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#1
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Carb Spacer.... Worth it?
there seems to be 4 different types... Wood, Aluminum, Phenolic, plastic
im assuming they all the the SAME thing with the big difference being Heat transfer... if im wrong please correct me... i have about 4" to spare for hood clearance so that doesnt seem to be an issue... any suggestions? Thanks JOe |
#2
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A spacer is a tuning aid which increases plenum size of your intake tract and will (usually) raise the torque peak. This will give you more peak horsepower at the expense of reduced horsepower at lower RPMs. This may be desirable, or not depending on how you drive.
The effects of heat transfer are secondary and could probably be measured on a dyno, but you likely won't notice it from the driver's seat. But then you could try all the different materials and write a review for us! Give you a chance to post some more smokin' videos... |
#3
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Quote:
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#4
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Hey D, tell him about the carb spacer you made out of wood and it started on fire. Oh wait, I just did.
Do you think if I had a wood spacer on my car and I was driving for two hours at a steady 75, and the engine temp was 185, that the carb would actually be cooler, or is this a dyno room gain only. Hmmmm? |
#5
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I like the MR Gasket plastic ones, four hole, for trucks. You notice off idle power, but I use them for cooling the carb when working hard.
Wood, I wood (LOL) think, would not be very reliable. |
#6
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The spacer did not have anything to do with the fire. IT was on a 2.6 4 banger and the coil tower cracked and it backfired into the intake and caught it on fire.
And yes, the carb temp will be a little cooler than with an aluminum one. |
#7
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But what about longevity?
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#8
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Vacuum leak if it is on for along time. Might be good on the dyno, or a short pass, but not something you would drive alot.
Carb spacers are wonderfull tuning tools, if you are tearing up the low end, then put a 2 inch spacer on there and it will raise up the power band. 4 hole to open, fun isnt it. |
#9
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I ran a Phenolic under the Thermoquad on the dirt track cars for years with no problems. I did use those thick gaskets on both sides though. As for the wood ones, I have one we made (cause they don't exist for this car) for a 2.2 asphalt car and it's 2 years old and has not been off the car yet. The 2.6 car mentioned before is my brothers dirt trrack car and it takes a beating and it held up for half a year before the carb fire.
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#10
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Great fun!
Or, you use tham on aluminum carbs, to keep them from boiling over, hehe. |
#11
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For most people the heat transfer issue is a moot point---not enough difference to notice. There are installations where it would make a difference such as endurance/oval track where engine temps are very high for long periods of time. This is especially true for cast iron intakes.
The design differences are far more important. Everyone knows about the basic four hole spacer vs. the open plenium. Generally, the four hole helps throttle response---the open spacer improves upper RPM performance. But what about spacer thickness? One inch, two inch, three inch? Which is better? For most people a one or two inch is all that is ever needed. But there are applications where three inch spacers are measurably better. W2 heads with Edelbrock or Holley intakes both work better with three inch open spacers at higher RPM(8000+). Then you get into the area where "fools and their money are soon parted". This is the area of speciality spacers. Less than 5% of racers ever need to even consider getting into this area. Here are some examples: * combination spacers---top part is four hole, the bottom part is open. * tappered spacers---as the name implies, the opening gets larger toward the intake surface. * angle spacers---front to back/side to side/ and front to back and side to side. This is generally high $$$ oval track stuff. * spacers that protrude down into the intake plenium. These direct the air/fuel mixture inside the plenium. This last category of spacer won't be found in Summit/Jegs. They are generally CNC spacers available from race intake mfgs like Wilson, Automotive Specialities or carburator people like Stealth. They aren't cheap---cost easily gets into the $200 to $400 range. They are usually bolted onto a $30-$40K engine. These things do work! They can change the driveability of a high HP engine considerably. They are worth the cost in very limited applications. No one on this site probably needs the exotic spacers---just thought you might like to know about them. |
#12
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Thanks sanborn, as always a well thought out post.
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#13
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a mid horsepower - typical muscle type rebuild you will see NO gain on the street from any of these. You may think you will but your only talking a few hundreths in the QTR mile anyways.
Now if your set up was off before you may see a large gain only because it may have corrected an already existing problem. |
#14
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Thanks for the great info guys!...
about the heat thing.. i mentioned that becausei had a 64' el camino with a 307 (pos) cast everything with a holley on it and it would actually get so hot it would boil the fuel and evaporate... we could come back and look though the sight glass 10 minutes later and it would be empty resulting in longer cranking starts... When i read the famous "Demon Tuning thread" they brought it up saying that very large carb's (mines a 1050... i know... too big but i didnt buy it ) usually have low bottom end power due to fuel just dumping in and not atomizing like it will when air starts to really flow and mix like it should.. so i read that and kinda thought it could be worth looking into.. and for 30bucks i'll probably just go aheady with it anyways... Question would be what should i go with? my intake is an edelbrock airgap open plenum... im looking for a little more throttle response below 1500rpm's.. THanks for all the info on this thread already JOe |
#15
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Quote:
I'm not to up on your engine specs. Things to increase torque work well in some engines and not so well in others. If you have room for a spacer, I'd try a 4 hole unit and not worry about what it is made of. If the choice was as easy as a catolog, in the order DW listed id how I'd go about it. Quote:
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#16
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Quote:
Now if your going with the tunning statement above and you think it's dropping fuel out of suspenion there is a way around that too. Usually when that happens the air/fuel hits the intake plenums floor and while trying to make the turn it ends up puddling on the floor. A taller spacer in in order here to make the turn less sharp and make the plenum look larger to the carb. This is also why you find ribs cast into the plenum floor. Never used one, but truck owners putting the big M1 intake on there trucks swear by using what is called a turtle instead of getting the proper intake for there trcuks. IT's an insert that sits on the plenum floor that directs the fuel/air's flow across the intakes floor. If you pick up the Mopar engine book they list some intakes and the mods made to them to prmote correct flow through the intake as well. |
#17
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Just thinking out loud again.......
In a perfect world the 4 hole helps bottom end and open helps top end. What about in a less than perfect world?
What if someones carb is smaller than needed? The air/fuel is pulled through faster than ideal and the air/fuel doesn't have time to make the turn and crashes into the floor and trubulance is the outcome. I beleive what I was told years ago, that a 1" spacer with a small carb could help botttom end AND top end by just correcting errors that exist. It's the whole package that must be considered by making sure you have the right parts or correcting for the short-commings. Of course a street engine that has lost too much of it's bottom end could be helped by the addition of a 4 hole spacer to speed up the flow. |
#18
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Good thinking out loud. If your carb is to small, you'll limit top end by a small amount. Depends on how small. A 650 where a 750 would be ideal isn't really that bad.
Fuel is hitting the floor anyways. How much is the question and when does it become bad is. I would not ever worry about air rushing through the carb so fast as it making a problem. Carbs are rated at a certain pressure drop. Exceed it and the carbs flow numbers go up. |
#19
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problem is im VERY over carbed i think.. its a race demon 1050 cfm on slightly more than mild modded 440ci...
if anything im OVER carbed... so im thinking i should go with a 4 hole then? JOe |
#20
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The only way you'll know for sure is to try it...
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#21
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whats the specs of the engine if you know.
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#22
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ok...specs...
Race Deamon 1050 Edelbrock heads (full race port and polish) 88cc 210cc 2.14"/1.81" Edelbrock Airgap Intake (port matched and polished) 4.375 bore 3.750 stroke Wiesco flat top porged pistons (2619's) Engle Cam: IN-.574 EX-.584 Solid lifters 1.5 Roller rockers 10.2:1 compression anything im missing? JOe |
#23
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Spec's.........
Stall speed
Rear gearing Cam duration @ 50 |
#24
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Quote:
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#25
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Quote:
3.91 gearing @.50 In-247 EX-253 |
#26
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Good combo.....
but I agree the comp could have been higher with the heads. I'd recommend a 4 hole spacer 1 inch thick. If it helps, you could try a 2 inch and see if that helps. Your combo sounds like it would have been happier with about 11 - 1 comp. The lower compression softens the bottom for this set-up and the 4 hole should help speed up the fuel/air flow some. Everyone likes the sound of the Dominator but for street/track you could have used an 850 or a little larger with good results.
Just thinking out loud. |
#27
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I have made my spacers out fo plywood. Dirt cheap and good insulator. The only problem with them is, that if you overtighten the carb flange it will compress the plywood from the corners eventually cracking the throttle plate. That can be solved pretty easily by putting tubes around the carb studs. I had some problems with mine without the spacer in jam traffic on hot days, the car died because of vapor lock. The plywood spacer solved the problem.
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#28
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wood carb spacers
On the subject of "home" built wood carb spacers that really work, check out Jim Hand's book on building and testing Pontiac's (How to Build Max Performance Pontiac V-8's). He also has a great chapter on "race" Thermoquads (although I don't personally use them). You can find this book for $18.99 at major book stores or Amazon.com. I wish us Mopar folks had Jim working on our stuff. In the Pontiac world, he's like a "god".
Mark H. |
#29
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no jim butler is the Pontiac god, and why not use aTQ plentys of guys i know out ther can do them as amatter of fact on is a tech at store in Plesanton.
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#30
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Hi hotrod7043,
Interesting that you mentioned Jim Butler. Yes, he is also highly revered in the Pontiac world, so I'm told. Maybe a "near" god. Last weekend I got my "ass" kicked at Infineon in the first elimination round in Trophy class by a Pontiac 400 in a '74 Firebird. My bad luck. The Pontiac was running a "Butler" built short block with Edelbrock heads, Victor manifold, roller cam and big Holley. Why a 9 ~ 10 sec car was running in Trophy against us poor 14 ~ 15 sec cars is something to ponder. I guess for $25 more he could make more runs, doubling up in Trophy and one of the Pro classes. With the big "stagger", I beat him to the finish line, but broke out and lost ! Poor dual-quad 440 Roadrunner ! Ran like a scarred chicken with a Firebird on it's ass ! 1 or 2" carb spacers on the CH-28 with my old Carter AVS carbs might be worth some top end power, since the manifold has a relatively small plenum volume. I don't think Thermoquads will fit. Has anyone tried carb spacers on a CH-28 ? I'd need a 440 6-pack hood scoop to get the necessary hood clearance. Oh, what the heck, just take off the hood and lose some weight. Darn car's too heavy anyway ! No wonder we're so slow. Street tires also don't help. Thanks for the info, do you remember what store in Pleasanton,CA ? Mark H. |
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