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#1
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New cam, no power
I just finished rebuilding my w72 400 with a Crower 60240 cam, new lifters, valve springs, rings, and rod bearings, I didn't have any work done at a machine shop as the engine didn't need anything. After break-in, I took the car for a drive and it makes less power than with the stock cam, it can't get out of its own way! I have checked compression, firing order, spark, fuel, and timing and all seems to be as it should be. Compression was at 145-150psi for cylinders 1, 2, 3, and 4. I will be checking the other 4 cylinders after work today, as I just did a quick check on the easily accessible cylinders. Timing is set to 18 degrees btdc. I'm out of ideas as to what could be amiss. A friend of mine suggested that the issue could be the stock non-adjustable valvetrain preventing the valves from operating properly. I did a rough check on the valve lift with a valve cover off cranking the engine and measuring valve movement and came up with ~1/2", which is close to the advertised lift of .422/.446 with the stock rocker arm ratio. It doesn't look like the rockers are binding or otherwise hanging up.
Any help would be greatly appreciated! |
#2
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Quote:
Did you degree the cam? If so what is the ICL? Stan
__________________
Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm Last edited by Stan Weiss; 08-07-2023 at 12:01 PM. |
#3
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140 psi is not going to cut it!
Did you degree the Cam in? I bet it's installed retarded and not even straight up. Once 1972 came around Pontiac never used anything bigger then the factory 067 Cam in a 400 so as to maintain good drivability, that crower Cam your running is bigger then that.
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#4
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Make the valvetrain adjustable anytime you run an aftermarket cam. Yes sometimes you can get away with not doing that with some milder grinds but it’s always best to convert to adjustable.
You may not be able to perform a valid compression test until your valves are properly adjusted. Recurving your distributor would be wise as well.
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1964 Tempest Coupe LS3/4L70E/3.42 1964 Le Mans Convertible 421 HO/TH350/2.56 2002 WS6 Convertible LS1/4L60E/3.23 |
#5
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Yeah thats awful low compression, its either cam timing not degree in right, or valve adjustment bleeding off compression.
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The Following User Says Thank You to Gach For This Useful Post: | ||
#6
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#7
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what kind of timing chain/gear set was used with this?
Mistakes with multi keyway types is when cam timing can be a problem. Clay |
#8
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I installed an Edelbrock 7812, it does have multiple keyways. I made sure it was installed dot to dot, corresponding to no advance or retard.
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#9
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I would buy a set of ARP BB Chevy rocker studs (7-16-20 UNF top threads and 7/16-14 UNC bottom) and some polylock nuts and make the valvetrain not only fully adjustable but much more stable and durable. The 60240 is a very good cam choice for your application, just make everything else right and you’ll reap the benefits.
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1964 Tempest Coupe LS3/4L70E/3.42 1964 Le Mans Convertible 421 HO/TH350/2.56 2002 WS6 Convertible LS1/4L60E/3.23 |
#10
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I installed that same cam in my buddy`s `79 PWH, W72 400 as well. Ran well BUT, I did install aftermarket rockers, studs and poly locks.
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#11
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X2.
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#12
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I did not degree the cam when I installed it, I was not under the impression that it would be necessary for the engine to run well, just to make a few extra hp to squeeze out the full potential and the CR is stock at 8:1. How/why would the cam be installed retarded if it was installed according to procedure at tdc of the compression stroke on #1? What pressures would you expect for a compression test? I apologise of any of these questions are simple or things that should have been thought of before the engine went together, I was under the impression that this cam was a good choice for a stock low-compression 400 with minimal changes needed.
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#13
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JMO the problem is the cam.
It has 270/276 seat duration and 210/221 @ 0.050" 0.422"/0.446" 112 LSA I know some people don't like this cam, but I think it would have been much better in this engine. Comp cams xe256 - 256/268 seat duration and 212/218 @ 0.050" 0.447"/0.455" 110 LSA Stan
__________________
Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#14
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https://forums.maxperformanceinc.com...greeing+crower Crower cams are often retarded when dot to dot without degreeing.
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#15
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#16
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Clay |
#17
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That makes sense, its a lot simpler than I was expecting. Is the base circle of aftermarket cams larger to allow for greater duration and lift? Im trying to think of all the reasons that the valves would stay open.
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#18
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Just checked the rocker nuts, and when they are torqued down per the manual, I can watch the valve open. I backed the nuts off to adjust them like you normally would with an adjustable valvetrain, did a compression test and it returned 175 psi, a bit more than I was expecting, given the whole engine is stock except the cam. Regardless I am definitely switching the nuts out today! I had to swap the valley pan after break in and had a chance to check the cam and there were no wiped lobes or abnormal wear, thank god. I have also been using the car as a daily for the past year or so, which narrows down other potential problems it might have, but this is a really good starting point (hopefully the only problem)!
Thanks for all the input and ill report back with updates after the new rocker nuts. |
The Following User Says Thank You to Shockwave78 For This Useful Post: | ||
#19
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#20
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PS: 175 will be fine..no worries
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