292 with Holley carb

[old51sedan]

Been really slow finishing this truck, seems like life gets in the way. Took it to a shop this week to have the Vintage air charged, picked it up yesterday and was told that my Holley (550) is way to much carb. I haven't got but 10 miles on it, but it ran great on the way home. Just wondering how many of us have a 250/292 with a 4 barrel carb and how it runs. I'm thinking if it's too much maybe a fuel injection would be a nice option. Is by any chance my air cleaner to small? Engine is stock with the exception of carb and headers, does sound nice though.

[Steeveedee]

Are you experiencing performance problems? If it isn't bogging when you punch it, or when the secondaries open, it isn't too much carburetor. Why do they think that? I was watching a video of a fuel injected (stock) 283 SBC and was amazed at how small the air filter was. You aren't winding it that tight, so that air cleaner should be big enough.

[jjzepplin]

Everyone thinks they know all about carb sizing. I thought I did too until I started watching shows like Power Nation that have dyno experience and test them on the regular. I have seen them put 950cfm carbs on 350s. As long as it idles fine, your carb will only supply what your engine will demand. And que the responses...

[Steeveedee]

Right? I had a 650 CFM E-brock on my 305 SBC. That's a whopping 13 CI bigger than a 292. Not over-carbureted.

[RichardJ]

Carter AVS 4bbl on mine. The MC and booster crowding the carb like that would bother me. My booster isn't as deep and is mounted flush to the firewall. Not wanting to start a debate, but I think 4 bbl primaries should be mounted outward and as far away from cyl 3&4 as possible. It doesn't look like your Holley could be turned.

I don't think your booster would work at all with a Clifford manifold.

[truckster]

If it ain't broke, don't fix it...

[72SB]

500 cfm is fine for a 250/292. Like any carb, changeing jet size, up or down, stepper springs & metering rods to tune specific to the motor is common

I run a 600 cfm Eddy on a 357 and dyno 413hp/411tq...its all in the carb tuning and timing

IIRC 4 brl carbs want to be mounted sideways on 6 cyl....unless its just a Offy 4 brl manifold thing

I have thought about doing this to my 250 using a Eddy 500 cfm carb. I am not opposed to small air cleaner to clear PB booster which is what I have now

[old51sedan]

Thanks guys, I appreciate the feed back. I have an offenhauser manifold that I had removed the plate, turned it 90 degrees so that the Holley would face forward. It was so much easier for me to hook up the linkage, especially for the 200-4R. I only have 15 miles on it, but it does idle and seems to run decent, I haven't stuck my foot in it, but cruises nice. One of my problems is sum of the time it seems to start hard, which I don't like.

[72SB]

Originally Posted by old51sedan

Thanks guys, I appreciate the feed back. I have an offenhauser manifold that I had removed the plate, turned it 90 degrees so that the Holley would face forward. It was so much easier for me to hook up the linkage, especially for the 200-4R. I only have 15 miles on it, but it does idle and seems to run decent, I haven't stuck my foot in it, but cruises nice. One of my problems is sum of the time it seems to start hard, which I don't like.

what is your initial timing?

yeah I agree having the carb straight makes throttle and trans (auto) linkage easier. Didn't know the Offy manifold allowed mounting both ways

['68OrangeSunshine]

For the first 25 years on an L6 292, I ran a Holley 4160, 390 CFM R8007 with an Offy intake and Clifford headers.
When I rebuilt [on the streets in 2005] I was able to refurbish the headers and aluminum intake, but the Holley wouldn't set up after the 500 mile break-in run. Rather than mess around with ordering a new baseplate and rebuilding the 4160, I went for a 500 CFM Edelbrock Performer #1404. Would have preferred a Carter AFB, but Federal Mogul quit the aftermarket carburetor game, and the Edselbrck was the same thing, only more money.
Seventeen years later, it's still running fine.
I run a 12'' diameter Moroso air cleaner with a 3 - 4'' tall filter element. I replace the paper element every year, just around emissions testing time.
One Pic shows a 4'' K&N filter. Which I use optionally, [but not for emissions testing.]

[Steeveedee]

Cool. I'm interested in that valve cover. Is it a cast piece or just painted that way?

[RichardJ]

The little clip for the temp sense wire says stock tin.

[Steeveedee]

Originally Posted by RichardJ

The little clip for the temp sense wire says stock tin.

OK, but it looks pretty cool that color. I wondered about the clips. Ya never know what people are going to do.

[RichardJ]

I used a booster from a Chevy Van. They don't have that giant bracket with the bell crank so you can bolt it, flush with the firewall.
I put it on there 20 years ago, so I don't recall what modification to the firewall was required. I think 2 of the 4 bolts lined up, but I don't remember for certain. The rod length may have been modified, but I did use the original hole on the brake peddle arm. I think the booster was from a '80s van, but the '70s are similar.

There is a guy on this forum that sells a bracket to eliminate the bell crank, but the bracket is still about 2 inches thick and a thread about the bracket runs for 20 pages. https://67-72chevytrucks.com/vboard/...ke+peddle+hole
You could mount the Van booster in less time it would take to read the gazillion questions that guys ask about installing that bracket.

What ever you do, there are ways to get the MC moved back away from the carb on a inline engine.

[CanadianK10]

I put a Holley Sniper EFI 2300 on mine which I've been really enjoying, had a Holley two barrel prior to this.

If your truck runs great on the road I wouldn't worry about it





- Adam

[72SB]

Yep the 6 cyl will have challenges using a aftermarket 4 brl intake manifold with PB booster. A 9" dual bladder booster would help. Also running a smaller air cleaner or one with an offset base

My stock 1 brl Rochester after I put in the CPP 11" PB booster/MC left little room. Bought this little air cleaner from Speedway. Direct fit on the Rochester. $15

[Steeveedee]

Originally Posted by 72SB

Yep the 6 cyl will have challenges using a aftermarket 4 brl intake manifold with PB booster. A 9" dual bladder booster would help. Also running a smaller air cleaner or one with an offset base

My stock 1 brl Rochester after I put in the CPP 11" PB booster/MC left little room. Bought this little air cleaner from Speedway. Direct fit on the Rochester. $15

I saw your truck a few months ago, but don't remember now- how is the air for the PCV filtered? Is there a nipple in the little air cleaner's base, that the hose attaches to?

[72SB]

Yeah Steve there is a nipple on the base of the air cleaner for hose that runs from the front side of valve cover. PCV is in back of VC on top

[HO455]

Not exactly apples to apples but, Pontiac put Quadrajets on both of their 230 cid and 250 cid sixes. It's all about set up.

http://www.ohc6.com/history.html

[RichardJ]

The OHC6 had the Quadrajet mounted with the primaries outboard.
Just saying.

['68OrangeSunshine]

HO455 -- Is that Pancho intake compatible with Late Chevy 250 and 292 L6 heads?

[old51sedan]

Speaking of Pontiac's, I remember back in 1962, I know I'm old. One of my buddies ordered a new tempest convertible with the 4 cylinder and a 4 barrel carb. That little sucker was quick, would blow off 283's all day long. The good old days...

[HO455]

Originally Posted by '68OrangeSunshine

HO455 -- Is that Pancho intake compatible with Late Chevy 250 and 292 L6 heads?

I don't know. But t believe the answer should be here.

https://forums.maxperformanceinc.com...play.php?f=496

Or here.

https://www.speed-talk.com/forum/viewtopic.php?t=56420

And certainly here.

https://www.tapatalk.com/groups/sohc...0b6b9d117046c2

['68OrangeSunshine]

Originally Posted by HO455

I don't know. But t believe the answer should be here.

https://forums.maxperformanceinc.com...play.php?f=496

Or here.

https://www.speed-talk.com/forum/viewtopic.php?t=56420

And certainly here.

https://www.tapatalk.com/groups/sohc...0b6b9d117046c2

OK. I'll check those out.
Leo Santucci's book, [1st Edition] ''Chevrolet Six Cylinder Power Manual,'' shows an experimental L6 intake [in cast iron] built for the Quadrajet.
I have heard GM of Brazil actually produced them for cars and trucks for the South American market. Brazil is one of the world leaders in Sugar Cane production, so alcohol as motor fuel was common. [Well before lowering emissions standards became a political issue in the US, and We got gasahol, or E-10.] With the lower caloric value of alcohol compared to petroleum distillates [gasoline] a much higher CFM is required.
So a 5 liter [~292 - 301 CI] engine might require 1080 CFM on pure alcohol. [Just guessing at figures here. I am no expert.]

The carb application chart shows a 292 needs about 390 CFM on gas. My Edelbrock 1404 with 500 CFM is not overcarbureted on a .030-over bored 292 [=296''] because the AFB design is a demand type carb, and will only draw in as much air fuel mixture as it can handle.