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Old 04-01-2013, 02:41 PM
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won't idle and pops out the exhaust

Hey guys

I just insured my car on saturday and am having a couple issues. I built a new motor over the winter for it (see specs below). I have had it runing in the driveway a few times and everything was good. I drove it around for a bit on saturday afternoon and everything was good. I then took it out after supper. About 5 minutes in it started not wanting to idle and it was also poping out the exhaust. It seems to pop out the exhaust aroud 3000rpm and it is a little jerky of idle as well almost like it is starving for fuel but when I put my foot into it it takes off like crazy. I had my timing set at about 20 intial and about 40 all in at about 3500 rpm. Its hard to get an accurate timing reading know though as it won't idle. Another curios issue is I can crank the idle speed screw all the way in it does not change the idle speed. Also when I advance the timing it also doesn't idle up. This just started happening last night so I haven't had much time to look into it but I thought I'd through it out there to see what you guys thunk. I'm thinking vacuum leak or plugged carb?

72 Toyota Celica
SBC 355
10:1
Edelbrock cylinder heads ( ported and upgraded VT)
Comp 274 solid roller 235@50
Rpm air gap
Holley 670 stret avenger

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Old 04-01-2013, 03:24 PM
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my KARMA ran over my DOGMA
 

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Welcome to HRBB!

Could be related to vacuum leak, the carb idle screw should have an effect, have you checked the manifold vacuum with a gage? Also try spraying some starter fluid around the base of the carb and area and see if the idle picks up.(be careful)

What is the condition of the carb? were are the secondary throttle plates set? also these carbs are typically way to lean out of the box for a healthy engine such as this, it is going need more jets than the base number, I think they are 65/68, whats in it?

Check the fuel pressure.

What is the deal with the distributor? new or old & what type? plugs and wires new?

2 more of my cents
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Old 04-01-2013, 03:34 PM
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I have not check the manifold vacuum yet. I will do that tonight and post the results. I will also check for vacuum leaks using brake clean and post the result. The carb is fairly new. I bought it used from a guy who said it had about 250 miles on it. I put it on my old motor and ran it for a few months. Then it was in storage for about a year know it is on this motor. I haven't changed the jets in the carb. Unless the guy I bought from did it will have what ever it comes out of the box with. Jetting up is on the list of things to do. What size would you guys recomend?? Fuel pressure is at about 6-8#'s. Distributor is an MSD street fire HEI, 6al box, msd wires. All fairly new.
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Old 04-01-2013, 04:11 PM
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Check and make sure all the rockers are moving
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Old 04-01-2013, 05:06 PM
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my KARMA ran over my DOGMA
 

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best pull that carb and check out the idle fuel feed restrictions on the block they control the fuel to the transition slots, could be plugged, give the entire carb a cleaner bath and some TLC. basics, carb float level, needles & seats, base throttle plate position on primaries secondaries, transition slot exposure.

hard to pin down jet size that will work best but stock ones are most likely not going to cut it,,,try 70-72/74-76 ball park.

fuel pressure is getting up there 8# is allot, best to check under load too

roller, so should not be a lobe

heads are edelbrock VT? is this vortec style? intake gasket leak?, would not be the first time this happened, check plugs for oil
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Old 04-01-2013, 05:13 PM
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Originally Posted by T-bucket23 View Post
Check and make sure all the rockers are moving
This! Just went through the same situation and this was the issue. Rocker loosened up, do to the pivot ball cracking
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Old 04-01-2013, 09:52 PM
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OK. I checked for vacuum leaks and found nothing. I am getting about 6 at 800 RPM for manifold vacuum. I pulled the jets and cleaned/blew out with carb cleaner. I put the carb back together, warmed the car up, reset the timing and adjusted the idle screw. The car will know idle but I took it for a spin around the block. It was good for about 2 minutes but then went back to poping out the exhaust. Im thinking I could have an ignition issue as well as my tack was working intermittent and was abviously not reading the correct RPM. (ie reading 7000RPM when engine was maybe at 3000-3500RPM). Ive heard those ignition boxes can be tempermental. Apparently you have to be careful were you route the wiring as if they are to close to a plug wire can cause interfierence?????
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Old 04-02-2013, 08:53 AM
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Do you still have the original HEI module? you can reinstall it and try the ignition without the 6AL box, either way the make sure there is a good ground for the distributor.
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Old 04-02-2013, 09:22 AM
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Do you still have the original HEI module? you can reinstall it and try the ignition without the 6AL box, either way the make sure there is a good ground for the distributor.
I just dug around in my shop last night and found the HEI module. Im going to try that tonight to eliminate the box. I have the distributor grounded to the intake. Do you think that is good??
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Old 04-02-2013, 12:13 PM
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Internally the dist ground wire needs to be intact, solid and corrosion free, it should ground to the coil hold down screws but not sure on yours, the dist grounds through the engine and the dist hold down clamp. There is a gasket between the dist and the intake, the intake does not ground the dist.

I ground the block/head to chassis with strap/wire and then to battery with correct cabling. I do not ground the cap/dist directly. Some run a separate ground right out of the dist to chassis ground or battery negative terminal in some form or fashion.
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Old 04-02-2013, 08:58 PM
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Did you check your valves? Could simply need adjusted as me and the other guy was getting at... I am telling you, I went through the exact same thing.. Replaced module. Nothing. Had no intake or carb gasket leaks. All checked out ok. With it being a new motor, have you readjusted them since driving it a few times?



Here is why Mine came back lose, the second time.. But, it does just happen.. Especially with how you explained it being fine, then just happening randomly. Think about it. If the valve is not opening on the way, it will not idle right. And its going to miss and pop, whatever when you try to get up and go.. Mine would haula** Till about 4k. Then, would do what you are explaining. And to get it to idle at all, it'd have to be idled at 1300 or so in park. Then when in gear it was like 400-500, very sluggishly
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Old 04-03-2013, 08:30 AM
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Originally Posted by KyleG View Post
Did you check your valves? Could simply need adjusted as me and the other guy was getting at... I am telling you, I went through the exact same thing.. Replaced module. Nothing. Had no intake or carb gasket leaks. All checked out ok. With it being a new motor, have you readjusted them since driving it a few times?



Here is why Mine came back lose, the second time.. But, it does just happen.. Especially with how you explained it being fine, then just happening randomly. Think about it. If the valve is not opening on the way, it will not idle right. And its going to miss and pop, whatever when you try to get up and go.. Mine would haula** Till about 4k. Then, would do what you are explaining. And to get it to idle at all, it'd have to be idled at 1300 or so in park. Then when in gear it was like 400-500, very sluggishly
I haven't had much time to play with it. When I installed the msd box and distributor I didn't use the proper by pass harness. I ordered the harness and it will be here today. I'm going to tidy up the wiring. If thay doesn't do it I will pull the valve covers and check the lash as you said. Thanks for the help.
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Old 04-03-2013, 08:53 PM
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So it turns out my issue was ignition related. I installed the bypass harness recomended by MSD, re-routed the wiring from plug wires to avoid any interfierence and it is as good as new.
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Old 04-11-2013, 08:33 PM
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Good to hear that you found it!
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