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 Post subject: Re: No Power Under Load
PostPosted: Wed Mar 23, 2016 5:42 pm 
356 Fan

Joined: Tue Sep 16, 2014 2:11 pm
Posts: 32
Location: Greenville SC
I'm still leaning towards ignition, even though I've replaced damn near everything (except that lug nut).


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 Post subject: Re: No Power Under Load
PostPosted: Wed Mar 23, 2016 8:13 pm 
356 Fan
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Joined: Tue Mar 25, 2008 6:32 pm
Posts: 3317
Location: Harrodsburg, Kentucky
Tag: I wish I knew as much as I think I know.
I am going to guess that a previous owner did a rebuild and used stock heads or heads that were not adequately ported. Maybe he got it done by a rebuilder and got screwed or did it himself, but that would explain the lack of power after 4500 rpm.

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 Post subject: Re: No Power Under Load
PostPosted: Wed Mar 23, 2016 10:33 pm 
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Joined: Wed Nov 23, 2011 10:52 am
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Location: Cleveland, Ohio
The descriptions of the problem are so inconsistent that we should stop guessing what is wrong, somebody has it in his shop now and will be able to figure it out.

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Last edited by Martin Benade on Thu Mar 24, 2016 7:15 am, edited 1 time in total.

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 Post subject: Re: No Power Under Load
PostPosted: Wed Mar 23, 2016 11:35 pm 
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Location: San Francisco
Martin Benade wrote:
The descriptions of the problem are so inconsistent that we should stop guessing what is wrong, somebody has it in his shop and will be able to figure it out.

We were also told it was dyno'd twice and a leak-down was done, but somehow Chuck would rather withhold that data and suggest people throw darts.
Personally, I don't find that acceptable. If you have a problem and desire help, it behooves you to provide every bit of information you can. Or accept that quite a few people won't bother joining in your Dear Abby game.
Check that lug nut, Chuck!

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 Post subject: Re: No Power Under Load
PostPosted: Thu Mar 24, 2016 8:32 am 
356 Fan

Joined: Tue Sep 16, 2014 2:11 pm
Posts: 32
Location: Greenville SC
I'm not asking for further remote diagnosis, but to reply to a few posts:

Jon - no smell from clutch.

Dave - It's entirely possible that someone swapped the heads at some point after the original build.

Martin - If you could be specific about the inconsistencies in my description I would be glad to clarify.

Ron - "We were also told it was dyno'd twice and a leak-down was done, but somehow Chuck would rather withhold that data and suggest people throw darts."

Dart Received!

Here is the compression and leak-down info from an earlier post:

Compression and leak down results below.

#1: 168 psi, 40% dry, 14% oiled
#2: 172 psi, 33% dry, 18% oiled
#3: 205 psi, 9% dry
#4: 205 psi, 14% dry

Wish they all looked like 3 & 4! Hissing on 1 & 2 was mainly from crankcase. So, looks to me like a rings/rebuild issue.


I can assure you there is no conspiracy to withhold valuable data that would help you help me! The dyno's were chassis dynos which I realize wont help much with a drivetrain/clutch issue. The first one was so erratic due to both ignition AND fuel issues the operator said to focus on one and then come back. It was a complete scatter-graph. I made changes to the carbs and got the AFR in line. The second run was still a scatter-graph due to ignition issues (per the dyno operator), as I mentioned previously. The results were so erratic and poor that neither the operator nor I felt a need to further analyze the charts and left it at that. So that's where the process started with changing all ignition components. At the time it seemed like a major electrical component had failed - coil, Pertronix, etc.

Thanks to many others out there for positive suggestions and good humor.

I'll report back when this is resolved.


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 Post subject: Re: No Power Under Load
PostPosted: Thu Mar 24, 2016 9:10 am 
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Joined: Tue Oct 27, 2009 5:02 pm
Posts: 6599
Location: SE Michigan
I have seen stock intake manifold gaskets installed over ported heads. Power loss at mid to upper RPM range.

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 Post subject: Re: No Power Under Load
PostPosted: Thu Mar 24, 2016 9:19 am 
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Joined: Mon May 12, 2008 12:58 pm
Posts: 292
Location: Vancouver,Washington
Ron LaDow wrote:
Martin Benade wrote:
The descriptions of the problem are so inconsistent that we should stop guessing what is wrong, somebody has it in his shop and will be able to figure it out.

We were also told it was dyno'd twice and a leak-down was done, but somehow Chuck would rather withhold that data and suggest people throw darts.
Personally, I don't find that acceptable. If you have a problem and desire help, it behooves you to provide every bit of information you can. Or accept that quite a few people won't bother joining in your Dear Abby game.
Check that lug nut, Chuck!


Ron, do you mean axle nut? And the stripped drum spline syndrome? :shock:

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 Post subject: Re: Cheap Quick Test
PostPosted: Wed Mar 30, 2016 5:52 pm 
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Location: Shoreline, Washington, USA
Tag: Ex 356 Mechanic
If the carbs have air cleaners on them, take them off and try a run. My dim memory says that years ago there was an issue with some Solexes with the vent tube not getting enough air with some air cleaners. Or, hole in the carb top gasket not big enough? I think checking for full butterfly opening with full throttle was already mentioned.

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 Post subject: Re: No Power Under Load
PostPosted: Fri Oct 12, 2018 7:21 am 
356 Fan

Joined: Fri Jun 29, 2018 2:54 pm
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Location: San Diego, California
No end to this story? I read all 6 pages as I'm experiencing a similar problem in a '65C just purchased. Couldn't wait for the final outcome. Chuck? Any wisdom to share?


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 Post subject: Re: No Power Under Load
PostPosted: Fri Oct 12, 2018 5:03 pm 
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Location: Harrodsburg, Kentucky
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Lawrence, the information in this thread related to a vintage race car with Solex PII40 carbs and you have a 356C which if stock has Zenith carbs so you may want to start a new thread with your engine information and your particular symptoms. Also welcome to the forum where most of your questions will get mostly sensible answers but levity is not outlawed.

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 Post subject: Re: No Power Under Load
PostPosted: Sun Oct 14, 2018 10:39 am 
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Joined: Tue Oct 26, 2010 2:21 pm
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Couple of months ago, I had a vintage racer come into my shop with a similar problem. The chief complaint was lack of power. He had the car in several shops, all doing the same diagnostic procedures (leak down, carbs etc.) with no improvement or solution. In all the stories, no one looked at the distributor. I started there, took the cap off, twisted the rotor to see if the advance action with working. Nope it wasn't and the distributor internals were worse. The Teflon slide plate had bunched up which was the main culprit along with missing shims etc. So the distributor was repaired and installed in the correct position (I think it was 180 out if I remember). Problem solved with a lucky guess and basic diagnostics. My point is to be sure the basics are covered first, make small changes to evaluate the results, then move to the complex.
Lots of great intel in this thread, copy and keep for future reference.

ed
klasse356

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 Post subject: Re: No Power Under Load
PostPosted: Tue Oct 16, 2018 10:44 am 
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Ed: Wouldn't that problem i.e. advance action not working have been quickly diagnosed if someone checked the advance at 3K+ rpm to see if it was in the 30-37 degree range rather than simply checking static advance? Of course, your method of twisting the rotor is a quick and easy check.

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 Post subject: Re: No Power Under Load
PostPosted: Tue Oct 16, 2018 11:57 am 
356 Fan

Joined: Thu Feb 05, 2009 8:13 pm
Posts: 638
Location: Texas Panhandle
PaulAhnell wrote:
Ed: Wouldn't that problem i.e. advance action not working have been quickly diagnosed if someone checked the advance at 3K+ rpm to see if it was in the 30-37 degree range rather than simply checking static advance? Of course, your method of twisting the rotor is a quick and easy check.


Paul, Ed"s check is simple and quick, and answers a lot of questions easily.

Like Ed, i've found the Teflon slide plates to be troublesome. I recently disassembled an 022 I'd run for over 15,000 miles, relatively trouble free, stored for likely 10 years, but... the edges were curled, and would have caused trouble in the near future. I had 2 new Teflon ones, back about 10 years ago, which when run on the Sun, had no curve, and when I opened them up, found the curled edges. I replaced them with the then newly available phenolic replacements, and an 031, and 022, both ran up fine, and performed well in the cars, just my experience.

Your timing check will work, but the "spring back" advance check, is quick, easy, and reliable, my $.02

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