Inliners International Forums General Discussion Hi Performance holley 390 cfm carb

I need the base plate traced or something on this order so I can have it sent to the guy making a new intake for my car--anyone have one of these carbs handy? Pics from all sides would be great too. The pics that Holley has doesn`t show all angles. Any help would be appreciated...Thanks

you can use any holley 4B gasket(390,450.600 Square bore)

More detail, please?
Not nagging - just remember that the orientation is 90° to "normal", with the throttle shafts parallel to the crank. Be sure to put "circles and arrows" on the gasket so he doesn't just auto-pilot it like a V8.
There is some difference of opinion as to which side should be facing the engine: primary or secondary.
IMHO having the primary facing away is a safer choice if the runners are short, and the carb is close to the plenum's inner wall since it reduces the amount of bias to the center ports on light throttle.
Anyone done or seen any comparisons?

Also as a side note for you The carb linkage will not clear the intake(sitting 90deg.) with out spacing it up higher.

I have had carbs sit in three directions.
Normal, where the linkage will bolt right up. Primaries fwd.
Primaries,closet to the cyl head & primaries furthest from the cyl head.


IMO,it really did not make any difference on my street car.

Maybe if I had a wide band O2 reader,I might have been able to see/read a difference.


MBHD

It's not necessarily going to feel different, it will vary based on the manifold, engine vacuum, etc.
However: mileage will be down compared to correct orientation because the distribution means some cylinders are wasting gas and the throttle must be open more to compensate for this.
The engine is also knock limited, and the lean cylinders determine when this occurs - which will reduce max HP.

Panic, this is going on a Chrysler 265 cube flat six--having it sit like a V-8 would is the easiest way to hook up throttle linkage, more info on the best way to have it face would be helpful. Would like it to perform well and still get reasonable fuel consumption. The engine is to be bored 60 over with the head shaved 65 thou and a camshaft with 260 duration and 410 lift. The engine has dual carbs now and I thought the four barrel would be different. I haven`t seen anybody do one on these flatties---any thoughts from anybody would be appreciated....Thanks 52er

Before you go any farther:
what don't you like about the duals now?
What carbs?
Are you making the 4 bbl. manifold? From what?
I suspect that complete kits (4 bbl. + manifold) may have had minor tweaking done to the carb position or plenum floor to minimize any known mixture problems - you'ld be starting from square 1.

The carbs work well---they are the Ford glass bowl single barrel type--just a thought on the four barrel, like I said it`s just different. The guy making the intakes is----www manifoldsbymoose.com. He makes some very impressive stuff. Take a look, tell me what you think.........52er The carb is just what`s avaliable in a small cfm

The 4 bbl. linkage isn't difficult, just annoying. A simple bellcrank on a vertical post converts the linkage motion to fore-and-aft.
My preference would be 2 progressive 2 bbls. (Holley 5200), but depends on your taste.
My argument against "classic" carbs such as Holley 94, Stromberg, etc.:
1. most of them are far beyond their sell date, and even "rebuilt" are not completely fresh
2. price is 10 X their replacement value as a modern 1 bbl. (Rochester M)
3. very few people alive who know how to jet them, and parts not easily available (the only way to jet a 390 wrong is not listen)

A carburetor is no more a fashion statement than a heart transplant: if it doesn't work, there's no point to it at all.

Do you think the 4 barrel will work? Or am I just fishing. Sounds like a lot of r&r on my account and could end up with a dud---still like the idea tho......Thanks

Sure, it will work. I'm just not sure how much of an advantage it's going to be, or what to do if you have some mixture distribution problems.

Panic brings up an excellent point regarding fuel distribution. Too often intake manifold design doesn't give enough consideration to fuel distribution, it just connects the carb to the engine. Will it work? Sure, but when I see exhaust temperature variations of 250-300 degrees during dyno testing it tells me the manifold is questionable. I've seen the front 4 cylinders of an engine run 100 degrees hotter than the rear 4 cylinders, the center 4 cylinders run colder than the corner cylinders on a V8, etc. That tells me the intake manifold isn't doing everything it should.

Sometimes a carb spacer will change things but that is just a band-aid fix. One of the best manifolds...as far as fuel distribution is concerned, was a sheet-metal tunnel ram built in our shop for a BB Chrysler. Was it perfect? Far from it, but the exhaust temps were within 100 degrees and the engine made 1032 HP.

Ron

A 4 bbl. manifold has a slight advantage in that the open flange is big enough that you can make fuel dams out of popsicle sticks, carve drains across the front of wet cylinders, partially mask port runners, etc. across the plenum floor where a 2 × 1 etc. would be inaccessible.
Except it's a lot of work, and going by plug color is far too crude to be effective. You need EGT sensors, etc.

I've messed around with 4 barrels on several 261 Chevys and a 302 GMC.I got them to carburate quite well after some working with jetting.But I was never convinced a single carb on an inline 6 is the way to go.2 or 3 carbs should be better than one for fuel distribution.
On an engine like the old Chevy and GMC having several shared exhaust ports you might think exhaust temperatures might vary quite a bit.

I've also noticed that there is considerable difference as to carb placement between different 2 × 1 manifolds.
Some (Edmunds, Tattersfield, Offenhauser) take the obvious (but may be no more than "this seems right") of centering one carb opening between the 1-2 and 3-4 ports, and the other between the 3-4 and 5-6 ports.

The other school (Fenton) places the openings father from the center, perhaps 60/40, on the basis (just guessing) that the center will draw from both, but the end pairs only from 1 and should be "favored" somewhat.

It might be interesting to compare EGT, plug temp, etc. between brands using the same carbs?

Redarding EGT, how about useing one of those hand held infared thermometers? They ae getting cheap...I use mine to check the BBQ, but racers use them to check tire temp across the contact patch. Seems like you could drive up a long hill and look at each part of the headers.
Here's the first link I came to....
http://www.cabelas.com/cabelas/en/templa...requestid=50003

Leif

You would need to check it with the engine under a load. It will still cool to fast before you could pop the hood after it has returned to an idle to be accurate. The best way will be as Ron mentioned, using an engine dyno or even a chassis dyno, will yield the best results. You also could modify your manifolds or headers to accept thermocouples, and get a multimeter that can read the results. I got mine from Snap-on, Mac tools even has one. Its an EM710, and has a bar graph function as well,and comes with its own thermocoupler lead. It can even be used to diagnose oxygen sensors and fuel injectors and set TPS voltage on fuel injection equipped cars. You probably can only do one exhaust port at a time, but its a start. You can put it on the dash or hold it in your hand as you drive in different terrains and see the effects in real time. Or you could take your hood off and have a friend ride in the engine compartment and use the BBQ hand held infrared checker(LOL) :D,just don't let any cops see you!

An iron split manifold may retain enough temp to be clocked with an IR gun, the alloy intake cools too fast to get actual data - any remaining fuel will boil off and use up the BTU.
But... it may show a trend. If the ends (1-2 and 5-6) are consistently hot, and about the same, you know you have something.
Remember that a mixture diff may be at idle only, high vacuum only, or WOT only, or any combination, so try to load it specifically where you want before taking a read. The usual plug check applies: after enough time at your test conditions (several minutes), pull the clutch in and kill it in neutral, then coast to prevent false reading.

I guess the bottom line is,does it matter? There's 10's of millions of modified carbureted V-8's running around with less than equal fuel distribution.Add to that millions of older inline engines and whatever else.We're not talking race engines,but a street engine making maybe 3/4 HP per cubic inch on a good day?

Panic...please clarify your 390 statement. I have yet to throw my new one on the 250 but am anxious to get it right when done.

Still wondering which way to go on this carb stuff--like the idea of the four barrel if it will work. This fuel distribution problem has to be explained a little better to me. Is it going to hurt the engine? Will it increase the performance? I want to get the most performance without any damage. Moose can make me any intake so it`s important to make it right the FIRST time. So may the best minds prevail and you will help me build it correct------Thanks guys........52er

52er

Use three side draft Webers,that will give you even fuel distribution,& the most power & better street diveability bar none.
W/a change from all the different two bbl & 4 bbl carbs I have tried (which is a lot BTW) then switching to three side draft Webers I had wished I had done this swap much sooner.

I wasted a lot of time & $ on using all these different types of carbs.

I just could never afford the Webers ,that is why I tried all other forms of carburation first.

I got a deal years ago from the recycler paper,three 48 MM Webers on a Datsun 240-280 Z Cannon intake manifold ,all for $200.

Even though 48 MM's were too big,it still ran better than anything I had ever tried.


Second choice three downdraft Webers.
Just some examples http://cgi.ebay.com/ebaymotors/Weber-45-...sQ5fAccessories

http://cgi.ebay.com/ebaymotors/VW-PORSCH...sQ5fAccessories

MBHD

What about 3 side draft injectors?

IIRC ther's a fellah converted SU carbs to throttle body injectors over on the Megasquirt site.

Not sure why you couldn't do that with some of the small TBI units from the '80s domestic econo boxes (I'm sure there's a reason, I just don't know what it is, certainly not because it would screw up the float adjustment ).

That and a Megasquirt controller (not sure how you'd wire it with 3 injectors as I haven't looked at that).

Of course if you are dead set on carb-o-tation, the SUs in original form are supposed to work well, rumor has it #4's or #6's are the setup to have (I call it rumor because I haven't been able to see one set up in real life and ask the person that set them up).

Agreed,
EFI will be best.
I just thought he wanted to stay old school.

It's just a lot of $$$$ if you want multi side draft FI throttle bodies,looks great though!
http://www.twminduction.com/ThrottleBody/ThrottleBody2900.html
Then buy a Clifford DCOE intake.

http://www.twminduction.com/ThrottleBody/bmw.html

http://cgi.ebay.com/ebaymotors/BMW-M30-I...A1%7C240%3A1318

MBHD

Hank, your correct---I want old school---carbs

What he said.