Notices

Bucking / Power loss at Full Throttle

 
  #181  
Old 04-18-2019, 02:07 PM
pmuller
pmuller is offline
Senior User
Join Date: Nov 2015
Posts: 183
pmuller is starting off with a positive reputation.
I installed the Duraspark first and got the same thin spark with signs of yellow.
Then I plugged the MSD 6AL directly into the Duraspark distributor, added the MSD coil and the spark became very bright, thick, loud and no signs of yellow.

The only problem was the timing changed and went advanced so moving the distributor to correct the timing put the rotor phasing too far out.
The Duraspark box triggers when the magnetic based signal crosses zero and the MSD must trigger when the signal begins to rise.
So I hooked the Duraspark back into the system and let the Duraspark box trigger the MSD and the Duarspark is there as a backup in case of an MSD failure.
Timing back to normal.

Ported head 232 .050" duration cam (288 advertised duration), Quick Fuel HR650 carb, Hedman header, 1977 2WD pickup, T18 tranny.
Rear tires break loose as soon as the engine hits 1200 rpm in second gear and gets 17+ MPG at 70 mph highway @ 2400 rpm. 15 mpg around town.
 
  #182  
Old 04-18-2019, 02:14 PM
pmuller
pmuller is offline
Senior User
Join Date: Nov 2015
Posts: 183
pmuller is starting off with a positive reputation.
I installed the Duraspark first and got the same thin spark with signs of yellow.
Then I plugged the MSD directly into the Duraspark distributor and the spark became very bright, thick, loud and no signs of yellow.
I had a different spark tester but the MSD spark would jump the 40k distance on yours.

The only problem was the timing changed and went advanced so moving the distributor to correct the timing put the rotor phasing too far out.
The Duraspark box triggers when the magnetic based signal crosses zero and the MSD must trigger when the signal begins to rise.
So I hooked the Duraspark back into the system and let the Duraspark box trigger the MSD and the Duarspark is there as a backup in case of an MSD failure.
Timing back to normal.

Ported head 232 .050" duration cam (288 advertised duration), Quick Fuel HR650 carb, Hedman header, 1977 2WD pickup, T18 tranny.
Rear tires break loose as soon as the engine hits 1200 rpm in second gear and gets 17+ MPG at 70 mph highway @ 2400 rpm. 15 mpg around town.

Ask 250-restorer about his MSD experience.
 
  #183  
Old 04-18-2019, 02:14 PM
AbandonedBronco's Avatar
AbandonedBronco
AbandonedBronco is offline
Moderator
Thread Starter
Join Date: Dec 2007
Location: Boise, Idaho
Posts: 7,190
AbandonedBronco is a name known to allAbandonedBronco is a name known to allAbandonedBronco is a name known to allAbandonedBronco is a name known to allAbandonedBronco is a name known to allAbandonedBronco is a name known to all
Am I understanding right that the MSD didn't work properly with your application, and you had to revert to the DS box?
Maybe I'm not following.

Still, your gas mileage makes me scratch my head.
I'm averaging 11 in town, maybe 13 - 14 on the highway.
70mph is 2000 RPMs.

I mean, I know I have 32" A/T tires, which makes a difference, but it shouldn't be that much.

Did you see my question about what voltage range I should be looking for on my tester? I know what results I'm getting, but I don't know what I'm shooting for, or what I'm comparing against.
 
  #184  
Old 04-18-2019, 02:22 PM
pmuller
pmuller is offline
Senior User
Join Date: Nov 2015
Posts: 183
pmuller is starting off with a positive reputation.
The MSD box is still suppling the spark but it is being triggered by the DS box.
And yes the MSD will jump the 40K gap on your tester and further.

Ask F-250 restorer about his MSD experience.
 
  #185  
Old 04-18-2019, 02:33 PM
pmuller
pmuller is offline
Senior User
Join Date: Nov 2015
Posts: 183
pmuller is starting off with a positive reputation.
Here are the MSD 6AL instructions. https://www.jegs.com/InstallationIns...1/121-6425.pdf
I started with the wiring shown on the bottom of page 15 using the PN 8869 adapter cable.
When I found the timing change I changed to the wiring shown on the top of page 15.

You can also wire the MSD into the HEI system as shown on page 14.
 
  #186  
Old 04-18-2019, 03:36 PM
AbandonedBronco's Avatar
AbandonedBronco
AbandonedBronco is offline
Moderator
Thread Starter
Join Date: Dec 2007
Location: Boise, Idaho
Posts: 7,190
AbandonedBronco is a name known to allAbandonedBronco is a name known to allAbandonedBronco is a name known to allAbandonedBronco is a name known to allAbandonedBronco is a name known to allAbandonedBronco is a name known to all
I see what you mean.

Yeah, it looks like the MSD install is pretty straight forward and easy to do, with either the DSII or HEI.
If I went this route, though, I'm not sure I'd see much use in keeping the HEI, except that it's curved to my engine. Dunno.

Still, though, I contacted DUI about this. This isn't a stock HEI system, but a high output performance version, so it shouldn't be "weak"
Maybe something internally is wrong?
 
  #187  
Old 04-18-2019, 10:18 PM
pmuller
pmuller is offline
Senior User
Join Date: Nov 2015
Posts: 183
pmuller is starting off with a positive reputation.
The DUI should have a much stronger spark than the Duraspark.
What is the battery voltage when the engine is running?
 
  #188  
Old 04-19-2019, 09:47 AM
AbandonedBronco's Avatar
AbandonedBronco
AbandonedBronco is offline
Moderator
Thread Starter
Join Date: Dec 2007
Location: Boise, Idaho
Posts: 7,190
AbandonedBronco is a name known to allAbandonedBronco is a name known to allAbandonedBronco is a name known to allAbandonedBronco is a name known to allAbandonedBronco is a name known to allAbandonedBronco is a name known to all
Battery voltage is about 14v or so.
 
  #189  
Old 04-19-2019, 10:31 AM
pmuller
pmuller is offline
Senior User
Join Date: Nov 2015
Posts: 183
pmuller is starting off with a positive reputation.
I don't know what else to look at.
I'd hate to see you put money into the DUI by swapping the module and other parts. Their components are not cheap.

The DUI is curved for you engine and the plug wires are very good.
I would add an MSD to the DUI.
 
  #190  
Old 04-19-2019, 11:47 AM
AbandonedBronco's Avatar
AbandonedBronco
AbandonedBronco is offline
Moderator
Thread Starter
Join Date: Dec 2007
Location: Boise, Idaho
Posts: 7,190
AbandonedBronco is a name known to allAbandonedBronco is a name known to allAbandonedBronco is a name known to allAbandonedBronco is a name known to allAbandonedBronco is a name known to allAbandonedBronco is a name known to all
Yeah, I'm at a bit of a loss. Hopefully DUI themselves have some answers.
Otherwise, I'll probably look into the MSD setup or the DUI and make a mishmash of both. Probably be a little while due to the $250+ pricetag.
 
  #191  
Old 04-19-2019, 07:38 PM
Guhfluh
Guhfluh is offline
Junior User
Join Date: Aug 2013
Posts: 67
Guhfluh is starting off with a positive reputation.
First big problem is assuming the EFI throttle body doesn't need manifold heat. It needs MORE heat than a carb. It does NOT "atomize" fuel better than a carb. It does not emulsify fuel at all, which a carb does, and it merely tries to squirt small streams of fuel into the air stream to be sheared. For that reason, when sheared across throttle blades, it will do a better job of "atomizing" than at full throttle, with worse air velocity and no vacuum to help with phase change, etc.

Second thing I see is the VE map is majorly over compensating for what looks like a poorly tuned acceleration enrichment. Problem is that the acceleration enrichment can't be properly tuned if it's causing a missfire from not having manifold heat. The system is definitely chasing it's tail adding way too much fuel when it isn't needed, and in my opinion you're fighting a rich miss. Cyl 6 plug is evident of it and is the first to miss from being overly rich and fuel dropout.
 

Thread Tools
Search this Thread

Contact Us - About Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.