Spitting back through carburator - Chevelle Tech
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post #1 of 33 (permalink) Old Mar 25th, 19, 1:34 PM Thread Starter
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Lou
 
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Spitting back through carburator

This is a 1965 Chevele all stock. I hate to go over all I've done to try to get this thing to start and to stop spitting back through the carburator.

All the wires are in order. I've reset the distributor when the timing marks say TDC. No BTDC. I tried 3 degrees already and it was spitting.

In regards to the position of the rotor. Should the rotor be pointing at the number one spark plug ?

When it's at TDC should the rotor be right in the center of the #1 distributor post with the points gap open ? Sounds like a dumb question but with what's going on I'm trying to pin point the problem.

I'm under the impression I'm getting pre-ignition and its firing back through the intake valve before it's closed.
Which would suggest I'm firing ahead of TDC. Which is why I don't understand why twisting the base doesn't resolve it. You can only be a few degrees off in either direction.

Based on what I've read it looks like there's 45 degrees of rotation between posts. 45 x 8 =360.

I'm on the compression stroke and the valves are closed because my thumb can feel the pressure and air escapes at the correct revolution. Two turns of crank puts you where it should be.

I've twisted that distributor one way and then the other and in every case I'm getting spitting. In some cases fire.

It sounds like it wants to start then I get a spit.

Any ideas ?

Thanks,

Lou
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post #2 of 33 (permalink) Old Mar 25th, 19, 1:42 PM
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Re: Spitting back through carburator

Is it popping through the carb while driving? Is it rhythmic with the rpm's? I had that happen and it was a flat lobe on my cam. Hopefully that isn't your problem.
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post #3 of 33 (permalink) Old Mar 25th, 19, 1:57 PM Thread Starter
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Lou
 
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Re: Spitting back through carburator

Quote:
Originally Posted by Daron Craig View Post
Is it popping through the carb while driving? Is it rhythmic with the rpm's? I had that happen and it was a flat lobe on my cam. Hopefully that isn't your problem.
I have not drivin it anywhere. It's a first startup. It's a new cam. Everything is new.

Thanks
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post #4 of 33 (permalink) Old Mar 25th, 19, 2:10 PM
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Justin
 
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Did you break in the cam if it’s a flat tappet? They’ll go flat and and have symptoms like this if a lobe is gone.
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post #5 of 33 (permalink) Old Mar 25th, 19, 2:13 PM
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Re: Spitting back through carburator

Are you using a timing light? You can't set the timing by looking at the rotor, that just gets it close. If the timing is set right, the cam is wiped like Daron said. Pull the valve covers and look for loose rockers.
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post #6 of 33 (permalink) Old Mar 25th, 19, 2:16 PM
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Re: Spitting back through carburator

Are you certain you got the timing gear marks lined up correctly?

Are your valves adjusted correctly? For hydraulic flat tappets, about 1/4 turn down from zero lash with the lifter on the cam lobe.

I hate to say this to someone who appears to understand what he is doing, but it does sound like your ignition timing and/or firing order is off. This has happened to most all of us at one time or another. Keep checking. If you have a knowledgeable friend, have him look over what you've got. Good luck, Lou, and let us know how of your progress.
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post #7 of 33 (permalink) Old Mar 25th, 19, 2:52 PM Thread Starter
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Lou
 
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Re: Spitting back through carburator

Quote:
Originally Posted by 69SS454 View Post
Are you using a timing light? You can't set the timing by looking at the rotor, that just gets it close. If the timing is set right, the cam is wiped like Daron said. Pull the valve covers and look for loose rockers.
That's a good idea. Let me see where the thing is firing. There's so many ideas floating around out there. Cam and crank are set up correctly.

I wasn't sure if I would get any responses since it could be so many things. I have this gutt feeling it's the distributor and my timing.

The shop manual says 3 degrees BTDC , Chiltons says "0" , You tube videos show "0".

I'm not sure I understand any of that regarding cam lobe and lifters. These are Hydraulic Lifters and a solid steel cam. Cam lobes are set. Can you clarify what you mean by break in. What's to break in. Are you saying my lifters are sticking ?

Lou
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post #8 of 33 (permalink) Old Mar 25th, 19, 2:58 PM
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When you initially fire up an engine with a flat tappet you need to run the engine at 1500-2000 rpm for 15-20 minutes to “mate” the lifters to the cam for break in using a high zinc oil. If you are using a roller lifter this is not necessary. Also you’ll want to run more than 3* of timing. Make sure that the TDC mark on the balancer is actually TDC.

What I do is I bring the engine up to TDC #1 on compression then drop the distributor in so the rotor is facing the #1 terminal on the cap. When I fire the engine and quickly set the timing to what I feel is necessary for the comobination.
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post #9 of 33 (permalink) Old Mar 25th, 19, 3:21 PM
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Bill
 
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Re: Spitting back through carburator

Like Justin said, the cam needs broke in. If you did not do this, it is now bad if you have let it idle for any length of time. The cam lobes and lifter faces will quickly wear off and yes the lifters will stick in the bores. Your oil will be saturated with metal and it will require a partial tear down to clean the block well enough. I have wiped cams several times and I know what I am doing. Cam break in is crucial and must be done to a 'T' with the right oil.
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post #10 of 33 (permalink) Old Mar 25th, 19, 3:48 PM
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Re: Spitting back through carburator

I read this as you never got it started ? If so , all suggestions still apply but double check basics , Cam timing is easy to miss the marks on timing gear installation. Use a straight edge to align marks . My guess is dist. is on no.6 ...180 out , or wires installed in wrong direction. Pull the cap an watch rotor direction , install wires 1-8-4-3-6-5-7-2 in same direction after you are sure # 1 is in fire position. Pull the left valve cover and watch rockers on # 1, When 2nd rocker opens and closes, # 1 is coming to ready to fire . Rotate engine by hand until timing mark is at TDC and start wiring using this as # 1. Rotor should point approx. at left headlight
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post #11 of 33 (permalink) Old Mar 25th, 19, 4:13 PM
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Quote:
Originally Posted by driveshaft-texas View Post
I read this as you never got it started ? If so , all suggestions still apply but double check basics , Cam timing is easy to miss the marks on timing gear installation. Use a straight edge to align marks . My guess is dist. is on no.6 ...180 out , or wires installed in wrong direction. Pull the cap an watch rotor direction , install wires 1-8-4-3-6-5-7-2 in same direction after you are sure # 1 is in fire position. Pull the left valve cover and watch rockers on # 1, When 2nd rocker opens and closes, # 1 is coming to ready to fire . Rotate engine by hand until timing mark is at TDC and start wiring using this as # 1. Rotor should point approx. at left headlight
I think you’re right, I misread, I don’t think the engine has ran yet. OP, Make sure you’re in #1 compression. I think you may be 180 out.
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post #12 of 33 (permalink) Old Mar 25th, 19, 5:43 PM
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Re: Spitting back through carburator

Quote:
Originally Posted by JF74chevelle View Post
I think youíre right, I misread, I donít think the engine has ran yet. OP, Make sure youíre in #1 compression. I think you may be 180 out.
Yep, sounds 180 out to me too. Been there done that.
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post #13 of 33 (permalink) Old Mar 25th, 19, 10:45 PM
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Re: Spitting back through carburator

Lou, how about I come over and take a look at it, You need more than 3 degrees advance timing. Let me know.
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post #14 of 33 (permalink) Old Mar 25th, 19, 11:16 PM Thread Starter
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Re: Spitting back through carburator

[QUOTE=JF74chevelle;11052360]When you initially fire up an engine with a flat tappet you need to run the engine at 1500-2000 rpm for 15-20 minutes to ďmateĒ the lifters to the cam for break in using a high zinc oil.

Wow, glad I asked this question. I had no idea I needed a special additive to break in the cam. Can I use one bottle of this or maybe two ? This is what Lucas makes. There are other's. I read that this whole issue regarding flat lifters and cam lobe wear is fairly new due to the cruddy oil they sell these days. What a shame. Thanks for the heads up.

I'm sure the timing marks on the gears are lined up correctly. Now I'm glad I haven't been able to start it. Saved me having to buy a new cam. Who would've thought.

Am I revving up and down to 1500 - 2000 or is it a straight 1500 for 20 minutes. Don't drop it down below 1500 , how's that work.

I hooked up the timing light and tried to start it but my funky battery gave out. Probably some piece of crap battery that can't hold a charge like the old batteries could. Anyway, it's on charge and what I did see was that the light would flash somewhere on the timing plate so , at least it's in the ball park.

Thanks for all the replies,

Lou
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post #15 of 33 (permalink) Old Mar 25th, 19, 11:29 PM Thread Starter
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Re: Spitting back through carburator

Quote:
Originally Posted by LeoP View Post
Lou, how about I come over and take a look at it, You need more than 3 degrees advance timing. Let me know.
Hi Leo,

You don't need to put yourself out. I'll figure it out eventually. Although I am beginning to have my doubts based on these new revelations regarding oil. What else do I not know. Gasoline ain't worth a crap , the oil is garbage. No wonder were going electric.

Lou
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