Just a little miffed...

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66durgederp

66durgederp

"pull hard, itll come easy"
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So this is one of those things that I can only hope im being too critical about. Im a little worried if i have an exhaust valve/seat taking a dump, or a spark plug issue, or something else. Here's the scoop, 87 vintage 318 highway patrol motor, 360 top end (factory) 110,000 miles on this monster. true dual exhaust 2 inch head pipes that turn into 2.25 inch approx 1.5 feet after the manifold flanges. msd 6A ignition, high vibration coil, napa belden 8mm red wires, aluminum tower cap, NGK V-power plugs, 91 octane no ethanol fuel. 36 degrees advance at idle (including vacuum) holley 4175 650 cfm spreadbore. 18 in. lbs manifold vacuum at idle, very consistent, no needle jumps whatsoever.

Heres whats going on, ever since i got this beast rolling earlier this year its always had this weird sound on deceleration, this is going to sound stupid but i dont know how else to explain it, its a sort of poof sound, instead of the nice rumble it has this intermittent poof/sputter sound more prominent out of the drivers side. Ive ran champion copper core plugs and now NGK V-powers, same thing happens. The thing runs like a raped ape though, but this has been driving me nuts. I pulled the plugs tonight, NGK's, the majority were a little black, honestly from shifting too fast under load (running really fat) because the original kickdown arm on the trans (for this drivetrain) was hitting the floor so i ran the shorter slant six 904 arm until i fixed it properly. I have since then modified the floor to clear the correct arm so the shift points (and lockup) are right where they should be. Ive messed with the idle adjustment screws until i achieved the highest manifold vacuum and idle speed. putting my hand over the end of the pipes i cant feel any sort of suction effect on the drivers side, even did the paper trick to see if it would suck it in, thankfully no such thing happened. Passengers side is nice and solid on the exhaust, nice strong exits, the drivers side though has this intermittent weak exit. its solid poof poof poof then it has a super weak "poof" then back to being solid until it does it again, but it NEVER has a weak exit twice in a row, usually every 10-20 solid exhaust strokes. This only happens at idle, and deceleration. Under heavy load it pulls nicely, part throttle, same thing. runs great. Ive taken my timing light to see if i had a wire that was being stupid and 1, 3, 5, 7 all hit throughout the entire length and i cant see any spark jump from the boot, wire, or carbon tracking on the cap at any RPM. Cylinder wires 5 and 7 are separated sufficiently to prevent inductive crossfiring as well.

so maybe, does anyone have any sort of idea what could possibly be happening? or am i just being too critical? sorry for writing a damn novel. Thank you for any input.
 
I dont have a solid answer but..
36 before at idle doesn't seem right to me. All in would be up in the 50s.
X or H pipe would level the exhaust pressure.
 
IMO, you have a tuning issue.
What is your idle rpm? Which vacuum port is it plugged into? Manifold or ported? If it was hooked up "properly" ( properly meaning how the factory designed it and how I hook them up - not that there's not other ways that might work...) then you should have no advance from the vacuum pod at idle. But if it's idling at 800-900rpm, you may be into the vacuum advance and you need to cow down the idle and close the throttle blades a little.
 
Is the heat riser butterfly open/ opening?

Have you run compression/ leakdown tests? If you don't have a leakdown tester, Google. They are easy to make, OR you can bring each cylinder up to TDC and simply introduce air. Listen at intake, exhaust, look in radiator for leaks

Run a cylinder balance test. Easiest way I've found is to pull up the distributor boots, and insert small brads down beside the wires into the plug towers. Then just take a grounded probe and ground one at a time, watch a tach or listen. Each cylinder should drop equally

What does the vacuum gauge act like?

Some vacuum gauge pages:

http://www.secondchancegarage.com/public/186.cfm

http://www.therangerstation.com/Magazine/Summer2003/VacuumLeaks.htm
 
36* advance at idle doesn't sound right at all. 36* should be pretty close to all in. But, assuming everything runs correctly otherwise, my guess would be that you either have a timing light issue or a mismarked balancer issue to come up with that number. The rest of your numbers seem in order, so I'm inclined to think the timing appearing that advanced is a measurement problem and not an actual timing problem.

The noise on deceleration is probably an exhaust leak on the driver's side pipe (since its more prominent on that side). You say you're running rich, which means there's more fuel in the exhaust than normal. On deceleration your exhaust will actually pull outside air in through a leak, so I'd bet you've got some kind of backfire making that "poof" noise. My Challenger straight up fires out of my header flanges if I'm doing any kind of engine braking. If I drop it into second to keep my speed down on a steep descent so the engine is doing the braking I get loud popping out of the flanges. But I also run a bit rich, and I constantly have header flange leaks, so I know why...

First, I'd see if I could find the exhaust leak on the drivers side pipe. Then I'd try a different timing light to figure out your advance, or find true TDC on the engine and see if it lines up with the indicated TDC on the balancer. With the timing set correctly dial in the carb, and that will make it less likely to backfire through the pipes.
 
X2 on the exhaust manifold butterfly valve. How tight does the spring hold it open when it's hot? Easy test is to wire it open for a test drive. If no change, then move on to next hypothesis and remove the test wire.

Good luck!
 
thank you for the input gents, theres a few things i forgot to mention and i apologise. the 36 degrees at idle, thats with vacuum advance, wich is hooked into manifold vacuum. no vac adv im sitting at 13 btdc static. 37 all in at 2500-2600 rpm, no vac adv. my idle rpm is 750. with a gauge hooked to the manifold vac port it holds very steady at 18 in. lbs as of last night. As for the choke stove valve in the manifold, its long ghandi, completely. Ill have to do a leakdown and compression test since i havent done that yet. Ill get back with numbers, and ill sea foam the motor to see if theres a leak at the manifold, collector flange, anywhere else. thank you fellas for the input. ill get some comp/leakdown numbers here soon.
 
Is there a reason you want the manifold vacuum? That engine should idle at 600 and have 15" of vacuum or more. Also - that total timing is retarded for that engine package and I'd wager the sputtering andd "jumpiness" of the idle is due to the vacuum hookup of the advance. The "putt putt" you hear in the pipes is unburnt fuel popping in the exh pipes when you decelerate.
 
My brother and I argue about timing just as I will argue about yours. He runs 32 degrees at full mechanical advance. With the vacuum attached and full vacuum he is at 55 degrees. That is waaaay to high. He argues that it isn't, that the vacuum advance is Mopars way to deliver better mileage. He is wrong. He is too high and so are you. That may give you the noise you are hearing, as valves may be open when they should be closed. That said, fix the timing and put in an H or X pipe. I had rapping on decel and slow accel. It was embarrassing. When I put in an H pipe it went away and I got extra power I could feel.
 
that seems to be a huge gray zone with the ported or manifold vacuum and the timing settings being at 50 something cruising. ive tried running it without the vac adv, its a dog off idle and runs pretty hot (211-214). my trucks the same way, my cordoba (400) was the same way. Mileage gains were slim, but driveability running the vac adv was very noticeable, for the better. I was involved in a thread a while ago where this same issue came up, and i was horrendously wrong on a couple things, but Demon 408 posted them, here they are: http://www.camaros.org/pdf/timing101.pdf
and http://www.diamondbackengines.com/te.../ignition-101/
So not to raise hate and discontent, but what do you guys run for timing? in the means of using the vacuum pod or not, static timing, mechanical advance....
 
alright so digging through other posts it seems to follow what ive done.
A: disconnect the vac adv. (i always do by the way, learned that years ago via my old mans backhand...)
B: Rev engine until the timing mark stops climbing. done deal.
C. Total timing no more than 36-38 degrees, max. NOT INCLUDING THE VACUUM ADVANCE. right? right?
Seems the general consensus is no less than 10 degrees btc static for a good curve on a dizzy. ie: not having too long of a curve, mine is 24 degrees.
I got lucky on my factory style "reman" unit. 13 static, 24 mechanical, for a total NOT INCLUDING VACUUM ADVANCE of 37 degrees. the dizzy is "all in" at approx 2600 rpm.
now at idle, i know mechanical advance isnt kicking in. im sitting at 13 static. once i hook up the vacuum advance to MANIFOLD vacuum, boom, im sitting at 36.

So heres my main questions:
1. total advance does NOT include vacuum?
2. Is the advance at idle, static of 13 plus vacuum advance of 23 degrees for 36 at idle acceptable?
3. cruising down the road, doing 65-70, im winging 3000 rpm. now my timing then, static 13, plus full mechanical advance 24, PLUS vacuum advance 23 (i have an old school "motor minder" gauge thats fairly accurate, 16-17 in lbs of vac cruising), will put my timing at approx 60 degrees btdc under light load. IS THIS BAD?!
From what ive read in books, the net, (including the article demon 408 posted, and I re-posted) this seems like a huge twilight zone that doesnt have a solid answer, some say yes, some say no (Mopar to ya i understand where your coming from)....my head hurts....
 
"Total advance" is a word often thrown around with different meaning.

Many racers talking about "total advance" for full power don't use vacuum, even if a can is on the dist, so they ASSUME we all mean "mechanical only"

I believe you have the idea

For troubleshooting, something like this I ALWAYS leave the vacuum disconnected, "one more thing" you can not worry about.

So yeah, get a max total of about 32-36, no more than 38, and AT LEAST 10 initial. This may not happen if you have a bone stock "smogger" distr. with a long slow advance. If you look on the bottom of the dist. advance piece (which holds the rotor) most will have a number stamped on the BOTTOM which indicates the amount of advance in DISTRIBUTOR degrees, which must be x2 to get crank degrees. IE 15* on the advance is way too much, being 30* at the crank.

I have a REALLY mild cam in my little 67, now in the 318, and It runs somewhere around 20* mechanical advance, with about 15-17 initial. So this give me 37, no vacuum, the vacuum being on ported vacuum
 
thank you 67. ive seen your posts on other threads about the stampings on the weights, i have yet to get into mine to see. jesus glad this is finally coming together. too bad im almost out of beer for the night....alright so on my next few days off ill get some leakdown and compression numbers up, and check for exhaust leaks. thank you all for chiming in!!! I appreciate it.
 
So heres my main questions:
1. total advance does NOT include vacuum?
A: When you read about total timing in terms of full throttle you are always referring to the initial timing, plus the mechanical timing. That's because at full throttle (with ported or manifold source), and at idle (with ported source), there is no vacuum advance present. There's no vacuum signal. Now in terms of engine diagnostics, total can include the vacuum advance amount because at light throttle it is present regardless of the vacuum source.
2. Is the advance at idle, static of 13 plus vacuum advance of 23 degrees for 36 at idle acceptable?
Aceptable is all up to you. Technically, if it starts, and it doesnt ping, it's usable. But some want it better than "usable", and some want it better for more throttle positions than idle and full throttle. I'm one of the latter. I would not use the vacuum can to try and make the idle better - which is what you're doing. It's not designed or intended to do what you want it to, and because of that, I believe it's costing you performance and overall satisfaction - enough that you posted about it.
3. cruising down the road, doing 65-70, im winging 3000 rpm. now my timing then, static 13, plus full mechanical advance 24, PLUS vacuum advance 23 (i have an old school "motor minder" gauge thats fairly accurate, 16-17 in lbs of vac cruising), will put my timing at approx 60 degrees btdc under light load. IS THIS BAD?!
From what ive read in books, the net, (including the article demon 408 posted, and I re-posted) this seems like a huge twilight zone that doesnt have a solid answer, some say yes, some say no
Here's the problems as I see them:
1. Your advance comes in fairly slow if it moves 24° over 1900rpm. Your engine is very mild and has a strong idle vacuum and smooth idle. It's made for torque.
2. You're normal cruise rpm window would be say, 2200-3K. If that's the case (stock convertor, mild gearing, around town type driving) you need to get the mechanical in earlier and faster.

What I'd set it up as is this:
Idle speed - 650-700rpm.
Initial advance - 15° BTDC
Mechancical advance - 24°; Use (1) aftermarket "light" spring and the lighter factory spring. The goal is the initial to start advancing around 1300 and be all in by 2K. That might take some doing in terms of experimenting with removing weight from the weights, and matching springs. You may end up with (2) aftermarket light springs. I've found Mallory advance spring assortments to be a great source of other tension advance springs to tailor the curve.
Vacuum advance - plugged into ported source, and adjusted to the lightest preload - this may also need to be tuned after things are set - and it should be adjustable through the nipple the hose goes on.
 
cool. Im liking these somewhat solid answers. one more question though, on the vac adv, ive adjusted it through the nipple to lessen the amount of advance, and it wont go any lower than 23 degrees, im thinking its just the nature of the beast, since ive had this happen on 3 different dizzys, and for some reason the little voice in my head says thats too damn much, but i dont know how to get it any lower without changing my static, short of just unhooking the damn thing, but in town driveability is hindered at that point. the 60 degrees with all 3 in cruizing down the road has me scared. i dont want to grenade the rings out.....keeping in mind i run 91 octane (because around here its ethanol free) and ive done all my tweeking on 91 only. ive never heard it detonate, and shut down on a hot summers day it isnt a problem, no dieseling, pinging, nothing.....that i can hear or feel....so maybe there isnt a rock solid yes or no answer to this....maybe its a situation of "whatever the motor likes".....maybe?.....the 60 degrees cruising under light load still has me feeling uneasy though....
 
alright i went home at lunch and pissed off the neighbors and the landlord :finga: so i re-checked my static, it crept on me, 17.5, checked mechanical advance, 24 degrees....plateaus off at 2600 then oh geez at 2900-3200 an additional 5 degrees shows its face and then thats all until 4000 rpm....great got a weight sticking....so time for a dizzy re-spring and find out why the weights hanging up....anywhore reset the static to 12.5, retweak the idle mix screws, recheck the total advance, now 37 degrees, plug in the vac adv aaaand......idles a little bit, just a little bit rougher but its plenty good enough for me, right at 700 too, the exhaust poof poof pluhh is still there but i still gotta check for leaks and compression/leakdown test, however in decelleration it doesnt do the annoying pluh pluh poof poof poof sounds anymore. now when i check overall timing with the vac adv hooked up what kind of reading should i expect? i didnt have time to do that....and my neighbor was getting pretty hot...
 
You can't adjust the amount of vacuum advance - only the amount of vacuum needed to start to advance. I say start at all the "loose" setting - which is counterclockwise until you feel the allen wrench "click". If you have surging at part throttle cruise, turn the adjuster clockwise two turns, and drive it again. Basically - add preload to the spring that opposes the vacuum until the advance operates smoothly.
Also - it's normal for the timing to continue to advance. Usually it will keep climbing until the weights reach the endd of thier travel, but most guys dont rev that high to notice it.
You will probably note total timing in the 50+° area with the vacuum plugged in. Vacuum advances usually add around 10°. The arm of the vacuum advance is stamped with the amount of advance it can supply.
 
hate to sound dumb but the year model of the engine....anyone plug the lil' a.i.r. holes below the exhaust ports with allen set screws yet??? no wonder it sounds like that :) anyone got a pic of a smog head to show him them lil' noisy holes i'm talkin about?
 
waggin said:
hate to sound dumb but the year model of the engine....anyone plug the lil' a.i.r. holes below the exhaust ports with allen set screws yet??? no wonder it sounds like that :) anyone got a pic of a smog head to show him them lil' noisy holes i'm talkin about?
Click to expand...

Hells yea i did!!!!! however i used 1/8 inch freeze plugs with green sleeve retainer.
vbpgimage.php
 
sounds more like some of them blew out just hold your hand under the manifolds while the engine is cold and you will feel em pukin out exhaust...or you could have an egr valve on the intake manifold that will do the same thing
66durgederp said:
Hells yea i did!!!!! however i used 1/8 inch freeze plugs with green sleeve retainer.
Click to expand...
 
good call. ill check for that when i sea-foam it to see if it had flange or pipe leaks. danka senor
 
UPDATE! i havent done a compression test or leakdown, and i dont think i really need to now. im pretty sure it was indeed a tuning issue. so i sea foamed the fuel (snows flying now so itll get parked soon) and did a bit down the carb, no leaks throughout the entire exhaust, on either side. flanges, weld joints, air port hole caps in the heads, everythings solid. (id hope so since the system is 4 months old) so i found an older thread about recurving the dizzy and since mine was a "remanufactured" unit lord knows what was in it. upon tearing it down the slide plate for the advance weights was stamped L15. so 30 degrees crank advance.....hell no the slots were just a kiss over .58 inches long. i brazed the slots and filed them to .420 for 23 crank degrees. Slapped a lighter spring in place of the heavy unit (lighter spring from a 68 383 2bbl points dizzy) and i achieve 34 degrees at 2300-2400 rpm now. instead of 3100-3300. Its much more responsive off idle now, much snappier. silicone greased the bushings, filed any slag and whatnots, triple checked everything, set the vac advance can to kick in at 16 in lbs, adding 13 degrees, and plumbed into ported vacuum. slapped it all together, set at 11 static. runs like a champ! The exhaust fluttering is gone, and the power curve is more consistent now. Anything else i could possibly do besides an H pipe and tail pipes? (wich will get done) thanx guys!
 
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