The Stovebolt Site Forums The Shop Area Engine Shop What size 2bbl Holley?

I'm getting tired of trying to get my Monojet carb to work right and was thinking of switching to a 2 barrel Holley and an adapter plate. What size carb for a 250? It's a stock '70 motor. As much as I would like to add a header and cam, that's not in the near future so I'm not looking for a alot of cfm, that's why I'm looking at 2 not a 4 bbl.
Ssooo...what size and are there specific years/models to stay away from?
Thanks in advance.

Freedo,

There are some models rated at 210cfm, don't have the part number, but worked with then a lot, good driveability, good mileage. They were used on Phord trucks. The 350 cfm(7448) can almost be considered a li'l bigger than desired, but some fine tune will make them good. There are models with 2 stages likages, You can search and You'll find it, also don't have the P/N here now. Stay away from the 4412 - 500cfm and the extra rare 6245, 600 cfm. They will be a lot more than desired even for a bigger and hotter engine.

And the cfm ratings are not the same on 2 bbl and 4 bbl carbs. Can't recall the differences, though.

Freedo
Have you considered a 2GC Rochester? What do others think?
OLD 42

You should choose the size carb based on your operating rpms. If it is a runner, and you spin it upwards of 4000 rpm, you may want to run a 300 cfm, if you are making big HP, you may want a 390 cfm. If it is just a driver, rarely seeing over 3000-3500 rpm, any carb around 200-250 cfm should suit you fine. Im not sure what all sizes are offered by diff makers, so you may need to look around, and others will give input as well. A progressive 2 barrel would be sweet. Anyone know who makes them?

As Fred says 4 bbl and 2 bbl carb cfm ratings cannot be compared directly as the the carbs are flow tested at different vacuum ratings.A two bbl of the same CFM rating as a 4 bbl will flow about 15-20% less than the 4bbl.I know of a few guys who tried a single progressive 2 bbl Pinto (Holly-Weber) on inline 6's.Part throttle power was noticably reduced by the small single primary throttle, while full throttle power was improved only slightly.A typical Holley style 350 cfm 2 bbl should work just fine on a 250 engine.I saw a Rochester 2GC as suggested by Olds 42 used with excellent results.You will be using an adapter which will restrict the flow into the intake anyway.Since your engine is stock maybe the easiest approach is to use another monojet or an older Rochester B.

The later 250 with the integral intake had a progressive Rochester 2 bbl. Worked pretty good, but also had the smog stuff on it. And in 86 a rebuild was $180. Mine had severe internal corrosion from standing water (before I bought it).

Thanks for all the responses to my question.
You have reminded me that I do have a few spare parts lying around including 2 other Rochester Carbs.
Tony is this a Model B. It came off my trucks original 230.
\'63 carb
The other carb is a VariJet II from an '84 with the integral head. It has a bunch of vacuum ports, fuel return line and a complicated linkage system, but it does have a manual, not vacuum secondary and it looks like it could be switched over to a manual choke. VariJet II
Has anyone done this?
I like the idea of the noticably bigger secondary on the VariJet, but I also like the simplicity of the older carb. I'll have to think about this one a while longer.

I had my 2 bbl rochester running with all but the advance port blocked off and it did okay. If you have the adapter, try it.

This is starting to sound interesting, but pardon my ignorance...which is the advance port?
VariJet other side

Did you hook up the electrics for the choke and idle? or were you able to bypass them?
Thanks again for all the help.

I can't view your pictures at work due to the firewall. And, it's been to many years to remember the details about the carb. I do recall it had some electrics hooked up, one was for a throttle shut off to stop detonation after you turned off the engine, that would be simple with a wire to the ignition. Can't recall if the choke was electric, probably was, but you should be able to rig up a cable. For a test you don't need the choke connected if you have someone to run it manually.

Hey, new guy here.
For the small motors, think outside the norm a little. I built a Jeep I6 a few years ago and put a 2bbl Weber on it with a mechanical secondary. It really woke that little motor up.
Mikuni makes a lot of stuff for smaller motors as well.
If the bolting to the stock intake is a problem, Offenhauser and Clifford Research have a lot of stuff for I6 motors.
Good luck.

Since this is carb post, I have a question about my carb. It is a bendix-stromburg model WW. How would I go about finding out how many CFM's it is?

Here's my tow-cents on the Rochester B model idea.

I too was mad at my Monojet. It was noisy, it wouldn't idle below 900 RPM, it wasn't the "right" carb for my '66 250. So brainyak me goes and buys a Rochester B. Now I have a noisy carb that won't idle below 900 RPM and washes the cyl. wall down with raw fuel between 2000-2500 RPM. It stumbles around worse than Chevy Chase in a SNL skit and generally stinks up the joint.

I've also exchanged it three times because the throttle shaft or float-bowl was leaking. I've had it bench checked, professionaly tuned, tweaked and twiddle with by every "Carb Expert" in Oklahoma City and it still runs like doo-doo.

It's the worst idea I've come up with since I decided to get even with my Air Force recruiter and joined the Marines (I showed him, I went to 16 weeks of Marine Corps boot camp instead of 8 weeks in sunny San Antonio learning to be a Zoomy).

So, it's comforting to hear someone else having carb problems on their 250. Misery loves company. Let me know how the 2bbl. works out. Going back to the Rochester B is fine if your doing a nice restoration, but I wouldn't do it again on a bet.

I know someone will read this and tell me I just don't know what I'm doing, and that may well be true. What would be nicer would be the solution to this. I'm thinking 350 SBC, and a nice easy to tune Holley, but that's giving up and that ain't no Stovebolt.

Still thinking about the 2-barrel set-up, however there is a guy at work that has a 283 for sale that I'm also thinking about. As much as I like the 250, I also would like to have a bit more go. And it's a period piece since they started coming out in the mid-50's.
Thanks for the advice on the B's.

While the 283 is a good engine, you might also look at the 292 and keep it in-line.

I know Fred, but there aren't alot of 292s popping up around here and this 283 is available. I still have to find out the details on it and have to cost out what needs to be done. I have another running 250 that I could build up. However as you know it costs alot more to fix up a 6 than an 8 especially when going for the go-fast stuff.

283's are sweet little engines,smooth, free reving ,but if money is tight, and power is desired, pass right by that 283.350's are less money to build,good used peformance stuff is every where.Once under the hood, just tell em its a good running 283, most can't tell the difference.

If the price is right and the 283 runs, I'd go for it. Not everyone wants a six. I like them both, but like to live in the past. Of course, if someone offered me a 500 Caddy or a 327, I'd have a terrible time saying no.

jeez.......we've gone from fixing a single barrel carby to fitting a 283........I like where this is going!

Give it another couple of days and FREEDO's car'll be a runnin' a Blown 632 cu.in MERLIN.
(with twin WW Strombergs!)

To get back on topic, why are you so opposed to a 4-barrel? Holley makes a sweet 390 cfm unit with a vacuum secondary so you'll essentially be running a 200 cfm 2-barrel until/if the engine needs more.

Holley 390 CFM

Czechman,
I've nothing against 4 Barrel HOLLEYS.......there are some pictures of my Burnout Competition Car on my photobucket site. It has won many rounds throughout the countryside and runs a 2 x 4 Barrel tunnel rammed 308 cu.in. HOLDEN V8 with twin 390 Vac Sec Carbies.
It spends a couple of seconds at idle, and the next couple of minutes at 8000 RPM until a new set of tyres are nothing but shreds!Would never knock them in the right application.
But would never run this set-up on a street engine.

A matter of using the right bits for the application.

Hi, Doc!
Is the Holden engine a rebadged GM product, or is it something unique to Australia? I'd like to see a picture link to that 2X4 barrel setup if one is available.

The one and only time I was down under was a 6-day US Air Force temporary duty to RAF Amberley near Brisbane in 1975. Fun times! Maybe I can get back there one day!
Jerry

Gudday Jerry,
The HOLDEN V8 is a 100% Australian designed and made Small block V8 that is found only in this country.
In the early 60's GMH ( General Motors Holden ) did not have a locally designed V8 engine as an option for it's locally produced vehicles.
F%#@D had it's imported American variant vehicles in the market running 289 and later 302, 351 cu. in. small block Windsor engines to which GMH had no local rival.

The first HOLDEN V8 vehicles ran imported Chev 307, 327 and 350 cu. in. Chev engines while General Motors Holden researched and designed their own locally produced V8 engines.
This resulted in the first all Aussie 4.2 Litre, 253 cu.in. V8 being introduced in 1969, followed by the upgraded 5.0 litre 308 cu.in. V8 in 1970.
These engines are unique to GMH Australia.
The stock 5.0 litre 308 was rated at 185 kilowatts.
The 4.2 litre 253 was around 145 kilowatts.

The exciting thing about the 308 engines, even to this day, is that they will way out-perform a stock 5.7 litre 350 Chev V8 engine in almost every application.
This had to happen for Holden Australia to justify to GM America the cost of r&d, tooling and production of a completely one off motor specific to one vehicle in one country.........something that would never be approved in this day and age!

I'm not sure how to post a picture of one, so I have uploaded some photos onto my PHOTOBUCKET site that you can suss out for yourself.
If you want any more info, Google some details and see what you come up with.

Interesting engine! It bears a strong resemblance to the small block Chevy, with just a bit of Buick/Oldsmobile influence in there. The bore/stroke combination is a close match to the Z-28 Camaro 302, which had a 4" bore and a 3" stroke. That one was actually developed by American hotrodders back in the late 1950's by boring the 283 engine to 4", (from 3 7/8") resulting in a gain of 18 cubic inches to 301.4 cubes. Chevy cheated half a cubic inch and called the 1967-69 Z-28 engine a 302. It spins along quite happily at 8,000 RPM, given the proper camshaft, carburetion, and valve springs. One of my major competitors on the dirt tracks in California built nothing but 302 engines, and outran those of us with 327's and 350's on a pretty regular basis.

With a roller camshaft, a rev kit to keep the lifters on the cam, and valve springs strong enough to to prevent valve float, those short-stroke engines sound like a bumblebee on steroids! At those extreme RPM ranges, it's also a good idea to run a magneto instead of a battery-powered ignition system.
Jerry

Jerry, you seem to have found out some good info on the HOLDEN V8's.
The strange thing is that although 100% identical to each other, there is no way you can turn a 253 into a 308 and vice versa.

Although sharing the same stroke, the 4" bore with the 308 is a completely different casting to cope with the increase in bore size over the 253.

They are very similar in design to the Chev, but for some reason seem to be a more tractable and "Revvy" engine.
This you have mentioned from yor previous experiences with smaller capacity Chev engines.

The stock factory 308 fitted to the L34 Torana that you bought off the showroom floor in 1975 pumped out 260 kiowatts !
Race engines climbed up to 350 - 400 kilowatt outputs by the end of their production in 1979.

The main upgrades for these motors are just as you have stated in regards to heads, valves, ignition and carburation etc.

Do yourself a favour and look on Wikipedia for some history of Australia's holy grail of V8 races......The Bathurst 1000 at Mount Panorama.

This race has been running since the early 60's and showcases some of the fastest Australian built factory race cars ever produced through the late 60's until the end of the 70's.

There is a lot of history there, but to hear one of HOLDEN's most famous race cars, the '79 A9X Torana, with 308 race engine at full noise down a long straight is nothing short of aural porn!

My little burnout car runs a stock 308 fitted with nothing but the home made pipes, electronic ignition and the tunnel ram.
Don't know the exact HP output, but it outperforms Big Block, Blown, Methanol and Nitrous fed engines in comptition.

Revability and reliability will win every time!

One engine with even better RPM potential than the 302 Chevy was the 289 Ford. That one has a 4" bore and a 2 7/8" stroke, and somewhat lighter-weight connecting rods and pistons. One of the local round track racers 40 years ago in the southeast USA was Red Farmer, who won just about every race he entered with a wildly modified 289. The last time I saw him race was about 8 years ago, at a little dirt track down the road from the Talladega superspeedway. He was driving a Camaro, and doing pretty well, at age 80!

I've got the bits and pieces of a 289 sitting in the barn now, and a C-6 automatic transmission that will bolt on behind it, and there's an 85 Ford Ranger pickup out behind the barn with a well-worn 2.3 liter 4-cylinder in it. Those parts are going to come together eventually, and I'll have a sleeper rig to embarass the kids with their rice rockets on a weekend stoplight cruise!
Jerry

Jerry.....great reading that has me relating to many of your remarks.

Parked in the Shed next to the Torana 308 SS Hatchback and the Chev is a 1968 F%#@ Fairlane fitted with..........a 302 cu.in Windsor, C4 Auto and L.S.D.diff.

This is another of my cars being worked on at the moment.
Blew up the gearbox getting it ready for our Nostalgia Drag Series held in February this year.
I bought this car as an unlicensed rolling shell for $400, and then spent a couple of months building the engine and driveline.
After building HOLDEN 5.0's in the past, I wanted to see how well a F@#% 5.0 litre would perform in comparison.

Bad Idea !!!!!!!!!!!
Twice as expensive and alot harder to identify/specify/locate some of the components ( Here in Oz anyway! )

I bored the 302 to 40 thou, resulting in a sleeved block!
Done all the usual machine work, assembled the bottom end and finished with a high performance, winged, baffled sump.
The heads are HIGHLY modified 289 units running 2.02 and 1.7 350 Chev valves, screw in studs, CRANE Gold Roller Rockers, Bronze guides and some amount of port and chamber machining.
These were topped with an EDELBROCK 289 Performer intake manifold,650 Vac Sec HOLLEY and some 4 into 1 pipes with 3' collectors and a custom built 3' straight through single exhaust.
The C4 runs a stage 2 shift kit behind a 2500 stall converter thru to a disc braked LSD diff.

Compared to equally modified HOLDEN V8's in similar weighted and geared cars....I must say that the F@#$ engine does seem to fall short of the mark.

Can't tell you how it ran down the 1/4 cause the gearbox let go before I got the chance to run.
This is also our daily driver for me to take to work and the missus does the shopping in it! Reckons it goes and sounds better than her '71 351 F@#$ Falcon!!!!

The Torana has run a best of 15.7 at 148kph with the stock 308, 4 speed and 2.78 LSD 10 Bolt.....not bad for a factory car crossing the line in 3rd gear with it's 2.78 diff !

Anyrate, hope you enjoyed the read !

Bob, if you can locate one, the transmission fix is to swap to a C-6. The C-4 has a habit of breaking down, particularly behind an engine with some good low-end torque. The bellhousing bolt pattern for the 289, 302, and 351 Windsor engines are identical, and there are two versions of the C-6 bellhousing. The most common use for the 351/C-6 combination here in the states was in the Econoline delivery vans. A C-6 from a 351C, 351M, 390, or 400 engine will not fit, nor will the ones from a 429 or 460 engine (wrong size bellhousing).

I'm building up a pretty healthy 302 at the moment for a former student who is restoring a 68 Mustang. It's .030" oversize, with hypereutectic flattop pistons, a pretty radical cam, and some extensive cylinder head work. It's getting an Edelbrock Performer intake, and an Edelbrock 600 CFM carburetor. That's a bit too much carb, but he's going to have to learn the hard way!
Jerry

Yep., I just dropped out the C4 yesterday.........and the torque converter looks decidedly different from the one that I put in it before the gearbox was supposedly rebuilt by the last expert shop.

I could feel straight away that it had less launch and was alot softer between changes. But you cannot dispute this on paper!

A fellow car club member is going to strip and report on the failure of the box, and inspect the converter at the same time.
He WILL rebuild and modify the whole package to suit the requuirements of my Fairlane.

The Missus's '71 XY 351 cu.in Falcon has a C10 attached to it that I was going to steal and put behind my Fairlane........but all that Cleveland to Windsor crap has put me off the whole idea!


All the best................Doc Bob.