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Old 10-06-2003, 02:39 PM
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283 stalling, carb size etc...

Hi

question from a newbie v8 owner....

I've just bought a Corvette 59 -283cui with a torker intake, camel hump heads, holley 650 double pumper, and some sort of performance cam with a TH400 with a shift kit.

Engine idle is quite lopey, and when ever I put the car in drive, it will drop in rpm until it dies!

Only way to keep it alive is to do some "two foot" driving, one for braking and one for accelerating.

The missus is not particularly happy with this , so I need to improve the situation, so that she can cruise with her friends...

Now if the timing, carb, vauum leaks, checks out OK (I have done some search...), what then?

can it be that the stall speed of the converter is too low, and combined with the cam, the 283 is "overloaded" when idling and put in drive?
Sorry, havent checked the stall, the tach drive i broken...
Is the 400 simply too big for the 283?

Unless it idles quite low , it'll engage drive quite hard, and I think that it does move quite a lot, considering the low idle speed....

carb question:
I'm planning to install a Street Avenger, most likely the 570, from the point of not overdoing it.
In case I would be overhauling the engine to a 327 (engine block is a # 3789817, so I take it should not be a problem) would it be better to look at the 670?

Having sniffed around a bit, I found that I would need some 570cfm with a 327 at 7000rpm with VE85%.

Since I'm not racing a lot, but more the cruising type, with an occational pull, it seems that the 570 would be a wise choice.

Any comments appreciated, - especially for the first part....

thx

Bjarne

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Old 10-06-2003, 03:29 PM
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if it were mine, first thing I would do is get rid of the Torker intake, a open plane intake sitting on a 283 with a 650 carb is a bit too much since one cylinder is drawing off the entire mass of the carb. I`d get a edelbrock performer or weiand action plus, with the use of one of these intakes, the 650 would work, and it`s cheaper to buy a intake than it is a new carb. if it`s still got the points ignition, dump them and get a pertronix unit that eliminates the points but keeps the use of the distributor, cap, coil and etc. after these mods check the spark timing, set it at 12 degree`s before top dead center, and 38 degree`s total all in by 3000 RPM.
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Old 10-06-2003, 04:15 PM
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I agree with DV. Sounds like you're "over-carbed" and "over-intaked". The 283 is a good little engine, but you're not going to win any national championships with it.
Any idea what the cam is?
I think you'd be better off with a dual plane intake and 570-600 cfm carb, preferably with a vaccum secondary. That should give you driveability...especailly if your wife likes to drive it.
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Old 10-07-2003, 07:36 AM
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Before swaping out intakes or carbs (which are both too big) go back through the 650 you already have. Make the mixture screw settings, float level settings, and primary, and secondary butterfly settings are where they need to be. This can easily cause a situation like this. You also may want to try adding some additional timing at idle to help cover up the fact of the big intake, and carb.
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Old 10-07-2003, 07:57 AM
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I would agree with BG. Changing the intake or carb is not going to help your idle situation much unless the existing combo is not well tuned.

Sounds to me like the engine is loading up on idle due to an overly rich condition. First would be to try to adjust the idle circuits(two mixture screws on the side of the carb). A good starting point is usually two and a half turns out from bottom. I also agree on timing. If the cam is very big, I would try starting with around 16 or 18 degrees at idle. It takes longer for the mixture to ignite with the low cylinder pressures at idle induced by the larger cam, and is agrevated further if compression is low. You will have to make sure this does not put you over 36-38 on mechanical advance. If it does, some distributor work could be in order.

Chris
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Old 10-07-2003, 08:41 AM
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Sounds like a tuning issue. A 400 Turbo tranny will not cause stalling in gear. 400's do consume more power when the car is moving though but that's due too it's larger internals which sap more power when the car is being driven.

If the car has a cam that makes it idle rough a low stall converter certainly doesn't help though, but that will be the issue with any automatic set up.

Sounds like ignition timing-distributor problems or a carb that's all out of whack. I had an "E-bay" holley that was almost new but blew huge puffs of black smoke out the car's tailpipe and would not idle below 1800 RPM's. I took it apart about 3 times before figuring out the secondary butterfly throttle stops were not set correctly which was causing the secondary idle circuit to run really rich along with a run-away idle and stalling when in gear.

Sounds like you need to go through the car and start through a process of elimination by going through the ignition system, fuel, compression test, read the spark plugs-could just be a couple of oil/gas fouled plugs causing your lumpy idle and stalling, maybe a vacuum leak. It's always about twice as hard to troubleshoot when you don't know the real history of the car. You don't really know if it's the mechanical state of tune causing the problem(cam, intake, heads,compession,carb) or just a dirty carb.

It's a for sure a single plane intake is a loser for the street especially on a 283 but I doubt that's your REAL problem you're having with it right now. I don't know how a street avenger would work on this set up but anything in the 600 cfm and under catergory should work ok, especially if it has vacuum secondaries.

BTW, many times you can clean out a dirty carb by removing the Idle circuit screws and blowing carb cleaner through the openings. This can be done on the car and can be a real labor saver.
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Old 07-04-2007, 01:14 PM
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re 283 stalling, carb sizing etc...

Here's a carburetor-sizing solution to your example... First say you have a setup that could operate @ 100% VE, all cylinders fill to 327ci (0.189ft³) every 2 revolutions (because it's a 4-stroke cycle engine). Every revolution, the intakes half of that, or 0.0946 ft³

At 1000 rpm (rev / min), whole engine's air useage = 1000 rev / min · 0.0946 ft³ = 94.6 ft³/min (cfm).

At 7,000 rpm, multiply 94.6 cfm by 7 to get 662.3 cfm.

If you think your engine can move 85% volumetric efficiency at that speed, multiply the result by 0.85 to get 563 cfm.

Use the method to solve that^ example to make a generic method:

IntakeCFM = CubicInchDisplacement · RPM · VolumetricEfficiency / 1728 cubic_inches/ ft³ / 2 rev / intake_charge

IntakeCFM = · CubicInchDisplacement · RPM · VolumetricEfficiency / 3456

(I like to use dot multiplication, most people seem to like the x)

I agree with everyone else above, a smaller sized carb is only going to limit the upper rpm capability on an engine in there that's already built to run like a bracket racer, and going to a higher stall converter won't take the racy-ness out of it (but the fuel loading at idle will be reduced). Sounds like you need a milder combination for smooth civilized powderpuff wife operation - small carb, mild cam, low-rise dual plane manifold, small intake ports feeding small valves, and somewhat low compression, and exhaust manifolds that make some back pressure at normal speeds. I'd reckon you've started with a fairly hot 12 second car and will probably end up with one that still may not be entirely to your wife's liking (since you are talking about spinning 7000 rpm).

What gear ratio is in it, and what is the rpm @ 60mph?
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Old 07-04-2007, 04:29 PM
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timing mixture

I would do timing mixture and tach. timing should be 12-14. Turn your mixture screws in all the way (not tight) turn them back out 1 and 1/8 turn. I bet your idle is to low. If you get a tack I bet you are about 650-700 rpm.
Yea that intake is not helping a performer rpm would be better later on. I would do the 670 avenger not the 570.
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