 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / June 2006350 motor has no power
I have a 66 belair. I put in a fresh rebuilt 68' 350 chevy motor with 410 hp. I got it all hooked up, and i have a problem when i try to accelarate, it feels similar to the power of my old original 283 motor. It literally feels like im getting maybe 150ish hp. When i push the pedal down, the car's power curve will increase slowly, even when i jam the pedal down further, the car just slowly steadily increases in speed at a slow rate.( 0 - 60mph in about 11 seconds). When i hit WOT, the secondaries kick in, and i get nothing except a very slight chug, as if it went lean for a split second. Im using an edelbrock 800 cfm thunder series carb. an edelbrock performance fuel pump (preset at 6psi), hooker headers, i have an HEI distributor with bosh platinum plugs gapped at .45, and 8mm wires. Ive only done the inital timing and it is set at 10 degrees BTDC (with the vacuum canister plugged). I havent determined my total timing yet, but the car seems to advanced quickly when i pulled the carb throttle linkage back, while holding a timining light on the timing mark I have a 2500 stall, and a cam with a 485 lift and around 287/287 duration. So the car likes to idle high, about 900 - 1100 rpms... But basically.... The motor sounds strong at idle, and sounds strong when im driving it. Just no power and poor accelaration. I should be feeling at least 200 more horses. this is my first motor swap, so im a newb. any ideas? thanks for any help or info you can give. ~Scotty >I have a 66 belair. I put in a fresh rebuilt 68' 350 chevy motor with >410 hp. I got it all hooked up, and i have a problem when i try to [quoted text clipped - 18 lines] >first motor swap, so im a newb. any ideas? thanks for any help or info >you can give. ~Scotty I would take the cap off and make sure your centrifugal advance moves back and forth freely...maybe experiment with different weights and springs for the right timing curve...maybe try using a vacuum gauge to make sure you have higher vacuum at 2500 RPM than you do at idle, otherwise you have a fuel restriction. If you're running too rich your car will also feel sluggish...maybe play with jet size, make sure the float level is right...maybe swap a smaller carb to see if there's a difference. >I have a 66 belair. I put in a fresh rebuilt 68' 350 chevy motor with > 410 hp. I got it all hooked up, and i have a problem when i try to [quoted text clipped - 18 lines] > first motor swap, so im a newb. any ideas? thanks for any help or info > you can give. ~Scotty Who sold you the motor and who said it had 410 HP? I would be asking them the questions you are asking us who have no idea of what went into that engine. They should be in a much better position to answer you and to offer suggestions as to what might be wrong. Kevin Mouton > I have a 66 belair. I put in a fresh rebuilt 68' 350 chevy motor with > 410 hp. I got it all hooked up, and i have a problem when i try to > accelarate, it feels similar to the power of my old original 283 motor. > Im using an edelbrock 800 cfm thunder series carb. an edelbrock > performance fuel pump (preset at 6psi), hooker headers Air in, air out. What comes after the headers? Hey thanks everyone for their help. Right now its open headers till i get someone who can weld my exaust on. ill probably try jetting the carb to its lowest setting if i can, otherwise ill try to get rid of it for something smaller. I got the motor from phoenix engines, so ill try calling them this afternoon. if you have any other ideas, let me know. thanks again > Hey thanks everyone for their help. Right now its open headers till i > get someone who can weld my exaust on. ill probably try jetting the > carb to its lowest setting if i can, otherwise ill try to get rid of it > for something smaller. I got the motor from phoenix engines, so ill try > calling them this afternoon. if you have any other ideas, let me know. > thanks again Ive seen carburetors in that size range used with similar engines before, and they worked out okay. It might be theoretically a little larger than you would calculate for the engine, but I dont believe size is your issue. >I have a 66 belair. I put in a fresh rebuilt 68' 350 chevy motor with >410 hp. I got it all hooked up, and i have a problem when i try to [quoted text clipped - 18 lines] >first motor swap, so im a newb. any ideas? thanks for any help or info >you can give. ~Scotty You are probably boggin't the hell out of it with that 800 CFM carb. You need something more in the 600-650 range for your small block. If you are going to run this carb, you are going to have to really hold off the the opening of the secondaries. You may have to run rich on the primaries to keep from bogging there. There are several carburetor size calculators on the net for free use. A 700 will take a 350 all the way to 7K at 100% volumetric efficiency with is rare w/o a respirator of some sort. At 90% which is high even for most modified engines that are streetable, a 600 CFM will take it to 7000. Basically, what you are doing with the 800 CFM is dropping the vacuum signal so low that it cannot draw fuel through the metering system. Swallow your pride and get a smaller phallic symbol (carb) to make it run right. A bigger carb des not translate into more power or better performance. An engine is a fixed positive displacement air pump. Once it gets enough air, it will not do any good to go to a bigger carb. This is not a case of bigger is better. You are much better off on the street with a slightly smaller carb than you think you need. A heavy car with tall tires and gears really brings this problem to the front. A lighter car with short tires and gears can more easily get away with over carbing. Your Belaire won't fall into the light category. Lugnut Plus, and I agree here, if everything else is set up right, it's got a 3.08 rear!! >>I have a 66 belair. I put in a fresh rebuilt 68' 350 chevy motor with >>410 hp. I got it all hooked up, and i have a problem when i try to [quoted text clipped - 45 lines] > > Lugnut well i also noticed when i took off one of my new spark plugs, its dark black. does this mean its getting way to much fuel? its been at idle most of the time ive had it in the car, ive actually driven the car 1 time for maybe 10 minutes 2 days ago. >>I have a 66 belair. I put in a fresh rebuilt 68' 350 chevy motor with >>410 hp. I got it all hooked up, and i have a problem when i try to [quoted text clipped - 25 lines] > secondaries. You may have to run rich on the primaries to > keep from bogging there. While what you say would be true for an 800 CFM Holley Double Pumper or a big Carter AFB, its really not the case AT ALL with this carburetor. The Edelbrock Thunder Series is a re-badged new-production Carter AVS. Like all air-valve-secondary carbs (such as the Thermoquad and Quadrajet) the AVS it is *very* forgiving about "over carburetion." If the carburetor is even close to properly tuned (and Edelbrock does a *great* job at getting these right "out of the box") then it should run better than what he's describing on anything from 300 to 500 CID. There are about a thousand potential problems with this engine (not the least of which might be the claim that it should have 410 HP), and while its certainly possible that the carb being mis-calibrated is one of them, I'd look at much more basic things first: Base timing Advance curve Vacuum leaks Fuel starvation to the carb I'd even look at the cam timing before I'd worry about a new-out-of-the-box AVS Thunder Series carb needing tuning. >>>I have a 66 belair. I put in a fresh rebuilt 68' 350 chevy motor with >>>410 hp. I got it all hooked up, and i have a problem when i try to [quoted text clipped - 46 lines] >I'd even look at the cam timing before I'd worry about a >new-out-of-the-box AVS Thunder Series carb needing tuning. What you say is very true. That is why I pointed out to him that he is going to have to hold off the secondaries if he is giong to use this carb.. I suspect that even if Edelbrock did their usual good job, they may have it calibrated for an engine of somewhat greater displacement. And, there is nothing he can do about the size of the primaries. The engine will need to be gaining some rpm's before it can take the whole thing. I agree this may not be the only problem and, it may turn out that it is nothing more than a minor bit of the overall problem. He should be starting from ground zero on the engine setup starting with the valve adjustments. I have seen quite a few "new" rebuilt engines with the valve train setup way off. It may be adviseable to re-adjust the lifter and check the valve timing while the covers are off. Next stop would be the distrubutor. A weak or ill timed ignition curve can kill it quick. Even a weak ignition coil or low voltage to the ignition system can result in a running engine with little power. He does describe a stumble or sag as the secondaries open which means it is either going lean, does not have the ignition setup to light it off or, the secondaries are opening too quick. If he is still running the 3.08 gears typical of that car, it may simply be overcammed and is not going to pull under 4k RPM. I would be curious to know if a cam grinder like Comp Cams or Crane were contacted about the setup before it was assembled. Even a 287deg cam can be a bit peaky for a heavy car with tall gears and tires. I believe an experienced technician with a dyno setup, a scope and a gas analyser could set it up in short order - not necessarily cheap but the results can be satifying to get it the ballpark the first time around. Barring that, he could benefit from the experience of others who may have put together a similar setup. Lugnut >>>I have a 66 belair. I put in a fresh rebuilt 68' 350 chevy motor with >>>410 hp. I got it all hooked up, and i have a problem when i try to [quoted text clipped - 46 lines] > I'd even look at the cam timing before I'd worry about a > new-out-of-the-box AVS Thunder Series carb needing tuning. I would also check to make sure the spark plugs are in the right order. Sounds like it is running on 6 cylinders rather than 8.... Let us know how you make out... Fwed Not to but into this thread but, yes, black sooty deposit means it is running rich, I agree with the other poster, a smaller carb to start, 650 is the largest carb the engine will take w/o forced induction etc. then you need to dial everything in, timing etc, as with any new motor, but it will be hard to do that with the wrong carb on it. after you put the smaller carb on you can try out jetting it larger to get the results you are looking for. just my trial and error experience's.  Signaturefuzzypuppy http://www.automotiveforums.com alright, well im starting to think im just having alot of flat spots. Is this caused by my fuel being to lean? > alright, well im starting to think im just having alot of flat spots. > Is this caused by my fuel being to lean? Too lean's a.s.... No, if the plugs are black, it usually means you are far too rich, or burning oil like a bitch. |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.