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Old 07-27-2007, 08:43 PM
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383 cam swap ?

ok i am pulling my engine and tearing it down to inspect it for damage. i've been hearing a rattling sound at idle. and i am very concerned about this. would like to see what the heck it is

383 vortec efi

1997 3/4 ton silverado hd 4x4
csfi converted to to mpfi
383 vortec 4 bolt main
bassani headers 1 5/8 shorty's
dual exhaust 2 1/2 with high flow cats
64cc edlbrock e-tec's 170cc runner 1.94/1.55 they flow 20% more than the vortec's on the exhuast
9.8-1 compression forged pistons kb forged -18cc dished
6.0 H beam 4340 forged rods
3.75 stroke crank

current cam
the cam is a roller xr258hr 258/264 adv. 206/212 @ .050 .485/.493 with 1.52 112 lsa

cam i am thinking about getting

08-503-8 Comp Cams "Extreme" Hydraulic Roller Camshaft, 224 / 230, .502 / .510 112 LSA,High performance street machines, 2000+ stall, gears, choppy idle

my question is would it be worth the extra money to do a cam swap ?

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Old 07-28-2007, 05:50 AM
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You have already started mixing and matching with your semi-stock fuel injection and ECM. I think in your previous thread about engine noise, you indicated it was a MAP based controller and the OEM controller will not handle the big cam well. You will need to really talk to Comp Cams techies to get an ideal as to how much manifold vacuum you will have with this cam and compare that with the vacuum requirements for your ECM. Don't think you will like the answer because you are going to looking at big bucks for a custom ECM and from my experience, you will need to have the car available to the supplier so he can provide you with an ECM that is going to control your fuel/spark through out your expected operating range.

By the way, I watched/listened to the clip you attached to one of your previous posts on noise at idle and if did not know otherwise, I would have sworn I was listening to a Cummings. I know you are in the process of tear down and hope you looked at your valve train closely before pulling the motor. If I understood you correctly, you changed your rocker geometry. Did you check the spring clearances and the push rod length to make sure every thing was set up correctly? Don't think that kind of noise is not going to be bottom end or piston related.

Trees
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Old 07-28-2007, 09:52 AM
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from what i saw based on the comp cams fast flash tuner compatible cams for my 97 vortec the 08-503-8 is the the biggest cam that i can go with the stock pcm.

as for the knocking sound i took my truck to a guy here in town that builds racing engines and he said he thought it was piston #8 that had to much piston to wall clearance. i didn't ask about the cam because i didn't want to take to much of his time it was at the end of the day when i went to see him.
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