240 ignition/carb issues

Engine, ignition, fuel, cooling, exhaust

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Youngfordkid
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240 ignition/carb issues

Post by Youngfordkid »

hello all,

after several weeks of ripping my hair out, with my 67's 240, i have decided to get some opinions on what to look at and fix.

first some specs so you know what i am dealing with,

-autolite 2100 off of a 71 with a 360-390

-mild RV cam

Duraspark conversion, new cardone dist. not a rebuild, new box.

manual trans without any exras, (power steering, brakes, a/c)

ok, so finally got the thing to run decent (after attaching a dedicated ground wire from the box to the cab-to-motor ground strap) i drove it some today, and ran fine, it seems to break up (lightly) around 25-35 mph (3.50 gears, 3rd gear np435 trans). When i got home i just decided to rev up the motor to 3k rpm, and noticed it breaks up terribly. i unhooked the vac. advance from the dist. and reved it up fine (note: using ported vaccum not manifold on the dist.) and didnt break up. also my measured manifold vac. at the high rpm maintains around 15''. from what i have read, it is supposed to drop off, after the throttle plates open up in the carb.

so logic says that my engine is either over advanced, or under advanced at 3k rpm. now i know most people dont speed a 6cyl. motor that fast, but at 70 mph, you still need to pass a car, and have the power to do so.


any thoughts, sugestions, comments, questions, are greatly appreciated.

thanks,

Wyatt
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guhfluh
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Location: Houma, LA

Re: 240 ignition/carb issues

Post by guhfluh »

Are you SURE it's ported vacuum and not VENTURI vacuum you are hooked up to? I'd swap to manifold vacuum and try it just for a quick check.

Manifold vacuum will stay high at high rpm with no load. 15" sounds fine depending on rpm and load.

What is your base timing with no vacuum to the distributor?
What balancer are you using and have you verified the timing mark is actually true TDC? Old balancers are known to slip and rotate.

It does sound like you are over advanced, so get the spark timing verified and corrected first, then move to fuel.
'67 F-250 Crew 2wd 300ci, T-170/RTS/TOD 4-speed overdrive
'96 Dodge Ram ECLB CTD
'99 Dodge Neon ACR 2dr - 10.64@130 (Sold)
'05 Infinity G35 Sedan
Youngfordkid
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Re: 240 ignition/carb issues

Post by Youngfordkid »

thanks for the reply,

about 10-14 degrees initial, i am using a single pulley balancer, rebuilt by the machine shop, so i doubt that it slipped.

what would be the best way to decrease the total amout of advance?

thanks
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guhfluh
Blue Oval Fan
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Posts: 650
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Location: Houma, LA

Re: 240 ignition/carb issues

Post by guhfluh »

Balancer rebuilt by a machine shop? I'd verify your TDC mark.
'67 F-250 Crew 2wd 300ci, T-170/RTS/TOD 4-speed overdrive
'96 Dodge Ram ECLB CTD
'99 Dodge Neon ACR 2dr - 10.64@130 (Sold)
'05 Infinity G35 Sedan
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