just rebuilt runs bad

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So what did they do and where was the cam degreed at? What cam exactly was used?
 
One item I haven't heard is what type of gas are you using? At 10 to 1 compression do you have enough octane? If not that could be at least part of it.
 
Still looking for some help. At TDC with a little advance the motor runs bad, has light clickity clacks, and backfires through the carb. Here's the latest based on many of your suggestions.


- Verified #6 cylinder valve overlap is within a half inch of the timing mark. It was about an eighth.
- Verified TDC using a piston stop. Right on the money.
- Verified both intake and exhaust valves closed at TDC compression stroke.
- Verified at TDC that rotor is pointing to the number one spark plug terminal.
- Verified spark plugs in proper firing order 18436572 in clockwise rotation.
- Removed new MSD6AL PN 6420 from its original location and isolated it as far as possible from any other electronics.
- Isolated orange/+ and black/- coil wires from 6AL to new Blaster Coil from other electronics
- Isolated Green and Purple wires running from 6AL to used MSD 8534 magnetic pickup distributor with mechanical advance.
- Grounded 6AL direct to battery negative
- Powered 6AL direct to battery positive
- Locked out mechanical advance on MSD distributor.
- Compression is consistent between 135 and 145.


Based on everything I've told him the builder says he does not believe it's a problem with the build. He said they took notes when they degreed the cam and everything looks right. TDC is where it should be, valves closed on the compression stroke, rotor pointing to #1. He thinks I should focus on the ignition, which I did after work today as noted above.


Ruling out:
- Sticking valve or bent push rod. It runs too good without any tapping or backfire at 60 degrees advance. Compression is even (although someone suggested it may be a little low for my setup) (comp cam CL-20-670-4 .474 lift @ .050, 233/240, 110 separation)
- Spark plug wire-674s are new MSD 8.5 super conductor.

Other observations:
- Half of the spark plugs tips seemed to be dry and black the other half were wet and black (more of a sheen)

Concerns:
Used distributor. Noticed some silicone around the one side of the pickup. Had some light surface rust that I cleaned up.

Thanks for reading.
 
Go to your nearest auto parts house & get a point type dizzy, set the points & drop it in, hook up the vacuum advance, trust me on this, you will be able to rule out all the electronics you installed, it very simple, you'll need a stock coil though, the dizzys are not exspensive, hook up the ballast, the brown wire to the + coil, distributor wire to the - side, set timing, don't be surprized if it fires up & runs like a raped ape, if so, THEN you'll know its either the Box/coil/distributor, I wouldn't trust a used dist., especially a mopar elec. unit, I'm guessing its in the pickup coil, they will cause all kinds of issues, includeing backfiring through the carb, its fireing when its not supposed too, simple as that.

Always check the obvious 1st., don't start digging deep for problems, it will get exspensive real fast & the problem still exist, I'm sure the machine shop did there job & all is good on there end.

The lifters can/will bleed out & clack when its firing in the wrong pattern, happens all the time, once you get it sorted out, you'll see the lifter/lifters will calm down, take a deeeeeeeeeep breath, its something simple & over-looked trust me. BTDT.

Let me add this, DO NOT use the MSD coil on the point dist., you'll fry the points in know time, you can get away with a factory elec. ignition coil, but one for points is better, Now you won't have to keep the parts :D, I know its wrong but oh well, if the problem is fixed with the points, just pull it out, clean it off nicely & bring it back, don't get grease on the box, the points shouldn't show any wear in a short time, just tell them you found the problem & didn't use the parts, they will give you a refund.
 
Thanks man. You just lifted my spirits!
 
I'm not even gonna read all this, remove the valve covers and then the rocker assemblies and lay a straightedge across the tops of the valves and see that they are all at the same height...if they are all at the same height then you have a half decent machine shop. now to check lifter preload without pulling the intake, from what you had said an intake valve is open when it should not be....that is not good...this happens all the time when a machinist is not familiar with a non adjustable rocker arm. so at this point in time you are faced with diagnosing what they did wrong and if they have the valve tips all the same height then you have a choice......you can get shorter pushrods but if they are all diffrent then the choice is two of two...adjustable rocker arms and a new machinist...sorry but thats the facts if the valve tips are all the same height then you just need adjustable rocker arms or shorter pushrods...either way I recomend the adjustable rockers.all of you pointing fingers at the ignition system need to remember he had the engine rebuilt not the ignition system go back to the basics and the beginning....start at the bottom...it has fire those who mentioned 5 and 7 being crossed good that is very possible but the rest is go back to the basics and when the do a valve job things change...ignition systems are pretty reliable just my opinion so think what ya want...i'd recheck the valvetrain
 
waggin said:
I'm not even gonna read all this, remove the valve covers and then the rocker assemblies and lay a straightedge across the tops of the valves and see that they are all at the same height...if they are all at the same height then you have a half decent machine shop. now to check lifter preload without pulling the intake, from what you had said an intake valve is open when it should not be....that is not good...this happens all the time when a machinist is not familiar with a non adjustable rocker arm. so at this point in time you are faced with diagnosing what they did wrong and if they have the valve tips all the same height then you have a choice......you can get shorter pushrods but if they are all diffrent then the choice is two of two...adjustable rocker arms and a new machinist...sorry but thats the facts if the valve tips are all the same height then you just need adjustable rocker arms or shorter pushrods...either way I recomend the adjustable rockers.all of you pointing fingers at the ignition system need to remember he had the engine rebuilt not the ignition system go back to the basics and the beginning....start at the bottom...it has fire those who mentioned 5 and 7 being crossed good that is very possible but the rest is go back to the basics and when the do a valve job things change...ignition systems are pretty reliable just my opinion so think what ya want...i'd recheck the valvetrain
Click to expand...

Don't need to get your panties in a wod, there just opinions, no need trashing others opinion just because your trying to get your point across.

Could it be the vavletrain, sure it can, but do you realize how much preload would be needed on a hyd. lifter to keep a valve hung open, a good .080", I'm sure the machinest isn't a total idiot that he didn't know it had fixed rocker shafts, the cam isn't that big, so the only way it would start hanging valves is if the heads were milled a ton or the block was decked quit abit.
 
63dartman said:
possibly 180 out. If the distributor was dropped in with timing marks pointing at each other then it was at TDC for #6 cylinder. Has happened before.
Click to expand...

It seems like every Comp Cam I've ever seen had this issue at first startup.
 
jos51700 said:
It seems like every Comp Cam I've ever seen had this issue at first startup.
Click to expand...

the engine fired and ran....it is not 180 out...it would never start...

comp cams?...lol.....you need to verify that that the engine is on the compression stroke prior to installing the distributor on number 1....


someone back on post #4 said to check the valvetrain...
 
really now......isnt wad spelled with an a ? no panties here just an observance from a day or two of playing with mopars and noticing all the chevy guy mentality sticking its nose in where it has no real place....really.... if I was building a chevy I'd demand the same quality that it takes to build a mopar if I wanted my chevy to outrun a mopar. if there are sixteen valves in an engine wouldnt you want them all cut to the same heights? and the seats cut to the same depth? and the assembled height to be the same with the same spring tension at the closed position to be the same and at open position to be the same? oh I forgot were not talkin chevy here...were talking mopar we dont just slap it together in the dirt and adjust the valves.......it has to be put back together with care we like to outrun chevys so git yourself in line, if you have a problem with what I said about doing the job right go right ahead and spout off here...I didnt put anyone down but I did point out that the mopar has a fixed rocker shaft and a good machinist that knows his stuff can do a valve job and get the preload on the lifters after cutting the valves the seats and the stems correct without changing pushrods or needing adjustable rocker arms so if you can unwad your panties and figure out why I would say that then you would understand that .080 on one lifter and .060 on another lifter is unacceptable then you can explain this to these guys here, they want quality and what I had said gits them going in the general direction to get that quality....you wanna be a chevy machinist go right ahead and be all you can be buddy boy but a mopar guy can make a chevy run faster farther and longer
JoeDust451 said:
Don't need to get your panties in a wod, there just opinions, no need trashing others opinion just because your trying to get your point across.

Could it be the vavletrain, sure it can, but do you realize how much preload would be needed on a hyd. lifter to keep a valve hung open, a good .080", I'm sure the machinest isn't a total idiot that he didn't know it had fixed rocker shafts, the cam isn't that big, so the only way it would start hanging valves is if the heads were milled a ton or the block was decked quit abit.
Click to expand...
 
try not to forget when he cuts the valve then the stem to get his assembled height then the depth he cuts the seat, even if he doesn't cut the heads all of that needs to be equal and very few machinists will find the lowest seat to determine what will make the engine balanced, they will simply cut a seat to clean it up and assemble it with no clue because a chevy has adjustable rockers, that valve will need a shim under the spring to get the seat pressure that the other cylinders don't need, hell look for assembled height and spring tension at assembled height and send em out the door, mopars were built diffrent and the training they got rebuilding them was exceptional I'll put a stock 340 against any 350 chevy any day of the week because of that simple valvetrain knowledge, everyone that plays with engines should know about the process involved with doing a valve job and the process of doing it correctly would be the "advanced" course, so lets try to understand I was not putting anybody down for going after the ignition system to be the culprit when the engine was rebuilt and that I had admitted it is easy for some to get 5 and 7 plug wires mixed up ok, i'm sharing what I know and that is all...if there is a flaw in what I have said please feel free to point it out without referring to anyones panties some of the ladies reading this thread may be offended
JoeDust451 said:
Don't need to get your panties in a wod, there just opinions, no need trashing others opinion just because your trying to get your point across.

Could it be the vavletrain, sure it can, but do you realize how much preload would be needed on a hyd. lifter to keep a valve hung open, a good .080", I'm sure the machinest isn't a total idiot that he didn't know it had fixed rocker shafts, the cam isn't that big, so the only way it would start hanging valves is if the heads were milled a ton or the block was decked quit abit.
Click to expand...
 
I agree with stabbing a different distributor, Especially after you saying it runs good with 60 degrees of advance. I have had that happen before, Backfires no power idled like crap, Retimed still crap twisted the distributor all over to find it idled and revved clean with TONS of advance. I replaced the distributor with a known good one and fixed it, EASY place to start and rule out your electronics I would be surprised if this wasn't it.

Good luck,
Joe
 
I'm interested in the difference in the spark plugs,, if you got a spare carb,, I'd try that...

I sure hope we're not back to having an open Vacuum port on the carb, is the optional PCV port on the back of the carb plugged,.. will it idle???

Were the wet plugs all from one side of car?? or from one side of carb, ie, high or low manifold runner,,

AND again,, an engine WON'T run with dizzy 180 degrees out,, sure will backfire though
 
I would check the cam timing, you said he didn't use the double roller you gave him. He may have put one of those plastic timing gear sets on which have been know to strip teeth.
 
Some of these symtoms described are what you get when you have the wires to the distributor reversed. Especially the 60 degrees advance problem.
 
RUN A BACKYARD "cylinder balance test."

Pull the dist boots up off the dist. so you can get a probe in there, and/ or stick some small nails/ brads down into all of the plug wire towers, right beside the wires

Get it running at the lowest decent idle you can

Using a grounded probe, ground each plug one at a time. Do NOT try this by "pulling plug wires." The resulting high voltage will crossfire, confusing the results, and can "kill" modern electronic igntion systems

This should QUICKLY tell you what cylinder(s) are not doing "something."

Try timing it with a vacuum gauge, simple tune the dist for highest vacuum reading at the lowest idle you can manage.

Once you have done these two things, you should be able to tell a little more.

what do the plugs look like?

Depending on the "balance test," don't be afraid to check resistance/ continuity of plug wires, or to check spark at the plug end of a dead cylinder(s)

I think, it's time for a second set of eyes. Take a step back. Get a couple of buddies over there that are good with engines.
 
It's really awesome how everyone steps up to help out here. I hope to have the experience and knowledge to help others some day.

Here's the latest. With the MSD box sitting unattached on top of the fender and grounded to the battery, and MSD coil and distributor wires isolated from other wires to the extent possible, I started the motor. This time advancing the initial timing (turning dist. CC) from TDC a little more than I had in the past. I started the motor and NO Backfiring or metallic noises. The timing was between 15 and 17 BTDC, in the past it was anywhere between 0 and 12 BTDC. There is some hesitation when I gun the throttle but no metallic noises or backfire. I'm hoping hesitation can be corrected with some tweaking. It was late at night and I haven't had a chance to get back to it since. So I feel like i'm getting very close. Going to put the MSD stuff back where it was and see if the backfire and noise returns, also move the timing back to 10 BTDC or below.

To answer some of the new questions:
- The vacuum port in back of the carb is plugged
- I checked for vacuum leaks around the intake and carb by spraying carb cleaner
- Builder used PBM timing chain and gear set
- Didn't keep track of the plugs well enough to know which cylinders had the wetter plugs.
- Cylinder balance test and vacuum timing may be in the future if problems continue.

I'll have some time to work on the car tomorrow and will post an update.

Thanks for all the support and suggestions.
 
WHY ARE YOU so intent on retarding the timing???????
 
Oh.. I just want to see if the backfire and noise comes back at 10, then I will know if that was the problem or not. Don't want to keep it there. In fact after researching the Site I may want to try advancing initial even beyond 15.
 
I would think to look at those non-adjustable rockers too. I can't stand running them with ANY aftermarket hot cam. It just bugs me. Those are for grocery-getters. Second, there's always the possiblility that the harmonic balancer outer ring has slipped and the timing mark is incorrect. And then I'd think about vacuum leaks around the carb/intake manifold or even the brake power booster (if it has one). The fact that you mentioned "pinging" bothers me (if it actually WAS pinging and not valvetrain sound).
 
just do process of elimination. 3 things to make an engine run, fuel compression spark. ok so you have fuel, check. you have spark? obviously if its backfires through carb. so that leaves compression. now youve checked ignition timing over and over again, good great, but have you check your cam timing? it could be a degree or two advanced. now, if that is good, then the problem lies within the valvetrain area, ie stuck valve or something... just tossing ideas out there. and i DO agree, the machine shop where you had this built should figure it out, not you.
 
he's checked cam timing, and the damper, they're fine.

I'm just interested,, did you turn the carb upside down, for any reason,

I'm still on about the wet plugs..
 
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