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Topic Review (Newest First)
05-20-2005 07:44 PM
Hippie
Quote:
Originally Posted by 85Sierra
Well i have had the car out for a week now and it gets worse mileage then my truck even when i dont give'r, There is a 600 holley rebuilt in the local buy/sell for $100 might check that out
How much time have you spent dialing in the carb? Q-Jets are good but they aren't magic....... and the same goes for any carb you might try. You might get lucky and come close but the odds that it is optimal are pretty slim.

Also you may not believe this but with your combo that 2.73 might be hurting your mileage, a lower gear like a 3.08 or 3.23 may actually improve it and it certainly won't hurt the performance. With your cam you're probably having to give it a fair amount of throttle to get it rolling because it's not "up on the cam", in other words it isn't in the "fat" part of the torque curve yet. A loose converter doesn't help mileage either. A lower gear will help the torque multiplication and get it into the torque curve at a slower vehicle speed plus keep it in the curve at cruise RPM. That's where an OD transmission, lock up converter and a lower rear gear can really shine. I know there's a lot of argument that keeping engine RPM as low as possible is the key to good fuel economy but it's only part of the story. New cars are geared so incredibly high at least in part to reduce "emissions per mile", a slightly lower Final Drive Ratio in many cases would give better economy but increase emissions per mile. For example my '94 LeSabre has a 2.84 differential plus 30% OD for an FDR of 1.99 to 1 . It gets 25-26 HWY MPG when driven at a steady 55MPH, at a steady 70 MPH it gets a consistent 28-29. A swap to a 3.08 differential would boost my 55MPH gas mileage to 28-29 or even a tad better because of less wind resistance even though it increased engine RPM. I do most of my driving in that car at 55-60 and if it didn't have 176,000 on it I'd be swapping the differential. It's a piece of cake on a 4T60E.
05-20-2005 06:41 PM
lluciano77 Go with the 4010 600 CFM carb. You will get them cheaper then that on Ebay. You will get better mileage than the Avenger series, better idle quality, better cold starts, better atomization, and less leaks.

http://cgi.ebay.com/ebaymotors/ws/eB...sPageName=WDVW

http://cgi.ebay.com/ebaymotors/ws/eB...sPageName=WDVW
05-20-2005 06:38 PM
85Sierra Well i have had the car out for a week now and it gets worse mileage then my truck even when i dont give'r, There is a 600 holley rebuilt in the local buy/sell for $100 might check that out
05-20-2005 10:29 AM
SmallBlock_guy
Gonig to try the 750

I think I am going to try the 750 with new rods and jets (yea, its a carter). I appreciate all the good info. That is why I keep finding myself back at this site!
05-16-2005 08:14 PM
lluciano77
Quote:
Originally Posted by Huskinhano
In the latest Popular Hotrodding mag, they have a 75 Camaro that they're doing a build on. They just dyno'd the new "smog" 383 motor. It made 402 hp using a 600 emission Holley. I'd say the other guys who recommended a 600 cfm carb are right on the money!
I guarantee it would have made more with a bigger carb. My engine could make some respectable numbers with a 350 CFM 2 barrell.

Please note the "SMOG" 383 motor part of it. That kind of indicates on it's own that the engine we detuned.
05-16-2005 07:26 PM
club327 To the smallblockGuy. I'd say the 600 was delivering purely because the mixtures were spot on. I reckon the 750 would be better if you had it dyno tuned and rejetted to suit. Surely a worked 383's gonna want more then what a 600 can give regardless of what any theory says!

Just going back to what I was saying in my last post about my 750 fed 327. I forgot to mention that when idling well with a sweet CO reading of 4.5%, not only did the CO drop to 1.5% when in gear but the HC ppm (hydrocarbons parts per million) went from about 400 to over a 1000! Excessive HC readings indicate high levels of unburnt fuel in the exhaust and that's what made the stink in the exhaust. Not because it was running too rich which I never said.
05-16-2005 11:19 AM
Huskinhano In the latest Popular Hotrodding mag, they have a 75 Camaro that they're doing a build on. They just dyno'd the new "smog" 383 motor. It made 402 hp using a 600 emission Holley. I'd say the other guys who recommended a 600 cfm carb are right on the money!
05-16-2005 11:10 AM
SmallBlock_guy
Questions

I hate to hy-jack the post but I have a question and comment.
First, HotRod did an article a while back where they put 350,650,750, and 850 on a NASCAR style engine and did dyno pulls the numbers were very similar. I don't remember the specifics and would not want to trust what memory I have.

My question or comment: I have a 383 in a 71 chevelle. 10.75 : 1, iron heads, 1 5/8 headers, Performer RPM intake, Dart heads, Roller cam with mucho overlap. I had a 600 CFM carter / Edelbrock on it. The tune was perfect, 14.5:1 cruise and idle, and 12.5:1 WOT. However, I installed a Cowl induction hood (vac activated) and found that it was not opening under WOT conditions. I installed a VAC gage and was pulling a vac under load. I then installed a spare (borrowed) 750 CFM Carter / Edelbrock. The cowl door now open very easily (as expected) but the entier system runs rich and I will have to lean it out.
To the point: I wanted to get some opinion for some guys who have more experience then me. Does that seem reasonable or is there something I am missing with the 600CFM. I don't mind re-roding and jetting the carter but I like the 600 and the response.
05-16-2005 01:20 AM
club327 To answer you two, a carb will deliver the same quantity of fuel on any engine when the fuel signal reaches the same level. A 283 running at 1000 RPM would be similar to a 400 Idling at 650 RPM so to speak. So fuel draw and atomization on the bigger engine would be greater at lower RPM's. That I know you all agree. When the fuel signal drops below the desired level that's when problems arise. My 327 running the 750 would have the idle mixture screws turned out only 1/2 a turn to give an exhaust carbon monoxide reading of 4.5%. Yet, the CO reading would drop to a super lean 1.5% as soon as I put it in gear! Luciano that's when your theory of a 'bigger carb runs leaner' comes into play. The engine just could'nt pull enough fuel out when in gear, and the fuel that was pulled out was poorly atomized. What were my options? I could of screwed the idle mixture screws out more to get an eye watering 8% CO just to bring the idle mixture up to an acceptable level when in gear. That, was not what I wanted. So hence I've gone to the smaller 600 to address the problem.
05-15-2005 07:40 PM
stepside454 Club327, dont know what to tell yeah.as far as the 750 runnin to rich goes...it could be leaned to correct that, I mean, you could make a 1150 Dominator run lean...I can only assume its a mtter of tuning
05-15-2005 06:56 PM
lluciano77
Quote:
Originally Posted by club327
I better enlighten you all about my resent downsizing from a 750 vac sec Holley to a 600 vac sec Holley on my 327. The main reason I went to downsize was that the 750 was too big for efficient mixture atomization, particularly when cold. The stench of fuel carbon deposits was overwhelming and would find its was into my home and clothes and I just had enough. So I bought a used 600 vac sec Holley and rebuilt it using Holley parts. I expected the engine to run a lot better when cold, but it's only slightly better. I guess the engine does'nt really like inhaling its own farts due to the extra cam duration. But once warm it's good and the low speed throttle control and smoothness of power delivery puts a smile on my face. However, when on full throttle I feel it's not as good as the 750. It does'nt sound as menacing and I sometimes wonder if the secondaries are opening at all. I've fitted the lightest secondary spring which had no real improvement. But what I find questionable is all of you who say that putting a Holley 750 on a 350 or whatever would cause problems because it's too big. In reality, my 750 allowed my engine to give stupendous bottom end torque (before I changed the cam lol). So much so that when I drove it for the first time I thought it had only a small Holley due to the grunt. So it came as a big shock when I found out that it had the 750. Yes, the mileage was poor but I never bought the car for commuting anyway.
A smaller carb usually runs richer on a bigger engine. The opposite is true as well. A bigger carb on a smaller engine will run leaner.
05-15-2005 05:56 PM
steve t save yourself some money, keep the Q jet if it works
05-15-2005 04:58 PM
club327 I better enlighten you all about my resent downsizing from a 750 vac sec Holley to a 600 vac sec Holley on my 327. The main reason I went to downsize was that the 750 was too big for efficient mixture atomization, particularly when cold. The stench of fuel carbon deposits was overwhelming and would find its was into my home and clothes and I just had enough. So I bought a used 600 vac sec Holley and rebuilt it using Holley parts. I expected the engine to run a lot better when cold, but it's only slightly better. I guess the engine does'nt really like inhaling its own farts due to the extra cam duration. But once warm it's good and the low speed throttle control and smoothness of power delivery puts a smile on my face. However, when on full throttle I feel it's not as good as the 750. It does'nt sound as menacing and I sometimes wonder if the secondaries are opening at all. I've fitted the lightest secondary spring which had no real improvement. But what I find questionable is all of you who say that putting a Holley 750 on a 350 or whatever would cause problems because it's too big. In reality, my 750 allowed my engine to give stupendous bottom end torque (before I changed the cam lol). So much so that when I drove it for the first time I thought it had only a small Holley due to the grunt. So it came as a big shock when I found out that it had the 750. Yes, the mileage was poor but I never bought the car for commuting anyway.
05-14-2005 07:54 PM
stepside454 actually, sure, 517 probably will work..is it enough ? not in my opinion
05-14-2005 08:03 AM
Hippie
Quote:
Originally Posted by lluciano77
What I meant was you can't just go by the formula to get an accurate result. It wasn't really in reference to an argument that DIDN't happen between you and I.

Too many people on this board go with the new Hot Rod Magazine, smaller is always better theory. That is not always the case. When people start saying it will be a good idea to run 517 CFMs on a 9.7:1 406, that is when I'll speak up and say something. When they get offended and jump all over me about saying something, I'll stand my ground. If they prove me wrong I'll admit it or at least concede.



I'd rather piss someone off on this board off that may be giving bad advice, unknowingly. Than have someone not get the best answer to their question possible. If that takes debating between board members so be it. If that takes me standing up for my point and making an A S S of myself while doing so, so be it too.

Sorry I offended you Hippie, I'll keep it cooler next time.
I wasn't recommending a 517 cfm but it does read that way doesn't it? That wasn't the point I was trying to make but you'd never guess it from that post. Guess part of the thought process didn't make it to the post.....my bad, "glorious results of a mis-spent youth" as they say........ but I stand my ground on 600 being "enough". Been there done it, no magazines or formulas involved. It WILL work and I wasn't the only one voicing that opinion. Again, I wasn't the one that initially disagreed with you about the formula but when I used it I'm the one you climbed all over in THREE different posts one of which was in a thread that had NOTHING to do with carburetors. What is up with that? That's not about "protecting" people from bad advice that's about your ego being bruised because someone had the audacity to disagree with you. Offended? That's a nice way of saying it and I probably wouldn't have been if it hadn't been for this

Quote:
Originally Posted by lluciano77

[Quote:
Originally Posted by Hippie]
Quote:
I have them somewhere at home but I'm at work right now. As far as hood clearance goes any available dual plane intake that I know of should clear with a dropped base air cleaner. The '70-1/2 through '72 Z-28 came equipped with the LT-1 350 which used the Z-28/LT-1 high rise, 780 Holley and the AC 14 x 3 inch open element air cleaner under the stock Camaro flat hood. The Holley 300-36 Street Dominator dual plane and Edelbrock Performer RPM are very similar intakes, (OK the Holley is almost an exact copy but hey, if something works why reinvent it?) they should have the dimensions for those on their websites.
780 CFMs...But according to the formula it should have never worked on a 350. 400-something CFMs should have been more than enough...

Alright, I'll leave it alone now..
What was that all about? Hmmmm? Prior to the 4010 vs. Q-Jet discussion in another thread I'm not sure what button I pushed that gave you such a dislike for me but it sure looks to me that's what this all boils down to. You seem to be a pretty smart guy and you do usually have pretty good input and while we may disagree on occasion we're usually not too far apart but you DON'T have to be an a-s-s to people to make your point, in fact they'd be a lot more inclined to see your side of things if you weren't. I can be pretty stubborn, I'm Irish, it can't be helped and maybe I got a little too wound up. Actually we probably aren't all that different, might be part of the problem . I'm sure we'll bump heads again, all I ask is if you're going to bump heads with me do it over things I said not what somebody else said. I'd rather get along but that's up to you, disagree with me all you want but stick to the discussion at hand. I think we've beat this one to death.
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