Moparchat - Home of MOPAR enthusiasts worldwide!



Go Back   Moparchat - Home of MOPAR enthusiasts worldwide! > Technical Forums > Performance Talk

Click here to search for Mopar cars and parts for sale.


Reply
 
Thread Tools Display Modes
  #1  
Old 08-28-2001, 06:43 PM
Stans Customs Stans Customs is offline
Inactive User
 
Join Date: Aug 2001
Location: Ft. Worth,Texas
Posts: 42
Default 12,000 lb./440 torker/need vac advance suggestions

I've just installed a .030 over basically stock 440 in an older Pace Arrow motor home, and have realized I don't have any idea what would a good advance set up for a 12,000 lb streeter.
The cam is Comp Cams Xtreme 250H-10 (supposed to yield awsome torque and idle well at 600 rpm). The Thermoquad has been replaced with a 795 cfm '80 Quadrajet atop a Mr. Gasket 1" phenolic spacer ( to isolate carb from engine heat, and to align same with Edelbrock Mopar conversion throttle and kick down linkage). Stock 1979 440 intake manifold , EGR disabled etc. Carb final jetting will be done arter I figure out what to do with the vacuum advance. Engine has been balanced just to help it live under the extreme punishment it will go through in a motor home, along with a little close tolerance machine work (fitting pistons etc.) Point : Dead stock but not junk....so timing advance needs to be better than average for this beast, or the rest would be a waste of time.
I've seen some differing opinions regarding ported vs manifold vacuum...especially when deleting EGR, and as many opinions o max advance etc as there are degrees on the balancer. I'm guessing about 10 deg initial. 20 deg with vacuum @700 rpm, 34 deg or so total mechanical/vacuum @ 2500 rpm. If this is close, I still am not sure about total mechanical without vac under 2500 rpm .
The only thing I am sure of is that I'm guessing....and I could be upside down in my thinking..Any suggestions...???
Reply With Quote
  #2  
Old 08-28-2001, 11:18 PM
TT440's Avatar
TT440 TT440 is offline
Inactive User
 
Join Date: May 2001
Location: Irving, TX
Age: 53
Posts: 159
Default hmmmm.....

I really don't know on this one, but you may check the other boards too. I've noticed that the topics and discussions vary greatly.
There are bunches of technical type people at Moparts.com that may be able to help. I'll post it over there and see what comes up.
Reply With Quote
  #3  
Old 08-29-2001, 02:00 AM
PRO PRO is offline
Inactive User
 
Join Date: Nov 1999
Location: Grand Junction,CO.USA
Posts: 1,573
Default

Stan,total timing on a heavy vehicle is always less than a pass car due to higher temps and heavier loads,otherwise youll experience detonation,30-32* total is what most 3 ton or bigger trucks use,initial advance is a no brainer just find where it idles best,you can use a vac guage to determine "BEST" idle by advancing the timing until you get the highest vaccum reading then retardind it until it drops 1-1.5",I imagine youll have to shorten the curve up because youll probably find you initial is somewhere around 15* and with total being 30-32* itll be too long.Most likely you wont even need the vaccum advance.remember a motorhome is a severe duty application so change the oil every 2000mi,use the biggest radiator possible and run an oil cooler and tranny cooler if possible.......PRO.....
Reply With Quote
  #4  
Old 08-29-2001, 09:39 AM
Stans Customs Stans Customs is offline
Inactive User
 
Join Date: Aug 2001
Location: Ft. Worth,Texas
Posts: 42
Default

Thanks TT440...I'd be interested if the Mopar.parts folks have an opinion.....
Thanks Pro ...I'm not surprised that 3 ton trucks ran that low a max advance, makes sense to me. However these motorhomes come with a set up similar to a 1 ton , if not identical. This rig had (with 10 degrees initial) 30 degrees total@ 700 rpm and 43 degrees total at 2500 rpm. Which is to much for anything, probabably why this engine had to be replaced at 67k.
I don't why it never thought to try no vacuum advance. I believe that total mechanical only is about 16 degrees. Maybe I can set the initial advance at 16 or so (total now with 10 degrees initial/+vacuum is 20) and it still idle and start well. Then 16 degrees initial + 16 total mechanical should get the max total advance down to 32 degrees without fooling with the vac at all....What do you think?
Also one of my main concerns is to make this engine run as low a temp as possible. I'm not sure if no vac and a heavy load conditions are a factor...(maybe advance to slow mechanically or not responsive enough or a .....or a .... or a....and that other thing I did'nt consider)
No vac sounds like a good idea to me...I just keep thinking it's to simple or they would have done it that way to begin with, being injun ears and all. Hmmmm... What do you think?

Thanks again Stan..
Reply With Quote
  #5  
Old 08-29-2001, 10:52 AM
TT440's Avatar
TT440 TT440 is offline
Inactive User
 
Join Date: May 2001
Location: Irving, TX
Age: 53
Posts: 159
Default

HEy Stan... take a lookie here: discussion
A couple decent ideas popped up somewhat quickly.
If that thing had better heat rejection, I'd tell ya to turbo that beast and get better mileage/power out of it.

Better yet, ditch the 440/727 and drop a Cummins in there! That's fix what ails ya. You'll get MUCH better mileage too.

Pulling the TT440 to the Nats and moving 75-80 mph, I knocked down 14.7 mpg. That's a gross weight of just over 13,000 lbs with a little less wind resistancethan what you've got. It's also in a first generation truck with the less efficient engine. A buddy's 94 Cummins regularly belts out 17 mpg pulling a 36' travel trailer at 70 mph. Not too bad if ya ask me.

Since you're in FW, maybe I could swing by with the TT440 and convince you to take that approach.
Reply With Quote
  #6  
Old 08-29-2001, 01:34 PM
451boy 451boy is offline
Inactive User
 
Join Date: Dec 1999
Posts: 286
Default

I can't imagine why you would want to ditch the vacuum advance. The vacuum advance should only kick in above 10 or 12 inches of vacuum and be all in by maybe 18 or so. So going down the road at 60 mph you should have about 15 or more inches of vacuum. Those extra 10 or 15 degrees of advance (total of 45 or so) will really help the gas mileage. Even in a motorhome, 60 mph on flat road should only require 1/3 to 1/2 throttle opening. At that throttle opening, the engine is going to need about 45 degrees of advance to burn efficiently since the combustion chamber isn't going to have a full charge in it.

As soon as the driver steps on it to go up a hill or pass someone the vacuum advance will disappear and there should be no pinging.
Reply With Quote
  #7  
Old 08-29-2001, 01:52 PM
Stans Customs Stans Customs is offline
Inactive User
 
Join Date: Aug 2001
Location: Ft. Worth,Texas
Posts: 42
Default

Thanks for the follow up TT440.....I did use the 4 hole spacer, however I didn't block the crossover thinking I would need the flow for proper choke operation. Zippy was right the crossover needs to be blocked even if you live in Alaska, just the radiant heat would warm the cockpit in the winter to say nothing of boiling fuel. I would HAVE to re do it if I hadn't installed a phenolic spacer. Cracking open a fresh engine in the frame that just came off the motorstand goes against the grain, plus the intake gasket is nearly 30 bucks so..............I'll probably do it anyway....grumble...grumble.....don't have to, but I don't like all that heat even a little bit....grumble....grumble.
Anyway back to the other issues. You are exactly right the real cure is to pull the 440 and drop in a Cummins turbo diesel....as it happens I'm a big Cummins fan as well. I have a rolled '91 3/4 ton complete with a Cummins/ auto drive train and only 90K miles. (I drive a x-cab cummins dually and have 3/4 ton flatbed cummins work truck). I would like to have done this but I've been saving this engine for a little custom built 1985 1 ton Chevy, with a hide away wheel lift, that is my street rod these days. Gettin' old I guess. If you're in Irving ease over this way (Eagle Mtn. Lake area) and see it...its trick . I doubt that turbos on the 440 motorhome would be a consideration, though I'm always interested in custom rigs like your Belvedere ( hence the business name Stan's Customs) and would like to see yours. This motor home project needs to have some curb on cost, because they don't hold their value well and I'd like to be able to use it a while and sell it without loosing a Cummins or taking a bath on the labor and parts cost. Ain't nothing cheap done right...including reconditioning the factory stuff...This project will probably wind up costing $1800 just for parts and machine work (no labor), almost the price of a diesel but much easier time wise
Sorry about the meandering...mmm oh yeah timing! I had another cohort, whom I believe to have considerable knowledge swear that the best way to handle this issue is to use manifold vacuum, set timing with vacuum gauge to highest vac reading and forget it. Says it'll work every time on heavy haulers. (providing the vac advance is close to a factory setting). Again that would be to easy.......most stuff is, however. I would like the no vac at all senario to work, but I'm wondering about making bad fuel consumption even worse without vac advance ,or if it would affect it at all.
Any opinions about manifold constant vac/or mechanical advance only...or problems generated by eiher application???

Thanks again....... Stan
Reply With Quote
  #8  
Old 08-29-2001, 03:57 PM
Stans Customs Stans Customs is offline
Inactive User
 
Join Date: Aug 2001
Location: Ft. Worth,Texas
Posts: 42
Default

Thanks 451boy...guess I misssed your post while I was editing my reply. I was afraid gas mileage would be a factor without vac advance.
I am assuming that you're recommending a ported vacuum source?

There are some who think the use of vacuum advance is best when used with manifold vacuum , in order to compensate for no lead fuels and higher cylinder temperatures, without the induction of exhaust gasses ,(EGR), to bring down cylinder temps. The contention is ( as I understand it) that manifold pressure decreases as the throttle is increased retarding vacuum timing , how ever mechanical timing advance starts as throttle is increased aiding in acceleration. When settling back to cruise mode vacuum levels come back up increasing the vac advance, to help fuel economy and lower cylinder temperatures.

Having seen evidence to support both schools of thought, I have decided that I don't know which is best .


I do know that this 440 @2500 RPM had a total 43 degrees of advance, some 10 degrees more than several have indicated for this type aplication. I have retarded this setting accordingly though not necessarily correctly so.
Again thanks and all input is appreciated.........Stan
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
340 Torker II ewatts94ram Performance Talk 7 12-12-2005 12:25 AM
Torker II Dukes2fast Performance Talk 9 05-16-2005 09:45 AM
Torker and Torker 2 Olle B Performance Talk 17 08-28-2002 03:12 AM
Edelbrock Torker 340 = LD 340 ??? PlumCrazyChris Performance Talk 3 11-27-2000 10:12 PM
Torker 1 or Torker 2? DAVE JONES Performance Talk 3 05-19-2000 07:41 AM




All times are GMT -4. The time now is 08:10 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
. . . . .