GADJIT98
First let me say that the CJ7 is back from paint and looks great :lo1l:
I broke down and bought an Offy 2x4 manifold with a couple of junk Carter WCFB's on it. My question is what size carbs should I go with? I am in the process of stockpiling parts for an upcoming 401 build. This thing should be sorta nasty on the street with about 400-450 HP in a CJ7.
I was thinking 2 Holley 390 cfm's until I saw a Mustang on Barret Jackson with a 428 and 2 660 cfm's on it. That got me to thinking that 390's would be a bit undersize?????
What do ya'll think of 2 E-brock 500's, 2 Holley 390's, 2 E-brock 600's, or whatever other combo will work.
I am trying to get this motor to get 10 mpg under normal driving.........yes, I really said that out loud........the guy at the engine shop just kinda laughed
Other opinions are welcome
Thanks in advance
Dave
"photos coming soon"
jeep_man_401
I have ran that intake on a 360 using 2 450 holley econimiser's carbs...not a perfomance carb at all. But with 3.50 gears stock convertor I could pull 10MPG in town and 15MPG on the highway. Motor was in a '74 Hornet. It had very good throttle response in town and I could beat most anything around on the 1/4 mile marked out on the road we raced back then.
I pulled the intake and ported the heads and ran a torker with a stock carb and installed it in my '73 Javelin AMX...it dynoed 232HP at the rear wheels after sitting for about 5 years...Had the square port headers on the 360's dog leg heads and it stumbled big time at the start of the pull. One guy said one rear wheel was hopping on the dyno drum during the pull also, losing some HP I'm sure. Had I had the 2X4 offy and the right headers I'm sure it would have been much more than the 232HP I got. My guess is the motor is around 300HP running right with 2X450's.
Given that info I am now building my dream 401 with Indy heads and the Offy intake. I am using 2 E-brock 600's on the 401. If all things go right I should have the dyno numbers late next month. I can then let you know how the 600's work on it. The 401 is being built to make around 500HP...so it should be close to what you are doing.
By the way...when I did switch to a single carb I lost MPG...I averaged 6 to 8 all the time! I am hoping to hit the 10 t0 12 MPG with the 401 in my J10 :razz:
If I was going to street drive (all the time)my 401 I think I would have used a smaller 400 or 450 carb and went with the MPG and throttle response instead of all out HP. But I plan on pulling at the county fairs with this set-up.
Who knows, I might switch to a alky carb to run the Torker again...then my 600's will go on sale. :t:
Goose
I'll offer some past experience here.. Multiple carbs look cool..but they are a pain. That having been said. whatever you use (And I like the Edelbrocks ) you get more than about 700 cfm on that engine and you will be having tuning compromises that will defeat both your stated goals. to simplify, an engine is a vacuum pump on the topside and for driveability you need a reasonable amount of vacuum, otherwise the airflow through the carbs is sluggish and they wont meter correctly. I say this fully expecting to get slammed by the "My engine has a 1150 dominator and a .900 lift 362 deg duration cam and it make 1100 hp from a 262 C.I. guys" But over cammed and overcarbbed will make junk out of anything.
500 cfm will feed 350 cubes to 6500 rpm. 700 will feed a 454 to 6000.
If you think about it, ask the next guy who tells you they pulled the 650 off cause it "wasn't enough" then ask them wht size jets they tried before they pulled it.. odds are they didnt even open it up.
Whatever you put on it make sure it has tuneable vacum secondaries otherwise when you open those primarys (4 of them) the vac signal will dump the secondaries too and while 3 foot flame out of velocity stacks are cool they arent conducive to winning races.
Holeshot
As far as I am concerned, the ONLY carb to go with is the Holley 660 Center-Squirter!!! Get a good set and you should have no tuning problems. Holley's are about the easiest carb to tune and maybe that's why the vast majority of racecars that must use carbs use either Holleys or BG's Holley clones.
Edelbrock (Carter AFB) carbs are pretty complicated and may turn out to be a very bad headache.
Start with stock jetting, mount them sideways, use an electric pump & set the float levels with the engine stopped, use an MSD ignition box with .045~.050 gapped platinum plugs, and NEVER pump the throttle with the engine off!!
I always suggest mounting them sideways due to the way that all throttle plates open 1:1, get one in your hands and visualize the blast of richened mixture going into the engine. You will then understand why to mount them sideways.
Make sure that the linkage has not been modified to delay the secondaries!!! Holley designed the center-squirters SPECIFICALLY for 2x4 intakes!!!
Mods that I do like are to install center-hung floats & bowls and secondary metering blocks that have jets & idler screws, making them "four-corner" idlers.
A well built 401 should be in the 500HP+ range, and the ppl that preach little cams, carbs & intakes just don't understand what a good running AMC is like. Second to none!!!
Goose
See that didnt take long..
Before I start lets review "Sorta nasty on the street and get 10 mpg or better"
Not "Little" Cams, Reasonable cams and carbs.. I guess ALL of the winning racers use single carbs cause they are too cheap to buy two?
And I stand behind Edelbrock carbs..for a street vehicle.
Holleys are fine for WOT but for driveability on a daily basis they suck..
Look, Driving a performance vehicle on the street is a compromise. I have built several quick AMC's so I do know what they are like..but If you have to drive this pig to work all the big thumper cams and over carboruetted engine is going to do is piss you off.. like for instance Yea I drive it to work but If I get caught in traffic I have to shut it off or it will _______ (insert shortcoming here, Load up, overheat,Vapor lock, yada yada) I guess I have a different view point When I build one it works like this If this is a street car then It has to be as reliable as the damn thing was stock..other wise you have failed right off the bat. then you build performance without sacrificing the driveability. will it go as fast as someone who builds the car to cruise once a week and is willing to live with all the shortcomings? no. but if thats what you build it for whats wrong with that..If you want a trailer queen then build one..
Bigger isnt better and sometimes more is too much.
and last but not least, a pair of 660's on a daily street driven 400 cube motor? Rotsa Ruck!
Holeshot
I guess it just depends on how fast you want to go and how big of a smile you want when dusting the competition.
The original poster has ALREADY decided upon & purchased a 2x4 intake, I don't think you should be offering insults of his desires.
If your "quick" AMCs have run like a pigs and had to be shut off in traffic, I do believe that YOU made some serious mistakes!!!
I drove my 550HP '69 AMX with a pair of 660s sticking out of the hood on a tunnel ram daily for over 2 years, never a problem.
Before that, it was an 850 double pumper on my 390, ran low elevens and mid 120s in the quarter, in street trim, with big sway bars, stiff gas shocks, and street radials. Ran GREAT always!!!
My stock (R4b & headers, 401 cam) 360 AMX ran GREAT with an 850 double pumper as well, and ran 13 flat at 108 through the mufflers and street tires. Would have been better but stock fuel pump allowed bowls to run dry going in to third gear!!! There are quite a few 440 Road Runners, 442s, Mustangs, etc., that felt the sting.
Holley's work GREAT in everyday use and AMC offered several models of Holleys in their catalog, all the way up to 950CFM three barrels!!!
You simply can't apply chevy & ford rules of thumb to AMC engines, AMC heads flow WAY better than all but the best of the competition's heads, like as good as the early mopar hemi. Almost everything about the AMC V8 has been designed with performance in mind; hemi sized wrist pins & huge lifters, great flowing heads and manifolds, room for 2.08 & 1.75 valves (bb mopar valves drop in), great bearing overlap, great RSR, forged rods & cranks good for 8500. They should have spent a little more time on the oil system before releasing the design to production, however.
When you have an engine that puts out 500 ft/lbs of torque at 2 or 3 thousand rpms, you can afford to give away a verry little down low to make a bunch up high. Mid 500s in hp at 7500+ is easily reachable without giving away any reliability or streetability.
Of course it takes a true technician to make it all work together and stay running crisp. Someone just wanting to gas and go 365 days a year may as well use stock stuff anyway. The Edelbrock carbs could be referred to as stock, since they are just Carter AFBs anyway.
No insults intended, just my 100% honest opinion.
CJim7
Uhm....just curious here...huh....what do you plan on doing with this CJ7? If you plan on offroad use, i would start rethinking or at least ask a seperate set of questions.
Im hearing a lot input from the street performance side of things here. Not sure how your offroad performance will be with that kind of settup not to mention the double nightmare of tuneing dual carbs for offroad performance and street performance inconjunctively.
if your shooting for dragstrip performance strictly, then by all means build that thing until they cant build an axle to hold up to it. offroadwise, ask more questions. :-|
Mudrat
CJim7 wroteIm hearing a lot input from the street performance side of things here. Not sure how your offroad performance will be with that kind of settup not to mention the double nightmare of tuneing dual carbs for offroad performance and street performance inconjunctively.
Isn't that the purpose for 2 carbs? One street/one rocks?? :wink: Just mount a fuel selector switch and cut off the carb NOT being used and your golden - - - right :mrgreen: :razz:
GADJIT98
Great Idea Mudrat :lo1l:
Thank you all for the opinions, please keep them coming. I intend this to be a sort of "Old School" street rod running headers and header mufflers, 33's, and basically stupid amounts of horsepower just for the hell of it. I dont do offroad often and when I do it is just a clean trail now and then. This rig is intended to be a semi daily driver and something that makes you just say "damn" when you see/hear/ride/feel it.
If ya'll could put up some numbers like Holeshot did for the CFM's it would help. Right now the consensus seems to be a pair of 390's.....is that adequate? Is a pair of 500's or 600's too much or not enough? I want it to have a mean sound which means a performance cam, etc, but I would really like to keep it around 10 mpgs if at all possible so I can afford to drive it.
Flame suit on!
Thanks again, & keep the opinions coming!
Dave
Dallas Lemon
Dave, like you I find this thread extremely interesting. In my years of witnessing street rodder wannabes install the biggest Holley they could afford on their V-8s and think thay have a bad ass street machine, it has ussually resulted in disappointing performance. They do not understand, nor have they investigated exactly how much CFM an engine requires. I have contributed to other threads on this board, in particular the 401 Thumper thread. I installed a 401 in my CJ7 this past winter to replace the tired 360. The 360 had a Howell TBI on it with a 401 program in the ECM. I simply switched the TBI over to the 401, thinking it should work fine. It didn't. I had to switch to a 670 CFM throttle body. Holy Cow! This 401 is a STUMP PULLER! I got want I was looking for out of this engine. A good buddy of mine assisted in putting it together, and really wanted me to build a snotty high HP 401, which is exactly what I didn't want. I have not taken this engine past 5500 yet, and doubt that I ever will. It is a rock crawler, and works very well for that application. On the other hand,my CJ is lifted 8 inches and runs 37's, and handles horribly at road speeds. It will run 70 MPH down the road, but I hope like hell I never have to make a high speed manuever. It will be UGLY! My point is I built my 401 for torque, and got more than what I was anticipating. What I didn't expect was how the engine fell on its face at 3500 with the 500 CFM throttle body from the 360. The 401 flows much more air with the Edelbrock heads. Plus, with a CJ7 having the aeordynamics of a barn, I would think a 401 with more torque in mind would be a better fit. But, these things are naturally tourqey anyway. Is "torquey" a word? :-|
GADJIT98
What do you guys think of running to E-Brock 500 performers? I saw them on ebay for $180 each rebuilt. This is way cheaper than buying new Holleys, but will it be the right fit for a street rod? I need good low end but would also like to run 75 MPH when I am on the road with no issues. My interpretation is that the smaller the carb, the better the low end and vice versa but I dont want to drown out the engine with too much carb.
Dave
jeepsr4ever
Edelbrocks are almost the easiest carb to modify as they have a base and a top. Performers work well on the trail and street if setup right with a offroad needle and seat combo (spring needles) but cant come close to the performance of the bigger carbs on the track or for flat out racing of any kind. The edelbrock performer is a light to medium duty carb that fits most types of driving.
jeep_man_401
People may disagree here but I would think some cam numbers and compression numbers would help in picking a set of carbs.
As stated before I have ran this intake before. Some things you should know...the carb spacing is closer than most 2X4 intakes. You have to limit the air cleaners to 8" dia. Summit carries a Velocity Stack that will work(SUM-G3006) K&N's are 9" and they won't work. It also only takes square bore carbs, unless you buy spaces/adaptors.
I drove my 360 with this intake and 2 X 450 holley's for years without problems...well one carb would sometimes have the acc. pump check ball stick open after a long smokey burn out. Which was solved with a well placed hit of a hammer :t:
It is all in the set-up. I had to replace the stock AMC hornet rear after trashing the spider gears when I hammered the throttle at 40MPH. I went with a Ford 9" with 3:50 gears one wheeled wonder.
I raced many cars...350, 355, 454 and could beat them all. The 454 should have killed me as it was built to the hilt...but the guy was running 4:56 gears and I passed him half track as he ran out of RPM's.
Gearing can make or break a street car that is going to be FAST. Cam selection will make or break a motor also. It doesn't make since to get a cam that makes 500 HP at 7500RPM if you drive it on the street. You'll lose every time at the lights to anything with a little pepp.
Call the cam grinder (Crower, Reed) with your specs...weight of jeep, tire size, gearing, compression, intake manifold, stall convertor and what you intend to do with it. They can tell you what cam to run and how much carb you'll need.
If you're dumping alot of money into the motor with aftermarket exhaust, heads, high comp. pistons Don't settle for for one of their "book" cams. Have a custom one made. Every motor is different and requires a different cam.
Oh, one more thing...if you use a different dissy...buy a set of MC's matched gears. :oops:
And when you get done I'll run you with my sleeper J10! :lo1l:
Goose
Holeshot, Since I expected to get smoked for trying to help on a contraversial subject..all I am gonna say is go back and read the posts..
It's really easy to "say" 500 horse 401 it is another thing entirely to achieve it (In a usuable form)
Summarized all I said was: Decide what you want to do with it and build it for that.. but dont expect a racecar to perform as well on the street as a street car and vice versa (If you remember he wanted 10 mpg and to drive it on the street) and since he had already bought a dual four set up it would be ridiculously easy to overcarb it. in a jeep. so having said that and taking no offense. I will say this let us know how it works out.
GADJIT98
HERE IS WHAT i AM THINKING.....
After alot of opinion getting, and finding a calculator, it seems as if the following is the way to figure this out:
CID X MAX RPM / 3456 = CFM needed
or
401 x 6000 / 3456 = 696.1....
according to this equation, optimum CFM is 696. So, 2 x 390 Holleys will actually be a little too much carb but still acceptable.
Am I right? Please feel free to shoot this full of holes if I am missing something.
Thanks
Dave 111!!!
zero cool
GADJIT98 wroteHERE IS WHAT i AM THINKING.....
After alot of opinion getting, and finding a calculator, it seems as if the following is the way to figure this out:
CID X MAX RPM / 3456 = CFM needed
or
401 x 6000 / 3456 = 696.1....
according to this equation, optimum CFM is 696. So, 2 x 390 Holleys will actually be a little too much carb but still acceptable.
Am I right? Please feel free to shoot this full of holes if I am missing something.
Thanks
Dave 111!!!
That final number is modified by the volumetric efficiency and style of intake. A higher VE will increase the CFM needed by as much as 10% (or decrease the CFM needed by as much as 10-15%, depending on the intake). Also, a dual plane intake will like anywhere between 20-50% more carburetor than that equation tells you. A single plane intake likes somewhere between 10-30% more.
Goose
You are in the right area .. 650 to cfm should feed that motor but It wouldn't hurt to go to 750 cfm, as long as you don't get way out of control it should work. it would probably run with 1200 cfm carbs at WOT but the tuning on the street is the problem that and the fuel mileage question.
KJMac
If you plan on running the dual edelbrock set-up then be sure to plan on another 80 bucks for the tuning kit. It will take quite a bit of tuning to get it right. A friend of mine spent a lot of time tuning his 400 small block chevy, He then took it in for a dyno tune and the shop picked up 15hp and 23lb.ft. of torque. Not too mention an improved power curve. I wanted to to tell you about a guy who used to race at woodburn dragstrip here in Oregon that ran a 401 in a CJ7 that ran 12.2's, I was told he did get in to the 11's. He was running 2 edelbrock 600 cfm carbs....took him for ever to get it tuned though.
Good luck with your build!
