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Shhhh, I'm not here
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Discussion Starter #1
I have been told sooooo many things in regards to carbs.

I have been told recently by an auto shop that there is no such thing as new carbs, they are all reman carbs. Is this true?:shrug

The Holley 670 CFM Street Avenger are remans even when their website says NEW?

I've been told that rebuilding a carb would be the same thing as a reman one.

Also been told that rebuilding a carb does not give you new jets, thus if the problem is with the jets, you didn't fix your issue by rebuilding it.

So my question is, WTF should I do? I am currently running a Edelbrock 750 on my '77 F150 with a 400 engine that has a performance cam.

I was told that the 750 carb is over-carbing that engine, so I guess rebuilding (cheapest option) is not the smartest move since it isn't the best performing carb for my truck. I still want the 4-barrel carb since I like power on demand.
 

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ASSSSS-HOOOOOLE
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They are not re-mans, tell those guys they're idiots. And as far as over carbing a 400 with a 750? I'm gonna go ahead and call that B.S. as well. I run a 304 in my Cj5 and it breathes through a Q-jet, IIRC the Q-jets flow anything from 750+ cfm. Unless you are having some kind of problem, that carb should be perfect for your application.

Who is telling you all these nasty things?

EDITED: Even the smaller Q-jets didn't flow much under 750cfm, I don't know where i got 670
 

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why cant you just jet it down?that does sound like a lot of carb.Those guys are lying to you.I f you buy a new carb from holley then it is new. if you buy a reman carb from holley it should be fine i have used them and had good luck.If you dont mind me askin whats the problem with the one you have? is it the power valve thats busted Or has it always run rough?
 

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ASSSSS-HOOOOOLE
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rusty89 said:
why cant you just jet it down?that does sound like a lot of carb.Those guys are lying to you.I f you buy a new carb from holley then it is new. if you buy a reman carb from holley it should be fine i have used them and had good luck.If you dont mind me askin whats the problem with the one you have? is it the power valve thats busted Or has it always run rough?
Why would you jet it down?

Listen, all the max cfm rating refers to is the flow of mix that the carb is capable of wide open measured in Cubic Feet per Minute. You normally only run half of that at idle, and at most 85% throttle. (unless you like to mash the skinny pedal all the time). Besides, she's running a 400ci engine with a performance cam (i'm guessing prolly an RV cam). If I were to do anything to that carb, I'd upgrade to one of these:
http://www.rockcrawler.com/techreports/holley_truck_avenger_770/index.asp

And flow 770cfm instead of only 750.

Cost wise, I'd rebuild the 750 and run it like it is. 750 cfm should be perfect for you application.
 

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Discussion Starter #7
The problem started about 3 months ago, I was smelling lots of raw fuel and the idle was very low and rough. Had a guy from a local wheeling club stop by and he adjusted the carb and idle. The smell went away and it was running a little high on idle but okay otherwise.

Then, out of the blue a few weeks later, it was dieseling under acceloration and I run premium fuel due to the performance cam. I asked if the shop could check it out.

The shop indicated that the timing was 10 degrees advanced. What was strange is that the distributor was rusted solid to the engine block, so how did the timing get screwed up if it took them three days of soaking the distributor to get it to break loose?

Anyways, they have had to adjust it three more times and it still runs like crap (loads up when driving low speeds in town) and if I shut it off at a store, return to fire it up, it won't fire until I put the pedel to the floor and hold it while cranking it over.

Now the shop says that it is over flowing itself and needs to be rebuilt or replaced.

The local shop is causing me the most issues and is out and out lying to me, they also told me that a fuel sending unit is a FORD ONLY part for my truck but NPD has one. I asked them if they checked with LMC & NPD and they said yes, LIAR!
 

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ASSSSS-HOOOOOLE
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Sounds like the same problems I had when I blew the power valve on my Holley. You are not over carbed, you are just due for a rebuild, and the timing was either wrong the whole time (which is why it was still rusted to the block) or it was adjusted for the cam, and whoever checked it didn't know that. I run a 750cfm quadrajet on my little 304 (bored over, flathead pistons, RV cam-i have to run 91 in it too, and edelbrock performer intake) and it's a champ.

Bottom line, sounds like you just need a carb rebuild.
Yeller

EDIT: and if my sheot dieseled at any point, i'd be checking for bent pushrods. Sounds like you need a new shop if you ask me.
 

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I;d just replace it with a 600 or 650. 750 is alot of carb for a 400, unless you've done some serious work on it.

The Quadrajet OldYeller mentioned is different, it is entirely vacuum operated, and only pulls as much fuel/air as it needs (based on how much vacuum your engine makes). Your Edelbrock is quite different.
 

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I'd say you are definitely getting jerked around. The problem does sound like a rich condition in the carb to me, but I think it could be aggravated by your gasoline. Doesn't Wash. use different blends between winter and summer? That may explain why the carb is not holding it's tune. The next thing is probably that the carb is either worn or has a crack somewhere that is allowing fuel to leak into the intake. A rebuild may or may not take care of that. I think I'd find somebody I trust and have them diagnose the problem.
 

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Discussion Starter #11
Dallasbronco said:
I think I'd find somebody I trust and have them diagnose the problem.
There is a million dollar word and I haven't found that option as of yet.
 

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ASSSSS-HOOOOOLE
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FordFilly said:
The problem started about 3 months ago, I was smelling lots of raw fuel and the idle was very low and rough.
You're missing the fact that this is a recent problem, it ran fine and she was happy with it, then it started running like crap. I'm thinking that she's gonna need that bigger carb on that 400, especially if she's running a radical cam, I don't know alot about the vehicle, but most people don't put a cam like that into an engine, then just bolt up all the stock parts. I'm still saying stick with the 750, and if you're concerned with the local shop lying to you, buy a reman from summit or jegs, and have a RESPECTABLE shop install it.

MY .02
Yeller
 

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street carb cfm = rpm x displacement / 3456 x 0.85

racing carb cfm = rpm x displacement / 3456 x 1.1

we'll give a hefty 6000 RPM (for a truck)

case 1) 590 CFM

case 2) 760 CFM

So like I said, if its (really) well built, then stick with the 750, get it rebuilt. If your talking street power, 750 is probably a little much. Either way, like Old Yeller said, it sounds like your carb needs a rebuild before its any good to anyone.
 

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Discussion Starter #14
Here is a little more information on this whole thing. I've owned the truck for eight years, no issues UNTIL someone (won't say who) didn't like the fact that the accelorator was so responsive that the truck lunged when you barely touched it. So he replaced the spring on the accelorator. Then he didn't like the fact that it was tuned to idle real low (like high performance race cars) and he decided to adjust the idle. That is when the trouble started in. He also took the top off the carb and ripped the gasket that runs down the center and just left that part out.

So, I don't believe it is anything to do with motor trouble, just a screwed up carb.

I got the engine out of a rolled '78 bronco and the owner had just put the motor in before he rolled it down a 300 foot embankment and totalled it.
 

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FordFilly said:
He also took the top off the carb and ripped the gasket that runs down the center and just left that part out.
Ummm... well....
 

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if you smelled fuel did you look at any of the spark plugs? if they were black sooty then it is too righ it wet gas smell might be as easy as float jet cleaning or replacement. if the person that adjusted the carb did not look at the plugs he migh have leaned the mix too much and mad things worse. you should pull one or two spark plugs and see what picture they match on the chiltoon or service book or post here. 750 is not too much carb for a 400with the work you had done. if it worked fine in the past it just may need to be cleaned and inspected and rebuilt. you can get new jets but you want to see if the ones you have now are correct. time to get the hands dirty and see what your motor is trying to tell you what to fix.....mike
 

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ASSSSS-HOOOOOLE
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FORDFILLY said:
no issues UNTIL someone (won't say who) didn't like the fact that the accelorator was so responsive that the truck lunged when you barely touched it. So he replaced the spring on the accelorator. Then he didn't like the fact that it was tuned to idle real low (like high performance race cars) and he decided to adjust the idle. That is when the trouble started in. He also took the top off the carb and ripped the gasket that runs down the center and just left that part out.

hmmmmmmmmm, I'm gonna suggest you just get a reman carb, that one clearly has had unspeakable acts committed against it, and deserves to be retired. A moment of silence please........................
 

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Try replacing the top cover gasket and re-adjust the idle mixture and see if the problem goes away.
Jah, you keep talking about cfm, and you say the Qjet is different because it responds to vacuum (as all carbs do),but all the carbs being mentioned, Qjet, Holley, Edelbrock are available with vacuum secondaries. Next, the problem did not start until recently and this carb has been on this engine with no problems for some time.
 

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Discussion Starter #19
collinsperformance said:
time to get the hands dirty and see what your motor is trying to tell you what to fix.....mike
I've done that, the plugs were fine but the wires were toasted, so I bought the best available from NAPA and put them on along with a new cap and rotor.

Yes, I allowed my truck to be violated BUT NO MORE!:rofl:
 

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A 750 CFM carb is more than anything but a wildly built 400 can use..but certainly can be tuned and jetted to run just fine anyway. So on to the real issue...I have been rebuilding carbs for over 25 years - 5 of those as an carb rebuilding technician ful time - and one thing about the old AFB (which is all an Edelbrock is) is you can't kill them. Once properly set up, they stay that way. Sounds like all that is required here is a competent rebuild with a $35 renew kit. BTW...just ask for a renew kit at Advance or whatever for a late '60s vintage Chrysler 383 4V (not the Thermoquad..just the AFB) and you get all the gaskets and stuff you need for the job..mucho cheaper than the Edelbrock kit.

Jets and needles are never included in rebuild kits..those items are considered a) non-wearing parts and b) specific to the carb they came out of. Edelbrock and Carter both sell rejetting kits, either by individual needle and jet sizes or as 'track packs', with a wide assortment of both.
 
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