poly 318 vacuum leak help? - Mopar Forums

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Old 10-22-2007, 09:01 AM   #1
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Question poly 318 vacuum leak help?

Hey guys, I'm new here and need a little help. I'm not a mechanical genius by any means, but I'm trying my best.
I just bought a 66 coronet 440 with a poly 318 2bbl a few weeks ago. It runs alright (it stalls when put into gear or stopped). It acts like it has a vacuum leak but I checked all the hoses and around the base of the carb and all that stuff and can't seem to find anything (pcv valve..but i replaced it w/ no change in how it runs). Anyway, it has a Holley 2bbl on it and it's the "newer" style? Someone told me the poly 318 ran better with the old style carter or Stromberg carb. I can't seem to find any information on either of those carbs for this car... numbers etc that I would need to locate it and buy it. Hell, I can't even find a rebuild kit for the Holley thats on it (which is junk).
Can anyone help?
i also put a new 1 wire alternator on it and electronic ignition. Is there a need to re-gap the plugs when switching from points to electronic ignition?
Why does this car have single exhaust? Would converting to dual exhaust help the poor lil engine? It just seems so restricting to have 1 small tube for exhaust.
I found an aluminum 4bbl intake for it for $100, i doubt I could keep my foot out of it w/ a 4bbl, and gas prices aren't cheap right now. Would it be a decent idea to get the 4bbl intake and put a 2bbl adapter on it?
Also the timing.. a friend of mine told me 10* BTDC so thats what I timed it at..still runs like crap... then I was told (by a few diff people) between 2-6* and then told 8*... and maybe even 12* if the timing chain is a little slack. I'm a mopar idiot and non of my car friends have mopars... either way its still running like crap @ 10* btdc... whats the correct timing setting?
I've never owned a mopar before... Does this particular engine have any quirks or typical problems for me to look for?
If anyone owns one of these engines and could tell me a little about it, kind of familiarize me with it, that'd be great!!
I've been trying to find the service manual for it with no luck as well...if i could find it, maybe i wouldn't be here bugging you guys.
I have no plans for hotrodding this car or giving it more power. It is my cool granny mobile that I take my kids to school in and get groceries LOL
Thanks guys


Last edited by 66coronetgirlie; 10-22-2007 at 09:40 AM. Reason: added more info
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Old 10-25-2007, 06:07 PM   #2
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praise the poly!!

i'm glad somebody else in cali still drives one of these, and with it's 2bbl no less.

my '62 dart wagon has a poly318, a stromberg 2bbl, and a pushbutton 727 - all original to that car! i'm still tearing it down, but i did play with enough when i got it that i can help you a bit here, hopefully.

first off, polyhead 318's are their own world of engine. built to mimic the hemi's heavy breathing at a lower design/produstion cost, poly's are strong, reliable, and totally unappreciated. they were built with opposing valves (like all true hemi's), solid cams and adjustable rockers. remember this: solid cams are better performance items, but much less forgiving and require regular adjustment! the poly is big, with thick castings, and heavy, which is probably why no one likes 'em, but exactly why they're so reliable - they're tanks! i wouldn't trade my poly318 for a 360 of even a 383!

now, your poly is probably running poorly for multiple reasons.

how long has this car sat unused? that's always horrible for old cars.

what kind of electric ingnition did you convert to and what all did you swap?

unfortunately the holley 2bbl you have sure is crap. a stromberg will help, but they're VERY hard to find. my '62 uses a stromberg ww 3-199. your car should be able to use this carb, provided you have a hot air choke, and the kickdowns are the same (otherwise you'd have to just swap those parts too). i rebuilt mine with a kit from kragens @ $14, but it doesn't come with welsch plug or new screws. i reused & restaked my screws, but if you ever need a welsch plug for a strom ww, let me know (i may have found them by then). on the other hand, i'm sure rebuild kits are available for your holley, they're just hard to find sometimes. if you rebuild it and play with it, it may work better and save you lots of $.

your next dilema is your valvetrain. your solid cam hates your guts - it lives to make you miserable, but it makes your car happy). if your timing chain is stretched REPLACE IT! i got an edelbrock double roller for $50 @ kragens. next you need to adjust your valve lash. that means factory specs... for my '62 poly: 0.010 for intake 0.018 for exhaust with engine hot. rocker arm adjuster screw should have minimum 3 foot-pounds of tension or it needs to be replaced.

spark plugs stay the same with most electric ignitions to the best of my knowledge.

dual exhaust will only really help if you put that 4bbl on your poly. the 4bbl will allow it to breathe easier. it was a factory option, so legal even in the people's republic of california. you'll have more power, more fun, and it should run better with a decent 4bbl, but your mileage will go to the floor. also, even with a 4bbl, i'd only go with 2.25" if true dual exhaust, with a cross pipe. btw: i've been watching for a 4bbl dual plane intake for quite some time (debating that swap myself) and if it were no offence to you, i would be very interested in knowing where you know of one to be available if you don't want it.

timing...i'm still looking for a definitive resource. i have the 1962 lancer/dart/polara shop manual, but it doesn't say!!! i'm still looking and thinking i'll buy a spec card soon. i'd try fixing other things first, then time by ear if nothing else. 10*btdc @500rpm sounds at least reasonable, just make sure engine is at operating temp and vacuum advance plugged when setting timing.

particular problems: valve lash besides that, their so big with such thick castings that sometimes they like to get hot. to cool it better try royal purple's purple ice (noticeably lowered temp of my truck's magnum318)

hope this helps,
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Old 10-26-2007, 09:18 AM   #3
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wow! ok.. where do I start? You are extremely helpful. I will find out about the 4bbl intake for ya, it's from a friend of a friend. As far as I know, the guy I bought this car from was using it as a daily driver and it just needed lights, but he needed quick so he sold it. I drove it up and down the street when I got it and it's still driveable, it just likes to stall when put in gear or at a stop. It does fine if i drive 2 footed LOL keep givin' it gas the whole time.
I found the box YAY! it's a PERTRONIX Ignitor electronic ignition.
The valve specs on this car, according to the spec sheet i found is 0.013 intake and 0.021 exhaust. Sound right?
I'm still having issues finding a rebuild kit for this holley.. An internet mopar friend in Illinois has a 2bbl carter he took off of his poly 318 in his truck. He said I could have it for $100 plus shipping... does that sound decent for a used one?
I have no idea about the timing chain, I haven't dug that deep yet. As far as i knew when I got this car, it was a runner and only needed lights LOL. Well, the more i dig, the more I find, as with any older car, i guess. I really should check the timing chain, huh? The dash says 67K miles, but as we all know, it could be 167K lol I'll see about the timing chain today and let you know what I find.
I do know, after climbing under trying to find the block numbers (which were on the passenger side under the water pump!!! - that took a while, I was told drivers side front under the heads) I also have a rear main seal leak (i heard this was typical with this one), a leaky freeze plug and a very leaky tranny pan gasket.
Ok on the dual, that will come with time. For now, don't laugh, but the brackets were broken and the exhaust pipe looked really bad... so i cut it off right before the muffler with a cutting wheel, sounds kinda crappy LOL
I'm not sure what "valve lash" is.
You are extremely helpful, thank you so much.

Last edited by 66coronetgirlie; 10-26-2007 at 04:58 PM.
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Old 10-26-2007, 09:32 AM   #4
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This is the spec list I was talking about. It's 3 pages of every number imaginable for the 318... and the very 1st page is a history break-down on the Poly 318.
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Old 10-26-2007, 07:00 PM   #5
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i hadn't seen that page yet. its got a lot, but obviously no timing advance...

thanks on the manifold. as far as $100 =shipping for and old carb probably in need of rebuild, that's a bit steep. i'd offer him $75 if it wouln't offend the guy, but if he won't budge - its your call. personally, if it's a stromberg ww model, i'd buy it and rebuild it for $15.

definitely check that timing chain. and 0.013/0.021 is certainly what that page says, but my spec is 0.010/0.018 for valve lash (valve lash is the amount of play in your valvetrain between your cam, lifter, pushrod, and rocker in succession, measured between the rocker and valve using a feeler gauge). that page has scanned pages of a shop manual just like mine, same font/format/appearance. its probably just for a different year. the thing to do for you would be to web search "detroit iron manuals on cd." that's what mine is. it was $50 and you'll be able to order the one for your year.

i've heard good things about pertronix' conversion kit. i almost put one in my '65 a100 van's la318, but i ended up selling it.

well, at least these old mopars are woth the effort, not many other cars are...

take it easy
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Old 10-26-2007, 08:41 PM   #6
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i found the exact one you're talking about for a really good price and i'm working on getting it. Thanks for all of your help. You rawk.
yeah, i'm not doing the rebuilt carter in kentucky or whatever LOL... seemed steep if i could find a similar carter online, brand new for $149, i could probably find the appropriate one for around the same... so $100 used and not rebuilt, no thanks. LOL
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Old 10-27-2007, 05:23 PM   #7
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if you're not worried about staying completely original, you could find maybe a newer 2bbl of a more reliable design that would likely be a higher cfm as well. i've got an '85 carter 2bbl - a "bbd" model i think, overall a good piece - that i was going to use for my poly. i had it on there and running, but i've since decided to teardown my dart to restore it. besides the larger linkage/bracketry (throttle valves couldn't open completely cuz idle speed screws hit manifold), the only thing that really didn't fit was the choke mechanism of course. the linkage clearance is easily solved with a carb spacer, as far as the choke i would just run a manual choke cable to solve that issue, which could be done discreetly so as not to damage original parts or be permanent. i bought my carter remanufactured 3 years ago (for my a100's la318) for about $150. another thing to consider is the fact that a lot of old strombergs use a clamp on air cleaner (mine does) and the air horn won't accept anything else. does your car have a clamp on or standard air cleaner, and would you want to keep that original? would you be interested in putting a newer nonmatching carb on there instead of an older nonmatching one?
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Old 10-27-2007, 07:42 PM   #8
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i kind of wanted to stay original, but my outlook on that is if i keep the old stuff, i can throw it back on when the time seems right. I'm open for whatever will work at this point. I sold my 99gt and bought this car as my daily driver, like i said, under the impression it just needed headlights LOL Now, i just want it to be driveable lol.
It has the standard air cleaner..just the big black round thing that fits over the carb, onto a large piece of allthread LOL thats what you're talking about, right? haha
please don't laugh at me... a chuckle is ok.. but no laughing HAHA!!!
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Old 10-28-2007, 01:30 PM   #9
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what i meant by standard air cleaner is one like you see all the time, the lower half/housing slips onto the air horn's flange and the lid fits onto that, then the whole thing is secured by a threaded stud fixed to the carb in some way or another.
my stromberg's air cleaner is clamped on. the air horn has a ridge around the outside of it's opening and the air cleaner housing has a hose clamp style band at it's base which matches the profile of the ridge. you first clamp the lower section onto the carb, then the lid is secured by a threaded stud mounted in the lower section.

as far as keeping things original, i'm building an la360 for my dart that i'll use while i slowly find, save up for, and buy parts for my poly (rare + performance = ridiculou$ly expen$ive). i'm still collecting parts for the 360, but that's okay cuz i'm still tearing down my dart. i've got a lot of body work to do and i plan on completely stripping the underside and derusting/painting as much as practically possible. since these early b bodies had no independent frame, just front and rear subframes spot welded to the unibody assembly, it makes restoration harder. i've been debating cutting some frame out to replace those parts with upgraded members, but my budget and family probably won't allow me to. so far all i've really done is strip the interior, stop some floor rust, and play with the poly. next i've got to pull the engine&trans, replace most of my floorpans, fix some cowl cancer, then do tons of blasting and spraying...

but back to the point - i'll be using a newer engine&trans for some time, then when the restoration is complete and the poly is built, i'll put it back where it belongs. the differential is the only part of the car that i know isn't original, the casting #'s say its a '69 741 unit and its got 3.23 gears. it was probably a repair swap from way back, nobody touched this neglected beast for 25 years before i bought it. either way, i'll probably upgrade to a 742 w/ 3.91's eventually anyhow, so it doesn't bother me. originality is only truly of value if you keep the car stock and plan on selling it. otherwise, its more of a sentimental thing. keeping the original parts is intelligent either way.
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Old 08-09-2010, 10:41 PM   #10
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