600cfm OK for break in miles on a 489? - Chevelle Tech
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post #1 of 14 (permalink) Old Dec 3rd, 19, 3:58 PM Thread Starter
 
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600cfm OK for break in miles on a 489?

Finally wrapped up my hodgepodge 489 build last night, and starting to wonder about the carb.

I have a relatively fresh Edelbrock 1406 on the current 350 that worked well..had maybe 1,000 miles on it when the engine popped. Was planning on using it on the 489, largely due to budget reasons, at least initially, though I know the engine may want more carb on it.

Basic details of the engine - 72-79 2 bolt block, bored .030 over, stroker crank, -18cc domed pistons, untouched peanut port heads, 226/226 .514" 108LSA cam, Weiand 2P 180* intake.

I'm thinking that the peanut ports will keep RPMs and air flow down, so I may not be all that bad off with the 600cfm carb? I know going too small can cause a lean condition, but then I won't be hammering on it during break in either...
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post #2 of 14 (permalink) Old Dec 3rd, 19, 6:24 PM
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Re: 600cfm OK for break in miles on a 489?

A too small carb for break-in should be fine, but a lean condition never is. An overly-rich large carb that washes lube off the cylinder walls is also bad. A smaller carb at least will keep you from taking the revs too high during break-in

Also don't be afraid to hammer it briefly during break-in. As long as it is up to temperature (coolant & oil) it is generally beneficial to load & unload the rings & walls.

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post #3 of 14 (permalink) Old Dec 4th, 19, 1:38 AM
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Re: 600cfm OK for break in miles on a 489?

Won't hurt a thing. I run a modified 600 1850 Holley VS on my 461 last fall, it went 11.75 so I think you're ok.
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post #4 of 14 (permalink) Old Dec 4th, 19, 8:25 AM
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Re: 600cfm OK for break in miles on a 489?

It won't hurt anything. The engine doesn't know what carb is on it. And as far as going lean, I don't think it will happen. Its a carburetor fuel follows air. the carb can only flow enough fuel for the air that can go through it.

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post #5 of 14 (permalink) Old Dec 4th, 19, 11:10 AM
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Re: 600cfm OK for break in miles on a 489?

I did a test on the street back in 2005 with some Eddy Carbs, here is what I found with my mild 454.

1405 600 would pull like crazy to 5K and then fall off like a rock.

1407 750 pulled a lot harder up to 6K but suffered from a lean condition that we could not cure. Booster issues with them.

The New (at the time) 800 Thunder carb would pull to 6500 and worked fantastic, so good in fact we tested it at the track, it was only 1 tenth and 2 mph off the good Holley's at the time. The 800 does need to have the pri circuit leaned out a little for street driving but that's about it.
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post #6 of 14 (permalink) Old Dec 4th, 19, 1:10 PM
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Re: 600cfm OK for break in miles on a 489?

You will have no issues what so ever using the small carb for breakin as long as it functions properly.

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post #7 of 14 (permalink) Old Dec 10th, 19, 12:22 PM
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Re: 600cfm OK for break in miles on a 489?

I had the outboard carbs disconnected when I ran in the 427 the first time. It had no clue it only had 500 cfm atop it. Curiously, a 500 cfm will run a hot 427 to about 4500 cfm. ( that mill needed 800+ cfm to carry it to 7300)

Ya, no issue whatsoever. PS. my center tripower carb was jetted FAT (#73 for a 750), so it "high idled" not so lean. To Cam's point above.

FUN STUFF! Its a pretty big RODENT you got there!

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post #8 of 14 (permalink) Old Dec 10th, 19, 12:34 PM
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Re: 600cfm OK for break in miles on a 489?

Quote:
Originally Posted by noducksgiven View Post
Finally wrapped up my hodgepodge 489 build last night, and starting to wonder about the carb.

I have a relatively fresh Edelbrock 1406 on the current 350 that worked well..had maybe 1,000 miles on it when the engine popped. Was planning on using it on the 489, largely due to budget reasons, at least initially, though I know the engine may want more carb on it.

Basic details of the engine - 72-79 2 bolt block, bored .030 over, stroker crank, -18cc domed pistons, untouched peanut port heads, 226/226 .514" 108LSA cam, Weiand 2P 180* intake.

I'm thinking that the peanut ports will keep RPMs and air flow down, so I may not be all that bad off with the 600cfm carb? I know going too small can cause a lean condition, but then I won't be hammering on it during break in either...
No it will NOT cause a lean condition as long as it's jetted right, ( I believe the Edel carb uses fuel rods for jets). In fact, you can slap a two barrell carb and manifold on there if you wanted to. The only thing the smaller carbs will do is limit the revs since the carb veturi won't allow enough air to pass at higher RPM operation. But from idle to 4,000 RPM it should run strong even under hard acceleration. It will not hurt the engine at all. I had a 1970 Pontiac with a 400 CID engine that came from the factory with a 2 barrell carb.

70 Chevelle SS clone (632 CI powered).
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post #9 of 14 (permalink) Old Dec 10th, 19, 11:48 PM
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Re: 600cfm OK for break in miles on a 489?

You’ll be fine as long as the metering rods and jets are reasonably close. I ran a Holley 650 double pumper on a .030 over 454 for a while a few years ago. It ran great for a driver, even pulled 22”’of vacuum at 2200 rpm. It fell on its face after 5000 rpm. I had previously had the carb on a low compression 1970 Ford 360, and to get it dialed in properly I had to go from a 73 jet down to a 63. The vacuum that the bigger motor pulled through the carb also increased fuel.

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post #10 of 14 (permalink) Old Dec 11th, 19, 10:36 AM Thread Starter
 
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Re: 600cfm OK for break in miles on a 489?

Thought I had replied to this a few days ago, but apparently it didn't go through..but anyways, thanks again for the help!

Almost got everything buttoned up last night, but the "cold" temps here in Phoenix took over early for me (yeah yeah, I know....it's not cold. Spent 25 years in Detroit, and now 60 degrees feels like it's freezing to me, and 40 degrees is the time to go inside, get the fireplace going, and park my butt 6 inches away from it, lol).

Down to just wrapping up the wiring for coolant temp and oil pressure senders, fuel lines to regulator and carb, bolting the core support and radiator back in, half-arsing the exhaust manifolds to the rest of the exhaust (had long tube headers on the SBC, and will be running stock manifolds for a short time on the BBC to get it going, then likely custom building a set of fenderwell headers) and fingers crossed I'll be priming and firing it up early Saturday morning
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post #11 of 14 (permalink) Old Dec 11th, 19, 11:32 AM
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Re: 600cfm OK for break in miles on a 489?

I ran a holly 700cfm on my car when I first got it going.

It ran much better with a demon 850, but that 750 did alright.
It would sign off about 4800 with the 700cfm.
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post #12 of 14 (permalink) Old Dec 11th, 19, 3:22 PM
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Re: 600cfm OK for break in miles on a 489?

Quote:
Originally Posted by Cam View Post
A too small carb for break-in should be fine, but a lean condition never is. An overly-rich large carb that washes lube off the cylinder walls is also bad. A smaller carb at least will keep you from taking the revs too high during break-in

Also don't be afraid to hammer it briefly during break-in. As long as it is up to temperature (coolant & oil) it is generally beneficial to load & unload the rings & walls.
my thinking exactly.

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post #13 of 14 (permalink) Old Dec 11th, 19, 4:56 PM
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Re: 600cfm OK for break in miles on a 489?

Quote:
Originally Posted by 427L88 View Post
I had the outboard carbs disconnected when I ran in the 427 the first time. It had no clue it only had 500 cfm atop it. Curiously, a 500 cfm will run a hot 427 to about 4500 cfm. ( that mill needed 800+ cfm to carry it to 7300)

Ya, no issue whatsoever. PS. my center tripower carb was jetted FAT (#73 for a 750), so it "high idled" not so lean. To Cam's point above.

FUN STUFF! Its a pretty big RODENT you got there!
Main jet has no influence on idle or even high-idle low throttle opening break-in.

CFM doesn't matter at all. Fuel curve does. GM put Rochester 2GCs on 455 Oldsmobiles.
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post #14 of 14 (permalink) Old Dec 26th, 19, 1:59 PM Thread Starter
 
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Re: 600cfm OK for break in miles on a 489?

Finally started to get into the tuning stages on this motor, and it's falling a bit short..pulls hard up to about 4000, and then it's like hitting a smooth rev limiter, which though I have my shift lite currently triggering at 3800, actually is pretty handy to keep from over revving it during break in.

On the other hand, I also realized I have a partially smashed exhaust pipe about a foot off the manifold, which can definitely cause some issues too, and I figure until I get that fixed early next year, there's not much point in wondering whether the limiter is in the carb or the heads. I was hoping to wait until after I get the headers built, and do it just once, but I don't want to see it sitting in the garage for another few months either, and I'm not likely to even start fabricating until the weather warms up at least into the 70s during the day.

Haven't gotten into tuning the carb either, other than setting idle speeds and mix screws. At an idle timing of 36* (16 initial, 20 vacuum), it's pulling about 12" vacuum, which is actually far better than what I was expecting given the cam that's in the motor, and enough to run the power brakes. I can feel that they're not quite as strong as they were with the old motor, but still plenty enough to haul this heavy beast down.

All told though, I'm pretty happy with the way this hodge podge mix up of parts turned out so far. Kept having nightmares that I was going to get it fired up, and find it sounding like crap and performing worse than the 350 that came out. It's no 500hp monster, but it definitely scoots along just fine for me, and I have a decent base to slap a better set of heads on later
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