FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: ewo357 on July 26, 2016, 01:17:08 AM
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Everyone seems to have a different opinion on what type and size of carburetor to go with so let's see what you guys think would work best for my build.?
My main focus is low end torque, throttle response and drivability. Is just going to be a street cruiser that probably won't see 5000 RPMs but of course I don't want to leave any power on the table....
My car is a 1966 Country squire (around 4500 lbs?) with a TKO 5 speed and air conditioning!
The engine is a 445 with stock C6AE-R heads, a port matched Edelbrock F427 intake, hydraulic roller cam (270 276 218 224 .563 .563 110') and shorty headers.
So far I'm leaning towards a Holley 4150 650 cfm #0-80783 electric choke and vacuum secondaries.
Thanks in advance! I know there are a lot of experts on here!
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Not to derail your thread, but how was the TKO install? I've got a 63 Colony Park with the original Merc O Matic. Be interested to know how your trans swap went.
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I'd use a 750, mechanical secondaries. Choke if you need it.
I can understand your reasoning in thinking a 650 would give better throttle response, but you can go to an extreme with that, to the point where you critically rob horsepower. A 445 is a decent sized engine and will fare just fine in both horsepower and throttle response with a 750.
A Quick Fuel Q-750 would be what I would recommend if you didn't need a choke. There are some other QFT models that would work well if you needed a manual or electric choke.
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Agree, 750 is as small as I go, except I'd likely go cheap on that one and go with a stock 3310. Heavy car, big cubes, the vacuum secondaries will open very quickly when you want them
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+1 on the 750 double pumper. As Brent said, you will be leaving a lot of power on the table with the 650, and the 750 will give great throttle response too.
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Swimming up stream again. ;)
I would recommend a vacuum secondary carb in the same 750 to 800 watts.
The gas mileage with a DP in town will be terrible.
It's just a better to have the VS working in your favor.
Now if you are going full throttle all the time pretty much every time you drive it
then yes use the DP.
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Alrighty then, so far it looks like everyone is saying I should use a 750 (or bigger...?)
blykins why do you like the Quick Fuel over Holley?
My427stang what's the story on the 3310? It looks like there are a few different ones, some 4150 and some 4160, also either 750 or 780?
Thanks for the help guys!!!
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http://www.gtsparkplugs.com/CarbCFMCalc.html
Get in the ball park and go from there. Try a Q-Jet if your up to the challenge. There is a big difference between kitting and tuning these carbs.
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I just installed a QF 780VS for the first time on my 440. I've always used Holleys (I know it's the same company now).
I reeeeeally like the "tunability" of the QF, however don't expect to throw it on and have it run well.
They need tuning. I feel like I had to adjust it a bit more than any Holley I've run (if that makes any sense at all, that's just a general feeling).
However was really able to get it to what I would call a perfect tune. Nice carb.
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So there are a bunch of different 3310s over the years, for the most part though, it is really how much adjustability you need. There are some booster changes as well, but in general, I haven't seen a small carb like the 750 need much. Out of the box 3310 4160s are pretty easy to dial in for the street, generally the most they need is fuel level and a/f mixture set, and occasionally like a little more aggressive pump cam. The nice thing is they are dirt cheap.
FWIW, on my 445 4x4, I slapped a cheap bare bones 3310, adjusted it and added a blue pump cam and it drives like a dream. If the truck didn't have a factory choke cable in the dash, it would only be better with an electric choke, but I like having the stock pieces working
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There are about 6 or 7 different variations of the 4150/60 3310. The orig 3310 was OEM on 66-67 396 Chevelles and 427 Corvettes. These carbs are 780 cfm due to the down leg boosters, other 3310s [4160] have straight leg boosters and are rated at 750 cfm. If you can find an orig. 3310 off of a Chevelle/Corvette it can be identified by the small tabs on the OD of the primary [downleg] boosters. These little tabs are there only to correct a air/fuel distribution problem associated with the factory GM dual plane aluminum manifold. These carbs are quite valuable to the matching number Chevy restorers. When built properly this OEM carb is a very good running carb as the fuel metering is more precise than the 'aftermarket' 4160 3310 and as the OEM carb had to pass emission testing. Think along the lines of the 4150 735 428 CJ carbs for a good fuel curve, relative good fuel economy and power. To add: I think the 4150 735 CJ carb would be fine for the O/P application.
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Couple thoughts on leaving the 650 out of the picture.
Yes low end will be ok but, you can actually feel the engine wanting more as you apply throttle. It feels, umm, not good (for the lack of a better technical term).
The big thing for me was mileage. I actually got worse mileage with the smaller carb. If you've got a big breathing machine pulling a bunch of air through the venturis the signal is very strong and sucks a lot more fuel out of the idle and transition circuit. I proved this to myself by being moron and thinking, "smaller carb, smaller fuel use". Not the case.
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Your low end torque "feel" is going to be less carb than rear gear, tire height, first gear ratio, exhaust diameter size, and flywheel weight, none of which we know. Also, know that the C6-R head has a downturned lip at the top of the exhaust port to match production exhaust manifolds that will be a restriction when used with shorty headers. It needs to be removed with a grinder. And patience. And beer.
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And if you can only come up with two of the three it would be a grinder and beer!
KS
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And if you can only come up with two of the three it would be a grinder and beer!
KS
Or, you can step into FElony's World. I wrapped strips of 40-grit paper around my index and middle finger, grabbed a bottle of Jack Daniel's out of the freezer, and used a wall calendar to track progress. I found, through experimentation, that just the right amount of whiskey per hour negated concern with the fact that it took me April and May to expertly port the 7 (!) pairs of C6-R's I somehow acquired. Yes, I am a Pro, and a ground-breaking pioneer to boot. OK, the JD tab was higher than I can get for all the heads combined, but hey, I'm not in this hobby for the money.
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Your low end torque "feel" is going to be less carb than rear gear, tire height, first gear ratio, exhaust diameter size, and flywheel weight, none of which we know.
Rear gear is yet to be determined (3.70ish maybe?) 28 inch tall tires. 3.27 first gear ratio. 2.5 inch exhaust. and 29 lbs flywheel.
Does that help for a carb recommendation?
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+4 (or is it 5, or 6?) on the 750. Any smaller and you're killing power with no advantage.
I don't know about the QFT's, never ran one, but on EVERY new or used Holley carb I use or mess with, I check the flatness of the main body. They are almost always warped, even from the factory, and it will give you problems sooner or later. True it up with a file and it'll give you much better service. Sometimes they're so bad I've had to use 40 or 60 grit sandpaper over a file, then finish it off with just the file to get rid of the sandpaper scratches. It seems ridiculous to have to do this stuff on a new part, and it is, but it can save you some headaches and chasing your tail trying to find a problem.
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+4 (or is it 5, or 6?)
What are you asking here...?
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+4 (or is it 5, or 6?)
What are you asking here...?
I was just agreeing with the comments made above about the 750 being a good choice. I just lost track of how many people I was agreeing with.
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Oh I gotcha.
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Do you already have the TKO? The 3.70 is darn close if you already have it, I wouldn't come off that gear ratio with a TKO or TKO-500 in my experience with a bunch of TKO installs. If you haven't bought it yet, a TKO-600 with a 4.11 gear and .64 would be a little stronger and work slightly better IMHO.
1st gear X 3.70 in the TKO is 12.099:1 (absolutely as deep as I'd go, but good) but puts 5th at 2.51:1, about as tall as I would go.
With the TKO 600 and a 4.11 you get 11.79:1 in 1st and 5th at 2.63:1. Not a huge difference, but if you haven't bought it yet, it buys you about 3% in 1st and 5% in 5th in the right direction, but it is also stronger and I like the gear spacing better.
Some guys like the TKO-600RR, I generally do not use it, but in this case I absolutely would not use it because the .82, your build will have enough torque that you will end up wanting more OD and if you gear it for the OD, you'll lose the 1st gear benefit
Again, if you own it already, the 3.70 is the gear for you
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for street I like Vacuum secondary's best for most applications .... and like mentioned earlier I think the early GM 3310's are the best if you can find one , I've had 7 of them and they all have adjustable idle air bleed near the air horn , truly a beautiful working carb that will work on anything from a 289 with Carol Shelby factory 1x4 cross ram intake to a 468 BBC jet boat with victor intake ... truly a great carb
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May as well toss in late, the 3310 gets my vote for street use, after initial setup on my 445 I haven't had to touch it. Expert sources (such as Barry in his book) will tell you that a bigger carb can be tuned down, but you can't make a small carb run bigger. If I was thinking about placing heavier demands on the engine I'd go bigger, but for my purposes the 750 is just fine.
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1st gear X 3.70 in the TKO is 12.099:1 (absolutely as deep as I'd go, but good) but puts 5th at 2.51:1, about as tall as I would go.
Again, if you own it already, the 3.70 is the gear for you
A minor point here. For comparison of SLR's, I always factor in tire diameter. Personally, I use a 26-inch baseline, as that is about what most of the OEM tire sizes average out to. In this case, a 12.09 SLR adjusts to 11.22. That makes things apples-to-apples, essentially what an RPM calculator does.
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Good technique
My recommendation was based on experience with a 28 inch tall tire, however, I do like that idea. All the ODs I have put in are 28 inch tall tires or occasionally bigger, so I tend to just reference my unadjusted numbers
In this case, an tire-adjusted SLR of 11.22 would be comparable to a stock wide ratio tranny with a 4.03 gear and stock tires, or a close ratio with 4.86s and stock tires. The close ratio comparison is ridiculous and shows why those trannies were silly in a drag car, but your technique does really help when compared to a wide ratio
I will say, adjusting the compound OD ratio is equally important, because you can see how some tire size can get the ratio real tall on the other end. In my case, my 489 far preferred highway cruising with a 4.10, 28 inch tall tires and a .64 over the same setup with 3.70s.
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I will say, adjusting the compound OD ratio is equally important, because you can see how some tire size can get the ratio real tall on the other end. In my case, my 489 far preferred highway cruising with a 4.10, 28 inch tall tires and a .64 over the same setup with 3.70s.
Absolutely. I think many people get fixated on Overdrive RPM's without realizing how inefficient a carbureted engine becomes under 2000, worse yet with a bigger cam. I think the 2.75-ish OEM gearing on factory cruisers remains ideal even today. I think the recommendation for a 4.11 for this wagon is good for cruising under 100 mph. Makes first real deep, but it will tow strong, show off well from a standstill, and help offset that middle-weight flywheel.
As for carburetion, for a weekender at some cruise-ins or something, I suggest dual 600's. Doubles up the wow factor from a wagon with a stick. Still need to work the R head exhausts.
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750 Quadrajet. :o ;)
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I suggest dual 600's.
Still LOL ing. I approve of wretched excess.
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Holley 80529-1 750 cfm vacuum secondaries, down-leg boosters work extremely well on just about anything you want to put it on. Summit HLY-0-80529-1 $639.95. Joe-JDC
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I do have the TKO already but I will be starting out with the stock 3.00 rear gear and some old 24 inch tires until I decide what kind of RPMs it feels good at on the highway. Then I will fill up the rear wheel wells, break out the calculator and decide on a rear gear.
Joe-JDC What makes the 0-80529-1 cost so much more than the 3310 that others are recommending?
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I don't know about the QFT's, never ran one, but on EVERY new or used Holley carb I use or mess with, I check the flatness of the main body. They are almost always warped, even from the factory, and it will give you problems sooner or later. True it up with a file and it'll give you much better service. Sometimes they're so bad I've had to use 40 or 60 grit sandpaper over a file, then finish it off with just the file to get rid of the sandpaper scratches. It seems ridiculous to have to do this stuff on a new part, and it is, but it can save you some headaches and chasing your tail trying to find a problem.
What do you think of the Holley ULTRA street avenger? They have an aluminum base that is supposed to be flatter. I don't like the half shiny, half colored look of them (I like the old school gold look) but it will be under the air cleaner. I see they have a 770 cfm that is in the size range everyone is recommending.
Thoughts...?
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It is one of their Pro Series, and the calibrations are excellent out of the box. Contoured body, notched floats, jet extensions, four corner idle system, reusable gaskets, power valve blow out protection, etc. I have seen this carburetor perform on many dyno test comparisons, and it always comes out on top of the other regular Holleys. It is within a few hp of a dominator on the engines I have witnessed it installed on. Just my opinion, but it flat works. Joe-JDC
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Seems many people have forgotten the "discovery" years back that the Avenger series was rated under different flow conditions than the traditional Holleys, and you should essentially yank the last 70+ or so cfm off them to compare apples to apples. Thus, an 870 SA would be more in line with the 750/780 standard Holleys.
I have little doubt that the carb Joe (aka The Duke of Windsor) recommends is kool, but at some point you are splitting hairs against the thickness of your wallet, and then again versus the amount of miles this car will see. I am presently stitching up a voodoo doll to force you into dual 600's. I hope you are really ticklish.
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If you have any experience with a Thermoquad, try one of the old Superquads they sold in the '80s. Can't be beat for a heavy car. On e-bay all the time. Mopars in NHRA stock classes cleaned up using these. And will get great mileage if you stay out of the secondary's. Just another option.
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Holley 80529-1 750 cfm vacuum secondaries, down-leg boosters work extremely well on just about anything you want to put it on. Summit HLY-0-80529-1 $639.95. Joe-JDC
^^^^^^^ very good carb , worth the extra money and you get what you pay for !! ^^^^^^
.... the 3310's we all love are the older ones and a little tougher to find these days but rewarding when you do , the new 3310's are not as nice my in my opinion
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Well, I picked up a couple of older 3310s. One is a -1 and one is a -3. Any tips for when I rebuild them?
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Well, I picked up a couple of older 3310s. One is a -1 and one is a -3. Any tips for when I rebuild them?
The -1 is downleg booster, and the -3 is straight leg. Look closely. The -1 is more desirable.
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Well, I picked up a couple of older 3310s. One is a -1 and one is a -3. Any tips for when I rebuild them?
Get a big table and put a clean white table cloth on it.
Take it all a part and place each part like the exploded view.
Clean and put back together and adjust it on the table.
Bag it.
Those Holley SA carbs, I ran the big of the box for years on a 390
and I can't ever remembering even putting a screw driver on in all the years I ran it.