At this point, I just don't know...HEI problem?

[don t. - 72gmc]

Where's what I do know..changed plugs, cap, rotor, plug wires, vaccum hoses, rebuilt carb, timing s/b close enough, all advances test out ok. Each time I replaced something, engine got a little better.
Now she idels great, spins tires at stop but once she shifts into 2nd, seems to be a hesitation or two(or 3) and then off she goes. Doesn't happen all the time but enough to where I don't like it.
In a prior post, someone said to run a new wire (12 ga.) for the HEI, straight from fuse box. I wanted to check things first, I get 11 volts at the HEI. Stripped tape from HEI to firewall. Prior owner had replaced the resistor wire w/a hot from the firewall plug. Half way from firewall to HEI is a splice, one lead goes to starter selnoid (which post don't know, didn't follow yet), the other to the HEI. I tested at the splice, 11 volts.
Im gonna replace this wire cuz it just don't look right (maybe 18 ga. wire) but I don't think this is gonna fix my problem. Any thoughts/ideas that I can check.
BTW...this hot from firewall is keyed.
T.I.A....don t. .....

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It aint gonna be a trailer queen, its gotta work, just like me.
3/4 ton,350 w/HEI, 79 q-jet, th400.

[Longhorn Man]

Try rewiring that. 11 volts just isn't right. Should be 21/3 to 12.6 with engine off, and 13 and some chainge to 14.5 while running.

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'69 G.M.C. 350/350. Trying to clean up the left over damage from the Dope-Smokin-Old-Man
I've been dubbed the Longhorn Freak/Fanatic/Expert, I just hope I can live up to it.
FINALLY got the HORNIAC...a '70 one ton Longhorn with a Pontiac 350/350 and lots of 'personality'. Check out The Longhorn Webite.
If you need a pic posted, E-mail me at longhornmail@yahoo.com
Andy, in Columbus Ohio

[COBALT]

You have a 4bbl carb, right? Sounds to me like your hesitation is happening when the secondaries are supposed to kick in. Maybe the throttle, metering, or or other secondary systems are having problems...in other words sounds like a carb problem.

I have the same problem with my little 2bbl carb off the line (anoying hesitation). I have to feather out my throttle a bit to allow the engine to perform without completely choking. Haven't rebuilt it yet though.

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'69 3/4 ton C20 2wd w/ 350ci/400THM and a wood bed!
'69 3/4 ton Custom 20 2wd w/ ORIGINAL 350ci/4sp Manual and a wood bed (parts beast).
Seattle, WA.

*See pics of my trucks and project at www.webshots.com!

[Longhorn Man]

with that thought, have you looked/chainged the fuel filter? Whoats your fuel line look like?

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'69 G.M.C. 350/350. Trying to clean up the left over damage from the Dope-Smokin-Old-Man
I've been dubbed the Longhorn Freak/Fanatic/Expert, I just hope I can live up to it.
FINALLY got the HORNIAC...a '70 one ton Longhorn with a Pontiac 350/350 and lots of 'personality'. Check out The Longhorn Webite.
If you need a pic posted, E-mail me at longhornmail@yahoo.com
Andy, in Columbus Ohio

[don t. - 72gmc]

Yes 4bbl, but everything measured out according to the info sheeet (actually didn't have to do much but give it a GOOD cleaning). Fuel filter was replaced. Did not check fuel pressure but I don't think thats an issue.
BTW...Battery volt was 12, straight up. When I checked HEI volts the key was on, motor not running.

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It aint gonna be a trailer queen, its gotta work, just like me.
3/4 ton,350 w/HEI, 79 q-jet, th400.

[BigDave]

I would check the float level. When that motor starts sucking fuel and the float level is too low it won't refill fast enough to keep up with the demand. I would also check the fuel pressure and fuel quality. Finally, I would check all my lines to be sure air wasn't entering the system from somewhere.

I had and interesting problem recently. At the top of first and second at WOT I experienced a HUGE loss of power and I had to get out of it, let the truck coast, before it would come back.

After checking the float level, carb adjustment, and fuel pressure I started checking the fuel line. I looked everything over closely but still had a problem. Finally, I thought is had to be bad gas so I began to evacuate the system. I opened the line at the fuel pump, put the gas tank under pressure from compressed air and vioala problem found. The previous owner had installed a rubber hose from the tank pick-up where it exited the tank and connected it to a steel junction. The hose had a small crack in it and when it was placed under pressure it seeped air.

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1972 Chevy Blazer 2WD - 400 SBC, bored, ported/polished heads, 9.5:1 dished pistons, Lunati 480/292 cam, electronic ignition, Edlebrock Performer intake, tricked out Rochester 850CFM Quadrajet, long tube headers, Flowmaster 40's, TH350-C with lock-up switch, 2800 rpm stall, shift kit, custom driveshaft, stock GM 12- bolt rear with Auburn Pro Series limited slip 3.73's, 2" drop spindles, 2" drop rear coils, track bar kit, front/rear stabilizers.

1999 30th Anniversary Trans-Am Coupe #1494 - M6, Flow-tech cut-out, Flowmaster, free mods. One of 292 coupes with M6 and in-dash CD.

[don t. - 72gmc]

When I rebuilt the carb the float was set at about 7/16". Instruction sheet said 3/16", I set it at 3/16".
On Tuesday I drove it to get gas. Got home, adjusted the jets and the auto. choke. Yesterday, I took it for a ride and noticed a heavy gas smell in the cab. I wonder if I have a gas leak/bad hose? I've got a compressor, how do you pressurize the tank?



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It aint gonna be a trailer queen, its gotta work, just like me.
3/4 ton,350 w/HEI, 79 q-jet, th400.

[COBALT]

Hmmm...we may be on to something...

------------------
'69 3/4 ton C20 2wd w/ 350ci/400THM and a wood bed!
'69 3/4 ton Custom 20 2wd w/ ORIGINAL 350ci/4sp Manual and a wood bed (parts beast).
Seattle, WA.

*See pics of my trucks and project at www.webshots.com!

[BigDave]

I've seen some people use a piece of flexible rubber, like from a tire tube, and they cut it larger than the opening on the filler neck. Then they poke a hole just large enough to fit the nose of the blow off attachment from their air hose into it. You use one hand to hold the rubber against the opening of the filler neck and the other to work the blower.

I don't like this method because most compressed air systems create and trap moisture and it will blow out of the system. I just use a clean shop rag, bunch it over and around the blower attachment, and stuff it just barely into the filler neck. You can hold the rag in between your fingers and get a good seal on the tank with your hand. You only need a little bit of pressure and this method has worked fine for me on several occassions.

[Don Smith]

The two wires coming from bottom of pickup will sometimes have damaged/worn insulation. The pickup will short to ground intermittenly, especially when vacuum advance mechanism is advancing timing. Can't see damage to wires without disassembling dist. Disassembly is straightforward just remember to mark gear and shaft so timing wont be 180 out when you reinstall dist.