Guys
What is the benefit of running a 1 inch open spacer or a 1 inch 4-hole spacer under a 4 barrel holley? Where will I see the gains if any? Right now im running a 600 vac sec with headers and performer manifold. The truck is a 75 with a 390
thanks
Ben

 

You might see an overall gain with the 4 hole. You probably will see an overall loss with the open spacer. This applies to your engine. It might be the other way around on a drag engine. I use a 4 hole but can't compare how it is without it. My fuel guage hits the manifold without it.

 

the spacer is supposed to be a insulator for the carb. It is supposed to help keep the carb cooler and thus the Air fuel mixture will be denser ..in my opinion save your money unless you have an EGR or clearence problem. I have seen those spacers oem on ford trucks . those trucks had egrs

Jon

 

They have showed some pretty impressive gains on some engines and very little gains on others. I wouldn't count it out. One of the ideas behind the spacer is also to increase plenum vloume. It will also decrease the angle that the air has to turn to enter into the runners. It all depends on the build. My 2bbl 360 seemed to run better without one. Its hard to tell by the seat of your pants though in a truck that won't even run 18 flat.

 

well the reason that I ran an open spacer is because I installed the 50cc Reo pump on my Holley 1850. I had a severe off idle bog that I just could not jet out no matter what, so I installed the larger pump. Without the spacer, I wouldnt have had clearance. Now it seems that my shooter is too big. I figured that by installing the spacer, I would need a larger shot bec the carb would be further removed from the manifold. Right now, these are my settings:

37 shooter
50cc pump cam in #1 position (not the yellow cam--the dark purple one that cam in the kit)
Black spring in the vac secondary housing (to keep the secondaries from opening---primarily for gas mileage reasons)
stock 1850 jets and powervalves
idle mix-2 turns out per side

I still have a bog somewhat--I dont know what else to check and I know its fuel related--floats, fuel pump/filter is all OK. Timing and ignition is all perfect

regards
Ben

 

try this web site you may find it very helpfull http://www.holley.com/HiOctn/TechSer...o/FMCTech.html

 

The way I remember carb spacers is,

Open spacer, like an open plenum on a single plane manifold. Better for higher rpm use. Tends to even out the fuel flow under high demand conditions. Helps with cylinder imbalances.

4 Hole, more like a dual plane or stock manifold. Helps with the vacuum signal to the carb for better throttle response, especially at idle and off idle conditions. Keeps the velocity of the air-fuel charge up.

Iwould think that if you are having an off idle stumble you would want to swap out that open spacer for a 4-hole one. I think that the open spacer will require an increased pump shot but not because of the distance. It's the increase in the plenum volume. More air that needs to get moving when you open the throttle.

Hope this helps,
Greg

 

that 37 shooter could also be the problem. Your center squirter needs to go down smaller which lengthens the duration, which allows the carb to catch up the weight of your truck. This may not be your problem, but you wouldn't believe how many guys I've had put in a #25 and it cured there problem. The size of the squirters do not affect shot volume, ONLY duration. I've got a hot 428 with a 750 carb that I ran with a #25. Try it if you haven't. Also, stick with an inch or less, four hole, plastic spacer for your application.

 

Hi
I tried the 25 shooter and boy did it run crappy. It wouldnt even accelerate. I since stepped down to the 31 shooter and it still has the bog during transition throttle. Funny thing is, this thing is burning really rich! I mean you can smell it. The float on the primary is pretty near all the way down too. I have since installed a black spring in the vac secondary housing when I put in that 1 inch open plenum spacer. I dont know what else to do at this point. Im ready to ditch the holley and swap in an edelbrock!
thanks for all the help guys
regards
Ben

 

Can I assume you double checked your powervalve....it sounds suspicous....? Eboks are good but I've got a feeling you are an hp nut like me so I wouldn't give up on the holley yet. Frankly, I've yet to get an ebok to run right on a high horse FE but they are great on the stockers...

 

proeliator:
NO I havent even peeked at the powervalve. I know that they can rupture and cause a full rich condition. However, if one is blown, wouldnt the truck fail to idle? mine idles fine; it just loads up (esp when VERY cold) Besides, this carb (1850), is the new variety that supposedly has powervalve blowout protection. So, I ASSUME ( i know a dangerous thing to do) that the valve is ok! I am not about to open it up now because I need my truck (we are getting killed with snow--so far ~~19 inches!
I was thinking, once I get the chance to check it, would you recommmend putting a plug in there (I have a holley powervalve plug) and just jet up 8 jet sizes to accomodate? I am really at my wits end here because the truck has a LOT of power above 1/2 throttle and it idles fine. Its this transition throttle bug that is giving me fits!!! I only with this holley had replacement air bleeds so I could fine tune the circuits! However, I think that adjustable bleeds are only found on the more expensive barry grant series carbs! Any more ideas??
regards
Ben

 

Ben,
Sorry to hear that the smaller shooter didn't fix your problem!
You mention that you are thinking about going to the Edelbrock. I have a 1405 on my 410, and it is so simple to tune that it's ridiculous, EXCEPT, I'm having trouble getting any high-end revs out of mine. Maybe we should work some sort of deal here, you give me some top end, and I'll share some of the low.
I'm greatly puzzled by my situation, as the manual for the carb says you can go down to 3 psi (if fuzzy memory serves) and I have used a fuel pressure gage and always show at least 5, usually 6. But it goes "flat" at about 4500 in 3rd gear, and about 3500 in 4th (high), and I'm convinced that it's fuel related. Not trying to hi-jack your thread here, just expressing my own frustration. I'm actually considering re-installing my Holley to see if I have the same symptoms with it!
BTW, I have had a sort of fiber 1" 2-hole spacer under both my Holley and the Edel, and the only real effect that I saw was that hot percolation problems/hard starting went away.
Steve

 

Steve
got carb probs too huh? Hey, Id gladly trade my prob for yours. I can do much high speed driving anyway with my truck. This is why this hesitation is a PITA! As for yr e-brock, do you have the metering rod tuning kit? Summit sells kits for specific models. I believe that they are in the range of 40 to 45 bucks. Also, have you checked out edelbrock online? they have some great technical help--ie tuning protocols. I checked out the holley site and everything that they suggested i pretty much did--and then some!
Im starting to wonder--this may be a longshot--but im starting to wonder if my driveability problem can be attributed to a non-heated carb spacer like some of the 2bbl carbs had. Its really cold where I am and maybe? fuel is not atomizing? Honestly, id like to put one on during the winter months ONLY but I dont know where to get a 4bbl heated intake carb spacer!!! OH well....
regards
Ben

 

Try ebay for the heated carb spacer, I see them all the time there!

I don't see any at this time, but they do pop up from time to time.

 

Ben,
Yeah, I've got a tuning kit for the carb, and swear I could just about recite the manual from memory! Any mods that I made away from the standard jetting, except for fattening the secondaries a little, seemed to make things worse. The frustrating thing is that it seems to be intermittent, and consequently really fun to try to track down! Think my next move will be to plumb a tank from inside the bed again, and use 3/8" hose all the way to the fuel pump inlet, and bypass both on-board gas tanks, lines, and transfer valve, etc., and see what that does. It seems like a long shot that both tanks could have a clogged "sock" (if these tanks even have them) or something, but desperation is setting in. I'm kind of like you, I've tried everything that anyone has suggested but still not winning.
FWIW, I have a heated carb spacer for a 4-bbl that came on my '65 Merc engine(I sold that manifold), but can't use it on either the Edel intake or "Code S" intake because it requires an extended manifold-carb surface to seal a PCV boss on the back of the spacer. The boss is open on the bottom, and would leak vacuum big-time without the surface to seal against, and I'm not sure if there are gaskets available anyway. I suppose one might be able fill it, but not sure about that. I think there are after-market models available tho, so you might check with your parts guy. I will try to ask my parts man what the brand is next time I'm in there and let you know if you don't have any luck from your end.
Good luck in your battle, we know that goodness and determination WILL PREVAIL.
Steve