TheAMCForum.com Homepage
Forum Home Forum Home > The Garage > AMC V8 Engine Repair and Modifications
  New Posts New Posts RSS Feed - what course of action is indicated?
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Click for TheAMCForum Rules / Click for PDF version of Forum Rules
Your donations help keep this valuable resource free and growing. Thank you.

what course of action is indicated?

 Post Reply Post Reply Page  <1234>
Author
Message
Trader View Drop Down
AMC Addicted
AMC Addicted


Joined: May/15/2018
Location: Ontario
Status: Offline
Points: 3147
Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Apr/06/2021 at 3:22pm
Here is a link to an older article:
This has the holes drilled into the Primary butterfly's that I did not recommend doing.
PHAT69AMX has more information on specific carburetors, but the basics of setting idle are in the article. Setting the Primary butterflies is crucial to have your idle circuit working properly. As the article also states you should be running your Primary circuit rich, especially on that massive intake. All the Mopar's were set quite rich on the primaries and idle circuits.
After reading the reply above, the newer carburetor may not be an option of cracking open the Secondary's without having fuel flow. Don't know about these.
I like the idea of running without the Secondary's to do an initial tuning, but the Primary butterflies and idle circuit have to be set up before adjusting your Primary jetting. At least on the older 4160's.
Back to Top
bikerfox View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar

Joined: Aug/02/2009
Location: USA
Status: Offline
Points: 3442
Post Options Post Options   Thanks (0) Thanks(0)   Quote bikerfox Quote  Post ReplyReply Direct Link To This Post Posted: Apr/06/2021 at 4:53pm
Thanks for your insights, Phat.  Yes, they are 9776s--right on with that!

Interesting info with the "...very small secondary Main Air Bleeds..."  A buddy who's
familiar with the carb issues wants to take off the secondary plates and etc...and blow air
through the secondary bleeds to see if the air is getting through the passages of the carb
w/o any blockages...but maybe we're just seeing as you mentioned, "small bleeds."  I had
a thought to use the correct sized drill just to simply push it through the bleeds to make sure
there's no blockage as well.


Oh, and I just have to bring up... has any adjustment at all been done to the Secondary Idle Speed Screw adjustment ?... Not to my knowledge, as they didn't remove the carbs.

There's a lot to it... sounds to me like I would not let those guys tune my Holley carbs at all.
imho I can tell from what's already posted they don't know what to do with those Holley carbs.
You need to find some older well experienced person with Holley carbs that actually knows what they're doing.  Funny you say this as this place is a nationally known dyno shop that dynos a substantial number of engines (and chassis dyno) for big name guys and tv productions.

Disconnect / removed the simple small primary to secondary linkage interlink rod on the drivers side of both carbs.  Then do a pull running only the Primary side of both carbs and see what the mixture does.
I'm unclear as to what the outcome would be and what I would do with that info.
1969 Rebel SST (1970-1987)--SOLD
1968 AMX (2005-2011)--SOLD
1969 SC/Rambler (owned 2011-2019)--SOLD
1970 Javelin (2019 to ?)--"Jane"
Back to Top
Trader View Drop Down
AMC Addicted
AMC Addicted


Joined: May/15/2018
Location: Ontario
Status: Offline
Points: 3147
Post Options Post Options   Thanks (1) Thanks(1)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Apr/06/2021 at 8:11pm
Disconnect / removed the simple small primary to secondary linkage interlink rod on the drivers side of both carbs.  Then do a pull running only the Primary side of both carbs and see what the mixture does.
I'm unclear as to what the outcome would be and what I would do with that info.

What he is trying to do is get the engine to run properly with 2x 2 barrel carburetors.
If you can get the engine to run with reasonable idle and good acceleration on the Primary's, then the Secondary's are the bonus that should be relatively easy to jet. You don't really care about the AFR, 3600 to 4000 RPM as long as it's rich and runs well on this intake. Once the Secondary's kick in the engine will go to it's maximum efficiency and start to lean out, and that's exactly what it's supposed to do.

The dyno shows a short rich to lean curve on the Primary's and also it's stated the Primary jetting was used to fix a rich idle. That indicates the Primary butterfly's are too far open at idle.
This is not the way to set these carburetors.
It also shows Secondary's not leaning out as RPM increases.
Well not the older 4160's at least and certainly not the way we used to set up Mopar's with similar intakes.

The subtilty of changing air bleeds for fine tuning, I've never play with.


Edited by Trader - Apr/06/2021 at 8:14pm
Back to Top
PHAT69AMX View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jul/07/2007
Location: West Virginia
Status: Offline
Points: 5242
Post Options Post Options   Thanks (1) Thanks(1)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Apr/06/2021 at 11:49pm
To back up... it is going rich at rpm, correct ?...


Edited by PHAT69AMX - Apr/11/2021 at 12:56pm
Back to Top
67 Marlin View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Feb/21/2015
Location: Nodak
Status: Offline
Points: 841
Post Options Post Options   Thanks (1) Thanks(1)   Quote 67 Marlin Quote  Post ReplyReply Direct Link To This Post Posted: Apr/07/2021 at 12:47am
If you want to dyno tune for max power based on AFR, a simple way is to square the jets and put a blank power valve in. That's your high speed circuit, and since it's WOT, all barrels are open with equal jets, so less tinkering. Find best power at say 4000-5000rpm or whatever your top-end WOT is. If smaller jets make less power, then go the other way. Then, if richer or leaner on one end of the WOT range, you can play with the air bleeds and see if that flattens it out or even bumps power along the whole range. I learned smaller or bigger bleeds don't always have the intended effects, so experimentation. The bleeds are for fine-tuning the curve, but it's the least tedious thing because you don't take the carb apart, and they screw right in. You can go up a size at a time or swing for the fences with 5 or 7 sizes to see what end of the curve they effect.

You'll need to drop the primary jets after, say 8 sizes and reinstall the power valve. Ideally the combo of the primary jet size and power valve channel restrictor will be equal to the AFR of the squared jets at WOT. That means more dyno testing, or buy an AFR gauge if you haven't already. Possible to maximize fuel efficiency while cruising and WOT power. After you know your max power with squared jets, if you don't have an AFR gauge, you could do timed runs with the stopwatch from say 3500 to 5500. Find the smallest primary jet with big enough PVCR to match the squared performance and it should consume less gas while cruising.

I think idle and especially transition tuning is way more tedious than WOT tuning, and not nearly as fun.
Back to Top
PHAT69AMX View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jul/07/2007
Location: West Virginia
Status: Offline
Points: 5242
Post Options Post Options   Thanks (1) Thanks(1)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Apr/07/2021 at 8:49am
In the 1989 edition of the Holley Illustrated Parts & Specs book for List 9776 it says :
"465 CFM Universal Off-Road Carburetor".


Edited by PHAT69AMX - Apr/10/2021 at 10:52pm
Back to Top
Boris Badanov View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Dec/14/2013
Location: NH USA
Status: Offline
Points: 3933
Post Options Post Options   Thanks (0) Thanks(0)   Quote Boris Badanov Quote  Post ReplyReply Direct Link To This Post Posted: Apr/08/2021 at 5:36am
  What model number Holleys are you using?


Gremlin Dreams
Back to Top
bikerfox View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar

Joined: Aug/02/2009
Location: USA
Status: Offline
Points: 3442
Post Options Post Options   Thanks (0) Thanks(0)   Quote bikerfox Quote  Post ReplyReply Direct Link To This Post Posted: Apr/08/2021 at 8:41am
Originally posted by Boris Badanov Boris Badanov wrote:

  What model number Holleys are you using?


It's just like Phat's post above yours:  4160/9776
1969 Rebel SST (1970-1987)--SOLD
1968 AMX (2005-2011)--SOLD
1969 SC/Rambler (owned 2011-2019)--SOLD
1970 Javelin (2019 to ?)--"Jane"
Back to Top
Boris Badanov View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Dec/14/2013
Location: NH USA
Status: Offline
Points: 3933
Post Options Post Options   Thanks (0) Thanks(0)   Quote Boris Badanov Quote  Post ReplyReply Direct Link To This Post Posted: Apr/09/2021 at 6:21am
  Ok, here's my spin on the issue.
I still feel that unless you  are running at high
engine speeds all the time, just drive it and enjoy it.

I suggest the issue has to do with that huge plenum
and the poor intake "signal" that comes with it.
Very poor at low engine speeds.

Jetted to be correct at lower engine speeds as engine speeds
increase the signal becomes strong and it goes rich.

I do not have a clue how to tune that issue out.

But I can tell you that having seen hundreds of Harley
and Harley Davidson based engines on the dyno that
power does not really go away till you get to 10:1 fuel air.
They smoke a bit and 13:1~ typically makes the best power.

Pushing the compression up in the 14:1 range makes an engine
more sensitive to being overly rich.

I could say that I am a confirmed Holley hater and toss a pair of 600
Carters on it, but as I see it your rig is making EXCELLENT power
and the issue is well out of the normal driving engine speeds.

As a comparison in big radial airplane engines fuel air ratios
are in "auto rich" settings and are typically in the 10:1 range for take off.
Best max power is in the 12:1 range.

As I see it you have no problem here unless it is running like pooh. 


Gremlin Dreams
Back to Top
bikerfox View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar

Joined: Aug/02/2009
Location: USA
Status: Offline
Points: 3442
Post Options Post Options   Thanks (0) Thanks(0)   Quote bikerfox Quote  Post ReplyReply Direct Link To This Post Posted: Apr/09/2021 at 9:33am
Thanks, Boris, for your feedback.
1969 Rebel SST (1970-1987)--SOLD
1968 AMX (2005-2011)--SOLD
1969 SC/Rambler (owned 2011-2019)--SOLD
1970 Javelin (2019 to ?)--"Jane"
Back to Top
 Post Reply Post Reply Page  <1234>
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.03
Copyright ©2001-2019 Web Wiz Ltd.

This page was generated in 0.203 seconds.
All content of this site Copyright © 2018 TheAMCForum unless otherwise noted, all rights reserved.
PROBLEMS LOGGING IN or REGISTERING:
If you have problems logging in or registering, then please contact a Moderator or