|
Bog when Engine is Warm
#1667982
09/06/14 10:49 AM
09/06/14 10:49 AM
|
Joined: Jul 2007
Posts: 1,526
North Carolina
cjskotni
OP
pro stock
|
OP
pro stock
Joined: Jul 2007
Posts: 1,526
North Carolina
|
Guys, I may have fixed my vapor lock issue  with the vapor separator and return line setup. I have noticed another tiny issue that is a little annoying now.. I notice when the engine is totally warm, maybe after 10 minutes of runtime, it has a bog when you blip the accelerator pedal. This happens right off idle or even if you're cruising. When the engine is cold/warming up it is spot-on but when it gets hot...this 1/2 second bog when you give it pedal. However, once the bog ends, the motor is strong and pulls pretty hard. The carb is a Holley 850 4150 vacuum secondaries. I have the silver (middle tension) spring installed right now. Am I right in thinking this might be an issue with secondaries opening too early maybe? If so, why only when the motor is warmed up? I have the spring kit and the quick change housing installed so if this might be my issue, what would you guys recommend as far as the spring to use? Thanks as always! 
|
|
|
Re: Bog when Engine is Warm
[Re: BSB67]
#1667988
09/06/14 03:30 PM
09/06/14 03:30 PM
|
Joined: Jul 2007
Posts: 1,526
North Carolina
cjskotni
OP
pro stock
|
OP
pro stock
Joined: Jul 2007
Posts: 1,526
North Carolina
|
Quote:
You really did not answer the key question. Will it bog/hesitate at quick part throttle?, or just WOT.
I don't ever really "floor" this car but I can tell you that it bogs at quick part throttle for about a 1/2 second or so and then picks right up and pulls hard. This feels a bit like what I had last year when I had a 32 squirter on the carburetor and I fixed it by going up to eventually settle on the 42. The 32 was the original squirter size and was confirmed to be too small on the dyno by the shop who tuned the engine originally. I tried a 38/40/42 and the 42 seemed to act the most responsive at the time....
In my fuel system troubleshooting I have swapped to a factory style hemi pump with return line/VS (from the Holley w/o return) which seems to be lower pressure according to my fuel pressure gauge. I have no idea if this is affecting anything or not.
|
|
|
Re: Bog when Engine is Warm
[Re: cjskotni]
#1667989
09/06/14 04:06 PM
09/06/14 04:06 PM
|
Joined: Feb 2005
Posts: 4,310
Prospect, PA
BSB67
master
|
master
Joined: Feb 2005
Posts: 4,310
Prospect, PA
|
Quote:
Quote:
You really did not answer the key question. Will it bog/hesitate at quick part throttle?, or just WOT.
I don't ever really "floor" this car but I can tell you that it bogs at quick part throttle for about a 1/2 second or so and then picks right up and pulls hard. This feels a bit like what I had last year when I had a 32 squirter on the carburetor and I fixed it by going up to eventually settle on the 42. The 32 was the original squirter size and was confirmed to be too small on the dyno by the shop who tuned the engine originally. I tried a 38/40/42 and the 42 seemed to act the most responsive at the time....
In my fuel system troubleshooting I have swapped to a factory style hemi pump with return line/VS (from the Holley w/o return) which seems to be lower pressure according to my fuel pressure gauge. I have no idea if this is affecting anything or not.
Not to sure a dyno is the best way to determine squirter size and duration. I've been to a couple of dynos, and I would also caution that a dyno guy is not necessarily a good carb tuner by default.
Your fuel pump is not the problem.
|
|
|
Re: Bog when Engine is Warm
[Re: BSB67]
#1667990
09/06/14 04:25 PM
09/06/14 04:25 PM
|
Joined: Aug 2006
Posts: 2,497
God's Country Maryland
GODSCOUNTRY340
top fuel
|
top fuel
Joined: Aug 2006
Posts: 2,497
God's Country Maryland
|
At idle, your accelerator pump arm should have NO play in it. It must start moving the instant the throttle starts moving. Look down the carb with a flashlight to confirm there is actually fuel being squirted into the carb, you can do this with the engine turned off. That 8.5 power valve may need to be replaced with a 9.5 or even a 10.5. A vacuum gauge will help here or just try the 10.5 to see if it helps. If the squirter is too big it can be confirmed with someone watching the exhaust for a puff of black smoke when you "blip" the throttle.
I love the smell of Deer guts in the morning, it smells like... VICTORY!
|
|
|
Re: Bog when Engine is Warm
[Re: GODSCOUNTRY340]
#1667991
09/06/14 05:47 PM
09/06/14 05:47 PM
|
Joined: Jul 2007
Posts: 1,526
North Carolina
cjskotni
OP
pro stock
|
OP
pro stock
Joined: Jul 2007
Posts: 1,526
North Carolina
|
Alright. I went and inspected the adjustment on the pump arm and it seemed to be adjusted right where the arm would start to get depressed instantly when moving the throttle. Now this is something I have always wondered about but the accel pump arm has a little play in it. In other words, it can be pushed down a bit (maybe .030-.040) from its resting position before I 'feel' resistance like its pushing the diaphragm. I had the throttle arm adjusted so it was holding the accel pump arm just 'south' of that resting position but maybe .020-.030 from where it began to feel resistance. There as no gap at all between the throttle lever arm and the accel pump arm. I went ahead and backed off the adjuster nut 1/2 a turn or so which puts more tension on that arm and brings it where it will start to feel that resistance as soon as the throttle is moved. Does that sound right? Hopefully this makes sense... So anybody care to explain why if this was misadjusted, why it would be crisp while the engine was cool and get a bog when warmed up? This particular circuit should operate identically hot or cold, right? Thanks for the suggestions so far.
|
|
|
Re: Bog when Engine is Warm
[Re: BSB67]
#1667993
09/06/14 07:44 PM
09/06/14 07:44 PM
|
Joined: Jul 2007
Posts: 1,526
North Carolina
cjskotni
OP
pro stock
|
OP
pro stock
Joined: Jul 2007
Posts: 1,526
North Carolina
|
Quote:
Does the carb have a choke? If the choke is actuated before it is warmed up, you cannot compare.
Electric choke. It starts to come off after about 20-30 seconds.
|
|
|
Re: Bog when Engine is Warm
[Re: cjskotni]
#1667994
09/06/14 09:00 PM
09/06/14 09:00 PM
|
Joined: Jan 2003
Posts: 5,443
Indiana
YO7_A66
master
|
master
Joined: Jan 2003
Posts: 5,443
Indiana
|
Your choke could be richening the idle/transfer circuit when the engine is warming up. Then when the engine is warm and the choke is open, the engine could be seeing a lean spot off idle and during tip in.
I always adjust my pump cam linkage when the engine is idling and with a flash light. I lean over the engine "just enough" to see the front squirter while shining the flash light on that squirter. Then I move the linkage and watch how soon the fuel starts to pump out. If the fuel does not pump out as soon as I move the throttle, then I readjust it and check it again. I move the nut about 1/8 of a turn until I see fuel.
What pump cam color do you have? Do you have a hollow squirter screw with the 42? If not, then you won't see much of a difference in pump shot larger than a 37 squirter.
Note: A 42 is a large squirter. Maybe it is time for a pump cam swap.
1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
|
|
|
Re: Bog when Engine is Warm
[Re: cjskotni]
#1667997
09/07/14 09:30 AM
09/07/14 09:30 AM
|
Joined: Feb 2005
Posts: 4,310
Prospect, PA
BSB67
master
|
master
Joined: Feb 2005
Posts: 4,310
Prospect, PA
|
Quote:
What else could be wrong that the large pump shot might be compensating for?
Really?
Quote:
I had the carb jetted on the dyno with wideband O2 sensors so I am pretty sure the jetting is right...
Jetting should be very close and likely not the problem IMO. However, there is no down side to stepping up the jets in the primary side at some point just to see, but I don't think you are there yet. Curious, do you know what changes they made in jetting at the dyno?
Is this the 870 Avenger carb?
|
|
|
Re: Bog when Engine is Warm
[Re: cjskotni]
#1667999
09/07/14 10:40 AM
09/07/14 10:40 AM
|
Joined: Jan 2003
Posts: 5,443
Indiana
YO7_A66
master
|
master
Joined: Jan 2003
Posts: 5,443
Indiana
|
The PINK cam is the ""least"" aggressive off idle of the entire selection of pump cams!!!!!
I would suggest a white or red (very similar to each other and twice as aggressive off idle than the pink cam.) cam on position #1. If that helps but not all the way, then I would suggest the Orange pump cam which is more aggressive than the white or red cams and it also has more overall pump volume (which you may or may not need), But for testing purposes, I would leave the 42 in there and just swap out pump cams for now.
Note: you will need to shorten the pump arm screw to install the larger pump cams. Maybe 1/2 turn before insalling the white or red cam and then once the cam is in, readjust.
1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
|
|
|
Re: Bog when Engine is Warm
[Re: cjskotni]
#1668000
09/07/14 12:02 PM
09/07/14 12:02 PM
|
Joined: Feb 2005
Posts: 4,310
Prospect, PA
BSB67
master
|
master
Joined: Feb 2005
Posts: 4,310
Prospect, PA
|
Do you know how many turns out the idle mixture screws are?, and what the A/F ratio is at idle(from the dyno session)?
Better yet, do you have the A/F graphs?
Last edited by BSB67; 09/07/14 12:04 PM.
|
|
|
Re: Bog when Engine is Warm
[Re: BSB67]
#1668001
09/07/14 01:17 PM
09/07/14 01:17 PM
|
Joined: Jul 2007
Posts: 1,526
North Carolina
cjskotni
OP
pro stock
|
OP
pro stock
Joined: Jul 2007
Posts: 1,526
North Carolina
|
Idle mix screws are about 1.25 - 1.5 turns out from bottom. I have the graph but it only shows 3500 RPM+ so it might not be that useful here. Another thing we may be grappling with is the tune was done with a marginal fuel pump which failed totally shortly afterwards. I also later found the ignition as marginal and had to go to a lower ballast resistor to get the coil output voltage back up. At the time of tune, the output was in the 10-15kV range...new ballast...in the 45kV range. No idea if this will affect anything here or not. I have thought about experimenting with the cams but I didn't know enough to make an educated guess as to which one to try. I am appreciative of the specific suggestion on which color to try. My friend has the set of cams so I will see if I can steal his set to play with... Thanks for the help so far....
|
|
|
Re: Bog when Engine is Warm
[Re: cjskotni]
#1668002
09/07/14 01:31 PM
09/07/14 01:31 PM
|
Joined: Sep 2007
Posts: 14,889
up yours
Supercuda
About to go away
|
About to go away
Joined: Sep 2007
Posts: 14,889
up yours
|
Problem with most dyno tunes is that the tune WOT. Transition and driveability are not addressed other than to make sure it isn't totally horrible.
Your best best bet is to install a wideband O2 and data logger to tune it right. Otherwise your sorta guessing what needs to be done.
They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
|
|
|
Re: Bog when Engine is Warm
[Re: davenc]
#1668005
09/14/14 01:20 PM
09/14/14 01:20 PM
|
Joined: Jul 2007
Posts: 1,526
North Carolina
cjskotni
OP
pro stock
|
OP
pro stock
Joined: Jul 2007
Posts: 1,526
North Carolina
|
Quote:
On a dual-plane manifold, a 042 shooter seems quite large. As others have mentioned, the pink cam may not be the best for a street car since it is lazy in lift right off idle. I would suggest changing the pump cam first, and then come back down on the shooter. Every setup is slightly different. Try an orange cam to start. I suspect the shooter can come down into the range of 031 with the right cam but change one thing at a time. In my opinion, the cam is the more important of the two on a street car.
FWIW I have the MP single plane manifold, not a dual plane.
I played around a little today with the car (more trying to test for vapor lock) but got it good and hot and tried to note this issue. It seems the bog only occurs if the throttle is blipped pretty fast and over 50% or so. Just giving it some moderate pedal or a blip under half throttle seems fine...no bog.
If the bog occurs at quick throttle opening over 50%, this means I need a cam that gives more fuel in that range (>50%)?
Either way, I will get my buddy's set of cams and try the red or orange and see what happens. I have a 32/38/42 squirters here I can try later if that helps the problem.
Thanks so much guys!
|
|
|
Re: Bog when Engine is Warm
[Re: davenc]
#1668007
09/14/14 08:45 PM
09/14/14 08:45 PM
|
Joined: Jul 2007
Posts: 1,526
North Carolina
cjskotni
OP
pro stock
|
OP
pro stock
Joined: Jul 2007
Posts: 1,526
North Carolina
|
Quote:
Was the "blip" with no load on the motor, or while the vehicle is in motion?
I did the blip with the car rolling and/or at a standstill in gear so under a load. The engine doesn't stumble at all when it's out of gear so not that far off!
|
|
|
Re: Bog when Engine is Warm
[Re: cjskotni]
#1668008
02/23/15 06:05 PM
02/23/15 06:05 PM
|
Joined: Jul 2007
Posts: 1,526
North Carolina
cjskotni
OP
pro stock
|
OP
pro stock
Joined: Jul 2007
Posts: 1,526
North Carolina
|
Ok guys, I know it's been awhile since I posted this but I finally have the restoration part of the car done so now I have more time to circle back on these little mechanical gremlins. I got the Holley tuning kit and swapped in the red cam (from the pink there) and went to a 37 squirter (from 42). I had to shorten up the accel pump lever adjustment screw a lot...like 7-8 turns to get it where it was just resting on the pump lever with the throttle closed. I did the 15 thousandths feeler gauge as well on open throttle to make sure it didn't over extend the arm and all is good there. Whoa what a difference! I scared myself a time or two when I blipped the throttle. Now I can break the tires loose at 40 mph when I blip it! Of course now I notice that when I have it under WOT for more than 2-3 seconds, it is pinging a little bit so I guess it's time to roll the timing back a degree or two. Man that stroker can pull now! Thanks guys!
|
|
|
Re: Bog when Engine is Warm
[Re: RapidRobert]
#1668010
03/07/15 05:43 PM
03/07/15 05:43 PM
|
Joined: Jul 2007
Posts: 1,526
North Carolina
cjskotni
OP
pro stock
|
OP
pro stock
Joined: Jul 2007
Posts: 1,526
North Carolina
|
Quote:
Quote:
what a difference! I scared myself a time or two when I blipped the throttle. Now I can break the tires loose at 40 mph when I blip it!
Of course now I notice that when I have it under WOT for more than 2-3 seconds, it is pinging a little bit so I guess it's time to roll the timing back a degree or two. Man that stroker can pull now!
Thanks guys!
You sound pumped! On the timing you might go to a slightly heavier spring for either of the two springs in there (I'm assuming 2 light ones) until the pinging stops under WOT, since if your initial and total are correct as is you would not want to compromise them for the pinging
I measured the total timing which is 36 degrees...so 20 degree advance (16 initial). Do you have a part number and a recommendation as to what springs I need to use to back this down to maybe a 16-18 degree advance? This is the standard MP distributor.
Thanks!
|
|
|
Re: Bog when Engine is Warm
[Re: cjskotni]
#1668013
03/08/15 01:49 PM
03/08/15 01:49 PM
|
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
|
Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
|
Quote:
Wouldn't it be better to shorten the slots to just limit the timing advance? Any ideas? Does it work?
(1) no (2) of course! (3) yes I hear the FBO plate works OK but 36 total is fine but it coming in too fast. 35 is a tried & true total for a std sb but strokers do have alightly different tiotal requirements but 36 ain't a dealbreaker. I am a fan of experimentation & wouldn't see an issue with trying the plate and or going to a heavier spring & seeing which one of the two works the best for your app. I'm sure the plate is cheap. EDIT Do you have a BB or SB? If BB I would stay at 36 & go to a heavier spring
Last edited by RapidRobert; 03/08/15 02:44 PM.
live every 24 hour block of time like it's your last day on earth
|
|
|
Re: Bog when Engine is Warm
[Re: cjskotni]
#1668015
03/08/15 04:12 PM
03/08/15 04:12 PM
|
Joined: Aug 2003
Posts: 43,112
Bend,OR USA
Cab_Burge
I Win
|
I Win
Joined: Aug 2003
Posts: 43,112
Bend,OR USA
|
Quote:
I had to shorten up the accel pump lever adjustment screw a lot...like 7-8 turns to get it where it was just resting on the pump lever with the throttle closed. I did the 15 thousandths feeler gauge as well on open throttle to make sure it didn't over extend the arm and all is good there.
Whoa what a difference! I scared myself a time or two when I blipped the throttle. Now I can break the tires loose at 40 mph when I blip it!
Of course now I notice that when I have it under WOT for more than 2-3 seconds, it is pinging a little bit so I guess it's time to roll the timing back a degree or two. Man that stroker can pull now!
Thanks guys!
Two suggestions, try a 32 or 35 squirter next,get the smalest one in it that won't bog with the accelerator pump arm set up properly At the same time back the timing up to 34 degrees total with the motor at or above 4000 RPM  Don't change the amount of mechanical advance  , just the initial If it still pings try a colder plug by one heat range lower  BTW, what brand and heat range, plug number, are you running now? Now that you have opened the door to more power we need to maximise it so you can really get pump up, scare the poop out of you     Mopowered 
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
|
|
|
Re: Bog when Engine is Warm
[Re: Cab_Burge]
#1668016
03/08/15 04:22 PM
03/08/15 04:22 PM
|
Joined: Jul 2007
Posts: 1,526
North Carolina
cjskotni
OP
pro stock
|
OP
pro stock
Joined: Jul 2007
Posts: 1,526
North Carolina
|
With the dizzy advancing 20*, this would mean only 14* of intial timing. On the dyno, we determined that the engine made the most power with 18* initial but of course pinged when you opened it up. I don't think rolling back to 14* is enough timing? I am running Champion RC12YC. EDIT: I am going to try Autolite 3923 which is one heat step down from these Champions. I am guessing with the 10.4:1 compression this might not be a bad idea.
Last edited by cjskotni; 03/08/15 04:49 PM.
|
|
|
Re: Bog when Engine is Warm
[Re: RapidRobert]
#1668018
03/09/15 08:45 AM
03/09/15 08:45 AM
|
Joined: Jul 2007
Posts: 1,526
North Carolina
cjskotni
OP
pro stock
|
OP
pro stock
Joined: Jul 2007
Posts: 1,526
North Carolina
|
Quote:
Quote:
I am guessing with the 10.4:1 compression this might not be a bad idea.
You need more octane, if you build a monster you gotta feed it want it wants (needs). You're timing numbers ain't out of line but your SCR (& therefore DCR) is too high for your (current) choice of fuel.
I realize this number is high but I am running aluminum heads. I know people here have run much higher with pump fuel.
BTW I did take it out today with the colder plugs and took it up to WOT for a few seconds...enough to open the the secondaries and I didn't hear any pinging. I will keep testing and maybe try a heavier spring as well...
|
|
|
|
|
, if it ain't pinging you're set 
