62radarlove

Hi all, i got my 455 rebuilt motor with about 10k on it. Its a 2 barrel with "E" heads & they appear to be small valve. I just picked up an Edelbrock performer 455 manifold, & a AFB edlebrock 1406 series carb @ 650cfm for it. My question is do i need a spacer that came with the carb? Its a 1" spacer. Also since i have the manifold off i'm going to block the shared exhaust ports on the heads. So knowing that i probably have a low compression engine that is getting headers on it going back in, do i want to up the cam? I really dont have much funds rt now & want to make it a little more umph, & more than likely it will be coming back out once i get my other 455 built, which wont be for about 5yrs or so. Appreciate all input & opinions....thanks.

droptopron

For that set up you would not need a carb spacer. The spacer has the effect of upping the RPM of the power band, something you would not want.

copper128

I wouldn't mess with the cam on that engine right now. Try it as-is and see how it runs, in the mean time save up some cash for your future build.

x2 on the spacer. You don't need it.

Rickman48

You do realize the original 4-barrel that would've come on the car would have been a 750 CFM Quadrajet, don't you?
IMO, 600 is a bit small for your application, and will be lean from the factory.

62radarlove

I hear you Rickman & since i'm new to olds & engine building in general i have considered the options. The options were to go bigger spend more money,(than i can afford rt now), or go a bit smaller spent a bit less, but keep a little better gas mileage & torque till i get to know what kind off these 455 i'm dealing with. I appreciate all opinions & understand that i would sacrifice a bit of hp, but still trying to get more bang for my low bucks. I dont really know how these bbo will perform on the low end torque so while i get to enjoy my ride cruzing around i can also keep it alive while getting to know what the torque band is. I'm gonna run it since i got the parts & considering i really didnt pay much for this setup i figure i can resell it for a break even or maybe even gain a profit from what i bought it from. Thanks all. Erick.

cutlassefi

Whether it ends up being rich or lean has nothing to do with whether or not you should use the spacer.
The spacer adds plenum volume and makes the transition from the bottom of the carb into the runners more gradual.
Try it with and without, I'll bet in runs better with it.
Jmo

oldcutlass

Fuel economy and performance, there is a conflict here. Performance is achieved by running as much air/fuel through an engine by the most efficient means. More a/f = less economy and more power. If you wanted fuel economy I would have left the 2 barrel on there.

What Rickman was trying to say is that you may run into problems from a lean condition created by running too small of carb on there. At that point the best possible fuel economy will be attained, 60 mph on the back of a tow truck, infinite mpg.


I believe the 1" spacer you describe is a spreadbore to squarebore adaptor ( or visa versa). It is not necessary on the performer manifold if it has both bolt patterns.

bigD

you will give up some top end power but that 600 will be great for that engine. i have the same carb on a 460 in an older 2wd pickup and it is perfect for a daily driver!

the carb, intake & headers will wake the 'ol girl up... i too would try the spacer. i've got a 1/2" phenolic spacer under the AFB on my 460 but it's more for heat control than rpm concerns.

cutlassefi

With all due respect, let me dispel the misinformation once and for all.
You can make a small carb too rich the same way you can make a big carb too lean, by changing jets, metering rods power valves etc.
Would a smaller carb come with smaller jets and consequently be too lean for a larger motor? Of course, but please don't assume it's that way for every application.

Case in point, on Kyles 455 build. We took a brand new 870 Street Avenger out of the box. This carb was supposed to be jetted for engines up to 500hp according to the Holley website. This motor only made about 455hp yet we needed to go up 1 size on the jets, not down like many here have mistakenly assumed you'd have to do.

oldcutlass

The key word in what Rickman and myself were trying to convey is "may".

My point was that power and economy are a direct conflict of terms.

cutlassefi

I understand, but maybe a more accurate way to say that would have been that carb "may be jetted too lean given it's only a 600 and typically used on smaller, less hp applications".

Jmo.

RAMBOW

Since you plan to run it for another 5 years, i say go ahead and get a new cam & timing chain to put in while you have it out. Something small like an XE262 would be a big imrpovement over stock, yet still work well with the low comp. The new timing chain is a must for a 40 year old worn out motor.

You could even pull out your current cam, and take it down to Deta Cams in tacoma and have them regrind it to whatever spec you want. I think its like $50 for the service if you have a core to start with. They do a lot of work for the circle track & drag racers, and of course all the engine rebuilders down in the south end. Couple guys in the local club have their cams & run them hard.

Just be sure to break the engine in with good offroad racing oil with plenty of zinc in it, and you'll probably be good to go for a few years until you're ready to build the other one the way you really want.

If the carb winds up being too small... the monroe swapmeet is coming up in may (and portland is in april)... There are always a ton of Qjets for cheap, you can always grab one of those to rebuild too.

62radarlove

Ok, 1st the engine is still pretty fresh from rebuild so at this point i'm gonna leave the cam in as is. i was putting the manifold & carb on for a "little" more umph than the 2 barrel that it came with. Now if i get the umph kool, if i get decent fuel mileage then ok. Really i have no idea what to expect other than just do it & go from there. Will i be staving the engine with lean jets? Definitely dont want to do that so if i need to up it its at a minimal cost.I just like cruzing the good ole girl for what its worth. I figure 5 yrs to give the economy to ante up or just get the savings rebuild back for as i'm starting my "Lizzy" fund. Now with that being said wouldn't the engine be starving with the 2 barrel on it? Or is it more that i'm not filling the performer manifold with what it should be? Air in & air out is where i stand now after last night budget crunch......gotta love a womans touch.....Another area i was thinking of upping is the wires & plugs, maybe even the distributer. So i thank all as this has definitely given alot to think about not only for now but my future build as well. Erick.

allyolds68

I have a 70 E headed 455 with a Holley 6497 which is a 650 CFM direct replacement carb for the Q-Jet. Are you sure the factroy Q-Jet is a 750?

MDchanic

The 1960s to early-'70s QuadraJets were considered to be 750CFM, but work well at lower rates because of the airflow-actuated secondaries.
Many of the engines they were installed on never came near using 750CFM, but it was cheaper and easier for GM to make a single casting than different ones for different engines, and the versatility of the Q-Jet design allowed them to do that.

Lots of people think that since the maximum airflow of a QuadraJet is 750CFM (850 for some later models), they need to use a 750CFM carb as a replacement. As you have seen, that is not always true.

- Eric

62radarlove

Ally how does it run? any probs running to lean? Hows the fuel mileage? Thanks Eric that makes sense.

allyolds68

It runs great. Mechanical secondaries seem to dump a ton of fuel. I haven't pulled the plugs to check how lean or rich they look. It's gets about 12 mpg on the highway and 9 mpg around town. Holley's aren't exactly know for getting good gas mileage because of the mechanical secondaries

oldcutlass

The Quadrajet design is different than the old AFB Carter/ Edelbock design. It's a more efficient metering system with the spreadbore than it is with squarebore.

Down and dirty rule of thumb for cfm is, cu in x 2 x .8 efficiency = cfm (728 cfm, so I would use a 750)

Yes, the Rochesters were 750 cfm.

allyolds68

FWIW the Holley 6497 is a spreadbore

oldcutlass

His Edelbrock is not.

Rickman48

9 + 12, MY SUBURBAN GETS BETTER THAN THAT, W/187K!!
Seriously - that'd be unacceptable in my book!!
Find a used Q-Jet, re-curve that distributor and watch it go up, a bunch!

I had a '75 Cad limo with a 500 inch engine and 2:70 something rear, and got 18 average! Re-curve and re-jet only!

The Q-Jet, with it's small primaries, gives you velocity, which means better mileage.
The Holley double-pumper has much less velocity, and squirts quite a bit, just about every time you touch the gas - NFG for economy!

I've used 1" spacers on Holley applications, and they've worked well, with the proper jetting! You can't just bolt 'em on and hope they work

Performance and mileage go hand in hand with effiency, the more efficient, the better all the way around!
And the right combination will get you there.

MDchanic

Always wanted one of them, back when Junior was small - just park him back there with some toys, close the divider window, and have a peaceful trip!

- Eric

Rickman48

Dividers were cool, except if you were 5'10" or taller, which I am!
My first limo, a '72, even had the 'performance' 3:23 posi rear end, and the divider.

allyolds68

I have no doubt I could get better but considering you don't know:

1) what rear I've got

2) what tranny I have

3) how I like to drive

It's really not a fair statement. I've put less than 2K miles on it and I'm still tweaking it. Gas mileage really isn't high on my priority list.

I should add that the carb came with the motor. I rebuilt it myself and have had zero problems with it. Maybe you can afford to go out and buy a rebuilt Q-jet, but I can't. The difference in gas mileage isn't going to pay for a carb in one season of driving 2000 miles.

62radarlove

i was on the summit site looking at this carb. I went to the car cfm calculater put in engine size 455, rpm range 5000, it gave me 559 for cfm, so i figured that this carb would be good. By the way this carb is a spreadbore.

Rickman48

Check your local C/L - on there for $35 - 75 all day - a rebuild kit is under $20.

My 'burban has a 3:73 gear, 350, 700 trans and weighs 6000+ lbs.
And every stoplight is a 'tree' to me, and 'I can't drive 55'!
And it's got that crappy throttle body!

Carbs can be intimidating - try rebuilding a Q-jet - there's directions in the package.
Just don't loose anything! They're not that bad!