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Old 04-16-2017, 06:44 PM   #1
DJ S
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Default Sputter at high RPMs

My car is sputtering, or occasionally missing at high RPMs and under load. When it's sputtering, I've tried richening the mixture and pulling the choke but it doesn't help. I've cleaned the plugs, cleaned the points, readjusted point gap, readjusted timing, change the distributor body, change the rotor, changed the cap, and chased all the wires, checked all the wiring for 6 volts, and nothing. I tried all of these, one at a time, and absolutely nothing has helped. Could it be a weak valve spring as I just tore the engine down, cleaned it, put all new gaskets, lapped the valves and this problem didn't exist prior to this? Suggestions are greatly appreciated!!
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Old 04-16-2017, 06:53 PM   #2
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Default Re: Sputter at high RPMs

Instead of cleaning maybe try another set of plugs
Just a thought
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Old 04-16-2017, 06:57 PM   #3
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Default Re: Sputter at high RPMs

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Instead of cleaning maybe try another set of plugs
Just a thought
I cleaned them and then stole the plugs off my Grandpa's car, still didn't help.
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Old 04-16-2017, 07:57 PM   #4
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Default Re: Sputter at high RPMs

Did you check valve clearance ? after doing valve job. ? Seen weak points spring, what revs is it missing at , ??
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Old 04-16-2017, 08:01 PM   #5
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Default Re: Sputter at high RPMs

Model A's, you need to understand and use the spark lever. The spark needs to be adjusted for speed and load. Also sounds like a fuel issue maybe too, not enough flow. Do you have an added filter between the sediment bowl and carb?
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Old 04-16-2017, 08:23 PM   #6
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you didn't say anything about changing or testing the coil. Borrow your grandpa's coil and try that if you don't have a coil tester.
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Old 04-16-2017, 08:30 PM   #7
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Default Re: Sputter at high RPMs

Valve clearances were all over the place. Non-adjustable tappets, so I couldn't do anything about it. The block is no good, long story, so I didn't want to sink too much money into it. I just need to get it to last me this year. No added filtee, good fuel flow, this doesn't appeae to be a fuel flow or carb problem, we also tried a different carb. I couldn't give you a number but the revs are quite high, nearing the end I would say.
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Old 04-16-2017, 09:10 PM   #8
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Default Re: Sputter at high RPMs

Not enough ignition dwell time try setting the points to .017
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Old 04-16-2017, 09:51 PM   #9
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Default Re: Sputter at high RPMs

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Not enough ignition dwell time try setting the points to .017
Done that.
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Old 04-16-2017, 09:58 PM   #10
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Default Re: Sputter at high RPMs

Do you know about what RPM your in? I do Mfg a better distributor cam for the Model A-B It will give you more dwell time about 9 more degrees, that is if it is an ignition problem.
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Old 04-16-2017, 10:08 PM   #11
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Default Re: Sputter at high RPMs

I read your post a little closer I see you had the engine apart do you have split valve guides or the one piece guides, just thinking if there the split ones you could have a valve sticking the split ones can be a problem with a little miss alignment and if you had them out and reinstalled a valve could be sticking? just a thought.
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Old 04-16-2017, 10:09 PM   #12
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Default Re: Sputter at high RPMs

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Valve clearances were all over the place. Non-adjustable tappets, so I couldn't do anything about it.
???
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Old 04-16-2017, 10:17 PM   #13
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Default Re: Sputter at high RPMs

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???
The sputtering wasn't a problem before and now it is.
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Old 04-16-2017, 10:20 PM   #14
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Default Re: Sputter at high RPMs

yes judging by what you said a few posts up on the valves and adjustment I would say you have a valve problem. If you don't want to make that right than you may as well just run it and deal with the problem. just my 2 cent worth.
Have fun with it this summer and rebuild in winter.
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Old 04-16-2017, 10:53 PM   #15
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Default Re: Sputter at high RPMs

So let me just make some clarifications on the situation concerning the valves. This engine has split valve guides and non-adjustable tappets. I removed the entire valve train for inspection. I noticed that #1 exhaust was severly pitted and worn, so I replaced it. I ensured to achieve proper valve clearance by grinding down the valve stem (.013"). This valve, however was tight in the valve guide but with some oil and movement, it began move easier, still not overly easy but it could be moved my hand. The other valves had far more clearance than they needed, which is why I couldn't make any adjustments. I reinstalled all the valves lapped them and reinstalled all the old valve springs. The reason I didn't overhaul the entire valve train is because this motor has several cracks on the exterior water jacket that can't be repaired because the remaining metal is too thin. So I used high-temp JB Weld to patch them for now just to get through this year, while rebuildig a motor over the summer, to be installed this coming winter.
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Old 04-17-2017, 12:23 AM   #16
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Default Re: Sputter at high RPMs

With the car parked rev up the motor and short out the plugs to see if you can find the clylinder thats missing. It's probably #1 with the tight vavle, remove the tight valve spring and with some polishing cloth polish the stem. Use some mmo or penetrating oil and spin the valve stem in place, I had a tight valve stem and was able to free it up some. I think I use a heavy rubber band wrapped around the stem twice spinning it like trying to start a fire caveman style. The more it run the better it got, any way might be worth a try. Don't tell anyone what I did when I didn't have much green stuff:-)
You might be able to slip a lengh of rubber fuel hose over the stem and spin the valve with a drill, with the spring off

Last edited by Big hammer; 04-17-2017 at 12:39 AM. Reason: Addition
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Old 04-17-2017, 01:26 AM   #17
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Default Re: Sputter at high RPMs

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Originally Posted by DJ S View Post
So let me just make some clarifications on the situation concerning the valves. This engine has split valve guides and non-adjustable tappets. I removed the entire valve train for inspection. I noticed that #1 exhaust was severly pitted and worn, so I replaced it. I ensured to achieve proper valve clearance by grinding down the valve stem (.013"). This valve, however was tight in the valve guide but with some oil and movement, it began move easier, still not overly easy but it could be moved my hand. The other valves had far more clearance than they needed, which is why I couldn't make any adjustments. I reinstalled all the valves lapped them and reinstalled all the old valve springs. The reason I didn't overhaul the entire valve train is because this motor has several cracks on the exterior water jacket that can't be repaired because the remaining metal is too thin. So I used high-temp JB Weld to patch them for now just to get through this year, while rebuildig a motor over the summer, to be installed this coming winter.
Hey DJ,
'and reinstalled the old valve springs'....
If you did not make sure that the OLD valve springs were/are all good (i.e.- via testing for equal seat pressure), there is your problem, IMO, especially at high speed, as you describe !

BTW...I think that you confuse, when you say that 'they have tooo much clearance and you cannot adjust that'. Why not ?
You can and maybe should have ground the seats while measuring clearance reduction. Especially , if you do not intend long time use of this engine due to other problems.

Excessive clearances plus any weak springs will not be good at high rpms, IMO.
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Old 04-17-2017, 01:32 AM   #18
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Default Re: Sputter at high RPMs

A weak points spring will do this. At high RPMs the spring cannot hold the point block on the cam.
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Old 04-17-2017, 05:20 AM   #19
Mitch//pa
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Default Re: Sputter at high RPMs

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Originally Posted by Bill Stipe View Post
yes judging by what you said a few posts up on the valves and adjustment I would say you have a valve problem. If you don't want to make that right than you may as well just run it and deal with the problem. just my 2 cent worth.
Have fun with it this summer and rebuild in winter.
As with most threads after getting more of the story i agree.

Last edited by Mitch//pa; 04-17-2017 at 06:40 AM.
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Old 04-17-2017, 05:25 AM   #20
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Default Re: Sputter at high RPMs

If you put on a new fuel line, make sure it is not hitting the filter in carb.
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