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Spitting back through carburator

2K views 32 replies 14 participants last post by  1943MB 
#1 ·
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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#27 ·
I disagree, to a point... While a flat lobe could cause similar symptoms, there still could be other culprets, such as a broken valve spring or valves too time, timing, firing order, etc...

But I disagree with the "flat cam" assessment. The cam may be junk now, true, but IMO, if the motor has yet to fire, I doubt its cranked enough to flatten a lobe to the point of running bad... Now IF it had been running for 5-10 minutes or more, even just a low idle, then sure, more likely a wiped cam lobe...
 
#5 ·
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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#7 ·
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
 
#6 ·
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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#8 ·
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.
 
#14 ·
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.

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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#9 ·
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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#10 ·
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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#15 ·
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
 
#16 ·
This is how I broke mine in. I fired the engine up with the cap off the radiator to get air bubbles out and I had the hose near by. I had a leaf blower blowing directly into the radiator to keep air flow going. Immediately bring the RPMs up to 1500 and hold there and fluctuate between that and 2000. Keep an eye on oil pressure and water temp and get a decent timing advance so it is not running too hot. Helps to have a buddy there for another set of eyes. Make sure to use oil with zinc additive. I used Joe Gibbs break in oil and a comp cams oil additive.
 
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#18 ·
Disaster narrowly averted!


Hey, I think Harold hit on it,....... the balancer will show TDC TWICE in a full revolution ( these are 4 stroke engines, right).... so its likely you are sitting on #6 TDC ( 360 out). You can verify by popping the drivers side valve cover and eyeballing #1 valves, THEY SHOULD BE CLOSED. I hope you find them hanging open, which means you are at #6. BTW, you can check the degree of the cam while its parked in #6 TDC. You want to see the INTAKE valve slightly more open ( closer to the head surface) than the EXHAUST.

Now, if you find the valves closed on #1,and that is the TDC you were using, then I suspect you have misadjusted valves, and I would have Leo drop by. Its a "feel" thing to set them, esp hydraulics. You'll ahve to go through the whole IO/EC procedure for all 16.

It is convention to have #1 plug post pointed at #1 cylinder, but it really is of no issue.
 
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#20 ·
I've checked the 180 issue. It's firing on #1. It's the rotor distributor that's out of wack or it's a fuel issue.

I checked the #1 piston by using the simple method of putting a rag or finger or thumb over the hole as per the 1964 Chevelle Shop manual. The timing mark on the balancer comes up on the timing plate on the engine on the firing stroke. It also lights up on the #6 during the first revolution. I've also checked it with the valve covers off and you get wiggle on the rockers at TDC.

Holy Crap I can't believe it. I hate to admit it but I just rechecked the cylinder numbering system.
Boy do I feel stupid. I've got the plug wires all screwed up. So sorry to bother everybody. I'm sure it will crank up now. But I have to wait for my special break in oil before I can try it again. Crap. Well, all I can say is I'm glad I posted this question since I found out about the break in of cams and flat lifters. So maybe it was meant to be to save me from disaster. Thanks to everyone for their help.

Lou
 
#24 ·
Here's a link to a good article on oils and cam break in. I'm still waiting for my oil which I had to special order since no one carried the Lucas brand locally. As you can see from the article Lucas has the highest concentrations of zinc. Apparently this issue regarding cam lobe wear at break in has been around for a while. Don't know why I missed it. Should be plastered in big letters on billboards across the country.

https://www.hotrod.com/articles/ccrp-1108-camshaft-break-in-guide/


Lou
 
#28 ·
I am no expert on cam manufacture but it was very surprising to me to see that a cam lobe pressing on a spring loaded lifter is going to go flat. And that's even if it doesn't get any oil. Both those surfaces are supposed to be in constant contact and if the metal is smooth as glass, which it should be, then the steel used on the end of the lobes of cams today is not as hard as the cams of old. And, it would appear the lifters made today have a surface that's harder than the lobes of the cam since I did not read that you hollow out the flat lifters. Or maybe you do both ? IMHO the only reason the cams today last as long as they do is thanks to rollers. Either in the cam or in the lifters. I think it's just something they took nickel out of to save money. That's not a scientific fact and I have no proof but when it comes to ways of saving money the auto industry is up there. So how about they concoct this business about using special oil. Running the engine up when you start it to get oil on the lifters. And what ? After I splash oil all over my cam and lifters for 20 minutes the cam gets majically super hard and I can idle it all day without a worry. How about when I start the engine. Do I have to rev it up everytime to splash oil on the lifters. I don't understand how my cam is so much better after I rev it and splash oil with zinc in it. Is the what morph's the cam into something other than what it was when it was installed. Sounds like the best option if putting in a new cam is to discard the flat tappets and use rollers because the cams today can't handle flat tappets.
 
#30 · (Edited)
Everybody knows you need oil to keep parts from causing friction which generates heat and wear.

There's too much talk about cams loosing their lobes. A cam that looses it's lobe because it's not getting oil is an inferior cam. The cam and lobes are always being submerged in oil at idle. You don't need to rev the engine to coat those surfaces with oil.

The instructions say that the reason you rev the engine is to get the lifter and the cam lobe to seat themselves. What they really mean to say is that the two surfaces are so rough that if it is run at a low RPM at intial startup due to the rougness and softer metals being used you can literally grind the cam down and that spinning the cam at higher RPM helps to smooth out those imperfections,hopefully, and prevent the sandpaper effect. Certainly sounds better to just say they need to seat themselves and get plenty of oil on the two surfaces than to say the cams are inferior in quality and the best way to insure longer life is to smooth out the surfaces at startup. Hense the caveat that if you did not spin out those imperfections at start up your cam will wear out fast and we don't take responsibility for it since you did not follow instructions. It's all a bunch of BS. That cam lobe and lifter surface should be the two hardest and smoothest surfaces in that engine. Abrams tank barrel hard. Show me where GM spent 20 minutes per car revving engines to break in cams.

Lou
 
#31 ·
Even a good cam with good lifters can go flat if proper lubrication and break in procedures are not followed. I hope you at least have used a good break in moly paste on the cam lobe and lifters.
 
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#32 ·
Are you using a point distributor or HEI? Ok begin by having the #1 cylinder up

1. Remove #1 spark plug put it on the plug wire lay it on the exhaust so it is grounded.
2. Grab the fan belts and set the balancer mark at the correct timing (check manual)
3. Drop the distributor so the vacuum advance will not strike the firewall. A long flat tip screw driver should be used to move the oil pump shaft back and forth to allow the distributor to drop where you want it. Double check the rotor is coming up to the #1 wire.
4. Lock the cap down, turn on ignition, do not crank, slowly turn the distributor until you see the spark fire from the plug.
5. After a few tries getting as close to the point of firing the plug, tighten the distributor down.
6. Reinstall spark plug and wire. Shot of starting fluid-screw diver to set idle at 2500 RPM for break in. PS don't run out of gas ;)
 
#33 ·
Hi,

I've decided to just walk away from this cam question and let it be as the song goes.

It is what it is.

On a lighter note and a joyous one at that I got the engine started and running this morning.

I reset my ignition wires correctly and then reset the distributor so that it fired where it should or should I say close enough to fire up. Cranked right up.

Was running fast which was okay since I needed to run it up to seat the cam properly. Was dying on me though and this threw me for a momentary loop.

I found that if I close off or connect all those air vacuum hoses from the carb and the intake manifold it would continue to run.

Still running fast so I adjusted the idle mixture screws out and it slowed to down to a reasonable idle. I think it was running lean and due to the added air into the combustion chamber it was getting starved for fuel.

Seems to be doing very nicely now. With all the rebuilds I did on this car such as the A/C air compressor and the fuel pump etc. and seeing no leaks from either of those and they apparently work smoothly things are looking good. And no oil leaks from the crank pully or the rear of the engine which is diffenitely a plus, knock on wood.

Anyway, next I need to time it accurately.

Thanks for all the advice and listening to my rant about cams. Ka sara sara
Follow procedure and let it go. Bigger fish to fry.

Lou
 
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