Slant Six Forum :: Slant six refuses to run smoothly......yarghhh

Didn't get a cam card back from the builder..........

I ordered the cam directly from Comp Cams myself, so I assume I must have had all the cam specs and documentation in hand before I gave it all to the builder to go to work with - is this what you are referring to when you mention a cam card?

I haven't re-set the valve lash since breaking in the motor. In fact, I was a bit surprised to find that the engine was making quite a bit of valvetrain clatter when I got it back from the builder........didn't have a chance to question him about this, as I was in the middle of moving across country and was too busy to chase this down.

What is the typical break-in period? I would guess the motor has been run perhaps a total of 200 miles since I got it back from the builder - probably less than that actually.

It does sound as if it needs the valve lash adjusted - but I've had slant sixes run with wayyyy more clatter than this in their valves and still idle smoothly.

Additional info - when I first start the motor, when it has been cold, it will idle on the hot idle setting pretty smoothly for about a minute. Even before the choke has kicked, though, it starts to chug and miss and get rough though.

Odd.

Cam Card - can you please tell me what this would include on it?

thanks thanks

Author:	dart_swinger [ Sat Sep 17, 2005 11:26 am ]
Post subject:	Slant six refuses to run smoothly......yarghhh
Hoping that someone here can offer a bit of advice / encouragement.... having a real challenge getting this slant to run like I know it should! The specs: 1970 Dodge Dart with 225 Slant Six / 904 auto trans stock 1 bbl intake and carb added MSD ignition and coil motor rebuilt to stock specs, with addition of competition cam's most mild cam, "High Energy" model #K64-240-4 with specs of 252 intake/exhaust, 215 @.050" intake/exhaust, valve lift .435", lobe sep angle 110. this cam also included stiffer valve springs. Motor builder installed Cox Brothers Double Roller timing chain at rebuild also. Since the motor rebuild, I've rebuilt the carb, replaced the alternator, battery, plugs, wires (with 7mm noise-supression wires), voltage regulator, distributor (triggering the MSD with an OEM electronic distributor) and installed a ground strap. The motor runs worse by the minute. It stumbles, surges up and down in RPM, and balks like crazy when I drop it into gear. The alternator guage swings wildly as the RPM's waver up and down, flipping between "charge" and "discharge" like mad. To me, this acts like there is some sort of vacuum leak, which I have done my best to check in all the immediately apparent locations. Vacuum lines are in good shape. Could this cam that I had installed with the rebuild have changed the air/fuel requirements for the motor drastically enough that the carb just isn't set up properly to supply it? I questioned the tech support individual at comp cams before selecting it, and was told that this is a basic replacement cam for most rebuilds. or any other thoughts.....? Hoping one of you fine slant six people can help me out......thanks! Sincerely, Mike T.

Author:	Dennis Weaver [ Sat Sep 17, 2005 1:15 pm ]
Post subject:
Sounds like the carb is junk or the valves are misadjusted. D/W

Author:	skraecken [ Sat Sep 17, 2005 1:34 pm ]
Post subject:
Who rebuild the engine, you or someone else. If it wasnÂ´t you, I would check everything from the beginning, start with cam gear, distributor, valve lash, manifoldgasket.

Author:	zedpapa [ Sat Sep 17, 2005 2:18 pm ]
Post subject:	engine
i have this same cam in my engine and have had no trouble with at all. can you get the engine to run smooth at any rpm, high or low? i would double check everything, timing, firing order, timing of the cam. as far as the amp gauge jumping, have you had it running long enough to recharge the battery? zedpapa

Author:	DusterIdiot [ Sat Sep 17, 2005 8:36 pm ]
Post subject:	Lash right?
After you 'broke in' the rebuild you relashed the valves to make sure everything was set correctly (and your rebuilder gave you the cam card with the correct specs?). The 1 barrel may also be at fault at this point in time, I have that cam and it is comfortable with a Carter BBD along with the Hpak intake... Hopefully your builder degreed tha cam in correctly also. good luck, -D.Idiot

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Author:	dart_swinger [ Sun Sep 18, 2005 6:43 pm ]
Post subject:
Didn't get a cam card back from the builder.......... I ordered the cam directly from Comp Cams myself, so I assume I must have had all the cam specs and documentation in hand before I gave it all to the builder to go to work with - is this what you are referring to when you mention a cam card? I haven't re-set the valve lash since breaking in the motor. In fact, I was a bit surprised to find that the engine was making quite a bit of valvetrain clatter when I got it back from the builder........didn't have a chance to question him about this, as I was in the middle of moving across country and was too busy to chase this down. What is the typical break-in period? I would guess the motor has been run perhaps a total of 200 miles since I got it back from the builder - probably less than that actually. It does sound as if it needs the valve lash adjusted - but I've had slant sixes run with wayyyy more clatter than this in their valves and still idle smoothly. Additional info - when I first start the motor, when it has been cold, it will idle on the hot idle setting pretty smoothly for about a minute. Even before the choke has kicked, though, it starts to chug and miss and get rough though. Odd. Cam Card - can you please tell me what this would include on it? thanks thanks

Author:	SlantSixDan [ Sun Sep 18, 2005 6:56 pm ]
Post subject:
For now I'm going to mentally chalk this up as another example of, er, inconsistent quality control on those Comp 252 cams. I've seen 'em not oil the top end properly...and I've seen 'em oil the top end just fine. I've seen 'em refuse to run smoothly...and I've seen 'em run fine. The 0.012" exhaust lash spec they recommend is a funny joke. Can't say for sure that the cam's causing your problemâ€”it could be a large vacuum leak (e.g. at the manifold-to-head gasket, or even in the manifold itself...what kind of manifold did you use?). Could be a cam timing or an ignition timing issue.

Author:	Dennis Weaver [ Sun Sep 18, 2005 8:05 pm ]
Post subject:
Quote: The 0.012" exhaust lash spec they recommend is a funny joke. Ok, Dan, I've asked about this here before, and I don't remember you commenting - I run the 264 "comp" cam in my Duster, I too questioned the .012" Exhaust spec, and was told by their tech it was no typo. Others here said it was Kosher. What say you? This is no pissing contest, I have a concern in this area, and I want all the facts and opinions. D/W

Author:	SlantSixDan [ Mon Sep 19, 2005 6:29 am ]
Post subject:
I've seen the 0.012" exhaust lash setting cause rough hot running as the exhaust valves heat up and take up some of that (minimal) lash. Backing off a little seems to clear it up. This is on their 252 cam; I'm guessing (but only guessing) the same thing could happen on their other cams.

Author:	Dennis Weaver [ Mon Sep 19, 2005 8:14 am ]
Post subject:
My Duster runs like a clock at idle and at speed. There is an occasional irregular/sporadic misfire at low speed/high vacuum no load cruising when the motor is hot (like soaking hot, after a run, not hot coolant-wise), I notice it the most with open headers, it is a little hiccup in an otherwise smooth sound. It goes away with throttle or load and is not present at high speed or idle. I have always attributed this to fuel distribution and a couple cylinders getting a wee bit lean under the above mentioned circumstances. Should I try giving it a few thous more exhaust lash and see what happens? Thoughts anyone? D/W

Author:	DusterIdiot [ Mon Sep 19, 2005 7:49 pm ]
Post subject:	Actually...
Doc a couple years back posted his 'preferred' lash settings for a Comp cam which came to something like .016-.018 on the exhaust side for the same reasons Dan talks about. I've tryed it on my stick as the mill heats up the idle gets choppy when hot with the .012 if set 'exact'...a little looser and she quiets down and smooths out a bit. I have also set the intake lash a bit tight just to 'fool' the bumpstick into a little bit more lift/etc.. with no real gains so I set that back to .012... -D.Idiot 'Whatever..."

Author:	dart_swinger [ Mon Sep 19, 2005 9:51 pm ]
Post subject:
To answer SlantSixDan's question - I am using the stock 1 bbl cast-iron intake manifold and exhaust, with the stock Holley 1920 1 bbl carb on top. I'm intrigued with the .018" valve lash you've mentioned on here now. But also intrigued with the whole concept of poor quality control on the Cam itself - how would someone determine definitively that the cam was the source of the problem? My next step - I have just ordered another carb. Since the rebuild didn't seem to have any effect - I will try this next. (stock replacement holley 1 bbl.) Once this matter is cleared up (god willing! ) I have a super six setup that I was planning on installing next.....just need to get this poor six feeling better first.....I know, I know, patience..... thanks again guys......!

Author:	SlantSixDan [ Tue Sep 20, 2005 5:38 am ]
Post subject:
Quote: To answer SlantSixDan's question - I am using the stock 1 bbl cast-iron intake manifold and exhaust, with the stock Holley 1920 1 bbl carb on top. OK, so a manifold gasket vacuum leak is possible, and a crack in the manifold floor is possible but not terribly likely. One question, is your '70 a California car or a Federal car? Quote: I'm intrigued with the .018" valve lash you've mentioned on here now. Give it a try! Quote: But also intrigued with the whole concept of poor quality control on the Cam itself - how would someone determine definitively that the cam was the source of the problem? Oh, that's easy! When you've swapped the carb, carefully checked the manifold gasket and replaced it, fiddled with valve lash, reviewed all other vacuum leak points, messed with the ignition system, double-checked the cam timing and have no money or hair left, and the car still runs poorly, it's the cam...!

Author:	dart_swinger [ Wed Sep 21, 2005 12:55 pm ]
Post subject:
Dan, the car is originally from South Carolina, I believe. (I bought it off of ebay when it was residing in Syracuse, NY, but it had been brought up from the Carolinas, as I was told.) haha, I think I can grasp the basic concept of your cam-testing-procedure! lol. I'll try the lash first along with the carb swap. going back to garage with proverbial fingers crossed! thanks thanks.....

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