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 Post subject: Re: No Power Under Load
PostPosted: Thu Mar 17, 2016 10:27 am 
356 Fan

Joined: Tue Sep 16, 2014 2:11 pm
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Location: Greenville SC
This is a merry go round, but Jeffrey may have pegged it. Test driving this morning with the car in first gear it revved but barely accelerated. Seems to be a worn clutch that is now really showing itself. Maybe this could explain it all?


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 Post subject: Re: No Power Under Load
PostPosted: Thu Mar 17, 2016 11:08 am 
356 Fan
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Fingers crossed. And please all my friends use "Jeff".

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 Post subject: Re: No Power Under Load
PostPosted: Thu Mar 17, 2016 11:12 am 
356 Fan
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Not a good test for a slipping clutch. Best way to check for clutch slip is in 4th gear with handbrake on. Drop the clutch about 3 to 4 K rpm and if the engine keeps running the clutch is toast. If it abruptly quits then the clutch is still good. Your original description of the engine not pulling past 4500 does not indicate a slipping clutch. You may have an issue with the transmission that is limiting rpm by putting excess drag on the engine. Do you know what the diff set up is? Jack the car up and spin the rear wheels. Both should spin freely, separately and together.

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 Post subject: Re: No Power Under Load
PostPosted: Thu Mar 17, 2016 1:16 pm 
356 Fan

Joined: Tue Sep 16, 2014 2:11 pm
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Location: Greenville SC
Back on the merry go round....

I don't have a handbrake but clutch seemed to be grabbing when released at 4K rpm. I don't know what diff is in place yet. Rear jacked up and each wheel spins freely in neutral. In gear they spin easily together by hand in opposite directions.


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 Post subject: Re: No Power Under Load
PostPosted: Thu Mar 17, 2016 2:30 pm 
356 Fan
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Does the engine stall when clutch is released at 4k in 4th gear. You may move but not far before the engine bucks and quits. Again if it does not stall then the clutch is shot.

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 Post subject: Re: No Power Under Load
PostPosted: Thu Mar 17, 2016 3:20 pm 
356 Fan

Joined: Tue Sep 16, 2014 2:11 pm
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Location: Greenville SC
Dave -

It would have stalled the engine. It had more grip than I expected so I'm off the clutch theory and back onto the engine. It's a lack of power. This weekend I will replace the carbs with rebuilt ones, check the valves again and replace the dizzy with a new one. Three more items to rule out.

On the carbs, the prior owner said he often had to blow out the carbs as they would get plugged with his disintegrating fuel cell foam. We replaced the foam, but maybe a piece still got lodged somewhere.


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 Post subject: Re: No Power Under Load
PostPosted: Fri Mar 18, 2016 4:48 pm 
356 Fan

Joined: Tue Sep 16, 2014 2:11 pm
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Location: Greenville SC
Today's update (I'm sure you guys are as tired of this as I am)...

Adjusted valves, a few were a little tighter than spec for this cam but nothing major. Tested the car. No change. I did take a close look at the tach during the test drive. Basically the engine does increase in rpm while the speed does not. I went from 1500 to 4000 rpm with less than a couple extra mph. As I think the clutch and drive train are not the problems, my thought is going back to fuel and spark. The motor could rev, but with a low spark or low fuel it wouldn't have much power, right?

I pulled the carbs and didn't find anything upsetting (other the typical warped bottom flanges) but I will replace them with a rebuilt pair this weekend. I also pulled out the instructions for the Pertronix Ignitor electronic points unit. This was interesting....basically it said a rough running car may be due to insufficient voltage when the red Ignitor wire is hooked directly to the coil (as instructed). And that a jumper wire directly to the battery could be used to test the issue. AND that this was a common issue! I ran out of time to test this out, but I wish I had seen that before pulling the carbs.

It's amazing how may possible explanations there are for my problem, but I'm learning a good bit going down these dead ends and my typing skill are increasing ;-)


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 Post subject: Re: No Power Under Load
PostPosted: Fri Mar 18, 2016 5:17 pm 
356 Fan
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I don't see it mentioned anywhere in this thread Chuck, so is this a 6 volt or 12 volt car? Apparently the Pertronix is sensitive to marginal 6 volt power.

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 Post subject: Re: No Power Under Load
PostPosted: Fri Mar 18, 2016 5:25 pm 
356 Fan

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It's a 12v system, but it's "total loss" race car set up, meaning there is no alternator and so you charge the battery when it gets low. Perhaps that is an issue for Pertronix systems.


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 Post subject: Re: No Power Under Load
PostPosted: Fri Mar 18, 2016 5:29 pm 
356 Fan
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You've been through everything else, so I'd go there next.

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 Post subject: Re: No Power Under Load
PostPosted: Fri Mar 18, 2016 7:08 pm 
356 Fan

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Chuck, what do you mean that "it would have stalled the engine"? Either it stalled, or it kept running because it slips. If the rpm increased while driving by 2500 and the car didn't speed up, that can only happen by slippage -clutch, or tires on icy road. Have someone who know cars drive it- they will know in about thirty seconds if the clutch is good or not.

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 Post subject: Re: No Power Under Load
PostPosted: Fri Mar 18, 2016 7:32 pm 
356 Fan
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Chuck,

Assuming you have drum brakes have you checked the centers?
If they've spun loose they might hold low load but slip when accelerating.

Pardon if this is covered as I didn't read all of the posts.

norm

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 Post subject: Re: No Power Under Load
PostPosted: Fri Mar 18, 2016 8:13 pm 
356 Fan

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Location: Greenville SC
Martin, I was in a confined space and had to limit my potential movement but the flywheel and clutch grabbed well and would have killed the engine had I let it. I may try it again after its back together and I have more room to test. I agree with your ice/clutch comment unless the dizzy spins without generating enough power to actually rotate the crank. It's very odd and some experienced folks have seen some of its symptoms without successfully diagnosing. I'm sure it will be something simple in the end, usually is....

Norm, it's a C so it has discs. Thanks for the idea though.


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 Post subject: Re: No Power Under Load
PostPosted: Fri Mar 18, 2016 9:32 pm 
356 Fan
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Chuck, cut to the chase and put the engine on an engine dyno. In less than an hour you will know everything you need to know to fix it. In the long run it will be the cheapest way to find and fix the problem and get the engine dialed in for best horsepower and you will know where your best shift points will be to boot.

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 Post subject: Re: No Power Under Load
PostPosted: Fri Mar 18, 2016 9:40 pm 
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David Jones wrote:
Chuck, cut to the chase and put the engine on an engine dyno. In less than an hour you will know everything you need to know to fix it. In the long run it will be the cheapest way to find and fix the problem and get the engine dialed in for best horsepower and you will know where your best shift points will be to boot.
Applause!
15 guys guessing over the internet is not really the way to solve the issue. Maybe someone might guess right, but it's still a guess.
Stick it on a dyno, do a leak-down, read the exhaust chem and the ignition timing and it won't be long before you know what the problem is.

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