Yeah some do some don't it seems hit and miss. In my experience Edlebrocks are more consistent for street cars though. Now with that said I run a Holley (based) 780 DP on a Vic Jr in my 306 street car. :evilsmile
Yeah I do agree with Holley over Eldebrock. Holleys seem to be a bit harder to tune from my expierance but i do think they preform a lil better. (only have expierance with mild street/strip carbs tho so i cant say anything about full race carbs.) And my Holley runs great, i dont have the hunting idle, and ive only had to barley re-tune it when i pulled it out after winter. I would choose to run a 650cfm but if your going for full out high rpm high speeds 700cfm could be helpful. I wouldnt sweat too much about running a 600 tho.
i have an original holley 4bbl that flows about 715 or 725 but i think that would be too much on a stock street motor thats what came off tha motor when i got it. i thnk and edelbrock has better fuel economy so i will go with that.
Well that's why I say Holley based. Carb ratings are pretty much marketing anyway unless you go to something like a pro systems. As far as what the motor would like....Same old story I get everywhere. The motor likes this carb just fine. Runs great, no "loss of low end" hype people always talk about. The only problem with the motor is it's a 50oz imbalance so I can only spin it to 7K max. I've got 17" of vacuum at a 900 RPM idle and it pulls a 3000 lb Mustang along just fine at 45 in 5th gear (about 1300 RPM). So much for big heads and induction not being streetable. Although my heads are only 195 cc intake runners so they aren't that big. Anyway this thread was about a carb for a basically stock street car. Either the Holley 600 VS or Edelbrock 600 would work fine I just like the Edelbrocks better in this application. But that's just my opinion doesn't make it right
Have you ever tried a smaller carb ? And since when does a 50 oz imbalance limit the rpms to 7 grand ?
yep have run 600 VS, 700 VS, 750 DP, and have settled on the carb I'm running now. IMO more than 7K is simply too high a sustained RPM for that set up. External balance increases the flexing load on the crank. The higher the imbalance and RPM the higher the load. I can tell you from personal experience a 1/2 second blip to 7900 will permanently bend the crank. Not a good idea running with no rev limiter On the same note stock crank, rods, and forged pistons on a 28 oz motor will rev to 7600 no problem. Can someone get away with reving over 7K on a 50oz motor. I've know people who claim they can but they usually wind up being the same guys who complain about bearing failures.
Who besides a dirt track racer ever subjects an engine to "sustained" high rpms ? We're talking about street and occasional strip cars here (mostly, I'd presume) I built a roller 302 that could and did get spun to 7500 regularly and bearing failures and cranks problems never appeared. The block did split the #4 wall midway in the bore, but the rotating assembly was fine and got reused in another block afterward. And this was all O.E. stuff aside from the ARP rod bolts. Which were installed in the assembled (reman at that) shortblock.
Well let me clarify "sustained". What I meant was while drag racing it is not advisable to cross at over 7K. I'm glad you had good luck with one motor spinning to 7500. Maybe the stars all aligned for that motor and it survived or maybe I'm too cautious but IMO you're asking for trouble by pushing stock components to that level. Then again I know people that are running motors with Comp Stud mount rockers and a girdle over 8K. To me that requires shafts. I hope I have properly explained my opinion. It appears we'll just have to agree to disagree because this back and forth is taking this thread away form its original purpose.
The external/internal balancing of an engine whether it is 28 or 50 ounce makes little difference in the ability of an engine to spin high rpm. Let me explain before you get ready to duel with words: Piston velocities, rod strength and rigidity of the block have more to do with how fast you can turn an engine than how it is balnced - AS LONG AS IT IS BALANCED. From the factory our engines come component tollerance matched - they are NOT balanced - either statically or (and more importantly) dynamically. At high RPM the pistons will fail due to the constant acceleration and decelleration and the limited strength of the casting alloys. Forged pistons can be made stronger and lighter to hold up to the G forces better. The big end and the beam of the rods are next to fail due to high rpm. Finally - mostly due to pressure loads - the block needs to be rigid to keep main caps in place and to take the loads of the power strokes at those high rpm. Any imbalance in the engine will aggrevate the loads on the parts affected. - especially the main caps.
My car will do sustained 7k rpm!!!! Road racing at open track and some short courses!!! Sustained is open to self interpretation
too ad to what Paul said......Harmonics come into play as well.....Harmonics are natural occurring vibrations in metals.rubbers/plastics etc... subjected to certain conditions. Some metals have harmonics at 3k rpm others 4k rp, and so on and so forth. It is a vastly deep subject. I have studied it cus I like that kind of stuff. I could right 10 pages on the subject but there is no need....IMO..... Harmonics are not from out of balance.....they are from natural occiring properties that can not be balanced out etc.....they can be dampened but never rid off completely. They will shatter the metal at some point if they are not handled carefully. Engineers design parts to operate in a certain rpm range and by doing so they munipulate the design so those harmonics are at there strongest in an rpm range that is never or rarely seen if possible. They do this with tires as well......there are many ways to do it as well....again I aint going into them all pick up a book and read if yo want to learn more:Handshake
I would agree with everything PaulS has said except the very first statement. External balance places a huge load on the end of the crank which is only supported on one side. As speed increases the load is squared. double the speed and the load goes up by a factor of 4. To place the same loads on the snout of a 50 oz motor at 7000 rpm (works out to be over 4000 pounds) you would have to spin a 28 oz motor to 10K. You can calculate it for yourself here http://www.calctool.org/CALC/phys/newtonian/centrifugal remember it's oz/in so use 1" for the radius and 50/28 oz for the weight I'm not trying to be argumentative here but I've bent a 50oz (balanced rotating assembly) crank at RPMs where a 28oz lived and I've pulled apart several motors that have been over revved to find wiped bearings. Truth be told most guys don't run a memory tach as I do so I have no idea what RPM they were at when they wiped the bearings but it was somewhere over 7K. Again I am probably being a bit conservative with my self imposed 7K limit but better safe than sorry.
