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cfm carb ??? Updated post 22

TC4x4

TC4x4

1/2 ton status
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Can someone explain what cfm with a carb means and what size i can put on my 78' 454 engine. 600, 800??? I am pretty sure the bigger the cfm the higher performance the carb is. Anyone want to shine some light.
 
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CFM = cubic feet per minute or how much the carb can flow. A "600 cfm carb" will flow 600 cfm, etc.. The average 454 would be happy with something around a 750 but maybe more depending on the performance level of the engine.

Fyi, while diagnosing a problem once I tried to use a 600 on my 454 and it wouldn't even crank with the throttle closed. So with that said, I'd consider any carb under 700 to be too small to adequately run your motor.
 
Now, im asking because im replacing my carb, intake and cam. What would change with the carb then, bec the engine would not be stock, and thanks for the responses
 
Unless the cam is crazy big the 750 should work fine. Post up the specs on the cam.
 
http://www.jegs.com/i/Comp+Cams/249/11-218-4/10002/-1

I am thinking of this cam, i have all you on here, and a lot of friends here in town that will help, i want to make sure i am getting the right parts on my list before i order any. So what do you think of this cam, I am looking to add some power to the old girl, because i am building a around town street machine, not to be raced but want power to be able to do something with. So this is a cam i was looking at.....anythoughts... or suggestions.
 
Since you aren't racing it there is no need for a solid lifter cam. Also that cam will require a stall convertor if you're running an auto trans.
 
I agree with Scott, that's a lot of camshaft + it's mechanical so it requires frequent valve adjustment. Any particular reason you picked that one?

For a non-racer, daily driver you're better off with a "flat tappet, hydraulic" type camshaft. Something with the lift in the .500-ish range would be more average and street friendly. I'm not saying absolutely stay away from a cam as big as you listed but it's not a great choice for a daily driver.
 
I have a 800CFM carb on my 305. I guess that explains why it runs rich as hell.
 
I've had a lot of big engines that ran best with LESS carb,than those with a huge 850 cfm Holley double pumper did..I had a 455 in a 68 Olds that came with a factory 2 bbl carb,and it felt stronger than several of the other big blocks I owned afterwards that had larget 4 bbl. carbs..One 454 I had in a '74 GMC C10 had a Holley 750 on it that caught on fire right after I bought it ,the carb was off a '69 396 Camaro,and a guy wanted it for his,to keep it all numbers matching,so I sold it to him and bought a brand new 450 CFM carb,a Holley Economaster 4 bbl (Model 4360),that made that 454 feel twice as strong as it did with the "toilet" 850 that nearly burnt the truck up..

The same analogy applies to cams as well--a "hotter" or 'full race" cam is only good for wide open,highest possible RPM and speeds,at lower engine speeds they will actually hamper perfomance,not enhance it..I proved this to myself when I had a 454 that lost 2 cam lobes on its lumpy spec'd cam,and I decided to replace it with a used 260H Competition Cam that was a "off road and towing/RV" cam,and the engine really woke up..the previous owner had piled on a high rise intake,a cam more suitable for a 1/4 mile drag car and did no port matching,on top of stock peanut port heads that were best for low RPM power,a combination that was dissapointing to say the least,in an off road/crawling situation where good low speed torque was needed...the intake was also a dual plane,that didn't help either--but was not as much of a factor after the milder grind cam was instaled...it felt like it gained a good 100+ hp just from the cam swap..the 450 CFM carb also delivered about 15 mpg in daily driving compared to a maxumum of 9 with the other 850 carb and "race" cam in it..
 
These things are good to hear, i am learning from many about this topic currently, and the advice and knowledged shared so far have been helpful. I am also going to call edlebrock and tell them the truck i have and what i want to do, and see what they can come up with. I just put that cam up earlier thread as an example obviously i did know know the varity of cams out there.
 
I think we could give better answers if we knew the purpose. What's the intended use of the truck? Daily driver? Mud bogger? Tow rig?
 
7162 cam part number
7561 intake part number

What do you guys think of these parts, a little more what you guys were saying...I am looking to buy a carb, intake, and cam, so these two plus a 700-750 cfm carb. Would these be reasonable matched up, this is coming from Eddlebrock also.
 
Intended purpose...

Its a 1978 1 ton, 2wd, with the sm465 (i think its called), i want it to be a nice cruiser, with good power off the line, i want it a couple steps above stock but not crazy, something that can hang with some newer rides to surprise people.
 
TC4x4 said:
Intended purpose...

Its a 1978 1 ton, 2wd, with the sm465 (i think its called), i want it to be a nice cruiser, with good power off the line, i want it a couple steps above stock but not crazy, something that can hang with some newer rides to surprise people.
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first- i would take a valve cover off and get the casting number of the cylinder heads.
then pick a cam that will work well with them. there is no reason to put a performance cam in an engine with sh$$ty peanut port heads. just my opinion.
for peanut heads, get an rv/towing cam, headers, intake, stock q-jet carb

049-781 heads, get a descent cam like barneybasher linked, a big dual plane intake, headers, and.... modified q-jet carb

dont forget about proper valvesprings for the cam.
q-jets = fuel mileage when driving normal
 
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nvrenuf said:
Fyi, while diagnosing a problem once I tried to use a 600 on my 454 and it wouldn't even crank with the throttle closed.
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FYI, that wasn't the carb, a 600 CFM carb on a 454, even at 100% VE, would still be fine up to just past 4500 RPM. And most engines aren't 100% VE. At 85% efficiency it would be fine up to 5400 RPM. Also, if the throttle is closed, it doesn't matter what size carb it is, it's closed. Must have been a coincidence that your battery was getting low or your starter hot during that particular try.
nad said:
I have a 800CFM carb on my 305. I guess that explains why it runs rich as hell.
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A carb works by pulling fuel through based on the amount of airflow going through it. So contrary to popular believe, a bigger carb won't necessarily make a small engine run rich. In fact, if the larger carb does not have enough venturi signal to pull fuel from it's bowls, it will most likely run leaner. This is why too large of carbs have less part throttle driveability. If your engine is rich, then the carb tuning is probably way off.

TC4x4 said:
7162 cam part number
7561 intake part number

What do you guys think of these parts, a little more what you guys were saying...I am looking to buy a carb, intake, and cam, so these two plus a 700-750 cfm carb. Would these be reasonable matched up, this is coming from Eddlebrock also.
Click to expand...

That intake is the best intake you could pick for that application (assuming oval port heads). The cam, will depend on your heads. If your heads are peanut port then it's probably a little large. If they are a decent oval port then it would work well since you have a 2WD truck with a manual trans (although not exactly a fast shifting one). I suggest you get headers for that thing as well, and you will most likely need matching valve springs. If you can afford it, spring for the retro-fit hydraulic roller, much better performance than a flat tappet, and no break-in worries, just make sure you set camshaft endplay as well, using a cam button and a torrington bearing cam sprocket. I agree with these guys, I wouldn't get a mechanical cam for what you want to do. Also, once you figure out what heads you have, your best bet is to call up at least 2 cam manufacturers(such as Comp cams, Crane, Crower, Lunati, etc) with all your info, and see what they suggest.
 
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new part numbers

Here is what I got from my phone call with eddlebrock.

60499
2162
2161
1411

What do you think, i was told they are made to go together and i told him the truck i have.

Also I dont think i said, this truck is driven only in summer on nice sunny days, one MAYBE two days a week, i think i put 200 miles on this whole summer. Its just to clean to wreck. And yes pics are coming.
 
So you must be done driving it this year then huh?

What are those part #'s, I don't feel like looking them all up.
 
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