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Old 04-23-2005, 10:20 AM
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Bigger converter, or lower gears?

(I'll start out by trying to explain what I have as much as possible)

1979 Chevy 1/2 ton pickup, 2WD (I know... it's heavy)
305 V8, fresh rebuild, .030 over, Comp 280H - (280/480), stock heads, 9.5:1
Quadrajet, Weiand 8004 intake, Hedman headers, 2 1/4 pipe, x-pipe, Flowmasters
1800-2500 converter, TH400 transmission, 12 bolt rearend, 3.73 gears
275/60/15 tires, 15x8 wheels.
I plan on replacing the carb with an Edelbrock 600 cfm unit, and a 1" 4-hole spacer.

The problems I'm having are - 1) No matter what I set idle at, when I put it in gear it drops down to about 400 to 500 rpms. 2) When I take off, I have to ease my foot into the gas to get going. Once I get above 1000 or more like 1500 I'm ok, and it has "plenty" of power. I'm not looking to make this a race vehicle, but my take-offs (for lack of a better term)... "suck". I couldn't spin the tires if I wanted to! hehe (unless the pavement was wet)

My thinking is, that the converter we picked out isn't much over what a factory unit would be. (?) I had a another guy who builds motors/hotrods... tell me I should get a converter that was rated at about 3000 rpm because it would lock up around 2500 or 2800 rpm, and that I would enjoy driving it alot more. (power band of the cam is 2000-6000)

Should I go with a bigger converter, 4.11 gears in the rearend, or both? I know I'll lose some highway driveability with the lower gears. Right now I'm turning 2000 rpm cruising at 40 mph in town. Hope I haven't left anything out. Thank you for your advice, and patience with me. <grin>

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Old 04-23-2005, 11:35 AM
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Converter

Hey,
Your current gears really aren't all that far away from a set pf 4.11's. 3.73's should be sufficient. It is pretty obvious to me though that your cam is rather large for a 305. So, I would recommend putting in something along the likes of 3000 rpm converter. They aren't really expensive, and if you don't mind dropping the trans, which is fairly easy in my opinion, they are literally a bolt in unlike a gear swap. Call up Comp cams with your combo and ask them what converter they recommend. It sounds like you got a reworked stock one that only stalls like 500 rpm over stock, not high enough.

Essentially you are just seeing alot of bog from the cam. I even should install a looser converter in my '72, since despite being a mild-cammed 455 with tons of torque (400 ft/lbs), the 3.08 open rear end gears and stock converter make it a crap shoot of either sluggish or spinning the tires off the line.

JMO -

Andy
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Old 04-23-2005, 08:43 PM
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stall

I would use at least 2800 stall. I wouldn't expect that motor to spin the tires in a vehicle that heavy. Especially if you have a posi rear end.
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Old 04-23-2005, 09:35 PM
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Check what your cam manufacturer recomends for the stall, you usually do this before you put the came in so you know what you are getting into...I lovve the hard way too, i do goofy crap all the time damn noobies, i should have picked a cheaper hobbie.Fishing flies or basket weaving.
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Old 04-23-2005, 09:35 PM
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its a 305?
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Old 04-23-2005, 11:20 PM
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* fearsomefairmont - I'll try to give Comp a call sometime during the week, to see what they recommend.
* bracketeer - It's just a regular open carrier.
* gROCERYgEtteR - yes.

In case anyone missed it in an earier post, here's an audio file I made of it. It was recorded with a camcorder, which tends to "clip" the audio if it gets too loud. Gametech's 305 (mp3 file)
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Old 04-24-2005, 01:49 AM
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http://www.compcams.com/Technical/Cu...ML/128-169.asp

this kind of tells you where you need to go to

http://www.compcams.com/Technical/Cu...ML/366-367.asp
you advertised duration is 280 so it says you need a big fat stall a

274 somethingorother.
Dont feel bad I didn't know a bunch of this crap until just recently either, but thats half the fun of it. Man if it wasn't for the net my car would be so......I should just stop now its still apart.
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