new 400 runs like crap - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

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post #1 of 3 (permalink) Old Sep 1st, 02, 02:02 PM Thread Starter
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Join Date: Aug 2001
Location: davisburg, michigan, united states
Posts: 114
hello, 3 days ago, i put a rebuilt 400 chevy in my cutlass. It has a comp cams, 268 cam, edelbrock performer rpm intake, 750 edelbrock carb,accel coil on mechanical advance hei, and exhaust manifolds because i couldnt find a pair of headers to fit it, but that isnt my problem, the problem is, when i first started it up, it ran good, but when given throttle, gas would shoot out of carb. So i adjusted my valves and it ran good, but doesnt have any performance when driving, i nail it and it goes like 20mph, it makes me mad. This isnt because of the straight exhaust manifolds is it? I sprayed carb cleaner around the intake and carb base and it never raised idle, so im guessing it doesnt have a vacuum leak, although my vacuum gauge shows very low and tells me that i have late ignition timing or valve timing. The timing is right on, but runs rough at idle until its at 8degrees btdc. What is my problem, and if it is the valves, whats the easiest way to adjust valve lash? is my distributor one tooth off or something?
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post #2 of 3 (permalink) Old Sep 1st, 02, 08:20 PM
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Join Date: Feb 2002
Location: Williamstown,PA
Posts: 500
First of all if this engine had never been run before, did you prime the oil pump and do proper break in? Gas shooting out of the carb usually means the intake valves are open when the piston is still on it's way up on the exhaust stroke. With a 268 cam in a 400 you should have good vacuum at idle. Pull the hot wire off of the HEI and try adjusting the valves again. Start with the #1 piston at TDC on the compression stroke (both valves should be closed). Loosen the rocker nuts and give the lifters a minute for the plungers to raise up. Now while spinning the push rod with your fingers slowly tighten the rocker nut until you feel a slight resistance on the push rod. Tighten the nut half a turn past that and then do the same procedure on the other rocker. If you turn the engine 1/4 turn at a time you can follow the firing order. 1-8-4-3-6-5-7-2 If that doesn't fix the problem I think I'd check the cam timing.

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post #3 of 3 (permalink) Old Sep 3rd, 02, 03:10 PM Thread Starter
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Join Date: Aug 2001
Location: davisburg, michigan, united states
Posts: 114
hi, i think i found out what the problem is, today i lifted off the valve covers and started her up. To my surprize, only 5 of my rockers and valves were even moving!!. I freaked out thinking it was my cam and it got wiped out, but then i pushed on the ends of the rockers and the lifters popped down about a quarter of an inch, so then i tightened them and they finally started moving. Tomorrow i will adjust them and see how it runs. My question now is, will this lifter thing be reoccuring or will my adjusting them after pushing them down solve the problem for good? I have 60 lbs of oil pressure at idle so they shouldnt be starving for lube.
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