I have Chey 283 with an Edelbrock 1507 carb in a 1957 Chevy truck. I bought the engine used and never saw run, but it seems strong. It starts great, but stumbles really back under load, It can not be driven as is. I've re-timed it multiple times, firing order is correct, and appears like plenty of gas to the carb. I've tuned the carb as per Edelbrock, checked for vacuum leaks, but nothing seems out of sorts. What I did notice is that when I step on the brakes (vacuum assist from the carb.), the idle goes up. The brake master cylinder is new (dual with vacuum boost - not stock). I was wondering if this is normal, or if this is an avenue to investigate. Thanks. don
the buster may be ruptured and you have a vaccum leak inside. try unhooking the booster and plug the hole and see if it runs right. Also check the vaccum advance on the distributor and make sure it is working . Hope this helps RED
donsz, If your idle increases when you step on the brakes only a couple of hundred RPMs it nothing to worry about. More than that and you have a problem with the booster. That doesn't sound like the problem though. You didn'y say what kind of distributor is in your engine(aftermarket or stock- points or electronic). If you have the original points distributor it might do good to check the dwell or just change out the points and mabey change out the condenser too. You say its getting gas,do you have a pressure guage on it or have you checked out the pressure with a hand held gauge? You could have dirt in the tank plugging the pick up or the fuel filter. Let us know what you find. Normal Norman
I'm not worried about it being 750cfm, unless the engine is pulling for the fuel it should not be an issue. Though a 1403 (500cfm) would have been my choice. That being said is there a fuel regulator on there? If there is not and you have more than 5-5 1/2 lbs that can be an issue. How much does the idle change when you hit the brakes?
Where is the timing set at initial and total? how soon is the mech advance coming on? What do the plugs look like? are they sooty? I agree that 750 carb is too big but it should still run good enough to drive.
The problem with the 750 on a small engine is after you get them jetted down so where they idle and run good they get a nasty hesitation. I have worked on a ton of eddy carbs and the 1405 600 has been the best all around one that I have worked on for people.
You can put a 850 on a lawnmower and get it to start, or at maximum rpms , But there will be no midrange power. As soon as you open the throttle blades theres too much air, too big of a passage for the amount of air, no venturi vacume and no fuel. On the same thought you probably could get your 283 to start and idle with the lawn mower carb, it will run great until the rpm and air required thru the venturi exceed what its capable of delivering. On the street its mostly idle to midrange with an occasional WOT event. That's way too much carb for a 283. Here's your 1407 calibration. EDELBROCK PERFORMER SERIES 750 CFM, ELECTRIC CHOKE CARBURETORS CALIBRATED FOR ECONOMY WITH PERFORMANCE Designed for 402 c.i.d. and larger engines with Edelbrock Performer manifolds and other brands of similar design, these carbs are recommended only for stock to Performer level applications. They are not recommended for use on RPM or Torker II intake manifolds. Calibrated 2% leaner than #1407. Provides excellent fuel economy when used on 454 c.i.d. Chevy and 460 c.i.d. Ford with Performer manifold. Includes both timed and full vacuum ports for ignition advance. Comes with: Metering Jets - Primary .110, Secondary .107; Metering Rods - .075 x .047; Step-Up Spring - orange (5" Hg). Use our Carb Stud Kits #8008 or #8024 if needed, see Installation Items. For auto trans throttle lever adapters and more, see Tuning Accessories. Here's what you should be looking at. EDELBROCK PERFORMER SERIES 500 CFM, MANUAL OR ELECTRIC CHOKE CARBURETORS CALIBRATED FOR PERFORMANCE Designed and calibrated for small cubic-inch engines such as 305 c.i.d and smaller Chevrolet; 302 c.i.d. and smaller Ford and dual-quad applications such as Edelbrock C-26, F-28 and Street Tunnel Ram. Match with an Edelbrock Performer or Performer EPS manifold and other brands of similar design. Includes both timed and full vacuum ports for ignition advance. Comes with: Metering Jets - Primary .086, Secondary .095; Metering Rods - .065 x .052; Step-Up Spring - orange (5" Hg). Use Carb Studs #8008 or #8024 if needed, see Install Items. For auto trans throttle lever adapters and more, see Tuning Accessories. Quite a difference there. Perhaps its not the classic case of over carb ING, it may be that the carb is correct and your engine is just too small.
Did you set the float level? Don't assume it is correct. Are you running a pressure regulator that is set to no more than 5-1/2psi? Even if you are running a mechanical pump, pressure can be an issue. Both of these are, in my experience, mandatory when running any Edelbrock carburetor. Also, sell the 750 off and get a 500. I doubt you will ever get favorable results from a 750 on a 283.
Thanks for all the replies. I keep going back and forth between ignition and carb. The ignition is a HEI I bought off eBay. It isn't a name brand, but for my purposes I thought it should be good enough. I'm beginning to wonder if it is defective, but they are relatively simple devices. I do have the original points distributor I could use for testing. The carb. from all the feedback seems like way too much, and maybe I should just replace it. However, I do not have a fuel regulator, so maybe that is the first place to start regardless. The problem is that I just can't keep it running under load unless the timing appears to be way off. Even then it doesn't run well (no power). When I time it to where I think it should be, it almost doesn't run under load (in gear) at all without continuously slipping the clutch. I'm going to re-check my timing (mechanical and electric) and install a fuel regulator this weekend. And possibly re-install the original distributor. I will get back and let you know how it turns out. But at this time I am getting a bit discouraged, but it does help to get all the good advice from members, both technically and from a morale standpoint. Thanks. don
Lots of good advice in the previous replies. You mentioned though that you bought the engine used and never saw it run. It might be worth pulling the timing cover and make sure that the cam is timed corrrectly, and that the chain is not loose or jumped a tooth or two.
Have you looked at the spark plugs? They will usually give a pretty good indication as to what's going on
Well it really sounds like you got a brake booster problem not so much a carb problem. Like Red said unhook the hose and plug the hole off at on the carb then step on the brakes and see if it revs up.if it dosent the the booster is bad.If it does then you got a diffrent problem. Hope this helps.
Yeah; 750 cfm is WAY too much for the meager 283. Next, someone will try a 2X4 set up or maybe even fuel injection - you know; like the factory did.
+1..... make sure the fuel pressure is low as noted above...Eddy carbs do not like high fuel pressure.... Tom
Thought I would finish this thread. I tried to take the "easiest-to-do" recommendations first. I re-checked the timing and wires another few times. Then I took the Edelbrock off and rebuilt it using the re-build kit. Then I timed it again. Now it does run at least to the point where I can drive it. I checked the plugs and they are soot black, but I don't know if that is a hold-over from my previous attempts to run it. I will clean and re-check gaps and see what happens. Just "because I was there," I used a TDC tool (mechanical adapter you put in sparkplug hole with screw in stop if you never used one), to verify I wasn't 180 out. The procedure is to rotate clockwise. make a mark, rotate counter-clockwise and make a mark. The center point between the two marks is TDC. My question is, if use the shortest distance between the two marks, then my damper is marked accurately. I'm hoping that I am right on this. I didn't get a chance to pull the distributor cap to verify the number 1 firing position tracks with mechanical TDC. (HEI). I did want to thank everyone for their responses, sometimes when nothing seems to work and you get discouraged, it really helps to get good positive advice and a little perspective. Thanks, don
donsz, one last thing to check - Your fuel line diameter. If it’s too small, it could starve the carburetor under acceleration or load. If you do find that it’s too small and have to replace it, remember to check the diameter of the hole in the fitting on the fuel tank as well. It may need to be changed or drilled out (carefully) as well.
Has this set up ever ran well on this car? Or did the 1407 just end up on this 283... My point is that if it is a new carb to this intake maybe its that... I had the exact same problem on my 27 with a edel torquer2 and a 1406 Turned out it needed a plate under the carb ... Seemed strange to me since they were both edelbrocks. Anyway now I run 2 1406 edels on a edel c28 intake... Thats 1200 cfm! And it runs great! Its had 2 fours for over ten years and its fine and Im not changing it.
On the TDC mark: turn the motor CCW till it hits the stop, make a mark on the balancer where the timing pointer is, then turn clockwise till it hits the stop and again make a mark. Now half way between the 2 marks is true TDC and it should be where the factory mark is, if it is not, then make a new mark that is equal distance between the two marks and use that to time the engine. (I like to also locate and mark at 36* BTDC to verify total timing too)
Thanks, Russco, worked great! I took off the distributor cap to check the position of the rotor and found that a bracket I screwed in from inside of the firewall, protruded out to into the distributor cap and chipped a hole in it. The cap on the HEI is so large that it is really close to the firewall. I don't know if that is a problem, but it can't help. The rotor orientation and TDC were correct.
Read all the post and most seem right on, but another thing to check is if its a cheap ebay distributer it might have timing springs and weights set for an emissions era vehicle. Usually heavy springs limiting timing along the rpm curve. Check what rpm your total timing comes in and how many degrees it is.
4tford: Never thought of that, I will check that. That might explain why it still does not seem quite right to me when I take it out for test drives. Thanks, don
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