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Enging Run On -


snomobeelr

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Car has been starting and Running fine Except I have Engine Run-on. Even when I shut her down in Neutral. I have checked my timing I am at 18 initial and 38 WOT. I have attached a picture, all my Spark Plugs looked like this one. I run 93 Octane  
 

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idle too high. Shutting off in neutral makes it worst. shutting off in park will make it better.  hook up a tach even factory tach are often not accurate. Does your carb have a idle solenoid? Bob  

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need to know more about the engine, the plug looks rich and too cold (needing a higher heat range)

 

and depending on the cam and compression, 18 degrees of initial advance might be too much, and you didn't mention your idle speed, being in park of neutral makes no difference

 

does it run-on if you shut it off in gear? 

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I also was going to say lower your idle speed if you can and shut it off in gear. (I assume it is an automatic trans)

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I have seen the idle solenoid cause this.  If it is not adjusted properly or is not dropping out when you shut off the engine it can cause this.  It is easy to check the operation of this solenoid.  With the key off, turn it on, then move the throttle off of the solenoid nut at the carburetor and when you do this it should allow the solenoid adjust nut to move to the extended position. Then release the throttle and allow it to rest against the adjustment bolt head with the key still in the on position.  At this point have someone turn the key to the off position and the solenoid should release and bolt head should move inward causing the throttle to follow it to a position below the normal idle rpm and this starves the engine for gas.

rob

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Thanks guys. No Idle solenoid. I have always run 93 octane. Thought thats what she needed.  In park idle is 1000-1100 RPM. In drive its 800-900. I just bought a new tach and installed it and know it is now correct.  I haven't tried shutting her off in gear.  The kicker Is I believe my Trans is now just about to go out.   

 

MSD HEI Distributor

Carburator:    850 cfm

Engine Cubic Inches:    468
Compression Ratio:      10.1
Intake Manifold Brand:  Edlbrock AIR GAP RPM
Header full Patriot     1 7/8"
3 inch Exhaust
....................................................................
Cylinder Head Type:     Brodix race rite oval port
Intake Valve Diameter:    2.250 in.
Exhaust Valve Diameter: 1.880 in
...................................................................
Type of Camshaft:       Hyrdaulic Roller Lifters
Camshaft - Intake Duration @.050:       232
Camshaft - Exhaust Duration @.050:      244
Camshaft - Intake Lift at Valve:        595
Camshaft - Exhaust Lift at Valve:       581
Lobe Separation:        107
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the actual issue might be the fuel, you are real close to needing more than 93, although that set-up 18 degrees of base timing is very close, you might need to take some out (4-6 degrees)

 

what plugs are you using? it looks rich and the plugs too cold

does your carb have screw in air bleeds?

 

do you know...

 

piston deck height

piston dome CC's

combustion chamber cc

and head gasket thickness

 

we have discussed this engine before, it's a great combination, just needs some tuning, I'm wondering if you have more compression than you think, you might need to lean out the idle/transfer circuit of the carb

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I don't know what the piston deck height is. My fault for bad planning and not finding out all the specs when the motor was built.  

Not sure what you mean by combustion chamber cc. Do you mean the heads?  

How do I tell if Carb has screw in air bleeds ?  I attached the build sheet for the Carb.

 

Thank you

 

 

 

The Spark Plugs are NGK V-Power  R5671A-7  Gap is .35

................................................................................................................

Federal Mogual Forged      :   .095 Dome Pistons

Felpro 1027 Head gasket   :   .039 thickness

Broddix Race Rite              :   119cc Chamber, 270cc Intake Runner 

 

 

 

 

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usually Patrick is dead-on with his carbs, but your plugs are black and looks like you could go up one on the heat range

 

where is your float level set? 1/2, 1/4 in the sight glass

 

how far out are your idle screws?

 

I'm trying to get a feel for your complete set up, there are lots of things to try, just looking for the one thing that seems off a little

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Thanks Sam. Site glass at 1/3. The mixture screws are out I believe 2 turns which I thought was a bit much but seemed best there. Issue now is Transmission went out on Friday night and I need to get that swapped out. I need to find a place in Northwest suburbs in Illinois to get it rebuilt. Was driving fine then 1st was slipping. By the time I made it back to my driveway going up it started to sound like a coffee can with nuts and bolts inside it. 

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Pro-Systems has a forum board where Patrick answers questions

 

I would join it and throw this run-on issue at him, show him the picture of the plugs too

 

Patrick always says the float level should not be higher than 25% in the sight glass or main metering can pull fuel at an idle, if this is happening could explain the run-on, could also explain the black plugs

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  • 2 weeks later...

Trans is back in. Now trying to get it running right between the run-on and idle a bit off.  No run-on in gear.. I only tried that twice. I also placed a post on Pro-Systems.. Per their instructions the Timing at idle should be between 16-18. So I verified timing. Its better at 18 degrees at idle with vacuum advance disconnected Than at 16. I verified Bowls ar 1/4 over. 4-Corner mixture screws are out 2 turns. I tried going down to 1 1/2 turns . But when I get to the last corner Driver side rear I can hear the engine change.. So I left them at two . Car also drops from 1100 to 700 when placing into gear, just barley stays running. One thing I am unsure of how to check it the " throttle shafts " ? I am unclear on what they are and how to set them. 

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I am amazed that you have an issue with the engine run on with the plugs looking like that.

 

I tend to think that you have the idle set up high to compensate for the cam.

 

Does your MSD have the bushings to adjust the CENTRIFUGAL ADVANCE CURVE? If it does I would put the black bushing in that gives you 18 degrees of centrifugal and then try 20 degrees of initial. That may bring the Idle speed up and you can close the throttle plates a little bit, that may help run on.

 

What is the cranking compression numbers?

 

Was the cam installed straight up, or advanced or retarded?

 

A 107 lobe separation makes a lumpy idle.

 

What brand of cam?

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  • 4 weeks later...

Sorry hadn't looked back at this post in a bit. I had the Distributor degreed. I may need to pull it anyhow. Started another post should have just added to this one .. Car has been running great other than having to change the Battery. We were leaving to go to a car cruise/show and I pull out and going down the street she is backfiring/popping through the exhaust. Not horrible but enough. I pull over to the side of the road and place it in park . I rev it up and its fine , no popping through the exhaust. Start down the road and its popping. Drove home into garage. Checked Timing its fine. Checked plug wires connected - fine. Fuel pressure a 7 lbs and see fuel in bowls.

 

I don't think its an issue with the plugs but I pulled them all Anyway. Plug #7 I never cleaned before. I know the plugs are fouling out but timing seems to be correct. Ive tried adjusting the carb further but if I acre the corner adjuster's in any more it so sent run right. There out two turns. Should I run a different spark Plug ? Right now I have NGK V-POWER R5671-A

 

 

 

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I'd try a smaller jet size on the primary side of the carb, I'd start by going down 3 sizez, you may also need a hotter plug

 

I'm having a similar issue, mines misses in the exhaust at a light cruise condition

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Thanks, Now what spark plug would be hotter. I have a  NGK V-POWER R5671A-7.  There is no 6. I asked the parts guy what would be a hotter running plug and looked at me like I had 5 heads. 

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When I was pulling the plug wires off I noticed two of the wires were on the plug but not snapped/Tight. I also noticed the gap I had was 35, so I gapped the new plugs to 45.  I changed the plugs took her out and she is good. Bad Plug or combination with the wires ,I am not sure. I ordered a 70 - 80 jetting kit. I was just going to order the 73 jet but it was 15 dollars shipped through summit. So once thats in I'll change the jet and see how she is . Thanks everyone 

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