The Ford Barn

jrvariel48 · 03-21-2022, 12:59 PM

Looking for some troubleshooters for a high rpm (over 5000rpm) loss of power/miss.
This is happening at WOT with about 6 lbs. of boost. My fuel seems ok with the A/F meter showing 12.3
Mallory Unilite distr.
21* fully advanced
Valve spring pressure 70 lbs @ 2.120" 165 lbs @ 1.750" (this is from the builder)
The motor has been fine up tp 6000 rpm
Thanks,
Joe

Bored&Stroked · 03-21-2022, 01:47 PM

Give us a little history . . . is this a NEW problem? Has the engine ran fine before and now it has suddenly started having this issue? Has anything been changed as of late?

glennpm · 03-21-2022, 02:46 PM

I spent several hours yesterday reviewing Unilite curves and settings. I was doing this to best set my advance for a McCulloch s/c on a SBC. I noticed the values were listed for Flatheads too.

The 14° listed in the chart would be added to any distributor BTDC value you have. Do you have 7° of advance at idle, i.e., 14 + 7 = 21°? Is this a recent adjustment you made?

Desoto291Hemi · 03-21-2022, 02:48 PM

70 pounds of spring pressure sounds too low for a blown application .
That amount of boost will force past the valves at 70 pounds ,,,,,at least for the intakes .

Tommy

jrvariel48 · 03-21-2022, 05:09 PM

Quote:

Originally Posted by Bored&Stroked

Give us a little history . . . is this a NEW problem? Has the engine ran fine before and now it has suddenly started having this issue? Has anything been changed as of late?

Yes a new problem. I usually only drive on Sundays so I don't get a lot of seat time. I've noticed it a few of months ago, but only drove the car a few times since then. I'm mixing 110 octane with pump 93 to get apprx. 100 octane according to on line calculators. I know they're not perfect, but they get me in the ballpark. Engine ran great and still does until the rpm gets up there. I had changed the jets for winter driving when I noticed it most, but the problem was there before that though. I put the warm weather jets back in and also replace the accelerator pump gasket, but the problem was still there.
The only other thing I changed was the radiator from aluminum to Brassworks.
Hope this info helps Thanks Joe

jrvariel48 · 03-21-2022, 05:11 PM

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Quote:

Originally Posted by glennpm

I spent several hours yesterday reviewing Unilite curves and settings. I was doing this to best set my advance for a McCulloch s/c on a SBC. I noticed the values were listed for Flatheads too.

The 14° listed in the chart would be added to any distributor BTDC value you have. Do you have 7° of advance at idle, i.e., 14 + 7 = 21°? Is this a recent adjustment you made?

Glenn I'm set at 8* at idle and have been for about a year. I actually just check it this weekend.
Thanks Joe

Glenn I'm set at 8* at idle and have been for about a year. I actually just check it this weekend.
Thanks Joe

jrvariel48 · 03-21-2022, 05:13 PM

Quote:

Originally Posted by Desoto291Hemi

70 pounds of spring pressure sounds too low for a blown application .
That amount of boost will force past the valves at 70 pounds ,,,,,at least for the intakes .

Tommy

Tommy unless the springs are getting softer, I haven't had a problem with it, not saying it couldn't be. I put over 1000 miles on the motor pushing it to 6000 rpm sometimes with no issues. Thank you Joe

Bored&Stroked · 03-21-2022, 08:11 PM

The key is figuring out if it is a fuel or ignition problem. I've had coils that went bad and started behaving like this, have had bad plugs, have had bad plug wires, etc..

jrvariel48 · 03-22-2022, 02:30 AM

Quote:

Originally Posted by Bored&Stroked

The key is figuring out if it is a fuel or ignition problem. I've had coils that went bad and started behaving like this, have had bad plugs, have had bad plug wires, etc..

I believe it's an ignition problem. I can start checking plugs, wires, etc.
Is there a way to check the coil for this type of anomaly? If not I'll just replace it. Thanks Bored

glennpm · 03-22-2022, 05:52 AM

Joe how about your fuel filter but that wouldn't necessarily just be a high RPM issue?

Glenn

Bored&Stroked · 03-22-2022, 11:41 AM

Quote:

Originally Posted by jrvariel48

I believe it's an ignition problem. I can start checking plugs, wires, etc.
Is there a way to check the coil for this type of anomaly? If not I'll just replace it. Thanks Bored

Hard to test this unless you have a really good distributor machine and put it coil under load (and heat). In many cases a coil will start to fail when it gets hot and is put under a heavy load - it shows issues here first . . . so that could be it. When I have plug/wire issues - they are usually there all the time - not just at higher RPMs.

Also, make sure you don't potentially have any fuel starvation issues - filters come to mind.

jrvariel48 · 03-22-2022, 04:53 PM

Quote:

Originally Posted by glennpm

Joe how about your fuel filter but that wouldn't necessarily just be a high RPM issue?

Glenn

Hi Glenn, new filter and pump with 3/8" line with tank return. A/F numbers seem ok.
Thanks Joe

jrvariel48 · 03-22-2022, 05:00 PM

Quote:

Originally Posted by Bored&Stroked

Hard to test this unless you have a really good distributor machine and put it coil under load (and heat). In many cases a coil will start to fail when it gets hot and is put under a heavy load - it shows issues here first . . . so that could be it. When I have plug/wire issues - they are usually there all the time - not just at higher RPMs.

Also, make sure you don't potentially have any fuel starvation issues - filters come to mind.

My thoughts also. I ordered a new coil, it'll be here today. For $60 it's the quickest way to test this. I think the fuels ok. I re-did the entire fuel system to avoid lean out. New oversized, in-tank fuel pump, 3/8" line with return. 5 1/2 lbs at the regulator to the carb. I think I have about 600 miles on the filter. I watch my A/F VERY closely!
I don't want any lean out so I usually keep the octane high, the total advance kind of low and run on the rich side. This isn't a race car so I'm not concerned with squeaking out every drop of horsepower or gas mileage, just like it to rip when needed!!
Thanks Joe

supereal · 03-23-2022, 12:56 PM

Sounds like point "float" at high RPMs. Check spring tension. We have found that many new sets of points have insufficient springs.

glennpm · 03-23-2022, 12:58 PM

He has a Mallory Unilite so no points.

Glenn

jrvariel48 · 03-23-2022, 05:23 PM

Quote:

Originally Posted by glennpm

He has a Mallory Unilite so no points.

Glenn

Thank you Glenn

51 MERC-CT · 03-25-2022, 03:38 AM

Perhaps time to consider a Pertronix conversion ?

tubman · 03-25-2022, 09:07 AM

Quote:

Originally Posted by 51 MERC-CT

Perhaps time to consider a Pertronix conversion ?

I wonder; can a Pertronix even be mounted in a Unilite?

Bill OH · 03-25-2022, 09:11 AM

Use your ohmmeter on the spark plug wires from the distributor terminal to the spark plug terminal - I have seen wires cause the problem that you are experiencing. I am assuming that you are using Packard 440 or its equal, but I always strip the insulation back 1/2 inch and fold the bare wire back over the spark plug terminal or distributor terminal for a good resistance free connection. It makes a difference. Carbon wires are a no no and spiral wound wires can be problematic. And if the wires check out okay, then look at the coil - mounted on a hot engine or is it mounted in a cool air flow spot?. Coils are heat sensitive - I had one mounted on the intake manifold of a Chrysler 383 and when the engine got up to operating temperature, the misfiring began at 75 mph. Mounted the coil in a cool place off the engine and problem solved.

51 MERC-CT · 03-25-2022, 09:17 AM

Quote:

Originally Posted by tubman

I wonder; can a Pertronix even be mounted in a Unilite?

Yes, I converted my Mallory to a Pertronix.

03-21-2022, 12:59 PM	#1
jrvariel48 Senior Member Join Date: Jan 2012 Location: New Jersey Posts: 1,427	High rpm miss/power loss Looking for some troubleshooters for a high rpm (over 5000rpm) loss of power/miss. This is happening at WOT with about 6 lbs. of boost. My fuel seems ok with the A/F meter showing 12.3 Mallory Unilite distr. 21* fully advanced Valve spring pressure 70 lbs @ 2.120" 165 lbs @ 1.750" (this is from the builder) The motor has been fine up tp 6000 rpm Thanks, Joe

03-21-2022, 01:47 PM	#2
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,071	Re: High rpm miss/power loss Give us a little history . . . is this a NEW problem? Has the engine ran fine before and now it has suddenly started having this issue? Has anything been changed as of late?

03-21-2022, 02:48 PM	#4
Desoto291Hemi Senior Member Join Date: Oct 2019 Location: Carthage , Tennessee Posts: 199	Re: High rpm miss/power loss 70 pounds of spring pressure sounds too low for a blown application . That amount of boost will force past the valves at 70 pounds ,,,,,at least for the intakes . Tommy

03-21-2022, 08:11 PM	#8
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,071	Re: High rpm miss/power loss The key is figuring out if it is a fuel or ignition problem. I've had coils that went bad and started behaving like this, have had bad plugs, have had bad plug wires, etc..

03-22-2022, 05:52 AM	#10
glennpm Senior Member Join Date: Sep 2014 Location: Wiscasset, Maine Posts: 1,982	Re: High rpm miss/power loss Joe how about your fuel filter but that wouldn't necessarily just be a high RPM issue? Glenn

03-23-2022, 12:56 PM	#14
supereal Senior Member Join Date: Jul 2014 Location: Iowa Posts: 1,634	Re: High rpm miss/power loss Sounds like point "float" at high RPMs. Check spring tension. We have found that many new sets of points have insufficient springs.

03-23-2022, 12:58 PM	#15
glennpm Senior Member Join Date: Sep 2014 Location: Wiscasset, Maine Posts: 1,982	Re: High rpm miss/power loss He has a Mallory Unilite so no points. Glenn

03-25-2022, 03:38 AM	#17
51 MERC-CT Senior Member Join Date: May 2010 Location: East Hartford, Ct Posts: 5,898	Re: High rpm miss/power loss Perhaps time to consider a Pertronix conversion ? __________________ DON'T RECALL DOING SOMETHING FOR MYSELF BASED ON SOMEONE ELSE'S LIKES OR DISLIKES

03-25-2022, 09:11 AM	#19
Bill OH Senior Member Join Date: May 2010 Posts: 426	Re: High rpm miss/power loss Use your ohmmeter on the spark plug wires from the distributor terminal to the spark plug terminal - I have seen wires cause the problem that you are experiencing. I am assuming that you are using Packard 440 or its equal, but I always strip the insulation back 1/2 inch and fold the bare wire back over the spark plug terminal or distributor terminal for a good resistance free connection. It makes a difference. Carbon wires are a no no and spiral wound wires can be problematic. And if the wires check out okay, then look at the coil - mounted on a hot engine or is it mounted in a cool air flow spot?. Coils are heat sensitive - I had one mounted on the intake manifold of a Chrysler 383 and when the engine got up to operating temperature, the misfiring began at 75 mph. Mounted the coil in a cool place off the engine and problem solved.