New headers/exhaust, now it won't run!

Negative · Post by **Negative** » Sat Jul 26, 2008 9:38 am

So after a few grueling weeks with this beast, Brutus finally has everything re-attached and sounds amazing!

However he won't drive!!! It is the weirdest thing. I can start the truck no problem at all. It idles very very nice, everything is just perfect!

Then you push the gas pedal down. Here is what it is doing, hopefully someone can help:

From idle, in Park you press the gas slowly and there is a hiss from the carburetor and the truck dies. It sounds bogged down and kills it. If you remove the gas pedal it revs back up to idle and purrs like a kitten.

In gear from a complete stop you press gas to go and the truck dies. If you are already moving (Brutus idles in drive at about 20MPH) and press the gas to go say, 25mph, it will die. If you MASH the gas it will catch rev high and take off like a bullet. as long as the pedal is mashed it drives like a dream. Let go the gas it backfires through the tailpipes, and returns to idle purr.

I don't even know where to start.

rjewkes · Post by **rjewkes** » Sat Jul 26, 2008 10:32 am

Sounds like you are now running too lean. or maybe its too rich. some stuff changes when you change the exhuast to duals and headers.

and did you get all the plugs gapped to the same gap?

Negative · Post by **Negative** » Sat Jul 26, 2008 10:38 am

lean/rich was my first thought too, but I didn't want to mess with it too much without knowing. (This isn't my first engine, but it is my first Truck engine, and this truck is my baby, so I don't want to hurt it)

Is there a way to tell for sure? As far as gap they are the same, I need new plugs, but that wouldn't make the carb hiss (the hiss sounds like air is going in and no gas - could be wrong though) would it?

Thanks for the reply!

rjewkes · Post by **rjewkes** » Sat Jul 26, 2008 10:42 am

you could get carb cleaner with the straw and go around the carb sparaying to see if it idles up. if it does you have a gasket leaking.

if it doesn't rev up with the carb caner sprayed around the base of the carb then it may just be rich/lean condition happening.

as far as lean or rich goes it depends on if it backfires through the carb, i think this is lean and at the exhuast it is rich.

tis could mean adjusting the choke to leaner or richer settings.

not sure on the specs. they differ engine to engine and year to year. and the adjustment depends on the carb if you have a 67-69 or 70 and later you adjust the pullof differently.

BobbyFord · Post by **BobbyFord** » Sat Jul 26, 2008 10:44 am

You've got a vacuum leak somewhere, it sounds like...

Negative · Post by **Negative** » Sat Jul 26, 2008 10:57 am

I will spray the cleaner around and see what happens, I will also check the hoses again.

It won't be for a few hours (am at work). Is there anything else I can try?

I am sooo hoping I didn't do anything to the carb like bending it or anything... I can' afford a new one right now!

Thunderfoot · Post by **Thunderfoot** » Sat Jul 26, 2008 11:44 am

BobbyFord wrote:You've got a vacuum leak somewhere, it sounds like...

I second that!

It shouldn't idle that fast (20 mph) that is a good sign of a vacuum leak...
If you have the heat spacer under the carb spray around it good (it is common for them to warp)
Also, try plugging off the vacuum line to the distributor (the vacuum advance pot may have a leak)

The new exhaust will have some effect but usually just an adjustment of the idle mixture screws and possibly adjust the accelerator pump a bit is all that is needed.

Negative · Post by **Negative** » Sat Jul 26, 2008 12:28 pm

it's idled at a good clip since the beginning. 20 MPH my be an exaggeration, but from a dead stop to foot off the brake and no gas it has always gone forward and on my road I can let it and it gets up there until I hit the hill. I would say 12 to 14 mph at least.

I have a bunch of things coming off the carb. When I get home if after I try all the things listed here I don't get a resolution I will post a pic and maybe one of you can spot something??

I hope this is an easy fix, I want to drive my truck again!

Negative · Post by **Negative** » Sat Jul 26, 2008 8:38 pm

Well, thank you rjewkes!

I didn't even have to spray. First thing I did was twist the Lean Knob a few clicks and it sat up and begged.

Drove it and it never hesitated once. Took a few attempts to get the mix right, but I think I got it notched pretty perfect.

The bad news is that when I was done, my radiator sprung a leak from a fin. Pinched it off, it sprung another. Pinched that one off and it blew through the hose!

Time for a new radiator now! Cheese and Rice!

binder56jd · Post by **binder56jd** » Sat Jul 26, 2008 10:46 pm

one question--what part of the lone star u in that is soooo bad that it's "anywhere but here"???

glad u got the vacuum thingy fixed--now comes the fun part--"the weakest link" -- those little challenges will arise after every "fix"

we will stay tuned--be patient--u'll get it before it's all said and done

ps--houston is the only part of tejas that sucks so bad gravity is not in effect--the traffic holds everything in place there

Negative · Post by **Negative** » Mon Jul 28, 2008 8:49 pm

Texas flag cause that's where home is. Physically I am in the bitter hell called the Pacific Northwest, Washington State to be exact.

I hate it here and want to go home. And, actually... I was there for my Grandpa's funeral in March, and I made my sister take me to Ardmore cause I have been thinking of moving there instead.

Cute town I must say!

As for the truck, the radiator was shipped today, 4 bolts and a few beers later I should have this thing back on the road (and pics to post) by Saturday morning. (I hope, cause I work 4 a.m. Sat.

)

1971Blue390 · Post by **1971Blue390** » Wed Jul 30, 2008 12:45 am

If the carb is hissing or whistling I think you may have a serious vacuum leak. I made the mistake when I installed a new carb and couldn't figure out what the noise was until I hoked up a neglected vacuum line.

My guess is that you may have just bumped something loose when you were putting on the new exaust. Look around and chek that you don't have any cracked, loose, missing, disconnected vacuum lines, and that might solve your problem.

Oh and one more thing to check is if the carb is getting enough fuel, it might get enough to idle, but not engouh to run. Check the fue; filter and lines too. If it runs when you floor it this may be because you increased the RMP's quickly enough to get the fuel pump to work hard enough to force fuel through a clogged line/filter.

Negative · Post by **Negative** » Thu Jul 31, 2008 2:36 pm

Thanks for that, the problem did resurface and I found a leak at the little arm controlling the fuel flow. the fuel is squirting out this gasket and sucking air in when not open. Thus the hiss.

I need to get a rebuild kit cause I can't afford a new carb this week. But I can't find the ID tag for this carb!!

Gonna post that question here next!

<edit>
Turns out it was the stock one and I couldn't find the ID anyway. Its the F2 (whatever that means) and the Napa had a rebuild kit for 17 bucks. Fixed the gas leak and tested it... same problem!!

Turns out it was a bad EGR or something (yes, the vacuum

) took it off, pluged the holes and it runs so beautiful now! oh gosh it is pretty!

Thanks to everyone here, I rechecked it all and found it was a mix of all the posted problems!

Fixed now! On to tail pipes and oil leaks!

Thanks again!
</edit>

fomocoguy · Post by **fomocoguy** » Fri Aug 01, 2008 8:35 am

Just remember, at idle in gear the truck should barely creep at the most. You should be idleing down around 600 rpms or so. As long as everythings in a good state of tune this shouldn't be a problem.

Negative · Post by **Negative** » Fri Aug 01, 2008 1:22 pm

In gear it idles down low, I don't have a Tach hooked up but it drops a lot, and judging by my car of similar specs it is around 7 or 800 RPM.

I will keep an eye on it though! Thanks!

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New headers/exhaust, now it won't run!

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