Experience with 600 Holley on a 4.0 litre

[Anonymous]

After Execute made comments on how effective a 600 Holley can be on a 250 I went looking for this I stumbled across some time ago some time ago. It is on a 4.0 litre HO. AMC? These are the recommendation he has for carburation, note some of the mods he made to the 600.

Carburetion:

I’ve used two basic carbs, both Holleys. The general Holley 4-bbl. sizes best suited to this application are the 390, 450, and 600 cfm carbs. The 600 cfm should be used in vacuum secondary configuration only. Also popular are the 350 and 500 cfm 2-bbl. carburetors, although I feel that more precise mixture control is possible when using a 4-bbl. carb. I install a Ford-type automatic kickdown throttle shaft in all of my Holley’s to run the A904’s kickdown. A new linkage rod between the carb and transmission must be fabricated.

390 cfm- Although many people use a 390 cfm vacuum secondary carburetor, I feel that it presents too large a restriction at low rpm before the secondaries open. I have used a 390 cfm HP series double-pumper (#80157) with some success. For drag race use, the tunability of four-corner idle, and homogenity of mixture delivered by a symmetrical bore carburetor are hard to beat. The throttle butterfly plates must be replaced with those from a standard 390 cfm carburetor to eliminate the holes found in those of an HP series carb. An air cleaner stud must be installed in the HP series carburetor at all times due to the stud hole being drilled completely through the carb body, or a massive vacuum leak will exist.

450 cfm – I have not used this size carburetor, although it would appear to be an excellent choice.

600 cfm – I have done most of my racing with 600 cfm vacuum secondary carburetors. Many people feel that the 600 cfm carb is too large, but my experience is that the car will go faster when the secondaries of these carbs are allowed to open relatively quickly. Tuning one to work well on the AMC six takes some finesse, but is well worth the trouble. My basic setup is as follows:
Ford-style automatic kickdown throttle shaft.
Quick-change secondary spring kit.
Purple secondary spring.
Moroso clear bowl sight plugs.
Holley secondary metering block kit (or 4160 carb to start with).
Size 67 primary jets.
Size 70 secondary jets.
8.5 primary power valve.
Holley hollow accelerator pump shooter screw.
Size 41 accelerator pump shooter (tube type).
50cc accelerator pump system.
Orange pump cam on position 2 (yes, I am using the wrong cam for the 50cc accelerator pump).
Further gains can be realized by replacing the primary booster venturis with annular discharge booster venturis. The resulting increase in low RPM booster signal allows a minor reduction in main jet and accelerator pump nozzle size. This modification can be performed by any of the specialty carburetor shops, including The Carb Shop and Holley Custom Shop.

 

[xctasy]

If the dynamics of the engine are similar, then the jetting doesn't change a lot. But there are so many combinations that only dyno tunning will sort it, and give the correct drivablity and optimised air/fuel curve for the engine. And small changes, or setting at different altitudes, makes a lot of difference to the exhast gas temperatures.

But ....after looking at how Ford OZ have made the Powerpack ignition module from EF on Falcon SOHC'S, I'd be a carby man too. Shove in a cam in a post ED XR6, and it won't take the extra duration because of the dual phase spark discharge. Another electronic rework Mr. Sure.

Yay!

 

[Anonymous]

That 600 Holley that he is talking about sounds exactly like an '85 302 HO carb. They some times show up on Ebay very cheap.

John

 

[xctasy]

Was it the so-called Holley 4180, the emissions-legal carb?

 

[Anonymous]

Spoke with an auot parts salesman parts yesteday. He tells me that 265 Chargers experimented with four balley carbs when racing instead of the two barrel normally used and found that this was unsuccessfull.
He says that it was found to produce less power throughout the whole rev range with the four barrel and was subsequently abandoned in favour of the two barrel.
He also says that a 500 Holley was used in the 70s on Nascar racing on 7 litre V8s without a problem.
Maybe true but I found all this hard to believe.
Nascars ran on Alcohol (Im assuming that this breaks down any comparison) and I found that some of the Holley 500s were heavily modified with bigger bores jets ect. Does anyone know if they did run them on 7 litre V8s (about 400ci). This is still surprising if a 500 normally only flows 350 cfm in real terms.

 

[xctasy]

Afirmative for the 2-bbl 2300 series on big V8's. Don't think it was NASCAR though. The 650 cfm # 6425 2-bbl was used on oval track where the Americans had some cool cost cutting measures in some of the Econo racers. The carb had a vairation of the Dominator air horn, and was very much a hi-po item with virtualy no vacuum signal at low rpms. 2-BBL 396'S, FE390's, 400 Fords, that kinda thing.

The 650 was really 460 cfm, but on a big block 2-bbl, vacuum could be 3" hg easily. If they did run alcohol, the carby couldn'r flow any more than 200 hp, and support an engine. As a gasoline carby, 400 hp on a 400 cuber was a distinct possibility.
The 4412 and 4783 (500) is about 354cfm, or 220 hp on a six cylinder.
4782 (355) is 251 cfm, or 157 hp on a 4-cyl. A six may do 170 or so
7448 (350) is really 247 cfm, or 154 hp on a 4-cyl. Ditto for the six.

Holley rated these at 3"hg because they were destined for truck and undercarbed base engines...that had high-vaccum.

Afirmative for the AVS 500 Carter the Tonsley park crew used on the 250 cube Track Pack versions of the 245 Hemi. The carb was unable to produce a good progression form primary to secondaries without loosing intake velocity. The big inlet runners of that insect like 4-bbl manifold didn't combine well with intake ports that were 2.7 sq inches, very big.
It was a nice street car, with dollops of great torque, and more power than the 2-bbl Carter carbed versions. It was slower on the track, maybee because Chrysler didn't support it as well as the 2-bbl, or because of that progression issue form the two different sizes of throttle bores

 

[MustangSix]

I think we tend to undercarb these engines. A 600 cfm carb should be fine on a 250., actually better than a 500.

Keep in mind that the CFM ratings on 4V and 2V carbs are at different pressure drops, so it's apples and oranges. You can't compare CFM without accounting for that difference.

Every time a 250 takes an intake breath, it needs roughly the same amount of air as a 330 cube V8. It doesnt' do that as often, but the dynamics of that huge gulp of air would seem to make a larger carb a better performance choice. The 600 has actually got smaller venturis on the primary side than a 500 2bbl. The added capacity comes from the relatively small secondaries which only open on demand. The capacity is not used unless you reach a load whic requires more airflow, and that point is tunable.

BTW, in the 60's when 426 Hemis and 427 Fords ran in NASCAR, the carbs were much bigger, a 735 or larger, IIRC.