manifold vaccum for vaccum advance ?'s

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Now don't shoot me because the link I am going to give you is written about Chevrolets, but the theory of ported vs. manifold vacuum advance hold true regardless of what brand you're working on. It is written in common mans language for everyone to understand. I always used ported vacuum but now that I think about it, early on when I tuned up cars, I always unplugged the vacuum hose from the distributor and plugged it with a golf tee. You don't need to do that if the distributor is hooked to ported vacuum. There is no vacuum through the hose. It all makes perfectly good sense now! tmm

[ame]http://www.camaros.org/pdf/timing101.pdf[/ame]
 
Do yourself a favor and put the initial back at 16* where it was, and hook up your vacuum advance to ported. If it doesn't run any better then start looking at the carb. I as well as thousands of others have been running Carter/Edelbrock carbs for years and they work perfectly fine on mild performance engines as long as they aren't broken.
 
...............Just remember that Don is not GOD.........manifold vacc is 4 chevys...........the popping out the ex is because ur motor can only tolerate so much timing......obviously u have too much......dont forget, the heavier the vehical the less timing it can tolerate..........go to 12* initial.......+18=30.......then set vacc to 10.....12+18+10=40........anymore ur asking for detonation [that u cant hear] melt a piston.....kim.......
 
This engine has always ran good at 16 degrees intial timing. I dont know what the hellis going on, bbut it is frustrating to me. Ihave read that exact stoy on manifold vaccum for the vaccum advance and it makes sense to me. Running the vaccum advance off of manifold vaccum makes sense to me. I just dont understand why it is popping nd thudding out the exhaust.. Is it in any way shape or form possible that my exhaust may be restrictive and causing this issue?
And what is up with the smoke coming out my exhaust pipes once i put the vaccum advance hose on to ported vaccum? I got on it pretty hard and backed off the throttle while in second gear and some smoke came flying out my exhaust. This is the very first time i have ever seen this engine smoke out the exhaust before . I dont think its piston rings because it dont smoke when you first fire it up? Maybe the way my pcv valve system is hooked up is wrong or something? Just kinda freaked me out. This engine has had valvoline synpower 10w-30 ran it ever since break in and has always had a wix oil filter. And it dont even have 25 thousand miles on it??
I guess what i can do is turn the vaccum can back down to add 10 degrees of timing and set my initial timing at 14 degrees and plug the vaccum advance hose back into manifold vaccum and see if a new coil makes this issue go away. I did notice my coil was pretty darn warm.
And i have a yellow wire runnin from the positive terminal of the coil to one of the prongs of my 2 prong ballast resistor then on the negative side of my coil there is a blck/yellow wire and it runs to the ecu plug inn harness deal. I have read you are supposed to have a brown wire thaat also goes to the positive side of the coil to help with cranking? But i have never been able to find out where the other end of the brown wire would go if i added one to the positive side of my coil...
Could this be my issue? not having the brown wire hooked up to the positive side of the coil? And where would i wire the other end of the brown wire? I have been told that the brown wire from the positive side of the coil is only to help with starting the engine and that it is not a mut have.?.?.?. My engine fires up with the first turn of the key everytime, it has ever struggled to fire up ever. But i'm thinking maybe i am being hard on my coil by not having this brown wire that is spos to help with starting.
When my truck is running i get about 7.5 to 8 volts to the positive side of the coil and my ballast resistor has 1.2ohms of resistance. Wich is kinda low, but i didnt think it would be low enough to fry a coil? Would blaster coil from mopar or msd or even a crane cams canister coil help with this issue? I wanna do whtever i can to make my engine run well with the vaccum advance hooked up to manifold vaccum, so i need sugestions as to what could be causing this issue.
Obviously its easy to assume that it wans more fuel? but by pulling my vaccum advance hose off the carburetor i create a vaccum leak wich says the carburetor is rich enough, and i can smell the fuel in the exhaust, so i dont understand why it would need more fuel? My plug wires are nothing spectacular, they are borg warner select 7mm's, but none of them are broken that i can see. my firing order is correct, i have checked it 3 times. M plugs are fairly new ngk v-powers gapped at .035 my ignition module is new and its a wells ecu box and i have it grounded. So what could be the problem?
Is 24 degrees initial really too much for a 300hp 360 magnum? givin it is in a four wheel drive truck, my tempature never goes above 195 normally runs consistantly at 190 it never burns oil or smokes except for the smoke i seen today after i hooked my vaccum advance to ported vaccum and i backed off the throttle after gossing her pretty good wich also has me concerned....
Maybe i should wire inn an hei ignition, get a hotter spark, maybe that would help with this issue? And i do want to get 2 1/2 inch exhaust pipe very soon. i hate this dinky 2 inch exhaust pipe. And i read that bigger exhaust pipe diameter means more fuel. So more fuel at idle because of more exhaust ipe diameter might also help? I am running a 1 inch 4 hole phenolic carburetor spacer too, do this make the idle circuit more lean? Im just trying to come up with some possible causes and solutions. Please keep the help coming guys. As of right now i have the vaccum advance on ported vaccum set to add 15 degrees of timing at 18 inches of vaccum and my initial timing is sitting at 16 degrees and total is at 34. And i did still hear some popping thru the exhaust with it set up this way, wich shocked me and made me think this problem might not be a fuel related issue. I threw on my spare coil and couldnt hear the popping anymore... And the secondary resistance on my original coil was higher then it should of been untill it cooled off. but even with it totally cooled off it is reading 10.08 k and my repair manual says it shouldnt read anything over 9.50k. o thats why i was asking if i should get a little hotter coil like a blaster coil from mopar or msd ora crane cams or taylor canister coil?
 
So kim if i turned my initial timing down to 14 degrees wich would land my total timing at 32 degrees and i set my vaccum advance to add 10 degrees of timing at 18 inches of vaccum and run the vaccum advance off of ported that would set a total of 42 degrees.
And whats up with the smoke flying out the exhaust when i back off the throttle after getting on her pretty good? That isnt iston rings is it? Because i always though if the rings were shot yo'd see smoke upon first firing it up wich i never see smoke when first starting it.vThis is the very first time i have ever seen this engine smoke out the exhaust. kinda has me worried.
 
Just a thought, have you stuck the stock MP distributor in there?
They are adjustable with an allen key thru vaccum port.
Smoking while letting off is a sign of valve guide troubles.
I would do a compression test and leak down test before doing much more work.

Mopar has not made that crate motor for alot of years, I just tore down a machine shop fresh 340 that sat so long, the oil was dry on the piston skirts.
 
so whats an easy way to check if my valve guides are shot? I'm guessing the cylinder head would need to be pulled off to do that, correct? I thought these magnum cylinder heads used bronze valve guides? I heard they were pretty much industructable. But anyways i have been thinking about getting the iron ram cylinder heads from hughes anyways. Maybe i will have to do that alot sooner then i thought if my valve guides are going bad. What caused valve guides to go bad?
The wierd thing is this engine never smokes when you first start it up, and this was the first time i have ever sen smoke come out the exhaust pipe after getting on it good and backing off the throttle. It never did that when i had my vaccum advance running off of manifold vaccum.
A couple more questions about the popping the issue out the exhaust, just to make sure everyone is on the same page here, this only happens while the engine is idling, it never happens any other time only at an idle and it will be idling perfectly fine then all a suden you hear a thud thud from the exhaust then it will go back to idling fine and then thud thud thud thats how it goes.
I was told it was the engine wanting more fuel at idle, wich no matter how rich i turned my idle air mixture screws it would help, but it never really eliminated the issue completley. I am running a 1 inch 4 hole phenolic carburetor spacer on my dual plane edelbrock rpm air gap intake manifold, is it possible that the carb spacer is contributing to the issue of it not getting enoug fuel at an idle? Cuase obviously carb spacers will lean the engine a little bit. I'm thinking of taking the carb spacer off and setting my initial timing to 14 degrees and setting the vaccum advance to add 10 degrees of timing at 18 inches of vaccum (wich is what i get at idle) and then plugging the vaccum advance back into the manifold vaccum port on the carb and seeing if eliminating the carb spacer helps richen up the idle a little bit.
Even tho it is thudding out the exhaust at an idle the engine is running really good, thats the only issue when i had it set up at 14 degrees initial timing and 10 degrees from vaccum advance for a total of 24 degrees at idle, i can boil the 33 inch tires that are on the tuck with 3.55 gear ratio, so the engine is running real good, i just dont understand this issue at an idle with the vaccum advance hooked to manifold vaccum?
And my borg warner coil tested within the specs it should once it cooled off, so i dont think the coil was the issue? The distributer is brand new and curved and phased my cap and rotor are brand new brass contacts and my plugs are gapped at .035 and none of my wires are broken and my firing order is correct.
So please keep the suggestions coming, could the carb spacer be causing this? and could a restrictive ehaust system cause this as well?
 
ok, so tonight i adjusted the vaccum advance can to add 10 degrees of timing at 18 inches of vaccum. i checked my initial timing it is at 14 degrees, total timing is between 32 and 33 degrees all in by 3000 rpm.
I adjusted my idle to ide at 850rpm and i adjusted my idle air mixture screws to the highest vaccum reading on my vccum gauge. I let it warm up, tok it out for a drive and its running great, but i get in my driveway and leave the engine running and walk back to listen to the exhaust and it sounds good for abut 30 to 45 seconds but then i hear the thud thud thud sound coming from the exhaust.
So what in the world is causing this? This is pissing me off now. How on earth could 14 degrees of initial timing be too much for this engine? and how on earth could this edelbrock carburetor not feed the engine the fuel it needs at an idle with only 14 degrees of initial timing?
I need to know what all can cause this to happen and then do a proscees of inspect and elimintaion. Because this is really starting to annoy me , i'm about ready to just throw a for sale sighn in the window.
Could a vaccum leak cause this to happen? worn valve guides? restricted exhaust? A carburetor spacer making it to lean? I need to know, surely somone on this planet knows what causes this to happen, but i dont. Please help me figure this out. tommarrow i'm going to take the carb spacer off see if that makes it stop, if that dont i'm going to throw on my mopar gold ignition module that i know is still good and if that dont help it then i can eliminate my wells ignition module being the issue and i have already eliminated my coil as the problem. Is it possible my brand new distributer from fbo systems is at fault? This engine never did this untill i bought that disributer from fbo systems and installed it according to his instructions sheet.. ever since doing that this problem with it slighly thudding out the exhaust has never went completely went away, no matter what the timing is set at and no matter how rich or lean the carburetor air mixture screws are. I'm calling don at fbo systems tommarrow and asking hm if there is any way something in his distributer went bad or if they screwed up building it or whatever cause im almost ready topull my hair out over this.
 
...............u just answered ur question.....................u put in his dist, now trouble.....if u want to run 16 initial timing , u need less mechanical adv.......like i said b4 ur motor can only tolerate so much timing, i dont care if joe blows can, urs cant...make sure ur on ported vacc, NOT mani vacc...kim....
 
pjc360 said:
...But anyways i have been thinking about getting the iron ram cylinder heads from hughes anyways. Maybe i will have to do that alot sooner then i thought if my valve guides are going bad. What caused valve guides to go bad?...
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can't belive i just read all this...my head hurts :violent1:
please, i'm begging you, learn to tune and fix what you have. quit getting hung up on what one guy who's not spending his own $$ claims you need to do to fix this. you wan't to spend $500 on a high end carb, cool. send the old one to me for the cost of shipping. i'll bet at worst it just needs a rebuild. the new one will run just as bad as what you have because you don't know how to dial everything in. spending more $$ on a set of heads at this point is insane.
1- quit making more than ONE change at a time

2- maybe your coil's bad, i don't know. but if it's bolted to the intake in the stock location, ya, it's going to feel hot after a while

3- do the basics as has been suggested. set the timing like kim suggested. maybe even a little less total. i don't know how the gas is in your area. have you even LOOKED at the plugs after driving it??? lets see some pics

4- you can fix this. just work it through one step at a time

good luck

EDIT: if it was running good, why'd you change the dizzy?
 
I changed the distributer because i started changing spring combo's in my orginal distributer and could never get it to run right.
So i just bought a brand new one that was already curved and phased to my engine.
I just dont understand how in the hell 14 degrees of initial timing is too much for a 300 hp 360? Conusing....
I guess i wll turn the initial down to 12 degrees and see what happens lol
 
I run 91 octane fuel in it, its always had 91 octane fuel run thru it.
I swear this issue has to be something else other then too much timing or not enough fuel. Because once before i even started messing with new distributers and carburetor adjustments i could of sworn i heard this engine doing the same thing when it only had 5 degrees of initial timing i could hear the exhast going thud thud at an idle.
I wonder if i have e mechanical part thats messed up? I guess it could be too much timing, i just cant believe 14 degrees of initial timing is too much...
Back when i first started asking questions about timing everone laughed at me for running 5 degrees of initial timing and told me 14 to 20 degrees of initial timing is where i needed to be, so i get there and now i'm being told 14 degrees is too much.
 
Take a step back for a minute and relax. 14 to 16 initial should not be too much. The suggestions are being made to try and help you eliminate the problem.

You say your hearing a popping noise in the exhaust. Have you checked for vacuum leaks? How about an exhaust leak? Are you running headers?

I agree with an earlier post as far as not changing more than one thing at a time. When tuning it should be timing first and then carb.
 
There are several articles on ported vacuum advance from Mopar Action and Mopar Muscle. All say that ported vacuum advance is necessary for proper street performance. Richard Ehrenberg said that properly set up vacuum advance will increse FE by 30-50%. Enough to justify the time to get this right. I have run up to 60° total adance (initial+mechanical+vacuum) with no detonation on a 9.8:1 CR 340 with a 284/484 cam. Hooking up to manifold vacuum will only increase vacuum advance at idle beyond what is desired or needed to run the engine properly.
Good Luck!
 
I did have to take the intake manifold off to drill out 3 broken studs in the cylinder head on the drivers side.
And i put a new intake manifold gasket on it and then i put rtv silicone on all 4 corners of the intake manifold and put the intake manifold back on it. then my buddy grabbed his torque wrench and started trquing the intake bolts down and he broke another stud off into the cylinder head. At this point i was so tired of drilling because i had been sitting there doing it for about 5 hours that i just threw some silicone down in the hole where the stud broke. And i have not got around to fixing it yet, Could this be causing the issue with the thudding out the exhaust? a vaccum leak?
My uncle said when he had his vaccum gauge on it that the needle was moving around a little bit, and he said that it has a small vaccum leak somewhere. I need to know how to track a vaccum leak down, because i am sure thats what this is.
And yes i do have hedders, hedman hedders.
 
OldmanRick said:
At this point, if it just started, you have to look at whats been changed. The carb wasn't touched so i would rule that out for now. The distributor, the wiring for it and the plug wires are all parts that have had attention at this point. That's the first place to look as any of these could be a issue. If you have a spare coil it may not hurt to try it cause it's easy to do.
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When you recieved the dizzy did you get the spec that the can was set for and that was confirmed on a distributor machine. Do you have a timing tape and are you confirming the changes to the can when adjustments are made? (may be adding more advance then you think). Does the popping seem random or could it be just one cylinder? A old school trick is to find a very dark spot at night and observe all the plug wiring and distributor area for any arcing. Maybe even move some wires around to see if you see anything.

P.S. Nevermind! try to find the vacuum leak first. Probably why it smokes on decel......probably sucking oil out the valley. I'm out.
 
pjc360 said:
I did have to take the intake manifold off to drill out 3 broken studs in the cylinder head on the drivers side.
And i put a new intake manifold gasket on it and then i put rtv silicone on all 4 corners of the intake manifold and put the intake manifold back on it. then my buddy grabbed his torque wrench and started trquing the intake bolts down and he broke another stud off into the cylinder head. At this point i was so tired of drilling because i had been sitting there doing it for about 5 hours that i just threw some silicone down in the hole where the stud broke. And i have not got around to fixing it yet, Could this be causing the issue with the thudding out the exhaust? a vaccum leak?
My uncle said when he had his vaccum gauge on it that the needle was moving around a little bit, and he said that it has a small vaccum leak somewhere. I need to know how to track a vaccum leak down, because i am sure thats what this is.
And yes i do have hedders, hedman hedders.
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:violent1::violent1: :banghead:


here's what you do; take carb cleaner or brake cleaner and spray it on the intake when the engine is cold and see if the idle picks up or it smokes out the exhaust, if it does remove the intake and fix the bolt

as for the distributor run it whichever way that works best and don't take one person's word for everything, most people will try and sell you anything
 
A vaccum leak makes sense, I was having a real hard time beliving 14 degrees of initial timing was too much for this motor. What's the best way to track down a vaccum leak?
I have sprayed carb cleaner around the base of the carburetor and it never gains at an idle. Maybe i should i buy a new intake manifold gasket and take the intake off and re-do it, buy better gasket maker to do the 4 corners of the base of the engine where the intake sits? I like the right stuff gasket maker, would this stuff be good to put down on all 4 corners of the intake? or should i use the orange rtv silicone stuff?
 
ok, so i'll wait for the engine to cool down and spray carb cleaner around the base of the intake.
I'm not running the vaccum advance off of manifold vaccum anymore, i put it over on ported, and i confirmed with my timing light and my vaccum gauage that the vaccum advance is adding 10 degrees of timing at 18 inches of vaccum. My in itial is at 14 degrees and my total is between 32 and 33 degrees.
I drove it around, it runs great, but spoon as i put it in park and walk back to listen to the exhaust while its at an idle i hear the thud thud thud coming from the exhaust.
It does not do this while driving at all, it only does it while the engine is idleing.
 
and the popping defanatly seems random. It will be idling fine then all of a sudden i'll hear a thud thud thud from the exhaust pipe, and it does it thru both exhaust pipes, not just one. and i wouldnt call it a popping, its more of a thud thud noise thru the exhaust, its not a loud pop, just thudding. thats the best i can explain it. And whats got me thinking its something other then fuel or timing is ecause now that the vaccum advance is on the ported side and i only 14 degrees of initial timing and its still doing it, makes me think its something else. Vaccum leak is most likely the cause of this. and i'll bet its that broken stud or somwhere along the intake. cause i just had the intake off last year.
 
can even a small vaccum leak cause this to happen? becaus my uncle told me there was a vaccum leak somehwere according to his vaccum gauge but it wasnt a big leak.
 
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