

Oh yes there is no Detroit roll at all...ever. I like it this way. Each to their own.

Here is a link to the 1466 listing at Summit. You need one needle & seat set per carb. You need two primary jets, two secondary jets and two rods per carb. The orange springs (two) are the ones that come in the stock carb, so you don't necessarily need to order different springs unless you want to follow F-BIRD's advice to go with the stiffest springs available. I'm running the orange springs with no issues.

The Edelbrock carbs are going to cost you power. They can also be a hassle to deal with on blown applications. If you just want the truck to run decent and don't care about performance then you might be happy.

I think you started chasing your tail with the Holleys and ended up getting off the trail. They are easy to tune and are very blower friendly. I understand your frustration, but would hate to see you spend money on the new carbs and still have issues. Your Holleys only need a few parts to make them right. You could buy main bodies and metering blocks for cheaper than two new Edelbrocks.

There is nothing wrong with surging as long as the engine runs good. My car surges when the engine warms up. I have tuned it out before and I lost some throttle response. It runs the best when it surges. I also like the sound, so I don't see a need to make other adjustemnts to get rid of it.

Well, I bought the Eddy 750's and has not really helped. Still idles at 4000!!!!What is next??????

What is the initial base idle spark timing set at? (with a timing light)
Blower motors need lots of base idle timng and do not like the typical hot rod quicky light weight advance curve springs.

Did you equalize the throttle opening (relative to the idle transfer slots exposure at idle) idle speed pre-setting of both carbs before installing them?

You built this motor, what cam is in it?
With the cam specs I can recomend a timing curve that works.

1st thing I need to say, is I have only owned 1 blower and that was 14 years ago... so it has been a while but...

#2: when you say 4000 rpm idle .... do you mean it's revving that high with the carbs idle screws set all the way in, or you need to open the carbs idle screws all the way to keep it running?
and how about the idle mixture screws, on the old holley's you pulled off, where were they?

#3: when it is running at 4000 rpm, you have placed your hands over each carb and there is no vacuum? have you tried to cup your hands over the carbs and try to choke the motor out? if so what was that result.

if the motor died, good, go to #4
if you cannot kill the motor by smothering the carbs you need to seriously look for a vacuum leak ... intake gaskets/plenum gasket/ pop off valves / carb adapter plate / block off all PCV and vac hoses for now. check the case and intake very closely for cracks.

#4: The motor died, so we have eliminated most any vacuum leaks.
being that you were able to drill the IFR's and get close to an idle, I would put those back on and drill some more, b/c it does sound lean. I would also lock out the distributor for the time being if it's not already locked out.

What XNTRCI-T said. I have a 291 DeSoto Hemi, fresh rebuild, roller cam. I used 2 Carter Competition Series 500CFM carbs, rebuilt to 1404 specs for a blower engine, per the Edelbrock Manual. Stock distributor with a Pertronix unit in it, and an approximate initial timing setting. It didn't get to turn one complete revolution and it fired right up and ran beautifully. A little fiddling withe idle mix/ speed and it idles great. I think you've got other problems, rather than carburetor related. There's only 2 things an engine needs to run, and that's fuel and fire. Even a crappy carburator will let the engine run as long as it's getting SOME kind of fuel...that leaves fire. You're obviously getting that, or the engine wouldn't even light up. To get it to run RIGHT, the two need to be syncronized. SOMEthing is up with your timing...

I have a 1987 K5 Fullsize Chevy Blazer. everything on it is stock, and i want to increase the Horse power. ive been thinking about upgrading the air intake either cold-air intake, blower, etc....what kind of trouble am i going to face by putting a blow on it, and how much does a blow cost?

Venom, if you read this thread you will see the trouble that I am having. At the same time there are a lot of guys that haven't had any problem. There are a couple of guys that really know their stuff, F-bird, Camaroman, and others that names escape me. Best thing to do is start your own thread and ask your questions.

were you able to complete the steps i posted?

F-bird, I'll get back to you with some answers. I haven't been able to work on it for a few days. I'm not sure how to answer some of you questions about the carb adjustments. I'm a damn good converter man but carbs are not some place I shine. As far as the cam, I built this motor 5 yrs ago and don't remember much about it. The cam is a hyd. roller, 8.5 to 9 CR, and 461cid (I think) could be 468. Other than roller rockers and stud girdle it's pretty much stock. I didn't build this for a blower application, but figure it should work because I have no intention of running it hard. Just look and sound cool.