Slant Six Forum :: Lack Of Power After Cam Change

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Lack Of Power After Cam Change https://slantsix.org/forum/viewtopic.php?t=50823	Page 1 of 1

Author:	MTP65dartgt [ Mon Jan 14, 2013 8:54 am ]
Post subject:	Lack Of Power After Cam Change
Installed a Competition Cam as part of initial rehab of newly purchased 1965 Dart GT with a 1970-1972 Slant Six. A new timing chain set was also installed and lined up dot to dot at TDC as stated in the instructions. Ignition is converted to Electronic type. I have very little background on how vehicle performed before engine was broken down, head/valve job and cam install/carb rebuild were completed. It was running but only droven @ 1/2 mile before loading on a trailer to take home after purchase. Manufacturer's Part Number: 64-240-4 Product Line: COMP Cams High Energy Camshafts Summit Racing Part Number: CCA-64-240-4 Cam Style: Mechanical flat tappet Basic Operating RPM Range: 800-4,500 Intake Duration at 050 inch Lift: 215 Exhaust Duration at 050 inch Lift: 215 Duration at 050 inch Lift: 215 int./215 exh. Advertised Intake Duration: 252 Advertised Exhaust Duration: 252 Advertised Duration: 252 int./252 exh. Intake Valve Lift with Factory Rocker Arm Ratio: 0.435 in. Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.435 in. Valve Lift with Factory Rocker Arm Ratio: 0.435 int./0.435 exh. Lobe Separation (degrees): 110 Intake Valve Lash: 0.010 in. Exhaust Valve Lash: 0.012 in. Timing is set at 5 degrees before TDC. Car drops significantly in power on any incline but seems to run OK, but far from great, on the flat. The engine is showing about 15" vacuum. No leaks are noticed. Any ideas out there in FABO land on what I need to check to resolve the loss of power issue? Is 5 degrees BTDC the wrong timing? I've tried shifting the timing but without much success. Guess I'm looking for an experienced recommendation. Carb is recently rebuilt. Engine revs great when transmission in in Park. Carb linkage seems OK. Valve Lash is checked and rechecked. I've run out of ideas, admit my novice category and am now asking the experts for help. Thanks

Author:	Joshie225 [ Mon Jan 14, 2013 11:38 am ]
Post subject:
15" idle vacuum is low. It's all too easy to be off a tooth when lining up the marks on the sprockets. I own a degree wheel and dial indicator so I can degree a camshaft. Have you done a compression test? If it's low across the board (and there are no excessively leaky rings or valves) that would indicate retarded cam timing which will hurt performance substantially.

Author:	olafla [ Mon Jan 14, 2013 12:18 pm ]
Post subject:
Hi MTP65dartgt. I have no knowledge about your cam, but my immediate reaction is that the exhaust valve lash is set very tight. The lash for a stock cam is .010" intake and .020" exhaust, see this link to the FAQ in the engine section Valve adjustment procedure. Olaf

Author:	Rick Covalt [ Mon Jan 14, 2013 12:27 pm ]
Post subject:
The last 2 or 3 timing sets that I installed were all off one tooth when checked by using a degree wheel. I am guessing they are stamped wrong? But even if they are not you need to check it with a degree wheel so you know where it is at. Rick

Author:	DusterIdiot [ Mon Jan 14, 2013 3:39 pm ]
Post subject:	x2
Quote: The last 2 or 3 timing sets that I installed were all off one tooth when checked by using a degree wheel. Yes I have seen this as well...always check by the wheel... Quote: I have no knowledge about your cam, but my immediate reaction is that the exhaust valve lash is set very tight. The lash for a stock cam is .010" intake and .020" exhaust Comp uses tight lash chevy lobes so comparing it to the stock cam is not close in lobe profile, although the comp 252 I used was .012/.012....it was happier at .014/.014...degreed at 4 degrees advance. That being said I have driven engines with the Comp264 and it leaves much on the table compared to say the Erson 270/270, it will run and drive fine but it just seems to plateau in the higher rpm when getting on it...like it needs about 4-6 more degrees of duration and about .2 more inches of lift at 1.5 ratio.... -D.Idiot

Author:	Doc [ Mon Jan 14, 2013 4:11 pm ]
Post subject:
Quote: ... Any ideas out there in FABO land on what I need to check to resolve the loss of power issue?... Should we all sing a verse or two of: "This Land Is Your Land"... (Sung to the tune of: "This Land Is Your Land") "From a Mopar A-Body, to a Slant Six Dart Gee Tee... This car was made for you and me..." Seriously... Another vote that the cam timing is off and / or the lash is too tight. As a quick cam timing check, pull the valve cover and test to see how well centered the overlap event is, over TDCE. Loosen the lash to .016 In & .018 Ex while you are in there and give it a test drive. DD

Author:	terrylittlejohn [ Thu Jan 17, 2013 4:50 pm ]
Post subject:
i vote yea for both

Author:	RustyRamcharger [ Sun Jan 20, 2013 12:45 pm ]
Post subject:
fwiw I have the same cam in my '71 Valiant. Its happiest with the lash set to 0.010/0.020. Ken

Author:	MTP65dartgt [ Wed Feb 13, 2013 1:34 pm ]
Post subject:	Status Update
Things are coming together. Reset lash to 0.14 intake and 0.18 exhaust and improvement was noticeable. Still working toward several recommendations of 0,20 - 0,22 exhaust with the background of a CAM manufacturer recommendation of 0.010/0.012. Reset timing with a total of 36 degrees. Replaced previous owner installed stock electronic ignition module (silver) with a Orange Box. Seems like a significant improvement. The test was hills in my area that no longer require a manual downshift to 2nd gear on my automatic tranny. Gonna keep fine tuning with more valve lash tweeks. Next goal is convert to Dutra front/Stock conversion rear exhaust and 2BBL Carb if I can round up all the parts and find a good description of the Super Six Conversion. Looking for a good diagram that depicts the linkage and identifies the accelerator/gas pedal and kick down conversion necessary from rod to cable type assemblies. Thanks again to all the forum contributors on this.

Author:	terrylittlejohn [ Thu Feb 14, 2013 12:15 pm ]
Post subject:
what coil are you using with the orange box?

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